Irritable Bowel Syndrome (IBS)

What is Irritable Bowel Syndrome?

Irritable Bowel Syndrome, or IBS, is a common and chronic functional disorder of the gastrointestinal (GI) tract. This means it is a problem with how the gut and brain work together, rather than a structural or biochemical abnormality. People with IBS experience a group of symptoms that occur together, most notably recurrent abdominal pain associated with a change in bowel habits (diarrhea, constipation, or both). While IBS can cause significant discomfort and distress, it does not damage the intestines and does not lead to more serious diseases like cancer.

Common Symptoms

The symptoms of IBS can vary from person to person and often come and go in periods of flares and remission. According to the formal diagnostic criteria (Rome IV), the key symptom is recurrent abdominal pain that, on average, occurs at least one day per week. This pain must be associated with two or more of the following:

• It is related to defecation (either improves or worsens).
• It is associated with a change in the frequency of your stool.
• It is associated with a change in the form (appearance) of your stool.

Other common symptoms that often accompany the pain and altered bowel habits include:

• Bloating and distension: A feeling of fullness or swelling in the abdomen.
• Mucus in the stool.
• A sensation of incomplete evacuation after a bowel movement.

There are three main subtypes of IBS, based on the predominant stool pattern:

• IBS with constipation (IBS-C): On days with at least one abnormal bowel movement, more than a quarter of the stools are hard or lumpy (constipation) and less than a quarter are loose or watery (diarrhea).
• IBS with diarrhea (IBS-D): On days with at least one abnormal bowel movement, more than a quarter of the stools are loose or watery (diarrhea) and less than a quarter are hard or lumpy (constipation).
• IBS with mixed bowel habits (IBS-M): On days with at least one abnormal bowel movement, more than a quarter of stools are hard or lumpy and more than a quarter are loose or watery.

What causes IBS?

The exact cause of IBS is not fully understood, but it is considered a disorder of the gut-brain interaction. This means there is a problem with the communication between the nerves in the gut and the brain. Several factors are thought to contribute to this breakdown in communication:

• Visceral Hypersensitivity: People with IBS often have a lower pain threshold for stimulation of the gut. This means they feel pain and discomfort from gas or stool in the colon at levels that would not be bothersome to others.
• Abnormal Gut Motility: The muscles of the intestines may not contract in a normal, coordinated way. This can lead to the gut contents moving too quickly (causing diarrhea) or too slowly (causing constipation).
• Gut Microbiome Alterations: The balance of bacteria in the intestines can be different in people with IBS compared to healthy individuals.
• Post-Infectious IBS: For some people, IBS symptoms begin after a severe GI infection (like traveler's diarrhea or food poisoning). The inflammation from the infection may lead to long-lasting changes in the nerves and immune cells of the gut.
• Stress and Psychological Factors: While stress does not cause IBS, it can trigger or worsen symptoms. There is a strong connection between the brain and the gut, and psychological factors like anxiety and depression are common in people with IBS.

How is IBS diagnosed?

IBS is a clinical diagnosis based on a thorough history and physical examination, using the Rome IV symptom criteria. There is no single test to definitively diagnose IBS. The role of testing is primarily to exclude other conditions that can cause similar symptoms.

• Blood Tests: A complete blood count can check for anemia, and inflammatory markers like C-reactive protein can help rule out inflammatory bowel disease. Blood tests for celiac disease are also recommended.
• Stool Tests: These may be done to check for infection or inflammation.
• Colonoscopy: This is not needed to diagnose IBS but may be recommended if you have alarm symptoms, if you are of an age for colorectal cancer screening, or if other tests are abnormal. The colon will appear normal on colonoscopy in someone with IBS.

How is IBS treated?

There is no cure for IBS, but there are many effective treatments to manage the symptoms. Treatment is individualized and often involves a combination of dietary changes, lifestyle modifications, and medications.

Diet and Lifestyle:

• Dietary Fiber: For some people, especially with IBS-C, increasing soluble fiber intake can help soften stools and improve regularity. However, for others, some types of fiber can worsen gas and bloating.
• Low FODMAP Diet: This diet involves temporarily restricting foods that are high in certain fermentable carbohydrates (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols). These carbohydrates are poorly absorbed and can draw water into the gut and be fermented by bacteria, causing gas, bloating, pain, and diarrhea. This diet is often done with the guidance of a dietitian.
• Stress Management: Techniques such as mindfulness, cognitive-behavioral therapy, and hypnotherapy can be very effective in managing IBS symptoms.
• Exercise: Regular physical activity can help with constipation and may reduce stress and improve overall well-being.

Medications:

• For IBS-C: Options include fiber supplements, over-the-counter laxatives, and prescription medications that work by increasing fluid in the intestines (secretagogues) or by stimulating gut motility.
• For IBS-D: Options include anti-diarrheal medications like loperamide and prescription medications that can slow down gut motility or target specific receptors in the gut.
• For Abdominal Pain and Bloating: Antispasmodic medications can help relieve gut muscle cramps. Low doses of certain antidepressants (neuromodulators) can be very effective at reducing visceral hypersensitivity and managing pain.

Is IBS a psychological problem?
No. While there is a strong link between psychological factors like stress and anxiety and IBS symptoms, IBS is a real physiological disorder of the gut-brain axis. It is not 'all in your head.'

Do I need surgery for IBS?
No. Surgery is not a treatment for IBS. In fact, people with IBS who undergo abdominal surgery for other reasons (like gallbladder or appendix removal) often do not experience an improvement in their IBS symptoms.

Can IBS turn into a more serious disease like cancer?
No. IBS is a chronic condition that can affect your quality of life, but it does not cause inflammation or damage to the bowel and does not increase your risk of developing inflammatory bowel disease or colorectal cancer.

• Kunitake H, Staller K. Functional Disorders After Colorectal Surgery/IBS. 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; 2022:963-978.
• National Institute of Diabetes and Digestive and Kidney Diseases. Irritable Bowel Syndrome (IBS). Published November 2017. Accessed October 12, 2025. https://www.niddk.nih.gov/health-information/digestive-diseases/irritable-bowel-syndrome
• Mayo Clinic. Irritable bowel syndrome. Published March 17, 2021. Accessed October 12, 2025. https://www.mayoclinic.org/diseases-conditions/irritable-bowel-syndrome/symptoms-causes/syc-20360016