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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

Epidemiology

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

Causes of chronic diarrhoea1
Presentation
  • Symptoms suggestive of an 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 gastrointestinal 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.
Investigations
  • 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 under 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 and CRP. Thyroid function tests should also be tested.
    • Coeliac disease serology, e.g. IgA anti-endomysium antibodies.
  • Stool tests:
    • Inspection of the stool may be helpful.
    • 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.
    • Stool culture
    • 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 suspected, this needs to be specifically requested of the microbiology lab. It is not routinely looked for in stool cultures.
    • 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 Giardia 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
      • Pancreolouryl 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

Difficult diarrhoea

e.g. suspicion of laxative abuse, persistent symptoms with negative investigations, high volume diarrhoea.

  • Consider inpatient assessment
  • 24-72 hour stool weights
  • Stool osmolality, osmotic gap
  • Laxative screen
  • Gut hormones: serum gastrin, VIP, urinary 5-HIAA
Management
  • Will depend 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.

Document references
  1. P D Thomas, A Forbes, J Green, P Howdle et al; Guidelines for the investigation of chronic diarrhoea (tests for malabsorption), 2nd edition (2003); British Society for Gastroenterology
  2. Suhr O, Danielsson A, Nyhlin H, et al; Bile acid malabsorption demonstrated by SeHCAT in chronic diarrhoea, with special reference to the impact of cholecystectomy. Scand J Gastroenterol. 1988 Dec;23(10):1187-94. [abstract]
  3. Gastrointestinal (lower) cancer - suspected, Clinical Knowledge Summaries (2005)
Acknowledgements EMIS is grateful to Dr Colin Tidy for writing this article. The final copy has passed scrutiny by the independent Mentor GP reviewing team. ©EMIS 2007.
DocID: 1953
Document Version: 21
DocRef: bgp836
Last Updated: 26 Mar 2007
Review Date: 25 Mar 2009




















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