Chronic Diarrhoea

Finding the cause of persistent loose bowel motions

What is chronic diarrhoea?

Diarrhoea means loose or watery stools, usually with increased frequency. It is 'chronic' when it lasts more than four weeks. Unlike a short-lived gut infection, persistent diarrhoea deserves proper assessment, because the range of causes is wide and most are very treatable once identified.

Common causes

• Irritable bowel syndrome (IBS) — the most common cause in younger people, typically with cramping relieved by a bowel motion

• Bile acid diarrhoea — surprisingly common and underdiagnosed; often watery, urgent diarrhoea, especially after gallbladder removal. It responds well to bile acid binder medication

• Coeliac disease — an immune reaction to gluten (see our separate handout)

• Inflammatory bowel disease — Crohn's disease and ulcerative colitis

• Microscopic colitis — watery diarrhoea, usually in people over 50; the bowel looks normal at colonoscopy and the diagnosis is made on biopsies

• Lactose or other sugar intolerance, medications (including metformin and PPIs), an overactive thyroid, pancreatic insufficiency, and gut infections such as giardia

How is it investigated?

We tailor tests to your story. Typical first steps include blood tests (blood count, iron, thyroid, coeliac serology), stool tests for infection, and faecal calprotectin to look for bowel inflammation. Many people need a colonoscopy with biopsies — biopsies are essential, as conditions like microscopic colitis are invisible to the naked eye. Depending on the picture, we may also test for bile acid diarrhoea, pancreatic function or sugar malabsorption.

Treatment

Treatment depends on the cause — gluten-free diet for coeliac disease, bile acid binders for bile acid diarrhoea, budesonide for microscopic colitis, specific therapy for IBD, or dietary strategies for intolerances. While investigating, loperamide (Imodium/Gastro-Stop) is safe for symptom control in most situations, and maintaining fluid and salt intake is important if diarrhoea is frequent.

⚠ See a doctor promptly if you have Blood in the stool or black stoolsUnintentional weight lossDiarrhoea waking you from sleep (this suggests an organic cause rather than IBS)Fever, severe pain, or signs of dehydration (dizziness, reduced urination)New symptoms after age 50, or a family history of bowel cancer, coeliac disease or IBD

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This information is general and not a substitute for personalised medical advice. Please discuss any questions with your gastroenterologist or GP. If you develop severe symptoms, call 000 or go to your nearest emergency department.