Radiation, Microscopic, and Ischemic Colitis

[0:07] Guest:

Right. Yeah, You want a clear picture?

[0:08] Host:

Exactly. I mean, you have a patient presenting with localized peritonitis. The CT scan shows this unmistakable pocket of free air, some inflammatory stranding right next to a thickened sigmoid colon, and you just point at the screen.

[0:24] Guest:

Yeah, you point and say there’s the problem. Let’s go to the OR, right?

[0:28] Host:

The pathology is macroscopic, the decision tree is totally clear, and the anatomy just dictates your action.

[0:35] Guest:

It’s the kind of binary presentation that, well, it provides a lot of comfort for us as surgeons. Oh, absolutely. I mean, it’s either broken or not broken, perforated or intact. The surgical indications are just completely unambiguous.

[0:47] Host:

But The thing is, the moment you step into the world of mucosal inflammation, vascular compromise, or prior eye atrogenic tissue injury, that high evolution scan just, well, it stops giving you the whole story.

[0:59] Guest:

It really does. It’s like the map suddenly doesn’t match the territory.

[1:02] Host:

Exactly. We move away from the microscopically obvious and we enter this diagnostic landscape where the true pathology is hiding at the cellular level or the microvascular level, which is.

[1:13] Guest:

Frankly, a massive clinical trap.

[1:15] Host:

It’s a huge trap because if you aren’t paying close attention to the systemic context or the subtle histologic clues or even the latent effects of therapies they had decades ago, you can so easily be pulled into making a complication inducing misstep.

[1:29] Guest:

And you really don’t want to be the surgeon making that misstep. And that is exactly why we are focusing on this specific trifecta of conditions today.

[1:37] Host:

Yeah. So welcome to this colorectal surgery review. We are so glad you are joining us for this.

[1:42] Guest:

Absolutely. In this deep dive, we are taking a really granular look at the ASCRS textbook of colon and rectal surgery.

[1:49] Host:

Specifically, we’re looking at Chapter 53, which covers radiation, microscopic and ischemic colitis.

[1:55] Guest:

And we’re, you know, bypassing the rudimentary definitions here, we’re heading straight for the high yield concepts.

[2:00] Host:

Right, because our mission today is to review the clinically relevant material for you, the practicing and board certified colon and rectal surgeon.

[2:09] Guest:

We want to extract the critical minutiae that dictates those fundamentals, fundamental shifts in decision making algorithms, because I mean these are the exact nuances that are tested relentlessly on board exams and in service training exam.

[2:22] Host:

Oh for sure, The examiners love to see if we’re paying attention to the small details that actually make a difference in management. It’s what separates A competent surgeon from a masterful 1.

[2:33] Guest:

Exactly. And these three forms of colitis, they share this really unique ability to to see the clinician.

[2:39] Host:

Even though they’re just wildly different in their etiologies.

[2:51] Guest:

Right. I mean one is an iatrogenic Fallout, 1 is this often invisible autoimmune mediated process, and the third is a transient microvascular crisis. But they all require extreme diagnostic vigilance, so let’s just jump right in and start with the iatrogenic side of the equation, Radiation colitis.

[2:58] Guest:

Yeah, this is a big one.

[3:00] Host:

It is. We are dealing with hundreds of thousands of patients receiving pelvic radiation annually. I mean for anal, cervical, prostate and rectal cancers. Encountering the fallout of that radiation is just an everyday reality in a busy colorectal practice.

[3:15] Guest:

It is a really sobering reality of modern oncology, honestly. We cure the primary malignancy, which is great, but we leave the pelvis permanently altered, right? And the ACRS text draws a very hard line regarding the timelines of this fallout. Understanding the physiological difference between these timelines is really the first major hurdle you have to clear.

[3:36] Host:

So we divide this into acute radiation colitis and chronic radiation colitis.

[3:40] Guest:

Let’s define those parameters first. Sure.

[3:41] Host:

So the textbook defines acute radiation colitis as occurring during the course of radiation therapy or within six months of completing it.

[3:49] Guest:

Right. And then chronic radiation colitis is defined by symptoms persisting beyond that six month mark or, and this is the really insidious part, presenting after a prolonged latent period.

[3:59] Host:

Yeah, that latent period is wild, but the timeline itself is just a proxy really for the underlying pathophysiology.

[4:06] Guest:

Exactly. The pathology is entirely different between the acute and chronic phases.

[4:11] Host:

So unpack that for us. Why is the pathophysiology the key to everything here?

[4:16] Guest:

Well, acute radiation colitis is fundamentally just a cellular turnover issue. The radiation is doing exactly what it’s supposed to do.

[4:23] Host:

Right, it’s killing cancer cells.

[4:25] Guest:

Exactly. It’s indiscriminately destroying rapidly dividing cells by inducing DNA double strand breaks, but because the superficial rectal mucosa has a very high baseline rate of cellular turnover, it takes a massive hit right alongside the tumor.

[4:41] Host:

So the normal tissue is just collateral damage.

[4:43] Guest:

Basically, yeah, the crypt cells undergo apoptosis, the epithelial barrier breaks down, and the patient experiences those classic acute symptoms.

[4:51] Host:

You mean the watery diarrhea, tenesmus, urgency, mucus discharge, all that?

[4:55] Guest:

Right, but because it’s an epithelial injury, it’s generally self limiting.

[4:59] Host:

So once the radiation therapy concludes those surviving stem cells down at the base of the crypts, they can repopulate the mucosa.

[5:06] Guest:

Exactly. The epithelium heals over the course of a few weeks or maybe months.

[5:11] Host:

So if acute is like a terrible sunburn that eventually peels and heals up, is chronic more like, I don’t know, slow moving drought that permanently dries up the local water supply?

[5:21] Guest:

That is a perfect analogy, yes. Chronic radiation colitis is an entirely different disease process. It is not an epithelial problem anymore. What is it though? It is a progressive microvascular and missing chymal problem. The radiation induces profound changes in the local vasculature.

[5:39] Host:

Creating that slow moving ischemic drought you mentioned.

[5:42] Guest:

Exactly. It permanently alters the tissue architecture, and for board examinations you absolutely must commit this specific histologic buzzwords associated with this process to memory.

[5:54] Host:

Oh, examiners love their buzzwords. So the textbook highlights obliterative and darteritis.

[5:58] Guest:

That’s the big one. Obliterative and darteritis.

[6:01] Host:

We are looking at a process where the blood vessels are literally just scarring close from the inside out.

[6:06] Guest:

Right. That is the primary driver. Yeah, the endothelial cells lining the small arterioles in the pelvis, they sustain this sub lethal radiation damage.

[6:14] Host:

So they don’t die immediately, but they’re deeply injured.

[6:17] Guest:

Right. And this triggers A chronic inflammatory cascade heavily mediated by cytokines like TGF beta.

[6:23] Host:

OK, TGF beta.

[6:24] Guest:

And TGF beta stimulates local fibroblasts to just over produce collagen, an extracellular matrix.

[6:30] Host:

No, they just go into OverDrive.

[6:32] Guest:

Total OverDrive. You end up with vascular intimal fibrosis without active inflammation.

[6:36] Host:

Without active inflammation. That’s a key distinction.

[6:39] Guest:

It is, and that happens along the focal distortion of those small arterioles.

[6:43] Host:

So the lumen of the microvasculature just progressively narrows down until it occludes entirely.

[6:49] Guest:

Exactly. And because this is a slow, relentless fibrotic scarring process driven by dysregulated fibroblasts, that localized drought can take years to fully manifest.

[7:01] Host:

Even decades, right?

[7:02] Guest:

Yes. The text notes that chronic hemorrhagic proctitis can present up to 30 years after the initial radiation exposure.

[7:20] Host:

That is just terrifying. 30 years after beating their cancer, a patient can present with life threatening rectal hemorrhage just because the microvasculature finally reached a critical threshold of ischemia. It’s wild. Which brings us to the physics and the dose symmetry of the initial treatment.

[7:23] Host:

Right, because the dose matters.

[7:25] Guest:

It matters immensely. The risk of developing this chronic obliterative end arteritis is heavily dose dependent. The ASCRS textbook lays out the exact numerical thresholds you need to know.

[7:37] Host:

So let’s talk numbers. Standard long course neoadjuvant treatment for rectal cancer typically falls in the range of what, 45 to 54 Gray?

[7:44] Guest:

Yes, 45 to 54 Gray. But when we look at treatments for other pelvic malignancies, specifically cervical cancer, the protocols are way more intense.

[7:53] Host:

Right, because they often combine external beam radiation with focal BRCA there.

[7:58] Guest:

Exactly, and that combination pushes the localized dose up to 90 Gray.

[8:02] Host:

Wow, 90 Gray, that’s a massive jump. And those specific dosage numbers explain a really vital clinical presentation pattern that we see all the time in practice. Yes, they do. I mean, as colorectal surgeons dealing with a rectovaginal fistula is, well, it’s one of the most challenging scenarios we ever.

[8:18] Guest:

Faced without a doubt, it’s a miserable problem for the patient and a really difficult technical problem for the surgeon.

[8:23] Host:

But the textbook points out that rectovaginal fistulas are actually exceeding rare complications following standard rectal cancer treatments.

[8:31] Guest:

Right, because a dose of 45 to 54 grey induces that fibrosis we talked about, but it rarely causes the sheer depth of tissue necrosis required to just meltdown the rectovaginal septum.

[8:43] Host:

It’s not enough energy to cause a full thickness meltdown.

[8:46] Guest:

Exactly. However, they are the absolute classic textbook complication of cervical cancer radiation.

