Differentials
Common
Rotavirus
History
common in children from day care centres; may infect adults, immunocompromised people; fever, vomiting; diarrhoea: watery, yellow, no blood or mucus
Exam
normal with mild disease; signs of severe volume depletion seen with prolonged or acute diarrhoea
1st investigation
- no testing needed:
history usually supports diagnosis
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Other investigations
- faecal leukocytes:
may be positive
- FBC:
normal
- blood chemistry:
raised urea and creatinine
- stool enzyme-linked immunosorbent assay or latex agglutination:
positive
- stool polymerase chain reaction:
positive
Norovirus
History
consumption of shellfish, prepared foods, salads, sandwiches, fruit; symptoms: nausea, abdominal cramps, followed by diarrhoea and vomiting; diarrhoea is watery, moderate, contains no blood or mucus; fever, malaise, myalgia, headache common
Exam
normal
1st investigation
- faecal leukocytes:
negative
Other investigations
- stool polymerase chain reaction:
positive
Enteric adenovirus
History
common in infants, older adults, and immunocompromised people; secondary to contaminated food and water; common in day care centres and institutions; symptoms: mild, self-limiting diarrhoea, no fever
Exam
normal
1st investigation
- stool for viral culture:
positive
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Other investigations
- adenovirus-specific enzyme-linked immunosorbent assay or immunofluorescence assay:
positive
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Campylobacter enteritis (Campylobacter jejuni and Campylobacter coli)
History
ingestion of undercooked poultry, raw milk, or cheese; diarrhoea either watery profuse or bloody with mucus, usually self-limiting, and resolves after 5 to 7 days; associated severe crampy periumbilical abdominal pain and fever; bloody diarrhoea can be present from third day of illness
Exam
fever; abdominal examination: generalised or localised tenderness, right lower quadrant tenderness may resemble acute appendicitis; rarely toxic secondary to toxic megacolon
1st investigation
- faecal leukocytes:
positive
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Other investigations
- FBC:
normal or raised WBC count with high percentage bands
- stool culture:
isolation of Campylobacter species
More - stool polymerase chain reaction:
positive
Shigella
History
usually in children attending day care centres; also acquired from eating vegetables; sexual transmission increasingly reported, particularly among gay, bisexual, and other men who have sex with men; fever, then develops diarrhoea, watery becoming mucoid and bloody; stool: small in amount, ranges from 10 to 12 stools/day; fever and tenesmus in one third of patients
Exam
may be normal; fever; abdominal examination: generalised tenderness, distension, or absent bowel sounds, dependent on severity; rectal examination: tender, and rarely rectal prolapse
1st investigation
- faecal leukocytes:
positive
More
Other investigations
- stool culture:
positive
More - stool polymerase chain reaction:
positive
Salmonella
History
source usually food (beef, pork, poultry, eggs, raw milk, ice cream, orange juice) and faecally contaminated water; common with pets (pet ducklings, reptiles, and lizards); symptoms of nausea, vomiting, fever, diarrhoea (can persist for 10 days), cramping; usually self-limiting
Exam
usually normal, might present with mild volume depletion; abdominal examination: usually benign, abdominal tenderness may be localised to lower abdomen; enlargement of liver and spleen not uncommon
1st investigation
- faecal leukocytes:
positive
Other investigations
- FBC:
anaemia, leukopenia, or leukocytosis
- blood and stool culture:
positive
- stool polymerase chain reaction:
positive
Escherichia coli (enterotoxigenic, enteropathogenic, enteroinvasive, enterohaemorrhagic, enteroaggregative)
History
occurs in travellers, children; dysentery; source usually contaminated food; depending on site and strain of infection, symptoms include profuse watery diarrhoea or bloody diarrhoea; abdominal pain but no fever
Exam
can be normal; minority of patients dehydrated with low blood pressure and high heart rate; mild diffuse or lower abdominal tenderness common
1st investigation
- faecal leukocytes:
positive (invasive strain)
Other investigations
- FBC:
anaemia in haemolytic uraemic syndrome
- stool culture:
positive
More - blood chemistry:
renal dysfunction in haemolytic uraemic syndrome
- stool polymerase chain reaction:
positive
Clostridioides difficile
History
history of antibiotic use, hospitalisation, chemotherapy, development of diarrhoea in 2 to 3 weeks (up to 3 months); acute watery diarrhoea; milder disease: 3 to 4 stools/day, mild lower abdominal pain; severe disease with pseudomembranous colitis: profuse diarrhoea, up to 15 times/day, lower abdominal crampy pain; fulminant colitis: fever, chills, diffuse abdominal pain, volume depletion
Exam
signs of mild volume depletion; may be hypotensive, hypothermic, or have high fever; diffuse abdominal tenderness, abdominal distension, and absent bowel sounds in severe cases
