Definitions
Diarrhoea is defined as the passage of loose, liquid stool. Urgency is the sensation of the need to defaecate without being able to delay. It may indicate rectal irritability but also occurs where the volume of liquid stool is too large, causing the rectum to be overwhelmed as a storage vessel. Frequency merely reflects the number of stools passed and may or may not be associated with urgency or diarrhoea. Dysentery is an infective, inflammatory disorder of the lower intestinal tract resulting in pain, severe diarrhoea and passage of blood and mucus per rectum.
- Bloody diarrhoea is always pathological and usually indicates colitis of one form or another.
- Infective causes are common in acute transient diarrhoea.
- In diarrhoea of uncertain origin, remember the endocrine causes.
- Consider parasitic/atypical bacterial infections in a history of foreign travel.
- Alternating morning diarrhoea and normal/pellety stools later in the day is rarely pathological.
- Diarrhoea developing in hospitalized patients may be due to Clostridium difficile infection – check for CD toxin in the stool.
Important Diagnostic Features
Acute Diarrhoea
Infections
- Viral: rotavirus, enteric adenovirus, calicivirus, e.g. norovirus (acute watery diarrhoea).
- Bacteria: Vibrio cholera (severe diarrhoea, ‘rice water’ stool, dehydration, history of foreign travel), Shigella/Salmonella, Campylobacter, Yersinia (bacterial dysentery – diarrhoea + blood + mucus), Clostridium difficile (green, offensive diarrhoea).
- Protozoa: Giardia intestinalis, Cryptosporidium parvum (watery diarrhoea), Entamoeba histolytica (occasionally diarrhoea + blood + mucus – amoebic dysentery).
Antibiotic Related
Due to disruption of the normal colonic flora. Usually short-lived, self-limiting, mild colicky abdominal pain. May be prolonged and slow to resolve (possibly associated with microscopic colitis on biopsy.
Pseudomembranous Colitis
Most severe form of Clostridium difficile infection, characterized by severe diarrhoea which may be bloody but occasionally acute constipation may indicate severe disease. Characteristic features on colonoscopy (‘baked bean’-like adherent mucopurulent pseudomembranes). Treatment is with oral metronidazole or vancomycin for 10 days.
Chronic Diarrhoea
Small Bowel Disease
- Crohn’s disease: diarrhoea, pain prominent, blood and mucus less common, young adults, long history, chronic malnourishment and weight loss. May be signs of perianal disease. May follow from surgical resection.
- Coeliac disease: history of wheat and cereals intolerance rarely clear, may present in adulthood with chronic diarrhoea and weight loss, abdominal pains, iron deficiency (anaemia).
- ‘Blind loop’ syndrome: frothy, foul-smelling liquid stool, due to bacterial overgrowth and fermentation, usually associated with previous surgery, may complicate Crohn’s disease.
- Whipple’s disease: malabsorption caused by bacterium Tropheryma whipplei, weight loss, arthritis, diarrhoea, lymphadenopathy. M : F = 10:1.
Large Bowel Disease
- Ulcerative colitis: intermittent, blood and mucus, colicky pains, young adults. May be a short history in first presentations. Rarely presents with acute fulminant colitis with acute abdominal signs.
- Colon cancer: older, occasional blood streaks and mucus, change in frequency may be the only feature, positive faecal occult blood, rectal mass.
- Ischaemic colitis: elderly, other evidence of cardiovascular disease; abdominal pain, fever, diarrhoea and rectal bleeding.
- Irritable bowel syndrome: diarrhoea and constipation mixed, bloating, colicky pain, small stool pellets, never blood.
- Spurious: impacted faeces in rectum, liquefied stool passes around faecal obstruction, elderly, mental illness, constipating drugs.
- Polyps (villous) (rare): watery, mucoid diarrhoea, K+ loss, most common in rectum.
- Diverticular disease (rare).
Systemic Disease
Thyrotoxicosis, anxiety, peptides from tumours (VIP, serotonin, substance P, calcitonin), laxative abuse.
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