[8:52] Host:

And that’s precisely because that tissue is absorbing 90 grey.

[8:56] Guest:

Yes. The inverse square of bracha therapy means the tissue immediately adjacent to the applicator, so the anterior rectal wall and the rectovaginal septum receives a massive obliterating dose of radiation.

[9:07] Host:

It’s just point blank range.

[9:09] Guest:

Basically, yeah. Similarly, rectorethal fistulas are the hallmark complication for prostate cancer. Bracha therapy. The tissue simply cannot survive that level of localized energy deposition.

[9:19] Host:

OK, so the text establishes that anything under 45 grey rarely leads to significant chronic issues, but anything over 70 grey means deep, irreversible tissue injury is almost guaranteed.

[9:31] Guest:

Absolutely guaranteed.

[9:32] Host:

But dosage isn’t the only variable here, right? Patient specific comorbidities play a massive role in amplifying this risk.

[9:40] Guest:

They do. You have to look the whole patient. Pre-existing inflammatory bowel disease, diabetes mellitus, hypertension, peripheral vascular disease and smoking.

[9:50] Host:

The usual suspects the.

[9:51] Guest:

Usual suspects, yeah, but the textbook highlights them as major risk factors for a very specific reason. It all comes back to the concept of microvascular reserve.

[10:01] Host:

Right, because if a patient already suffers from systemic microvascular disease due to say, decades of poorly controlled diabetes or chronic hypertension.

[10:09] Guest:

Their baseline capillary perfusion is already compromised.

[10:12] Host:

It’s already hanging by a thread.

[10:14] Guest:

Exactly, if nicotine is actively causing vasoconstriction and further endothelial damage on top of that, the addition of radiation induced obliterative and arteritis is going to push that rectal tissue into critical ischemia much faster.

[10:27] Host:

And much more severely than in a patient with a healthy baseline vascular tree.

[10:32] Guest:

Precisely the compounding effect of these comorbidities just drastically lowers the threshold for developing symptomatic chronic radiation proctitis.

[10:40] Host:

So given how devastating this progressive ischemia is, prevention strategies have got to be paramount.

[10:47] Guest:

They are obviously the primary prevention lies in the hands of the radiation oncologists.

[10:52] Host:

Right, utilizing CT based 3D conformal planning, intensity modulated radiation therapy and proton beam therapy to spare the normal tissue as much as possible.

[11:02] Guest:

But from a pharmacological standpoint, the textbook mentioned a drug called amaphostine.

[11:07] Host:

Amaphostine. Let’s unpack that, because it’s a fascinating compound.

[11:11] Guest:

It really is. It’s an organic cytophosphate that acts as a highly potent oxygen free radical scavenger.

[11:17] Host:

So how does it actually work in practice?

[11:19] Guest:

Well, when it’s administered systemically before the radiation therapy, it accumulates in healthy tissues more readily than it does in tumor tissues.

[11:26] Host:

Oh, that’s clever.

[11:27] Guest:

Yeah. So during the actual radiation exposure, it neutralizes the reactive oxygen species generated by the ionizing radiation.

[11:34] Host:

Right, thereby protecting the cellular DNA and the vascular endothelium from that initial hit.

[11:40] Guest:

Exactly, it’s literally scavenging the free radicals before they can cause damage.

[11:44] Host:

But the textbook is really careful to note that while it is a promising protective agent, it’s use is definitely non routine.

[11:52] Guest:

Yes, it is not standard of care for everyone.

[11:54] Host:

Because it carries significant toxicities of its own right. Yeah, primarily severe hypotension and nausea.

[12:00] Guest:

Severe nausea and that toxicity profile really limits its widespread prophylactic application.

[12:07] Host:

Makes sense? And what about other preventative measures? Things like probiotics, short chain fatty acid enemas, sucrophate.

[12:14] Guest:

They’ve all been studied extensively, but honestly, none have demonstrated a clear, definitive, statistical significant benefit for routine prevention.

[12:22] Host:

OK, so medical prevention is tricky, but here we encounter a very firm gourd relevant negative that examiners just love to test.

[12:30] Guest:

Oh, the prophylactic surgery question.

[12:32] Host:

Yes, you will see clinical scenarios describing a patient scheduled to undergo massive pelvic radiation, say 90 Gray for recurrent cervical cancer.

[12:40] Guest:

And the question will ask for the best surgical prophylactic step.

[12:44] Host:

And the instinct, the trap is to physically protect the bowel.

[12:48] Guest:

But the ASCRS guidelines are explicit here. Performing a preoperative laparotomy solely for the purpose of placing synthetic mesh, a pelvic sling, or in a mental pedicle flap into the pelvis to exclude the small bowel from the radiation field is absolutely not recommended.

[13:04] Host:

It is the classic trap answer.

[13:06] Guest:

It really is.

[13:07] Host:

Because a prophylactic laparotomy carries immense morbidity. You’re talking about the risk of adhesions, bowel obstruction, incisional hernias, wound infections.

[13:16] Guest:

The text is basically telling us that the morbidity the prophylactic operation far outweighs any theoretical unproven benefit of anatomical exclusion.

[13:25] Host:

Now obviously, if you are already operating in the abdomen for another appropriate oncologic indication, then utilizing an omental flap or a mesh sling to keep the small bowel out of the pelvis is perfectly reasonable.

[13:36] Guest:

Right. If you’re already there, do it, but you do not open a pristine abdomen just to place a sling.

[13:41] Host:

It’s about weighing the iatrogenic harm of surgery against the iatrogenic harm of radiation.

[13:46] Guest:

Exactly. So moving to diagnosis, let’s establish the clinical scenario.

[13:49] Host:

Okay, paint the picture.

[13:51] Guest:

A patient who underwent treatment for cervical cancer, say 5 or 10 years ago, presents to your clinic with chronic low volume rectal bleeding and tenesis.

[13:59] Host:

Classic presentation. So you perform a flexible sigmoidoscopy in the clinic.

[14:04] Guest:

And the endoscopic appearance is just unmistakable. You see this pale vascular looking mucosa interspersed with dense networks of fragile telangitacious.

[14:14] Host:

And they bleed easily upon insufflation or even just slight contact with the scope.

[14:19] Guest:

Right. And that pallor represents the underlying fibrosis and obliterative and arteritis.

[14:24] Host:

The tissue is basically starved for blood, yes.

[14:26] Guest:

While those cholangitasias are the tissues desperate, disorganized attempt at neo vascularization to bypass the ischemic zones.

[14:35] Host:

Now as surgeons, our fundamental training, I mean this is drilled into us from the first day of internship, dictates that any abnormal friable mucosa absolutely must be biopsied.

[14:44] Guest:

You have to rule out a recurrent malignancy or a new primary tumor.

[14:48] Host:

Exactly. But in this specific scenario, the textbook raises a massive flashing red flag regarding biopsies.

[14:56] Guest:

This is one of the most critical clinical warnings in the entire chapter.

[14:59] Host:

And ignoring it will lead directly to a catastrophic complication.

[15:03] Guest:

It will if the diagnosis of chronic radiation proctitis is clinically obvious based on the patient’s archaeologic history and that classic endoscopic appearance of pallor and thalangitatias. You must not biopsy the tissue.

[15:16] Host:

You have to actively fight your surgeon reflex to use the biopsy forceps.

[15:20] Guest:

You must suppress that reflex completely. Do not do it.

[15:23] Host:

Let’s really labor on why. What happens if you do?

[15:26] Guest:

If you take a biopsy of irradiated, severely ischemic tissue, you’re creating a full thickness mucosal defect in an environment that possesses absolutely zero healing potential.

[15:36] Host:

Because of the obliterative end arteritis.

[15:38] Guest:

Exactly. The local blood supply is barely sufficient to keep the intact mucosa alive. If you create a traumatic ulcer with your forceps, the tissue simply cannot mount the necessary inflammatory and proliferative response to heal.

[15:52] Host:

It so that tiny biopsy side just sits there.

[15:54] Guest:

It sits there, it inevitably breaks down, and it will progressively ulcerate deeper and deeper into the submucosa and muscularis.

[16:03] Host:

And then you’re looking at an incredibly high risk of fistulizing directly into the vagina, the bladder, or the prostate, all because you took a tiny biopsy.

[16:12] Guest:

It’s a disaster. The only justifiable indication to biopsy in a radiated rectum is a very high index of clinical suspicion for recurrent cancer.

[16:22] Host:

So, for example, if you see a distinct fungating mass or a stricture with mucosal nodularity that really deviates from the classic flat telangioctatic appearance of radiation proctitis.

[16:34] Guest:

Right. If it looks like a tumor, biopsy it. Otherwise, you make the diagnosis clinically and you leave that mucosa intact.

[16:39] Host:

OK. So the diagnosis is safely established without a biopsy. Now we have to the management algorithms.

[16:45] Guest:

Which have evolved significantly.

[16:47] Host:

Yeah, historically, the management of refractory radiation proctitis involves some pretty complex systemic medical regimens like hyperbaric oxygen therapy or HBOT.

[16:56] Guest:

HBOT is heavily discussed in the literature.

[16:59] Host:

How does that actually work?

[17:00] Guest:

Well, it forces oxygen to dissolve into the plasma at very high pressures, which drives diffusion deeply into those ischemic pelvic tissues.

[17:08] Host:

OK. So theoretically stimulating angiogenesis and fibroblast proliferation to counteract the end arteritis.

[17:15] Guest:

That’s the theory, and the textbook acknowledges that HBOT is effective for a subset of patients. But practically speaking, the logistics are an absolute nightmare.

[17:25] Host:

Oh, I can imagine a standard protocol requires what, 36 to 40 separate daily sessions?

