Irritable bowel syndrome (IBS) is a diagnosis based on symptoms after excluding other causes of bowel symptoms. It is characterized by abdominal pain, discomfort, bloating, and change in bowel habits. Patients may have diarrhoea or constipation and a large number of patients have alternating symptoms.
IBS is a diagnosis of exclusion and has no known organic cause; however mast cell activation is thought to play a role and IBS is more likely to occur after infections or stressful life events. Abnormalities in the gut flora may also occur and result in inflammation and change in bowel function.
A diagnosis of IBS may be made on the basis of symptoms, in the absence of worrisome features such as age of onset greater than 50 years, weight loss, blood in stool, signs of infection or colitis, or family history of inflammatory bowel disease or cancer. Routine tests should be done to exclude other pathologies and may include blood tests, endoscopy or scans.
Other conditions that may present with similar symptoms include coeliac disease, fructose malabsorption, mast cell activation disorders, infections, inflammatory bowel disease, cancers, bile acid malabsorption, functional chronic constipation, small intestinal bacterial overgrowth, and chronic functional abdominal pain.
Although no cure for IBS is known, treatments to relieve symptoms exist. These include dietary adjustments, medication, and psychological interventions. Patient education forms a crucial part of management. Dietary measures that have been found to be effective include increasing soluble fiber intake, and intake of probiotics. IBS has a significant effect on quality of life of patients and can be a difficult condition to manage.
Investigations are performed to exclude other conditions:
- Stool microscopy and culture (to exclude infectious conditions)
- Blood tests: Full blood examination, liver function tests, erythrocyte sedimentation rate, and serological testing for coeliac disease
- Abdominal ultrasound (to exclude gallstones and other biliary tract diseases)
- Endoscopy and biopsies (to exclude peptic ulcer disease, coeliac disease, inflammatory bowel disease, and malignancies)
- Hydrogen breath testing (to exclude fructose and lactose malabsorption)