Chronic Diarrhoea in Adults

Diarrhoea is defined as the abnormal passage of loose or liquid stools more than three times daily and/or a volume of stool greater than 200 g/day. There is no agreement on the duration of symptoms that define chronic as opposed to acute diarrhoea. However it is usually accepted that symptoms persisting for longer than four weeks suggest a non-infectious aetiology and therefore should be further investigated.¹

Using a definition based on excessive stool frequency without the presence of abdominal pain, estimates of the prevalence of chronic diarrhoea in a Western population are 4-5%.¹

• Irritable bowel syndrome.
• Colonic:
  • Diverticular disease
  • Colonic neoplasia
  • Ulcerative colitis and Crohn's colitis
• Small bowel:
  • Coeliac disease
  • Crohn's disease
  • Other small bowel enteropathies (e.g. Whipple's disease, tropical sprue, amyloid, intestinal lymphangiectasia)
  • Bile acid malabsorption
  • Disaccharidase deficiency
  • Small bowel bacterial overgrowth
  • Mesenteric ischaemia
  • Radiation enteritis
  • Lymphoma
• Pancreatic:
  • Chronic pancreatitis
  • Pancreatic carcinoma
  • Cystic fibrosis
• Endocrine:
  • Hyperthyroidism
  • Diabetes mellitus
  • Hypoparathyroidism
  • Addison's disease
  • Hormone secreting tumours (VIPoma, gastrinoma, carcinoid)
• Chronic infection, e.g. amoebiasis, giardiasis, hookworm.
• Recent antibiotic therapy and Clostridium difficile infection.
• Previous surgery:
  • Extensive resections of the ileum and right colon lead to diarrhoea
  • Bacterial overgrowth, particularly in bypass operations such as in gastric surgery and jejunoileal bypass procedures for morbid obesity
  • Shorter resections of the terminal ileum can lead to bile acid diarrhoea that typically occurs after meals and usually responds to fasting and cholestyramine
  • Chronic diarrhoea may also occur in up to 10% patients after cholecystectomy²
• Drugs:
  • Up to 4% of cases
  • Particularly magnesium-containing products, antihypertensive and non-steroidal anti-inflammatory drugs, theophyllines, antibiotics, anti-arrhythmics, and anti-neoplastic agents
  • Also food additives such as sorbitol and fructose
• Alcohol: diarrhoea is common in alcohol abuse.
• Immunodeficiency.
• Autonomic neuropathy.
• Factitious diarrhoea.

• Symptoms suggestive of organic disease include a history of diarrhoea of less than three months' duration, predominantly nocturnal or continuous (as opposed to intermittent) diarrhoea, and significant weight loss. The absence of these, in association with symptoms suggesting irritable bowel syndrome and a normal physical examination suggest functional bowel disturbance but do not exclude organic gastro-intestinal disease.¹
• Malabsorption is often accompanied by steatorrhoea and the passage of bulky foul-smelling pale stools.
• Colonic, inflammatory or secretory forms of diarrhoea typically present with liquid loose stools with blood or mucous discharge.

• In young patients (under 45 years) with other typical symptoms of a functional bowel disorder and negative initial investigations, a diagnosis of IBS may be made in primary care without further investigations. However, patients under 45 years with atypical and/or severe symptoms should have further evaluation.¹
• Patients over 60 years old with a change of bowel habit to looser stools and/or increased frequency of defecation, which is persistent for six weeks or more, should be urgently referred under the two week standard, even if there is no rectal bleeding.³

Basic investigations

• Blood tests:
  • Abnormal initial screening investigations such as a high ESR, anaemia or low albumin have a high specificity for the presence of organic disease
  • The presence of iron deficiency is a sensitive indicator of small bowel enteropathy, especially coeliac disease
  • A basic screen for evidence of malabsorption should include full blood count, urea and electrolytes, liver function tests, vitamin B12, folate, calcium ferritin, ESR, CRP and TFTs
  • Coeliac disease serology, e.g. IgA anti-endomysium antibodies
• Stool tests:
  • Inspection of the stool may be helpful,and send for microscopy, sensitivity and culture
  • Specific stool tests, e.g. tests for pancreatic enzymes such as faecal elastase
  • Non-specific stool tests: are of questionable use
  • Measurement of stool (faecal fluid) osmolality and calculation of the osmotic gap are not usually of practical use but may provide an aid to diagnosis
  • Chronic diarrhoea due to infectious agents is rare in immunocompetent Western populations but stool cultures should be considered, particularly where there is a history of travel to high-risk areas
  • If Clostridium difficile is suspected then this needs to be specifically requested as it is not routinely looked for
  • Some protozoan infections, e.g. giardiasis and amoebiasis, are most likely to result in chronic infections. Send three fresh stools for ova, cysts, and parasites. If there is doubt about persisting giardial infection, stool ELISA has largely replaced the need for intestinal biopsies. Serological testing can be useful in amoebiasis, as positive serology by an indirect haemagglutination test or ELISA can differentiate invasive disease from the asymptomatic carrier state

Further investigations in secondary care¹

• History or findings suggestive of malabsorption:
  • Small bowel:
    • Distal duodenal biopsies
    • Barium follow-through
    • Endoscopy
    • Bacterial overgrowth: glucose hydrogen breath test, jejunal aspirate and culture
  • Pancreatic:
    • CT scan of pancreas
    • Faecal elastase or chymotrypsin
    • Pancreolauryl test
    • Further structural tests: endoscopic retrograde cholangio-pancreatography or magnetic resonance cholangio-pancreatography
  • History or findings suggestive of colonic or terminal ileal disease
  • Flexible sigmoidoscopy if aged under 45 years
  • If aged over 45 years, colonoscopy is preferred to barium enema
  • Terminal ileum: barium follow-through. 99mTechnetium-labelled white cell scanning is useful in testing for intestinal inflammation and has equivalent sensitivity to small bowel follow through in the assessment of terminal ileal Crohn's disease

Further investigations

If the above tests are largely unremarkable and diarrhoea is persisting then the following should be considered:

• Inpatient assessment - may help determine laxative abuse
• 24-72 hour stool weights
• Stool osmolality, osmotic gap
• Laxative screen
• Gut hormones: serum gastrin, VIP, urinary 5-HIAA

• This depends on the underlying cause.
• There may be a role for symptomatic treatment with anti-motility drugs, e.g. codeine, loperamide, in some cases but only when a definite diagnosis has been made and it is definite that there is no cause-associated contraindication.