[17:30] Guest:

Yes, 40 daily sessions in a specialized chamber is highly expensive, incredibly time consuming, and simply inaccessible for a large portion of our patient population.

[17:40] Host:

So because of those barriers, the clinical paradigm has shifted heavily toward highly efficient endoscopic solutions.

[17:46] Guest:

Yes, specifically focusing on 2 modalities, formalin application versus argon beam coagulation or ABC.

[17:52] Host:

Let’s examine formalin first, because it remains a highly preferred pragmatic method outlined by the authors.

[17:58] Guest:

It really is. Formalin is cheap, it’s ubiquitous in the hospital, and it is incredibly effective for hemorrhagic radiation proctitis.

[18:04] Host:

The mechanism of action is fascinating to me. It’s a potent chemical sclerosent.

[18:09] Guest:

Exactly when you apply it to the bleeding mucosa, it induces an immediate chemical mediated necrosis of the superficial epithelium.

[18:17] Host:

But more importantly, it’s specifically sclerosis and thrombosis, that fragile, bleeding neo vasculature.

[18:23] Guest:

Those superficial telangiectasias we identified on endoscopy, it essentially seals the bleeding vessels chemically without causing deep tissue destruction.

[18:32] Host:

And the textbook details a very specific streamlined outpatient protocol for formalin application that is just elegant in its simplicity.

[18:41] Guest:

It is so simple it requires no full mechanical bowel prep and no systemic sedation.

[18:46] Host:

Right. The patient simply administers a sodium phosphate enema at home prior to the clinic visit.

[18:52] Guest:

Then the surgeon uses a rigid or flexible sigmoidoscope to identify the bleeding segments.

[18:56] Host:

And they apply a 4% formalin solution directly to the affected mucosa, often using formalin soaked gauze, pass through a rigid scope or careful irrigation through a flexible scope.

[19:06] Guest:

But the critical technical detail here, the one you cannot mess up, is the contact time.

[19:10] Host:

Right. The 4% formalin is left in contact with the mucosa for exactly 2 to 3 minutes. Not 5, not ten. Two to three minutes.

[19:18] Guest:

Exactly. The surgeon then vigorously suctions out the remaining formalin and irrigates the rectum copiously with normal saline.

[19:25] Host:

To neutralize the reaction and prevent deeper chemical burns.

[19:29] Guest:

Right. It’s a rapid controlled chemical cautery and the data really supports it.

[19:33] Host:

Yeah, the studies frequently show a cessation of bleeding in over 80% to 90% of patients after just one to three brief outpatient sessions.

[19:42] Guest:

It’s fantastic, but Formalin’s primary competitor in the endoscopic arena is Argon beam coagulation, or ABC.

[19:49] Host:

So how does ABC differ from formalin?

[19:51] Guest:

ABC operates on an entirely different physical principle. It is a non contact form of thermal electrical coagulation.

[19:57] Host:

OK, so the device channels high frequency electrical energy through a stream of ionized argon?

[20:03] Guest:

Right. And because the argon gas is ionized, it creates A conductive plasma arc that naturally seeks grounded tissue.

[20:09] Host:

So as the surgeon hovers the probe a few millimeters above the mucosa, that electrical arc jumps to the bleeding telangitacious.

[20:17] Guest:

It instantaneously coagulates the proteins and seals the vessels.

[20:20] Host:

The specific settings for ABC in the rectum are highly testable, by the way.

[20:25] Guest:

Yes, definitely know the settings. The text recommends a power setting of 40 to 65 watts with an argon gas flow rate of 1 to 2 liters per minute.

[20:34] Host:

But while ABC is incredibly effective, it carries a very specific, dangerous physical risk that chemical formula does not.

[20:42] Guest:

And that risk is the depth of thermal penetration.

[20:45] Host:

Let’s unpack that.

[20:46] Guest:

The physical properties of ABC generally limit the depth of the thermal injury to about 1 to 3mm.

[20:52] Host:

Which sounds safe.

[20:53] Guest:

It does because as the tissues superficially charged and forms an Escher, the electrical resistance of that Escher increases.

[21:00] Host:

Which naturally deflects the plasma arc to adjacent uncoagulated tissue.

[21:04] Guest:

Exactly this self limiting depth is what makes it generally safe. However, the operator must maintain perfect spatial awareness.

[21:12] Host:

Right, because if the surgeon accidentally touches the probe directly to the mucosa or wait if they just hold the plasma arc over one specific spot for too long.

[21:21] Guest:

They overcome that protective Escher resistance.

[21:23] Host:

And then what happens?

[21:24] Guest:

If you discharge the energy too close or too long, you bypass the superficial telangications and you drive the thermal energy deep into the subducosa and the muscularis propria.

[21:33] Host:

Oh wow, and in tissue that is already suffering from obliterative and arteritis, a deep thermal injury is just catastrophic.

[21:41] Guest:

It is. You can induce deep indolent rectal ulcers that are notoriously difficult to heal, and in the worst case scenario you cause a delayed transmural perforation or a fistula.

[21:52] Host:

Right. So with formalin, the depth of chemical injury is naturally limited by that strict 3 minute contact time and the immediate saline flush.

[22:00] Guest:

But with ABC, safety relies entirely on the precise, millimeter perfect control of the endoscopist’s hand.

[22:07] Host:

Which is a much smaller their margin for.

[22:10] Guest:

Error. Yes, it is. OK, so we’ve utilized formalin, we’ve utilized ABC, maybe we’ve even tried hyperbaric oxygen, but the patient continues to experience life threatening hemorrhage or they develop a dense fibrotic structure causing a high grade bowel obstruction or they present with a frank rectovaginal fistula.

[22:26] Guest:

The worst case scenarios.

[22:27] Host:

Right. What is the surgical end game here?

[22:29] Guest:

The textbook is unequivocally clear on this. Surgery for chronic radiation colitis is the absolute last resort.

[22:37] Host:

The absolute last resort.

[22:38] Guest:

It’s strictly reserved for those specific catastrophic scenarios you just mentioned, refractory bleeding, total obstruction, or fiscalization.

[22:47] Host:

And if you are forced to operate, you have to understand the physiological and anatomical nightmare you were stepping into.

[22:54] Guest:

The statistics provided in the text regarding surgical intervention for radiation colitis are genuinely sobering.

[23:00] Host:

And they’re essential to quote during informed consent discussions with the patient honestly.

[23:05] Guest:

Oh, definitely. The Mayo Clinic review their historical data spanning from 1950 to 1983 regarding resections for radiation colitis.

[23:13] Host:

And what did they find?

[23:14] Guest:

They reported an 80% overall complication rate, 80%, and an astounding 14% mortality rate.

[23:20] Host:

14% of patients who underwent A surgical resection died as a direct result of the intervention. Yes.

[23:26] Guest:

And we cannot just dismiss that as outdated historical data. The fundamental biology of irradiated tissue has not changed since 1983.

[23:33] Host:

No it hasn’t. And look at the more contemporary studies cited regarding radiation induced rectovaginal fistulas.

[23:40] Guest:

Right. A study by Zelga analyzed attempts at surgical resection and primary repair for these fistulas. They found that successful resection and anastomosis was only possible in 4% of patients.

[23:52] Host:

4% so 96% of that cohort underwent permanent sequel diversion with an N colostomy.

[23:58] Guest:

Because the local tissue was simply too hostile to support an anastomosis.

[24:03] Host:

Another study by Zhang followed 26 patients who underwent diversion for radiation fistulas. Over the course of the study, only three of those 26 patients were ever able to have their ostomies safely reversed.

[24:14] Guest:

The reality is that when you open an irradiated pelvis, you are not operating in normal anatomical planes.

[24:20] Host:

You are operating in concrete.

[24:21] Guest:

Concrete is the exact word. The obliterative and arteritis and that massive overproduction of collagen by the dysregulated fibroblasts. It completely obliterates the holy plane of the mesorectal excision.

[24:33] Host:

The mesorectal fascia is just fused to the presacral fascia, the pelvic side walls, the urogenital organs.

[24:39] Guest:

And the dissection is entirely sharp, it’s bloody, and it is highly prone to iatrogenic injury of the ureters and autonomic nerves.

[24:47] Host:

Furthermore, let’s say you managed to resect the diseased rectum and pull down healthy colon for a colonal anastomosis.

[24:54] Guest:

That anastomosis is relying on the severely compromised microvasculature of the irradiated anal canal for healing.

[25:01] Host:

The tissue compliance is 0 and the healing potential is functionally non existent.

[25:05] Guest:

Exactly. Attempting heroic resections and anastomosis in this environment is just an invitation for an anastomotic leak, a devastating pelvic Abscess, chronic sepsis, and a prolonged, miserable clinical course for the patient.

[25:20] Host:

Therefore, if you are forced to operate for complication of radiation colitis, you must counsel the patient heavily beforehand.

[25:27] Guest:

You have to tell them that a permanent in colostomy is often the safest, most definitive and most humane option.

[25:33] Host:

Because fecal diversion controls the symptoms of fistulas and strictures immediately removes the risk of a lethal anastomotic leak, and restores the patient’s quality of life far better than multiple failed attempts at complex pelvic reconstruction.

[25:46] Guest:

It’s a hard conversation, but a necessary one.

[25:48] Host:

It is a stark, necessary warning, so we’ve spent a significant amount of time detailing the catastrophic macroscopic tissue destruction caused by radiation.

[26:05] Guest:

Right, the pale mucosa, the brittle fibrosis, the neo vascular bleeding, the gross tissue damage is undeniable. But this provides a perfect conceptual pivot to our next topic. What happens when a patient presents with miserable, debilitating, life altering diarrhea, yet when you perform a colonoscopy, the mucosa looks absolutely pristine?

