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Diarrhoea is defined as the frequent passage of loose or watery stools.
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Probability diagnosis
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Irritable bowel syndrome was the commonest cause of chronic diarrhoea in a UK study.
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Drug reactions, coeliac disease and chronic infections such as giardiasis and cryptosporidium are also important causes.
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Diarrhoea: diagnostic strategy model
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Probability diagnosis
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Serious disorders not to be missed
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Neoplasia/cancer:
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colorectal cancer
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ovarian cancer
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peritoneal cancer
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Infection:
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Pitfalls (often missed)
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Coeliac disease
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Faecal impaction with spurious diarrhoea
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Lactase deficiency
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Giardia lamblia infection
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Cryptosporidium infection
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Malabsorption states (e.g. coeliac disease)
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Vitamin C and other oral drugs
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Nematode infections:
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Radiotherapy
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Diverticulitis
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Post-GIT surgery
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Ischaemic colitis (elderly)
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In some instances, such as acute self-limiting diarrhoea, nil is required. Consider:
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microscopy and culture of stool
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FBE
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ESR/CRP
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C. difficile tissue culture assay
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U&E
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specific tests for organisms
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endoscopy
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selective radiology (e.g. small bowel enema)
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Diagnostic triads for diarrhoea
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Acute dia + colicky abdominal pain ± vomiting
→ gastroenteritis
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(Young adult) dia ± blood & mucus + abdominal cramps
→ inflammatory bowel disease (UC/Crohn)
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As above + constitutional symptoms ± eyes/joints
→ Crohn disease
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Pale bulky offensive stools, difficult to flush, weight loss
→ malabsorption
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Fatigue + weight loss + iron deficiency
→ coeliac disease
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Failure to thrive (child) + recurrent chest infections
→ cystic fibrosis
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Altered bowel habit –diarrhoea ± constipation ± rectal bleeding
± abdo discomfort → colorectal carcinoma
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Diarrhoea (fluid/incontinent) + constipation ++ + abdo discom + anorexia/nausea
→ faecal impaction
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Profuse watery dia. + abdo cramps (on antibiotics)
→ pseudomembranous colitis
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Variable dia/constipation + abdo discomfort + mucus PR
+ flatulence ++ → irritable bowel syndrome
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Pseudomembranous colitis (antibiotic-associated diarrhoea)
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This colitis can be caused by the use of any antibiotic, esp. clindamycin, lincomydn, ampicillin, the cephalosporins (an exception is vancomycin) and even metronidazole. It is usually due to an overgrowth of Clostridium difficile, which produces a toxin that causes specific inflammatory lesions, sometimes with a pseudomembrane and is becoming resistant to antibiotics. It may occur, uncommonly, without antibiotic usage.
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Profuse watery diarrhoea
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Abdominal cramping and tenesmus, maybe fever
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Within 2 d of taking antibiotic (can start up to 4–6 wks after usage)
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Persists 2 wks (up to 6) after ceasing antibiotic
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Diagnosed by characteristic lesions on sigmoidoscopy and a tissue culture assay for C. difficile toxin.
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Ischaemic colitis in the elderly
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Due to atheromatous occlusion of mesenteric vessels. Clinical features include:
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Diarrhoea in children
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The two commonest causes are infective gastroenteritis and antibiotic-induced diarrhoea.
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Toddlers diarrhoea (‘cradle crap’)
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Infants with loose, bulky, non-smelly stool with fragments of undigested food in a well-thriving child, solid in morning, ‘runny’ in afternoon
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Onset usually between 8 and 20 mths
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Associated with high fructose intake (fruit juice diarrhoea)
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Diagnosis by exclusion
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Treatment is by dietary manipulation
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Chronic diarrhoea in children
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Synonyms: carbohydrate intolerance, lactose intolerance.
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The commonest offending sugar is lactose. Diarrhoea often follows acute gastroenteritis when milk is reintroduced into the diet. Stools may be watery, frothy, smell like vinegar and tend to excoriate the buttocks. They contain sugar. Investigation: lactose breath hydrogen testing.
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Remove the offending sugar from the diet.
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Use milk preparations in which the lactose has been split to glucose and galactose by enzymes, or use soya protein.
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Cow's milk protein intolerance
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Not as common as lactose intolerance. Diarrhoea is related to taking a cow's milk formula and relieved when it is withdrawn. Replace with either soy, a hydrolysed or an elemental formula.
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Inflammatory bowel disorder
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These disorders, which include Crohn disease and ulcerative colitis, can occur in childhood.
