oPatientPlus articles are written by UK doctors and are based on research evidence, UK and European Guidelines. They are designed for health professionals to use, so you may find the language more technical than the condition leaflets.
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.
- Irritable bowel syndrome (IBS).
- Diverticular disease.
- Colonic neoplasia, including colorectal cancer.
- Ulcerative colitis and Crohn's colitis.
- Microscopic colitis: a type of inflammatory bowel disease, which typically presents in older age groups with chronic watery diarrhoea. Colonoscopy appears normal and a definitive diagnosis can only be made with multiple colonic biopsies.
- Ischaemic colitis.
- Constipation with faecal impaction and overflow.
- Small bowel:
- Coeliac disease.
- Crohn's disease.
- Other small bowel enteropathies (eg Whipple's disease, tropical sprue, amyloid, intestinal lymphangiectasia).
- Bile acid malabsorption, eg Crohn's disease affecting the terminal ileum, after ileal resection, cholecystectomy, coeliac disease, bacterial overgrowth and pancreatic insufficiency.
- Disaccharidase deficiency.
- Lactose intolerance.
- Small bowel bacterial overgrowth.
- Mesenteric ischaemia.
- Radiation enteritis.
- Chronic infection, eg amoebiasis, giardiasis, hookworm, Cryptosporidium spp., Entamoeba histolytica (may be bloody diarrhoea).
- 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 jejuno-ileal 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 colestyramine
- Chronic diarrhoea may also occur in up to 10% of patients after cholecystectomy.
- Drugs: for example, laxatives, antibiotics, digoxin, cytotoxic drugs, magnesium-containing antacids, metformin, non-steroidal anti-inflammatory drugs.
- Food additives such as sorbitol and fructose.
- Alcohol: diarrhoea is common in alcohol abuse.
- Factitious diarrhoea (may be associated with an eating disorder).
- 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 IBS and a normal physical examination suggest functional bowel disturbance but do not exclude organic gastrointestinal disease.
- 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.
- Assess for the presence of any 'red flag' indicators suggesting a possible serious underlying cause:
- Look for other features suggesting an underlying cause, eg recent travel abroad, laxative and other possible drug causes, features of systemic disease (eg thyrotoxicosis, diabetes, adrenal insufficiency, systemic sclerosis), features of pancreatic disease (abdominal pain, steatorrhoea).
- Assess for features that indicate a diagnosis of IBS. 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.
- Always do a digital rectal examination in people with unexplained symptoms related to the lower gastrointestinal tract, provided this is acceptable to the person being examined.
- FBC: anaemia or raised platelet count suggesting inflammation.
- LFTs, including albumin level.
- Tests for malabsorption: calcium, vitamin B12 and red blood cell folate, iron studies (ferritin).
- ESR and CRP: elevated levels may indicate inflammatory bowel disease.
- Antibody tests for coeliac disease - IgA tissue transglutaminase antibody (tTGA), or IgA endomysial antibody (EMA).
- Stool for culture and sensitivity and examination for ova, cysts and parasites: if an infectious cause is suspected or there is a history of travel to high-risk areas. Consider sending stool for testing for Clostridium difficile if a previous episode has resolved and the symptoms have recurred.
- Refer urgently under the two-week wait rules if red flag symptoms or signs are present:
- Symptoms suggestive of colorectal or anal cancer.
- Aged 40 years or older, reporting rectal bleeding with a change of bowel habit towards looser stools and/or increased stool frequency persisting for six weeks or more.
- Presenting with a right lower abdominal mass consistent with involvement of the large bowel.
- Presenting with a palpable rectal mass (intraluminal and not pelvic).
- 60 years or older, with a change in bowel habit to looser stools and/or more frequent stools persisting for 6 weeks or more with or without rectal bleeding.
- Men of any age with unexplained iron-deficiency anaemia and a haemoglobin level of 11 g/100 mL or less.
- Non-menstruating women with unexplained iron-deficiency anaemia and a haemoglobin level of 10 g/100 mL or less.
- Refer for further assessment and management if:
- History, examination, and blood test results suggest coeliac disease, Crohn's disease or ulcerative colitis.
- The diagnosis is uncertain.
Further investigations in secondary care
- History or findings suggestive of malabsorption:
- Small bowel:
- Distal duodenal biopsies.
- Barium follow-through.
- Bacterial overgrowth: glucose hydrogen breath test, jejunal aspirate and culture.
- CT scan of pancreas.
- Faecal elastase or chymotrypsin.
- Further structural tests: endoscopic retrograde cholangiopancreatography or magnetic resonance cholangiopancreatography.
- History or findings suggestive of colonic or terminal ileal disease.
- Flexible sigmoidoscopy if aged under 45 years (the diagnostic yield is not different to colonoscopy in this group).
- If aged over 45 years, colonoscopy is preferred to barium enema.
- Terminal ileum: barium follow-through. 99m technetium-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.
- Small bowel:
If the above tests are largely unremarkable and diarrhoea is persisting then the following should be considered:
- Inpatient assessment - may help to 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 antimotility drugs - eg codeine, loperamide - in some cases but only when a definite diagnosis has been made and it is definite that there is no cause-associated contra-indication.
Further reading & references
- Guidelines for the investigation of chronic diarrhoea (tests for malabsorption); British Society of Gastroenterology (2003)
- Diarrhoea - adults assessment; NICE CKS, December 2010
- 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.
Disclaimer: This article is for information only and should not be used for the diagnosis or treatment of medical conditions. EMIS has used all reasonable care in compiling the information but make no warranty as to its accuracy. Consult a doctor or other health care professional for diagnosis and treatment of medical conditions. For details see our conditions.
Dr Colin Tidy
Dr Colin Tidy
Dr Helen Huins