1st investigation
Vibrio cholerae
History
mild disease cannot be distinguished from other forms of gastroenteritis, can present as watery diarrhoea; severe cases: diarrhoea with massive volume loss, termed rice water stool (due to flakes of mucus), abdominal cramps
Exam
normal to acutely ill; severe disease, signs of severe volume depletion, including hypotension and mental status changes
1st investigation
- stool culture:
curved gram-negative rods
Other investigations
- FBC:
haemoconcentration
- electrolytes:
acidosis, hypokalaemia, renal dysfunction
- stool polymerase chain reaction:
positive
Staphylococcus aureus
History
ingestion of beef (hamburger), pork, poultry, eggs 4 to 6 hours prior to symptom onset; nausea and vomiting, later associated watery diarrhoea; no fever or abdominal pain
Exam
normal
1st investigation
- clinical diagnosis; no routine testing:
testing stool or vomitus for toxin is done only in suspected outbreaks
Other investigations
Bacillus cereus
History
classic history of eating reheated rice; within 6 hours develops nausea, vomiting, later followed by diarrhoea; also seen with consumption of beef, pork and vegetables; no fever present
Exam
normal
1st investigation
- none:
clinical diagnosis
Other investigations
Clostridium perfringens
History
nausea and vomiting followed by diarrhoea 8 to 12 hours after consumption of beef, pork (chitterlings), poultry, and home foods; no associated fever or abdominal pain
Exam
normal
1st investigation
- none:
clinical diagnosis
Other investigations
Listeria
History
consumption of beef, pork, poultry, milk, cheese, coleslaw, hot dogs, or potato salad; seen in pregnancy, neonates, immunocompromised people; watery diarrhoea, moderate frequency, nausea and vomiting, mild abdominal pain, fever; may be asymptomatic
Exam
volume depletion uncommon; febrile; abdominal examination may show mild tenderness; obtundation in central nervous system disease
1st investigation
- blood culture:
positive
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Giardia
History
travel to endemic areas; spread: person-to-person or contaminated food, water; may be asymptomatic; sudden-onset watery diarrhoea, abdominal bloating, and cramps, nausea, vomiting, foul-smelling fatty stool, and flatulence; symptoms usually prolonged
Exam
normal or mild volume depletion; abdominal examination: increased bowel sound, no tenderness or localising sign
1st investigation
- stool microscopy (ova and parasite):
positive for trophozoites
- direct fluorescence antibody test:
presence of green, glowing ovoid objects indicates Giardia cysts
More - enzyme-linked immunosorbent assay (ELISA):
positive for parasite antigens and/or cyst wall
More - nucleic acid amplification test, polymerase chain reaction of stool sample:
positive
More
Other investigations
- duodenal aspirate/biopsy:
usually normal, trophozoite can sometimes be identified
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Entamoeba histolytica
History
gradual onset over 1-3 weeks; abdominal pain; a minority of patients have fever and haematochezia
Exam
abdominal tenderness; enlarged liver with tenderness; signs of volume and electrolyte imbalance in patients with profuse diarrhoea; in patients with extraintestinal disease there may be signs associated with brain, lung, and liver abscesses
1st investigation
Other investigations
- serum antibodies:
positive for anti-amoebic antibodies
- radiological studies:
extraintestinal disease such as liver abscess, empyema, brain abscess
Microsporidiosis
History
immunocompetent people: self-limiting, mild or rarely chronic diarrhoea; chronic diarrhoea in older people; immunocompromised people: diarrhoea, non-bloody, watery, may be continuous or intermittent, can be associated with crampy abdominal pain; weight loss, wasting, nausea and vomiting, and malabsorption; fever is rare
Exam
may be normal; immunocompromised patient may present with fever, abdominal tenderness, and wasting
1st investigation
- stool or tissue specimen:
spores
Drugs
History
recently started drug, followed by development of diarrhoea within couple of days to weeks; important to inquire about antibiotics, antacids, proton-pump inhibitors, laxatives, non-steroidal anti-inflammatory drug use; diarrhoea watery, no mucus or blood
Exam
usually normal, mild volume depletion not uncommon; abdominal examination normal
1st investigation
- none:
clinical diagnosis
Other investigations
- stool for Clostridioides difficile toxins:
may be positive in antibiotic-related infection
- laxative screen:
positive if laxative-related diarrhoea
Ulcerative colitis
History
blood in stools; may present with toxic megacolon
Exam
normal in mild disease; severe disease: toxic, volume depletion; abdominal examination: variable degree of tenderness; rectal examination: mucus, blood; extra-intestinal manifestations: joint, eye, mucous membrane, skin involvement
1st investigation
Other investigations
- FBC:
may show raised WBC count, anaemia
