Irritable bowel syndrome

1. Big picture

Irritable bowel syndrome (IBS) is a functional disorder of gut–brain interaction: the bowel looks structurally normal, but the patient has chronic abdominal pain with altered bowel habits. The examiner usually wants three things:

1. Recognize the pattern: recurrent abdominal pain + diarrhea/constipation/bloating, often stress- or meal-related.
2. Exclude alarm features: weight loss, anemia, bleeding, fever, nocturnal symptoms, family history of colorectal cancer/inflammatory bowel disease.
3. Treat according to subtype: IBS-D, IBS-C, IBS-M, plus reassurance, diet, and gut–brain management.

IBS is not dangerous, but it greatly affects quality of life and is commonly over-investigated or misdiagnosed as inflammatory bowel disease, cancer, malabsorption, or chronic infection.