[26:19] Guest:

It’s one of the most perplexing scenarios in gastroenterology and colorectal surgery, and it requires a high degree of clinical suspicion.

[26:26] Host:

Because we are moving away from the visible destruction of radiation and entering the microscopic immune mediated world of microscopic colitis.

[26:34] Guest:

Yes, microscopic colitis.

[26:36] Host:

Or MC. It’s clinically defined as a chronic, relapsing and recurring inflammatory condition of the colon.

[26:41] Guest:

The hallmark presentation is chronic, watery, non bloody diary.

[26:45] Host:

But the absolute defining diagnostic criteria, the feature that separates it from standard inflammatory bowel disease like ulcerative colitis or Crohn’s disease, is that the colonic mucosa appears macroscopically normal or near normal on endoscopy.

[26:59] Guest:

Exactly. There are no gross ulcerations, no SIDO polyps, no spontaneous bleeding, and no loss of a normal vascular pattern.

[27:07] Host:

And we can no longer consider microscopic colitis a rare zebra diagnosis, can we?

[27:11] Guest:

Not at all. The epidemiological data highlighted in the text is alarming. In the late 1980’s, the reported incidents was approximately 3.1 per 100,000 population.

[27:22] Host:

OK, so pretty rare back then.

[27:23] Guest:

But recent epidemiological estimates indicate the incidence has surged dramatically, reaching up to 219 per 100,000 in certain populations. Wow.

[27:31] Host:

219 per 100,000 that’s a massive increase.

[27:34] Guest:

It has become one of the most common causes of chronic diarrhea in older adults.

[27:38] Host:

The demographic profile heavily favors older patients.

[27:41] Guest:

Yes, with a mean age of onset around 61 years old and it demonstrates a very strong female predominance.

[27:47] Host:

That specific demographic profile, older predominantly female patients points us directly toward a systemic immune mediated etiology it.

[27:56] Guest:

Really does, and the textbook establishes an incredibly strong link between microscopic colitis and other established autoimmune disorders.

[28:04] Host:

Like what kind of numbers are we talking about here?

[28:06] Guest:

The data shows that up to 40% of patients diagnosed with microscopic colitis have at least one concurrent autoimmune condition.

[28:13] Host:

So things like type 1 diabetes, myelitis, celiac disease, rheumatoid arthritis, or autoimmune thyroiditis.

[28:19] Guest:

Exactly. The statistical associations are staggering. The textbook notes that a patient with a diagnosis of polyarteritis nodosa carries an odds ratio of 20.8 for developing the collagenous subtype of microscopic colitis.

[28:33] Host:

An odds ratio of 20.8. That is huge.

[28:36] Guest:

When you see an odds ratio north of 20, you were looking at a deeply intertwined pathophysiologic mechanism.

[28:41] Host:

Likely rooted in shared genetic susceptibilities.

[28:44] Guest:

Right research has identified specific pleomorphisms in genes coding for human leukocyte antigens, or HLA, as well as genes regulating tumor necrosis factor alpha production.

[28:54] Host:

Which primes the immune system for this aberrant response.

[29:00] Guest:

Yes, the genetics set the stage. But genetic priming alone isn’t enough, right? I mean, if 40% of celiac patients demonstrate these histologic changes, there has to be an exogenous catalyst that actually ignites the inflammation.

[29:11] Guest:

There has to be a trigger.

[29:12] Host:

Right. What is the trigger that turns a genetically susceptible patient into a symptomatic microscopic colitis patient? Is it purely environmental?

[29:22] Guest:

The prevailing theory centers on mucosal barrier dysfunction. Let’s.

[29:25] Host:

Explore that.

[29:26] Guest:

The colonic epithelium acts as a highly selective barrier managing the complex interaction between the luminal microbiome and the dense network of immune cells residing in the lamina propria.

[29:36] Host:

OK, keeping the peace, essentially.

[29:38] Guest:

Exactly. In patients with microscopic colitis, this barrier function is compromised. It becomes excessively permeable.

[29:45] Host:

So it gets leaky.

[29:46] Guest:

Yes. This allows normal luminal antigens, bacterial byproducts, or specific external triggers to cross the epithelium and enter the lamina appropriate.

[29:54] Host:

And the textbook specifically mentions prior gastrointestinal infections as potential triggers, right?

[30:00] Guest:

It does A history of an acute infection with Ursinia enterocalinica, Campylobacter jajuni, or clostudioids. The fissile can severely damage that epithelial barrier.

[30:12] Host:

But wait, even after the acute infection is cleared and the pathogen is completely eradicated.

[30:17] Guest:

Yes, even then, the immune system in the lamina propria remains hyperactivated. It continues to mount an outsize inappropriate inflammatory response against harmless luminal antigens driving the chronic watery diarrhea.

[30:31] Host:

That’s incredible, and when discussing external triggers that exacerbate this mucosal barrier dysfunction, we absolutely must address cigarette smoking.

[30:39] Guest:

Smoking is a massive accelerant for microscopic colitis.

[30:42] Host:

The epidemiological data shows that current smokers have an odds ratio of 2.4 to 3.8 for developing the disease compared to non-smokers.

[30:50] Guest:

And the exact mechanism isn’t fully elucidated, but it likely involves nicotine induced alterations in mucosal blood flow and systemic immune dysregulation.

[30:58] Host:

Interestingly, the textbook notes a fascinating caveat for board exams regarding smoking.

[31:03] Guest:

The remission paradox, Yeah.

[31:05] Host:

While smoking is undeniably a major risk factor for developing the disease, smoking cessation has not been definitively formally proven in large randomized trials to induce clinical remission once the disease is active.

[31:17] Guest:

Which is counterintuitive but important for exams. However, as clinicians, smoking cessation remains a mandatory first line recommendation for these patients given the overwhelming epidemiological association and general health benefits.

[31:31] Host:

Of course, stop smoking regardless. But beyond smoking and prior infections, the most highly tested and clinically relevant external triggers are pharmacological.

[31:40] Guest:

Yes, the medication debate, the association between specific ubiquitous medications and the onset of microscopic colitis, is a major focus in both the literature and on board exams.

[31:50] Host:

It’s the classic medication reconciliation hunt. Non steroidal anti-inflammatory drugs or NSAI’s, selective serotonin reuptake inhibitors, or SSRI’s and statins are all strongly correlated with the development of MC.

[32:03] Guest:

But the quintessential culprit, the drug class most frequently tested, is proton pump inhibitors, or PPI’s.

[32:09] Host:

Right. Some observational studies estimate an odds ratio of 6.4 for the development of collagenous colitis in patients taking PPI’s like omeprazole or pantoprazole.

[32:19] Guest:

It creates a very clear clinical heuristic. If you evaluate a 65 year old female patient presenting with new onset chronic watery diarrhea and you note she recently started APPI for reflux, microscopic colitis immediately jumps to the top of your differential diagnosis.

[32:36] Host:

But the textbook highlights a massive, fascinating contradiction in the literature regarding PPI’s that is just perfect for academic discussion.

[32:44] Guest:

Yes, the Pennsylvania database study.

[32:45] Host:

Exactly. While many studies cite that 6.4 odds ratio, the authors detail a massive database study out of Pennsylvania encompassing a huge patient cohort that completely failed to show any statistically significant correlation between PPI use and microscopic colitis.

[33:02] Guest:

It’s a huge discrepancy.

[33:03] Host:

How do we reconcile this? How can a drug be the prime suspect in one study and completely cleared in a massive population database?

[33:09] Guest:

It comes down to understanding the nuances of epidemiological research and the concept of ascertainment bias or selection bias.

[33:16] Host:

Right, let’s break that down for the listeners.

[33:18] Guest:

To understand this, we have to look at the known side effect profiles of these medications. Both PPI’s and SSRI’s frequently cause mild to moderate secretory diarrhea as a direct pharmacological side effect.

[33:31] Host:

Completely independent of any colonic inflammation or immune activation.

[33:35] Guest:

Exactly. They alter gastric pH, change the upper GI microbiome, or alter serotonin signaling in the gut, leading to diarrhea.

[33:43] Host:

OK, so imagine a healthy 60 year old patient who starts a PPI and subsequently develops drug induced watery diarrhea.

[33:50] Guest:

Right. Their primary care physician follows standard clinical guidelines and refers them to a gastroenterologist to work up this new onset diarrhea.

[33:58] Host:

The gastroenterologist performs a colonoscopy, notes that the mucosa looks perfectly normal, but dutifully takes random biopsies just to be thorough.

[34:06] Guest:

Because that’s the standard of care for chronic diarrhea.

[34:09] Host:

And the pathologist discovers subclinical microscopic colitis on those biopsies.

[34:13] Guest:

Exactly. The patient had asymptomatic subclinical microscopic colitis sitting there quietly all along.

[34:19] Host:

So the PPI didn’t cause the colonic inflammation?

[34:22] Guest:

No, the PPI. PPI caused a secretory diarrhea that prompted the colonoscopy, which in a certainly uncover the pre-existing histologic changes.

[34:31] Host:

Because patients on PPI’s get scoped more frequently for diarrhea, the diagnosis rate of microscopic colitis is artificially inflated in that specific medication cohort.

[34:42] Guest:

Precisely this ascertainment bias likely explains the wildly disparate odds ratios seen in different studies.

[34:49] Host:

That is a brilliant breakdown of how statistical bias can mimic pathophysiology.

[34:53] Guest:

It really is an elegant explanation.

