Chronic diarrhoea

Understanding chronic diarrhoea

What counts as chronic

Acute diarrhoea, lasting days to a couple of weeks, is usually infective and self-limiting. Diarrhoea persisting beyond four weeks is classified as chronic, and the likely causes are entirely different.

This distinction matters practically. Chronic diarrhoea treated as though it were a persistent infection leads to repeated antibiotic courses that do not help and can make matters worse.

Understanding chronic diarrhoea

The causes to consider

The list is broad, which is why proper assessment beats guesswork:

• Irritable bowel syndrome, diarrhoea-predominant, the commonest cause overall
• Inflammatory bowel disease: Crohn's disease and ulcerative colitis
• Coeliac disease, under-diagnosed rather than absent in Nigeria
• Lactose intolerance, very common in adults of African descent
• Bile acid diarrhoea, often after gallbladder removal, and highly treatable
• Chronic infections and parasites, which do need excluding here
• Medications, particularly metformin, some antibiotics and magnesium-containing antacids
• Microscopic colitis, where the bowel looks normal but biopsies show inflammation
• Overactive thyroid
• Pancreatic insufficiency, causing pale, greasy, difficult-to-flush stools
• Colorectal cancer, particularly in older patients

Understanding chronic diarrhoea

The clues that narrow it down

The character of the diarrhoea guides us. Blood and mucus point toward inflammation or a growth. Pale, greasy, foul-smelling stools that float suggest fat malabsorption from the pancreas or coeliac disease. Watery diarrhoea that wakes you at night suggests a genuine organic cause rather than IBS, because IBS characteristically spares sleep.

Diarrhoea starting soon after gallbladder surgery strongly suggests bile acid diarrhoea, which responds dramatically to specific treatment and is frequently missed for years.

Understanding chronic diarrhoea

How it is investigated

Assessment begins with stool tests for infection and parasites, blood tests including thyroid function, coeliac serology, inflammatory markers and anaemia, and a stool calprotectin test to separate inflammatory from functional causes.

A colonoscopy is indicated where calprotectin is raised, where there is bleeding, weight loss or anaemia, in anyone over 50, or where the picture remains unclear. Biopsies are taken even when the bowel looks entirely normal, because microscopic colitis is diagnosed only that way.

Where malabsorption is suspected, a gastroscopy with small bowel biopsies confirms or excludes coeliac disease.

Understanding chronic diarrhoea

Treatment

Treatment follows the diagnosis rather than the symptom, which is why identifying the cause is worth the effort. Coeliac disease responds to a strict gluten-free diet. Bile acid diarrhoea responds to a bile acid binder, often within days. Inflammatory bowel disease requires specific anti-inflammatory treatment. Lactose intolerance is managed by dietary adjustment. Microscopic colitis usually responds well to a specific steroid.

Anti-diarrhoeal medication has a place for symptom control, but using it as the whole treatment leaves the underlying cause untouched.