Differentials
Food poisoning
SIGNS / SYMPTOMS
Typically history of acute diarrhoea (<2 weeks), recent history of travel, eating contaminated food, or contact with cases of food poisoning (family or friends with similar symptoms).
May have a history of bloody stools.
INVESTIGATIONS
Positive stool cultures and blood cultures for enteric or invasive bacterial infection, or positive stool microscopy for specific ova and/or parasites.
Foodborne E coli infection
SIGNS / SYMPTOMS
Typically history of acute diarrhoea (<2 weeks), recent history of travel, eating contaminated food, or contact with an infected person.
May have a history of bloody diarrhoea.
INVESTIGATIONS
Positive stool culture for pathogenic Escherichia coli species such as E coli O157:H7.
Crohn's disease
SIGNS / SYMPTOMS
Abdominal cramp or constant abdominal pain that may be partially relieved by defecation.
Perianal lesions may be present.
Family history of Crohn's disease.
INVESTIGATIONS
Ileocolonoscopy may show any or all of patchy mucosal nodularity, oedema, ulcerations, friability, and stenosis.[53]
Mucosal bowel biopsies may demonstrate transmural involvement with non-caseating granulomas.
Ulcerative colitis
SIGNS / SYMPTOMS
Diarrhoea is typically bloody, usually with associated tenesmus and abdominal pain.
Family history of ulcerative colitis.
INVESTIGATIONS
Ileocolonoscopy may show any or all of rectal involvement, continuous uniform involvement, loss of vascular marking, diffuse erythema, mucosal granularity, normal terminal ileum (or mild 'backwash' ileitis in pancolitis).[54]
Coeliac disease
SIGNS / SYMPTOMS
Pronounced weight loss, fatigue, lethargy, nausea, and vomiting may be present.
A skin rash consistent with dermatitis herpetiformis may be present.
INVESTIGATIONS
Elevated immunoglobulin A-tissue transglutaminase titre; however, a normal level does not exclude coeliac disease as seronegative coeliac disease occurs in a minority of patients.[51]
Increased intraepithelial lymphocytes, villous atrophy, and crypt hyperplasia on duodenal biopsy.
Irritable bowel syndrome
SIGNS / SYMPTOMS
Bloating, flatulence, and crampy abdominal pain relieved by defecation may be present; diarrhoea may coexist with periods of constipation.
Family history of irritable bowel syndrome.
INVESTIGATIONS
Normal colonoscopy and pathology from colonic biopsies. Diagnosis is clinical based on positive symptom criteria.[57]
Giardiasis
SIGNS / SYMPTOMS
A history of contact with contaminated water.
Bloating with cramps, frequent belching with a sulfur smell, nausea, anorexia.
INVESTIGATIONS
A stool microscopy for ova and parasites shows presence of cysts and trophozoites.[5]
Lactase deficiency
SIGNS / SYMPTOMS
Usually explosive, bulky and frothy watery stool after ingestion of lactose-containing products.
INVESTIGATIONS
A trial of dietary lactose elimination results in resolution of symptoms once lactose-containing dairy and non-dairy products are eliminated from diet. Symptoms resume when these are re-introduced.
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