[34:55] Host:

But regardless of whether the medication is the direct causative agent of the inflammation or merely the trigger for the diarrhea that unmasks it, the clinical management remains exactly the same, right?

[35:15] Guest:

Yes, step one in treating microscopic colitis is systematically discontinuing any suspect medications, particularly NSI IS and PPI’s to see if the symptoms resolve. Assuming medication withdrawal fails, we must definitively establish the diagnosis, and this brings us to pure testable exam minutiae regarding the endoscopic approach.

[35:24] Guest:

You have to know the criteria. The diagnostic criteria, heavily influenced by the Spanish microscopic colitis group, require three specific elements.

[35:34] Host:

Chronic or intermittent non bloody diarrhea, normal or near normal macroscopic appearance of the colon and characteristic histopathology on biopsy.

[35:43] Guest:

But the procedural execution of that biopsy is where surgeons often fail.

[35:48] Host:

Because if the patient’s mucosa looks completely normal on a quick flexible sigmoidoscopy in the clinic, it is incredibly tempting to just reassure them and diagnose irritable bowel syndrome.

[35:58] Guest:

It’s so tempting, but doing a flexible sigmoidoscopy to rule out microscopic colitis is clinically negligent.

[36:04] Host:

It’s an absolute violation of the diagnostic standard of care.

[36:07] Guest:

Yes, because the mucosal looks normal. The entire diagnosis rests on the histologic evaluation of the lamina propria, and the critical defining feature of this inflammation is that it is highly patchy and discontinuous.

[36:19] Host:

So the inflammation does not affect the colon uniformly.

[36:22] Guest:

Not at all. If you only perform a flexible sigmoidoscopy and sample the rectum and sigmoid colon, you have a massive risk of sampling a skip lesion area that is histologically completely normal.

[36:35] Host:

Thus entirely missing the active inflammation sitting in the transverse or right colon.

[36:40] Guest:

If the mucosa looks normal, doing a flexible sigmoidoscopy is like only searching the front hallway of a house when the burglar is hiding in the attic.

[36:48] Host:

That’s a perfect way to put it. Therefore, the absolute board requirement is that you must perform a full, complete colonoscopy all the way to the cecum.

[36:57] Guest:

Furthermore, you cannot just take one or two biopsies in the right colon and call it a day.

[37:01] Host:

No, you must take at least two random mucosal biopsies from every single anatomical segment of the colon, the ascending, transverse, descending and sigmoid colon, as well as the rectum.

[37:12] Guest:

You have to map the entire colon to guarantee you catch those patchy inflammatory infiltrates.

[37:17] Host:

Once those multiple segment biopsies reach the pathology lab, we rely on the pathologist to differentiate the two distinct histologic subtypes of microscopic colitis.

[37:27] Guest:

Because the clinical presentation watery diarrhea is identical for both, but the underlying cellular pathology is different.

[37:34] Host:

So we have collagenous colitis or CC and lymphocytic colitis or LC. Let’s breakdown collagenous colitis first.

[37:40] Guest:

OK. The defining histologic feature of CC is the presence of an abnormally thickened subbithelial collagen band sitting just below the surface epithelium.

[37:49] Host:

Because normally this basement membrane collagen layer is very thin, right?

[37:53] Guest:

Yes, normally it’s quite thin, but in CC, due to an imbalance in extracellular matrix turnover and dysregulation of local myofibroblasts, this collagen band expands significantly.

[38:06] Host:

And to meet the diagnostic criteria for CC, this collagen band must measure greater than or equal to 10 micrometers in thickness.

[38:14] Guest:

10 micrometers is the magic number for collagenous colitis on the boards.

[38:17] Host:

OK, So what about lymphocytic colitis?

[38:19] Guest:

In lymphocytic colitis, that’s epithelial collagen band is actually normal. It remains less than 10 micrometers thick.

[38:25] Host:

So what’s the defining feature then?

[38:27] Guest:

The defining feature is a massive infiltration of lymphocytes directly into the surface epithelium. We are looking for an abnormally high number of intrapithelial lymphocytes per 100 epithelial cells.

[38:38] Host:

And here is a crucial technical detail for pathologists and board exams. These intrapithelial lymphocytes can actually be difficult to quantify on a standard hematoxilin and eosin or H&E stain.

[38:51] Guest:

They can be very hard to see. The pathologist will very frequently need to utilize a specific CD3 immunohistochemical stain to properly highlight and count those T lymphocytes to confirm the diagnosis of LC.

[39:03] Host:

So just to recap, collagenous colitis has the thickened 10 micrometer collagen band. Lymphocytic colitis has the massive intrapithelial lymphocyte infiltration requiring a CD3 stain.

[39:15] Guest:

Correct, but there is one paramount histologic finding that is required in both subtypes.

[39:20] Host:

A finding that serves as the ultimate differentiator between benign microscopic colitis and severe inflammatory bowel disease like Crohn’s or ulcerative colitis.

[39:28] Guest:

This is arguably the most highly tested pathology concept in this entire section. And what is it? In both collagenous and lymphocytic colitis, despite the intense inflammation in the lamina propria and the surface epithelium, the underlying colonic crypt architecture must be strictly preserved.

[39:43] Host:

So the glands must be normal.

[39:45] Guest:

Exactly. When you look at a biopsy of active ulcerative colitis, the chronic transmural or deep mucosal inflammation destroys the glands. You see crypt distortion, crypt branching, crypt abscesses, and crypt atrophy. The glandular architecture is just wrecked.

[40:01] Host:

But in microscopic colitis, because the pathological process is restricted to the very superficial layers, the subpathelial collagen or the surface epithelium, the deep crypts and glands remain perfectly parallel, orderly and structurally intact.

[40:15] Guest:

Preserved crypt architecture with surface inflammation equals microscopic colitis.

[40:20] Host:

That distinction dictates the entire clinical outlook for the patient. Because the crypts are preserved and the deep tissue is undamaged, the disease is fundamentally benign.

[40:29] Guest:

The textbook explicitly reassures us that microscopic colitis does not increase the patient’s risk of developing colorectal cancer.

[40:37] Host:

Which is a huge relief for patients. In fact, some intriguing epidemiological data suggests it might actually be associated with a decreased risk of developing conventional colorectal adenomas, providing a strange sort of silver lining.

[40:58] Guest:

Because it is a benign, non malignant process, surgical intervention like a subtotal colectomy is virtually never the answer here. The management of microscopic colitis is purely medical and it follows a very specific evidence based stepwise algorithm focused on symptom control and mucosal healing.

[41:08] Guest:

Assuming we have already continue defending medications and counsel the patient on smoking cessation, step one of the medical algorithm is simple nonspecific anti diarrheal therapy.

[41:17] Host:

So we rely on agents like Lopiramide.

[41:20] Guest:

Right Lopiramide is a new opioid receptor agonist that acts directly on the myenteric plexus of the large intestine. It slows intestinal motility, allowing more time for fluid absorption, Which.

[41:30] Host:

Directly counteracts the watery diarrhea without really addressing the underlying immune process.

[41:35] Guest:

Exactly. If Lopormide is insufficient to control the symptoms, we escalate to Step 2. Bismuth subcellus slate, commonly known as Pepto Bismol.

[41:43] Host:

Bismuth is surprisingly effective in this specific disease process. The textbook sites a comprehensive meta analysis demonstrating an impressive 81% clinical response rate with bismuth therapy.

[41:56] Guest:

It’s an incredible response rate.

[41:57] Host:

But how does a simple over the counter stomach remedy achieve an 81% response rate in an autoimmune mediated colitis?

[42:05] Guest:

It actually has a dual mechanism of action. The salicylate moiety is systemically absorbed and acts as a localized anti-inflammatory agent down regulating the prostaglandin synthesis in the mucosa that drives the fluid secretion.

[42:18] Host:

OK. And the bismuth part.

[42:20] Guest:

Simultaneously, the bismuth moiety, which is not absorbed, basically copes the mucosa, providing a physical barrier, and it possesses direct antimicrobial properties that may alter the local microbiome and reduce the energetic load that’s triggering the barrier dysfunction.

[42:34] Host:

That makes sense. The specific dosing regimen required to achieve that 81% response rate is critical to note, though, you don’t just take a swig when you feel sick.

[42:42] Guest:

Oh no. The protocol requires three 262 milligram tablets taken three times a day for an entire eight week course.

[42:50] Host:

It is a heavy, sustained dose, but if an 8 week course of bismuth fails, we must move to Step 3, the heavy hitter and the undisputed gold standard for inducing remission in microscopic colitis.

[43:03] Guest:

Step 3 is bootsnide.

[43:05] Host:

Now a logical question arises here. If we need to suppress colonic inflammation, why use bootsnide Specifically, why not just prescribe a standard cheap course of oral Prednisone, which we use for everything else from asthma to ulcerative colitis?

[43:21] Guest:

The preference for bootsnide is entirely driven by its unique pharmacokinetics.

[43:25] Host:

Right Prednisone is a systemic corticosteroid. It suppresses inflammation everywhere, but it carries a massive burden of systemic side effects. Immunosuppression, Osteoporosis, Adrenal suppression, Hyperglycemia. Psychiatric changes.

[43:38] Guest:

Mucinide, however, is a highly potent synthetic glucocorticoid designed specifically for the gastrointestinal tract.

[43:44] Host:

It relies on massive first pass metabolism right?

[43:46] Guest:

Exactly when the patient swallows, A bucinide capsule is formulated to release the active drug, specifically in the terminal ileum and the right.

[43:54] Host:

So the drug bathes the colonic mucosa, exerting profound local anti-inflammatory effects by binding to glucocorticoid receptors and suppressing the production of inflammatory cytokines.