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Chronic enteric infection
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Responsible organisms include Salmonella sp., Campylobacter, Yersinia, Giardia lamblia and Entamoeba histolytica. With persistent diarrhoea it is important to obtain microscopy of faeces and aerobic and anaerobic stool cultures. G. lamblia infestation is not an uncommon finding and can mimic coeliac disease.
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Clinical features in childhood:
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usually presents at 9–18 mths, but any age
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previously thriving infant
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anorexia, lethargy, irritability
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failure to thrive
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malabsorption: abdominal distension
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offensive frequent stools
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characteristic duodenal biopsy—villous atrophy (gold standard test)
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IgA markers
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serum antigliadin (limited value), anti-endomysial and transglutaminase Abs—90% sensitivity and specificity
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Treatment: remove gluten from diet
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Note: Coeliac disease can occur at any age.
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Classic triad: diarrhoea, weight loss, iron deficiency.
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Cystic fibrosis is the commonest of all inherited disorders (1 per 2500 live births). Clinical features include:
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Diagnosis: can be diagnosed antenatally (in utero) neonatal screening—CFTR protein
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Treatment: oral pancreatic enzyme replacement for malabsorption attention to respiratory problems
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Acute gastroenteritis in adults
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Invariably a self-limiting problem (1–3 d)
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Other meal sharers affected → food poisoning
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Consider dehydration, esp. in the elderly
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Consider possibility of enteric fever
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Traveller's diarrhoea
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Symptoms are usually as above but very severe diarrhoea, esp. if associated with blood or mucus, may be a feature of a more serious bowel infection such as amoebiasis. Most is caused by an E. coli, which produces a watery diarrhoea within 14 days of arrival in a foreign country (
See Traveller's diarrhoea).
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It will respond to norfloxacin 400 mg (o) bd for 3 days.
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Persistent traveller's diarrhoea
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If there is a fever and blood or mucus in the stools, suspect amoebiasis. Giardiasis is characterised by abdominal cramps, flatulence and bubbly foul-smelling diarrhoea.
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Principles of treatment (adults)
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Maintenance of hydration
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Antiemetic injection (for severe vomiting): prochlorperazine IM, statim or metoclopramide IV, statim
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Antidiarrhoeal preparations (avoid if possible: loperamide preferred)—loperamide (Imodium) 2 mg caps, 2 caps statim then 1 after each unformed stool (max. 8 caps/d)
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Dietary advice to patient
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Keep to a modest normal diet and drink good amounts of clear fluids such as water, tea, lemonade and yeast extract (e.g. Marmite) until the diarrhoea settles. Then eat low-fat foods, such as stewed apples, rice (boiled in water), soups, poultry, boiled potatoes, mashed vegetables, dry toast or bread, biscuits, most canned fruits, jam, honey, jelly, dried skim milk or condensed milk (reconstituted with water).
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Avoid fatty foods, fried foods, spicy foods, raw vegetables, raw fruit (esp. with hard skins), Chinese food, wholegrain cereals and cigarette smoking.
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It is advisable not to use these except where the following specific organisms are identified. Use appropriate reduced doses for children.
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Shigella dysentery (moderate to severe)
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Campylobacter jejuni (if prolonged)
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Antibiotics are not generally advisable but if severe or prolonged use ciprofloxacin 500 mg (o) bd or azithromycin for 2 wks. It is a notifiable disease.
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Amoebiasis (intestinal)
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Specialist advice should be sought.
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Special enteric infections (treatment regimens)
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Typhoid/paratyphoid fever
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Antibiotic therapy reduces the volume and duration of diarrhoea but rehydration is the key factor.
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Inflammatory bowel disease
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Inflammatory bowel disease should be considered when a young person presents with:
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bloody diarrhoea and mucus
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colonic pain and fever
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extra-abdominal manifestations such as arthralgia, low back pain (spondyloarthropathy), eye problems (iridocyclitis)
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Two important diseases are ulcerative colitis and Crohn disease, which have equal sex incidence and can occur at any age, but onset peaks at 20–40 yrs.
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The main symptom of ulcerative colitis is bloody diarrhoea and of Crohn disease is colicky abdominal pain.
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Management principles for both diseases
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Treat under consultant supervision.
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Treatment of acute attacks depends on severity of the attack and the extent of the disease:
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mild attacks: manage out of hospital
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severe attacks: hospital, to attend to fluid and electrolyte balance
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Pharmaceutical agents (the following can be considered):
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5-aminosalicylic acid derivatives (mainly UC)
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corticosteroids
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immunosuppressive drugs (e.g. azathioprine, cyclosporin (acute UC), methotrexate and infliximab (Crohn)
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Surgical treatment: reserve for complications only.