Diverticulitis

What is diverticulitis?

Diverticulitis is a condition that occurs when one or more of the small pouches (diverticula) that can form in the wall of the colon become inflamed or infected. This inflammation is thought to result from a microscopic or macroscopic perforation of a diverticulum. The severity can range from a mild, localized inflammation that can be treated at home to a severe infection with an abscess or widespread peritonitis that requires hospitalization and, in some cases, emergency surgery.

What are the symptoms of diverticulitis?

The most common symptom of diverticulitis is abdominal pain, which is usually constant and located in the left lower quadrant. The pain often starts as mild and increases in severity over a few days.

Other common signs and symptoms include:

• Fever and chills.
• Nausea and vomiting.
• Changes in bowel habits, such as constipation or, less commonly, diarrhea.
• Abdominal tenderness to the touch.

What causes diverticulitis?

Diverticulitis is a complication of diverticulosis. It is believed to start when a hard piece of stool or undigested food gets trapped in a diverticulum, leading to increased pressure and abrasion of the lining. This can cause a small tear (microperforation) in the diverticulum, which allows bacteria from the colon to leak out into the surrounding tissue, causing inflammation and infection. Factors that increase the risk of developing diverticulitis include a low-fiber diet, lack of exercise, obesity, smoking, and the use of certain medications like nonsteroidal anti-inflammatory drugs (NSAIDs) and steroids.

How is diverticulitis diagnosed?

The diagnosis of diverticulitis is usually confirmed with a CT scan of the abdomen and pelvis. A CT scan is very accurate and can show the inflamed segment of the colon, the presence and size of any abscess, and can rule out other causes of abdominal pain. Blood tests will typically show an elevated white blood cell count. A colonoscopy is generally not performed during an acute attack of diverticulitis due to the risk of perforation.

How is diverticulitis treated?

Treatment depends on the severity of the attack. Diverticulitis is classified as either uncomplicated or complicated.

Uncomplicated Diverticulitis:

• This is a mild attack without an abscess or free perforation. Many cases can be managed at home.
• Selective use of antibiotics: For very mild cases in otherwise healthy individuals, antibiotics may not be necessary. For more significant symptoms, a course of oral broad-spectrum antibiotics is prescribed.
• Dietary changes: A clear liquid diet is often recommended for a few days to rest the colon, followed by a gradual advance to a low-fiber diet until the inflammation resolves.

Complicated Diverticulitis:

• This includes diverticulitis with an abscess, fistula, stricture, or free perforation.
• Hospitalization: Most cases of complicated diverticulitis require hospitalization for intravenous (IV) antibiotics and bowel rest.
• Percutaneous Abscess Drainage: If a large abscess is present, it can often be drained by an interventional radiologist who places a catheter through the skin into the abscess under CT guidance.
• Surgery: Surgery is required for patients who do not improve with medical management, or for emergencies like a free perforation with peritonitis or a bowel obstruction. The type of surgery depends on the situation:
  • Emergency Surgery: The most common emergency operation is a Hartmann's procedure, where the diseased segment of the colon is removed, and a temporary colostomy is created. The stoma can often be reversed in a second operation a few months later.
  • Elective Surgery: For recurrent attacks or after successful non-operative management of a complicated episode, an elective sigmoid colectomy may be recommended. This involves removing the affected segment of the colon and reconnecting the ends (primary anastomosis). This can usually be done with minimally invasive (laparoscopic or robotic) techniques.

When is elective surgery recommended after diverticulitis?
The decision to have elective surgery is individualized. It used to be recommended after two attacks, but this is no longer the case. Surgery should be considered for patients who have had a complicated attack (like one with an abscess), for those with frequent, recurrent attacks that impact their quality of life, or for those who are immunocompromised. The goal is a shared decision between you and your surgeon.

Will I need a colostomy bag if I have surgery for diverticulitis?
If you have elective surgery, a colostomy is usually not necessary. The bowel is typically reconnected at the time of the operation. In an emergency surgery situation, especially with severe infection, a temporary colostomy is often the safest option to allow the body to heal from the infection before reconnecting the bowel.

How can I prevent another attack of diverticulitis?
After recovering from an attack, the best way to prevent future episodes is to adopt a high-fiber diet, get regular exercise, and maintain a healthy weight. Quitting smoking and avoiding regular use of NSAIDs can also reduce your risk.

• Hall JF, Bemelman WA. Colonic Diverticular Disease. In: Steele SR, Hull TL, Hyman N, Maykel JA, Read TE, Whitlow CB, eds. The ASCRS Textbook of Colon and Rectal Surgery. 4th ed. Springer; 2022:665-679.
• National Institute of Diabetes and Digestive and Kidney Diseases. Diverticular Disease. Published September 2013. Accessed October 12, 2025. https://www.niddk.nih.gov/health-information/digestive-diseases/diverticulosis-diverticulitis
• Mayo Clinic. Diverticulitis. Published October 20, 2022. Accessed October 12, 2025. https://www.mayoclinic.org/diseases-conditions/diverticulitis/symptoms-causes/syc-20371758