[44:06] Guest:

But as the drug is absorbed into the portal venous system and hits the liver, the hepatic CYP 3A4 enzyme system metabolizes roughly 90% of the drug into inactive metabolites before it ever reaches the systemic circulation.

[44:20] Host:

So you get the immense local power of a steroid right at the site of the, but you drastically minimize the systemic toxicity. No moon facies, no massive bone density loss.

[44:30] Guest:

It’s brilliant. The clinical dosing regimen outlined for butanide is a 9 milligram per day induction dose to achieve clinical remission, which usually occurs rapidly within a few weeks.

[44:39] Host:

But the textbook highlights a very significant, frustrating pitfall associated with butanide therapy and microscopic colitis.

[44:46] Guest:

Yes, the relapse rate.

[44:47] Host:

While it is incredibly effective at inducing remission, the relapse rate once the drug is abruptly stopped is extraordinary fairly high because the underlying mucosal barrier dysfunction often just remains.

[44:58] Guest:

The text cites data showing that if you stop the drug, only 16% of patients transition to a placebo managed to stay in remission at the one year mark.

[45:07] Host:

That’s rough. The vast majority relapsed back into severe diarrhea.

[45:11] Guest:

Conversely, 61% of patients maintained on a lower dose of butanide stayed in remission.

[45:16] Host:

Therefore, the clinical reality is that you often have to taper these patients down from the 9 milligram induction dose to a 4.5 milligram or 3 milligram daily maintenance dose and just keep them on that maintenance therapy long term to preserve their mucosal integrity and their quality of life it.

[45:32] Guest:

Becomes a chronic management issue.

[45:34] Host:

Right. So, synthesizing our discussion on microscopic colitis, we must demand a full colonoscopy with random segmental mapping biopsies to overcome the patchy nature of the disease.

[45:45] Guest:

We rely on the pathologist to identify the subpathelial collagen or intrapathelial lymphocytes, but crucially, to confirm preserved crypt architecture.

[45:54] Host:

And we manage the condition medically, progressing from lopomide to an 8 week course of bismuth and finally to bootsnide, recognizing the high likelihood of requiring long term maintenance therapy.

[46:19] Guest:

That’s the algorithm. And this provides A seamless conceptual transition to our final topic. We have explored the massive visible tissue destruction of radiation colitis. We have navigated the invisible immune mediated cellular wars of microscopic colitis. Now we turn our attention to an anatomically precise perfusion driven failure of the colonic microvasculature.

[46:27] Guest:

We are moving into the low flow watershed territories to discuss ischemic colitis.

[46:32] Host:

Ischemic colitis, or IC, is a topic that consistently trips up residents and practicing surgeons alike because it requires us to completely separate 2 distinct concepts that are often conflated under the broad umbrella of intestinal ischemia.

[46:45] Guest:

We need to state this plainly right out of the gate to clear the diagnostic Muddy Waters. Ischemic colitis is absolutely not the same thing as mesenteric ischemia.

[46:54] Host:

It’s a classic board question. They are two entirely different pathophysiological entities with different presentations, different anatomical targets, and vastly different management algorithms.

[47:04] Guest:

The ASCRS text dedicates Table 53.2 specifically to differentiating these two conditions, and it is vital to internalize these differences.

[47:12] Host:

Let’s breakdown that table. Acute mesenteric ischemia is a macrovascular catastrophe.

[47:19] Guest:

It is typically caused by a sudden massive embolic event, like a clot thrown from a fibrillating atrium lodging directly into the main trunk of the superior mesenteric artery, or it’s caused by an acute thrombosis of a severely atherosclerotic SMA.

[47:34] Host:

It’s a sudden total blockage of the main water main feeding the entire small bowel and right colon.

[47:40] Guest:

Because the occlusion is sudden and total, the bowel immediately begins to undergo transmural infarction.

[47:46] Host:

The classic clinical presentation is a patient writhing in agony, presenting with sudden onset abdominal pain that is wildly out of proportion to their relatively benign physical exam findings.

[47:56] Guest:

Mesenteric eschemia is an absolute surgical emergency requiring immediate laparotomy, amylectomy, or massive bowel resection to prevent death.

[48:04] Host:

Ischemic colitis, however, is fundamentally different. It is not a macrovascular clot in a named main artery.

[48:10] Guest:

No, it is a microvascular low flow state. It represents a transient episode of severe hypoperfusion in the tiny vasorecta and capillary networks immediately adjacent to the colonic wall.

[48:20] Host:

It rarely happens suddenly. It usually develops progressively over hours or days in response to a systemic drop in perfusion.

[48:28] Guest:

Right with moderate tenderness and hematokeesia. So if mesenteric ischemia is a blown main water main flooding the street, ischemic colitis is a temporary drop in systemic water pressure that only affects the furthest houses in the neighborhood.

[48:44] Host:

The areas with the weakest collateral.

[48:46] Guest:

Flow. That is the exact physiological mechanism, and to understand which houses are at risk, we must review the vascular anatomy of the colon, specifically the collateral circulation.

[48:57] Host:

Let’s map it out. The colon is supplied by both the superior mesenteric artery and the inferior mesenteric artery. These two systems are connected by a meandering collateral vessel that runs parallel to the mesenteric border of the colon, known as the marginal artery of Drummond.

[49:12] Guest:

But the marginal artery of Drummond is not a perfectly robust Hwy. Throughout its entire length. There are specific anatomical zones where this collateral network is naturally tenuous or even absent in some individual.

[49:23] Host:

These are the highly testable watershed areas of the colon.

[49:26] Guest:

The two classic watershed areas you must know are Griffith’s area and Sudex Point.

[49:31] Host:

OK, let’s locate them. Griffith’s area is located at the splenic flexure. This is the precise anatomical border where the terminal branches of the SMA’s middle colic artery in astimose with the terminal branches of the Imas left colic artery.

[49:45] Guest:

The collateral flow here is notoriously weak.

[49:48] Host:

And the second area?

[49:49] Guest:

The second area is sudex point, located at the rectus sigmoid junction. This is where the lowest branches of the IMA, the sigmoid arteries, attempt to anastomos with the superior rectal artery.

[49:59] Host:

These watershed areas represent the furthest points of perfusion from the main arterial trunks. But why are they so incredibly vulnerable to transient drops in blood pressure?

[50:09] Guest:

It comes down to the aggressive auto regulation of the splanchnic circulation. The splantic vessels which feed the gut receive a massive amount of blood, anywhere from 10% to 35% of the total cardiac output at rest.

[50:22] Host:

That’s a huge portion.

[50:23] Guest:

It is, however, when a patient experiences a severe systemic low flow state. Perhaps they suffer a massive hemorrhage. They go into profound septic shock, they experience a severe myocardial infarction, or they become critically dehydrated. The body enters survival mode.

[50:39] Host:

The sympathetic nervous system and the renin angiotensin system activate to preserve core perfusion.

[50:46] Guest:

Precisely, the body prioritizes blood flow to the brain and the heart at all costs. To achieve this, the splanchnic vessels clamped down immediately and severely, shunting blood away from the gut to maintain central venous pressure.

[50:59] Host:

The colon is essentially the first organ to be physiologically sacrificed to keep the patient alive.

[51:17] Guest:

And when that splanchic vasoconstriction occurs, the fragile watershed areas at Griffiths Flexure and Sodex Point are the very first tissues to drop below the critical threshold of oxygen delivery, triggering the ischemic cascade. This physiological mechanism directly dictates the clinical presentation and identifies the high risk patient cohorts we must be vigilant for on exams and in the ward.

[51:26] Guest:

The textbook notes that I see is incredibly common. It is responsible for nearly 20% of all cases of acute lower gastrointestinal bleeding, making it second only to diverticulosis.

[51:38] Host:

You really have to look out for specific scenarios.

[51:40] Guest:

The Absolute Classic Board Exam Association for ischemic colitis involves a patient undergoing an abdominal aortic aneurysm or AAA repair.

[51:49] Host:

Let’s walk through that. During an elective AAA repair where the aorta is cross clamped in a controlled fashion, the incidence of ischemic colitis is relatively low, ranging from 0% to 4.6%.

[52:01] Guest:

Right. The IMA is often ligated during the repair, but if the patients collateral flow through the marginal artery is adequate and their blood pressure is maintained by the anesthesiologist, the colon survives.

[52:11] Host:

But consider the scenario of a rupture triple.

[52:13] Guest:

A That changes everything. The patient experiences a massive retro keratoneal hemorrhage. Their blood pressure plummets into profound hemorrhagic shock, and the splanching vessels clamped down completely to preserve the brain.

[52:25] Host:

The surgeon that emergently cross clamps the aorta, cutting off all flow and frequently ligates the IMA.

[52:31] Guest:

In this catastrophic systemic low flow state, the collateral circulation simply cannot compensate. The incidence of ischemic colitis following an emergent ruptured AAA repair skyrockets to over 21%.

[52:44] Host:

You must have a high index of suspicion for IC if that patient develops bloody diarrhea in the ICU postoperatively.

[52:51] Guest:

Another fascinating high risk cohort highlighted in the text is patients with chronic obstructive pulmonary disease, or COPD.

[52:59] Host:

The data shows a relative risk of up to 4.3 for COPD patients developing ischemic colitis. Why is that?

[53:06] Guest:

This is driven by their chronic baseline systemic hypoxia combined with right heart strain and mild systemic venous congestion. That congestion chronically lowers the perfusion pressure gradient across the colonic capillary.

[53:18] Host:

Beds but recognizing the high risk patient is only half the battle. You must recognize the clinical presentation, which varies significantly depending on which anatomical segment of the colon is affected.

[53:28] Guest:

Yes, the textbook draws a very important distinction between left sided and right sided ischemic colitis.

[53:33] Host:

The textbook mentions they present differently. Why should a surgeon care which side hurts?

[53:37] Guest:

It’s vital. Left sided ischemic colitis, which typically involves the descending colon and the sigmoid colon near Sudex Point, usually presents with the classic hallmark symptom, hematochezia or bloody diarrhea.

[53:49] Host:

The patient experiences moderate clampy lower abdominal pain, followed shortly by the passage of bright red blood and clots. The bleeding makes the ischemic event obvious.

[53:59] Guest:

However, right sided ischemic colitis affecting the ascending colon or the cecum presents entirely differently. The right colon has a larger caliber and the mucosal ischemia here is far less likely to present with over rectal bleeding.

[54:13] Host:

Instead, it often mimics the presentation of an isolated acute inflammatory process.

[54:17] Guest:

Exactly. An elderly patient comes into the emergency department with severe isolated lower quadrant pain, low grade fever and a mild Leukocytosis but no hematokesia.

[54:28] Host:

If you evaluate that patient and your differential diagnosis only includes acute appendicitis, infectious ileocytosis, or an acute flare of Crohn’s disease, you will completely miss the ischemic right colon.

[54:39] Guest:

You will likely manage them with observation or the wrong antibiotics until the ischemia progresses to full thickness necrosis and the cecum perforates.

[55:01] Host:

You must maintain a high clinical index of suspicion for right sided ischemic colitis in elderly patients presenting with right sided pain, especially if they have a history of cardiovascular disease or a recent hypotensive episode. This makes rapid, accurate radiologic diagnosis critical.

[55:05] Host:

The textbook is clear that an abdominal CT scan with intravenous contrast is the undisputed initial diagnostic step for suspected ischemic colitis.

[55:14] Guest:

The CT scan is invaluable here. According to the Ikabella study cited in the text, high resolution CT has a nearly 100% sensitivity for identifying ischemic colitis in the acute phase.

[55:24] Host:

The radiologist is looking for classic signs of mucosal edema and inflammation. Segmental bowel wall thickening typically in those watershed distributions alongside paracolonic fat stranding and trace free fluid.

[55:35] Guest:

The CT effectively maps out the exact anatomical territory of the low flow state.

[55:40] Host:

But beyond identifying the edema, the CT scan serves A vital triage function by ruling out transmural necrosis. And we need to discuss a terrifying radio graphic finding that immediately shifts the patient from medical management to emergent surgical intervention.

[55:56] Guest:

Pneumatosis.

[55:57] Host:

Yes, pneumatosis intestinalis, the presence of gas bubbles within the actual bowel wall, is a relatively rare finding, seen in less than 5% of acute ischemic colitis cases.

[56:08] Guest:

However, when you see pneumatosis in the specific clinical setting of acute eschemia, especially if it is coupled with the presence of portal venous gas, it is an incredibly ominous sign.

[56:18] Host:

It indicates that the ischemia has progressed beyond the mucosa. The entire thickness of the bowel wall has infarcted and died.

[56:24] Guest:

And the loss of the barrier allows gas forming luminal organisms like Clostridium species to invade the necrotic Muscularis propria. They generate gas within the wall, which is then swept up into the mesenteric venous system and carried directly into the liver, appearing as portal venous gas on the scan.

[56:41] Host:

In the context of ischemic colitis, pneumatosis with portal venous gas indicates advanced trans mural gangrene.

[56:48] Guest:

The mortality rate in that specific scenario jumps to over 70%. The patient does not need an endoscopy, they need a massive fluid resuscitation and an immediate exploratory laparotomy.

[57:00] Host:

But assuming the CT scan shows only segmental thickening and edema, with no signs of peritonitis, no free air and no pneumatosis, the next step is to definitively confirm the diagnosis.

[57:12] Guest:

Colonoscopy is the gold standard here, allowing us to visualize the mucosa directly and obtain biopsies to rule out mimicking conditions like severe infectious colitis or an acute initial presentation of inflammatory bowel disease.

[57:25] Host:

When you perform the colonoscopy, the endoscopic findings progress in a highly predictable manner depending on the severity and duration of the ischemia.

[57:32] Guest:

In the very early stages or in mild cases, you may only see pale mucosa with loss of the vascular pattern, similar to radiation proctitis, quickly followed by patchy erythema and significant submucosal edema.

[57:43] Host:

As the ischemia worsens and the mucosal capillaries into rupture, blood leaks directly into the oedematous submucosal space. This creates large, distinct, bluish black hemorrhagic nodules or blebs that protrude significantly into the bow lumen.

[57:57] Guest:

And those hemorrhagic submucosal blebs are the exact physical structures responsible for the famous radiographic thumbprinting sign.

[58:06] Host:

If you were to perform a barium enema, or even just look closely at the colonic gas pattern on a plain abdominal X-ray or CT scout film, these large blebs indent the lumen looking exactly as if someone had pressed their thumb repeatedly into the contrast column.

[58:21] Guest:

So we see the thumb printing, we perform the scope, we identify the hemorrhagic blebs, and we take biopsies.

[58:27] Host:

When those biopsies reach the pathology lab, we are looking for the Pythagan mnemonic histologic signature of a low flow ischemic event. This is the board goldmine. When the pathology report comes back. What specific findings absolutely guarantee the diagnosis of ischemic colitis?

[59:00] Guest:

The pathologist is looking for a combination of severe mucosal injury patterns. They will identify massive mucin depletion within the goblet cells, accompanied by intense haemorrhage into the lamina propria. But the two words that definitively clinch the diagnosis on a board exam or a pathology report are ghost cells. Ghost. Yes, ghost cells are the preserved pale outlines of completely necrotic epithelial cells that have lost their nuclei but temporarily maintain their cellular shape due to coagulative necrosis.

[59:14] Host:

But the most important conceptually fascinating histologic pattern is the distribution of that necrosis.

[59:20] Guest:

In classic ischemic colitis, you will see profound necrosis and ghost cells in the superficial crypts, the top layer of the mucosa facing the lumen, while the deep crypts situated down near the muscularis mucosa are relatively spared and remain viable.

[59:35] Host:

Superficial necrosis with deep crypt sparing. We need to explain the Physiology behind this because intuitively it makes no sense. If the blood supply is coming from the outside of the bowel wall inward, should the decrypts die first since they’re closer to the ischemic source? Why does the surface die while the base lives?

[59:52] Guest:

It’s a brilliant question, and the answer lies in the microscopic architecture of the mucosal capillary network. The arterioles Pierce the muscularis mucosa and immediately break into a dense capillary plexus that surrounds the base of the crypts. The blood then flows upwards, parallel to the crypts toward the luminal surface.

[1:00] Host:

So the blood travels from the bottom of the crypt to the top.

[1:00] Guest:

Exactly as the blood travels up that capillary network, the actively secreting epithelial cells continuously extract oxygen from it. Under normal conditions, there is plenty of oxygen to reach the top, but during a low flow state like ischemic colitis, the blood flow is incredibly sluggish.

[1:00] Host:

The cells at the base of the crypt, the deep crypts get first access to the slow moving blood.

[1:00] Guest:

They extract just enough oxygen to survive, but by the time that sluggish, depleted blood finally reaches the superficial mucosa at the top of the crypt, all the oxygen has already been extracted.

[1:00] Host:

The oxygen gradient drops to 0.

[1:00] Guest:

Precisely, the surface epithelium is starved of oxygen and undergoes coagulative necrosis forming the ghost cells. While the base survives, the body is literally rationing the limited oxygen from the bottom up. Superficial necrosis with deep crypt sparing is the absolute histologic hallmark of a low flow microvascular ischemic event.

[1:01] Host:

It’s a brutal but elegant physiological adaptation. Now let’s discuss the medical management of acute ischemic colitis.

[1:01] Guest:

The core principles of conservative management are highly logical based on what we’ve discussed. We admit the patient, institute strict bowel rest to decrease splanchnic oxygen demand, provide aggressive intravenous fluid resuscitation to optimize cardiac output, and immediately discontinue any medications that cause splanchnic vasoconstriction like pressors or certain anti hypertensives.

[1:01] Host:

And notably, the textbook emphasizes that we do not routinely administer systemic anticoagulation like heparin drips for ischemic colitis.

[1:02] Guest:

This is a vital distinction from mesenteric ischemia. In mesenteric ischemia, you are actively trying to prevent a macrovascular clot from propagating in the schema colitis. It is a low flow state, not a clot. Heparinizing these patients who already have intensely bleeding hemorrhagic mucosa will only exacerbate the severe hematokesia without fixing the underlying hypoperfusion. Wait.

[1:02] Host:

I want to push back on one specific component of the medical management algorithm laid out in the text. We have established that ischemic colitis is purely A hemodynamic problem, a failure of blood flow and oxygen delivery. Yet the textbook mandates the administration of broad spectrum intravenous antibiotics as a core component of conservative therapy. If this is a blood flow issue, why are we treating them with heavy antibiotics? We aren’t treating a primary infection, are we?

[1:02] Guest:

This touches on one of the most crucial physiological concepts in all of colorectal surgery. You are correct, we are not treating a primary infection. We are administering antibiotics to prevent a secondary lethal inflammatory catastrophe. It all comes back to mucosal barrier dysfunction.

[1:02] Host:

The same concept we discussed in microscopic colitis, but on a much more violent scale.

[1:02] Guest:

Exactly in the schema colitis, that superficial necrosis destroys the epithelial lining. That single layer of cells is the only physical barrier standing between the trillions of virulent bacteria residing in the colonic lumen and the patient’s systemic circulation.

[1:03] Host:

When that surface mucosa dies from hypoxia and sloughs off, the mucosal permeability drastically, exponentially increases.

[1:03] Guest:

The gates are thrown wide open.

[1:03] Host:

Wide open, this massive barrier failure allows for profound bacterial translocation. The colonic flora, both aerobes and anaerobes, seep directly through the necrotic mucosa into the submucosa, and from there into the systemic bloodstream and the portal circulation.

[1:03] Guest:

In the immune system’s response to that massive bacterial invasion causes further damage.

[1:03] Host:

Precisely, the immune system mounts a massive localized inflammatory response to the translocating bacteria, releasing oxygen free radicals, proteases, and cytokines that rapidly exacerbate the local tissue necrosis, driving the ischemia deeper into the muscularis.

[1:03] Guest:

Extensive animal models in clinical studies dating back decades have definitively proven that administering broad spectrum antibiotics specifically targeting gut flora and anaerobes like Encephalus, borin, and metronidazole neutralizes these translocating bacteria.

[1:04] Host:

By clearing the bacteria as they cross the broken barrier, the antibiotics dampen that secondary inflammatory response, significantly reducing the ultimate depth, length and severity of the ischemic bowel damage.

[1:04] Guest:

That is fascinating pathophysiology. The antibiotics aren’t fixing the blood pressure. They’re mitigating the secondary inflammatory cascade caused by the dead barrier.

[1:04] Host:

With this aggressive regimen of 5 E fluids, bowel rest and antibiotics, the vast majority of ischemic colitis patients, around 80%, will resolve their symptoms within 24 to 48 hours as the Splanchnik perfusion normalizes.

[1:04] Guest:

But we must be acutely aware of the long term prognosis and the strict surgical indications for the minority who do not improve.

[1:04] Host:

Even for the patients who recover acutely, you must monitor them for chronic circola. The ischemic insult initiates A fibrotic healing process.

[1:05] Guest:

Approximately 10% of patients who survived the acute episode will go on to develop symptomatic dense fibrotic strictures in the affected segment months or even years later, which will eventually require an elective surgical resection to relieve the chronic obstruction.

[1:05] Host:

Furthermore, another 20% to 30% of patients will never fully heal. They develop irreversible chronic ischemic colitis presenting with persistent weight loss, recurrent abdominal pain, and chronic bloody diarrhea heavily mimicking severe inflammatory bowel disease.

[1:05] Guest:

But the most pressing concern for the surgeon is managing the acute failures. The patient is in the hospital receiving maximum conservative therapy, but they start clinically deteriorating.

[1:05] Host:

Their abdominal exam shifts from localized tenderness to diffuse peritonitis, their fever spikes, their tachycardia worsens into the 1:30’s, and their serum lactic acid begins climbing rapidly despite adequate fluid resuscitation.

[1:05] Guest:

Those clinical signs indicate the ultimate failure transmural infarction. The ischemia has progressed from the mucosa through the muscularis and the serosa. The full thickness of the bowel wall is dead or actively dying.

[1:06] Host:

At this point, conservative management is over. You must transport the patient to the operating room immediately for an exploratory laparotomy.

[1:06] Guest:

And for both board exams and elite clinical practice, there were strict non negotiable surgical rules of engagement for acute ischemic colitis.

[1:06] Host:

Let’s lay out those surgical minutiae for the boards rule #1 resect from normal bowel to normal bowel.

[1:06] Guest:

You must resect the obviously necrotic bowel, but you must also resect far enough proximally and distally to ensure you are transecting through normal, healthy, vigorously bleeding bowel.

[1:06] Host:

Tissue. The mucosa at your resection margins must look perfectly pink and viable. You cannot leave any questionable or dusky tissue behind because it will inevitably progress to full necrosis postoperatively.

[1:06] Guest:

And rule #2 which is an absolute board example staple. You must completely avoid a primary anastomosis in the acute setting.

[1:07] Host:

This is a critical.

[1:07] Guest:

Rule. But why? I want to challenge this. If I follow rule #1 and I resect back to edges that are bleeding vigorously and look perfectly healthy to the naked eye, why can’t I put those healthy ends back together? Why leave the patient with a stoma?

[1:07] Host:

Because you cannot trust your naked eye in a systemic low flow state, you have to evaluate the entire physiologic state of the patient, not just the bleeding edge of the bowel. A patient.

[1:07] Guest:

Requiring emergent surgery for ischemic colitis is profoundly sick. They are in a state of severe physiologic shock. They have massive systemic inflammatory response syndrome from the necrotic bowel. They are highly catabolic and they are likely requiring high doses of vasopressors just to maintain a mean arterial pressure.

[1:07] Host:

All of which means there’s Splanchnik. Vasoconstriction is still maximized.

[1:07] Guest:

Exactly. Even though the edge of the colon bleeds when you cut it, the microscopic perfusion and oxygen delivery at that margin are still severely compromised by the systemic shock and the vasopressors.

[1:07] Host:

Furthermore, the massive systemic inflammation completely halts the anabolic processes required for collagen synthesis and tissue healing.

[1:08] Guest:

If you perform in anastomosis in this environment, it is virtually guaranteed to fail. The microscopic ischemia will progress, the anastomosis will break down, and the patient will leak feces directly into their abdomen a few days later, converting A dire situation into a lethal 1.

[1:08] Host:

The mortality rate for these emergent cases is already exceptionally grim, hovering around 40% even with perfect surgical technique and anastomotic leak guarantees death.

[1:08] Guest:

Your only objective in the operating room is damage control. Keep the patient alive. You rapidly recept the dead gut to remove the source of sepsis. You bring the healthy proximal end out as an end stoma. You staple off the distal stump, you wash out the abdomen, and you get the patient to the intensive care unit for resuscitation as fast as possible.

[1:08] Host:

Once the patient has recovered from the acute shock, then weaned off vasopressors and fully optimized physiologically months later, you can safely return to the operating room to reverse the stoma.

[1:09] Guest:

Resect, divert, and survive. We have covered an immense, incredibly detailed amount of ground today, navigating the deepest, most complex aspects of Chapter 53. Let’s synthesize our key takeaways to ensure these concepts translate directly to clinical mastery.

[1:09] Guest:

Today was entirely about walking a clinical tightrope and understanding the hidden physiologic traps of these diseases.

[1:09] Host:

We learned the critical importance of suppressing our surgical instincts, knowing exactly when to back away from the biopsy forceps to avoid inducing disastrous fistulas in the fibrotic ischemic landscape of chronic radiation proctitis.

[1:09] Guest:

We established the absolute necessity of demanding a full complete colonoscopy with random segmental mucosal biopsies to hunt down the patchy microscopic inflammation of lymphocytic and collagenous colitis, relying on preserved crypt architecture to guide us.

[1:09] Host:

And we define the strict life saving rules of engagement for ischemic colitis, learning to fiercely resist the urge to perform a primary anastomosis in the lethal, highly catabolic, low flow environment of acute transmural infarction.

[1:10] Guest:

True Clinical Excellence and success on high level board examinations relies on recognizing these subtle boundaries. It is never enough to simply memorize the diagnostic algorithm or the surgical technique. You must possess a deep structural understanding of the why behind those algorithms.

[1:10] Host:

Why is formalin preferred over ABC for radiation proctitis? Because of the physics of thermal spread in ischemic tissue.

[1:10] Guest:

Why do we use bootsanide instead of Prednisone for microscopic colitis? Because of the hepatic first pass metabolism that limits systemic toxicity.

[1:10] Host:

Why do we completely avoid primary anastomosis in acute ischemic colitis? Because the unrecognized microvascular shock guarantees an anastomotic leak.

[1:10] Guest:

Understanding the underlying pathophysiology. The relentless microvascular killer fibrosis, the immune mediated barrier dysfunction, the superficial mucosal necrosis driven by oxygen gradients is the fundamental key to elevating your surgical practice and protecting your patients.

[1:11] Host:

And as we close out this colorectal surgery review, I want to leave you with a final forward-looking thought to Mull over. As we’ve dissected these three incredibly distinct pathologies, the radiation induced fibrotic scarring of the microvasculature, the autoimmune mediated cellular wars of microscopic colitis and the pure perfusion driven cascade of ischemic colitis, a single unifying theme has emerged.

[1:11] Guest:

Across all three conditions, we see a profound, devastating disruption of the colonic mucosal barrier, leading to a deep consequential interaction between the patient’s immune system and the luminal microbiome.

[1:11] Host:

Whether it’s the radiation destroying the regenerating crypts, the immune system inappropriately attacking the barrier, or hypoxia inducing superficial coagulative necrosis, the loss of that epithelial shield drives the most severe, complicated patients of these diseases.

[1:11] Guest:

As we look to the future of colorectal surgery and gastroenterology, we have to ask will actively manipulating the microbiome and engineering a hyper resilient mucosal barrier become just as critical to our practice as manipulating the blood supply, modifying the immune system, or perfecting our surgical technique?

[1:12] Host:

Could the ultimate prevention for all three of these devastating complex conditions simply be fortifying that single layer of epithelial cells before the iatrogenic, autoimmune, or ischemic insult even occurs?

[1:12] Guest:

It’s a fascinating paradigm shift to consider.

[1:12] Host:

It really is. We want to thank you for joining us for this incredibly thorough colorectal surgery review. We encourage you to carry these deep pathophysiological insights directly into your next complex operation, your next busy clinic day, or your next board exam. Until next time, keep looking beyond the macroscopic and keep diving deep.