- erythrocyte sedimentation rate and C-reactive protein:
may be raised
- comprehensive metabolic panel (including LFTs):
non-specific ranging from normal to hypoalbuminaemia to significant electrolyte abnormalities in toxic megacolon
- radiological imaging (x-ray, barium enema, CT):
may show toxic megacolon, perforation
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Crohn's disease
History
abdominal pain, fever, weight loss; diarrhoea: more gradual-onset, large-volume watery diarrhoea suggests small-bowel involvement, frequent small-bowel movements with tenesmus suggest colonic involvement; blood may be seen in stools
Exam
normal in mild disease; can present with acute intestinal obstruction, intestinal perforation, peritonitis, and intra-abdominal abscess formation; severe disease: toxic, volume depletion, variable degree abdominal tenderness; mucus, blood per rectum, perianal fistulas, perirectal abscess; extra-intestinal manifestations: for example, joint, eye, mucous membrane, skin involvement
1st investigation
Other investigations
- FBC:
WBC count may be normal or raised; anaemia can be seen
- erythrocyte sedimentation rate and C-reactive protein:
usually increased
- comprehensive metabolic panel (including LFTs):
non-specific ranging from normal to hypoalbuminaemia to significant electrolyte abnormalities in toxic megacolon
- radiological imaging (abdominal x-ray, small bowel follow through and enema, CT):
toxic megacolon, fistula, abscess, or perforation
Irritable bowel syndrome
History
diarrhoea: small frequent loose stools, small to moderate volume, preceded by urgency, common after meals, no midnight waking, alternates with constipation; may be abdominal discomfort, pain, and bloating; may see mucus; blood is rare
Exam
usually normal; may show abdominal distension and mild abdominal tenderness
1st investigation
- none:
clinical diagnosis made by exclusion
Other investigations
- faecal calprotectin:
<50 micrograms/g makes IBD unlikely (and IBS more likely)
Uncommon
Astrovirus
History
common in children attending day care centres; winter months; usually a water-borne disease; symptoms: loose watery stool, up to 20 stools/day
Exam
usually normal; may show mild signs of volume depletion
1st investigation
- none:
clinical diagnosis
Other investigations
Yersinia
History
ingestion of contaminated pork, beef, milk, cheeses; diarrhoea insidious onset, watery, 5 to 10 times/day; classically abdominal pain localised to the right lower quadrant; can cause mesenteric adenitis mimicking acute appendicitis and Crohn's disease; associated with iron overload syndrome
Exam
may be normal or present as acutely unwell patient; abdominal examination will demonstrate right lower quadrant rebound tenderness and signs of peritonitis in severe cases
1st investigation
- stool culture:
positive
More
Other investigations
- FBC:
normal
- serology test (agglutination and enzyme-linked immunosorbent assay):
positive
- stool polymerase chain reaction:
positive
- radiological imaging (CT):
toxic megacolon or perforation
More
Aeromonas
History
self-limiting; variety of presentations including acute secretory diarrhoea, acute dysentery type with blood and mucus, chronic diarrhoea, choleric and traveller's diarrhoea (endemic in Southeast Asia); worse in children, older people, and immunocompromised people
Exam
usually normal
1st investigation
- stool culture:
positive
Other investigations
Plesiomonas
History
consumption of raw or undercooked shellfish and contaminated water; watery secretory diarrhoea or dysentery type with severe abdominal pain; usually self-limiting, can progress to chronic diarrhoea; vomiting uncommon
Exam
usually normal; patient may be febrile
1st investigation
- stool culture:
positive
Other investigations
Cryptosporidium
History
asymptomatic, mild diarrhoeal illness or severe enteritis with or without biliary involvement; malaise, nausea, anorexia, and abdominal pain; diarrhoea: acute, chronic, transient, intermittent, or continuous, scanty, or large volume up to 20 times/day; in immunocompromised people the disease may be frequent and severe
Exam
may be normal; signs of volume depletion, abdominal tenderness; patient with chronic diarrhoea may present with weight loss; immunocompromised patients present with significant wasting
1st investigation
Other investigations
- abdominal ultrasound:
enlarged gall bladder with thickened wall, dilated intra- and extra- hepatic bile ducts
- CT scan:
enlarged gall bladder with thickened wall, dilated intra- and extra-hepatic bile ducts
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Cyclospora
History
ingestion of infectious oocysts; may be asymptomatic; mild diarrhoeal illness and flu-like symptoms; flatulence, burping, malaise, and weight loss have been described; disease self-limiting, but in immunocompromised people might be prolonged
Exam
usually normal; in HIV/AIDS, may present with volume depletion and wasting
1st investigation
- stool ova and parasites:
Cyclospora oocyst
More
Other investigations
- small bowel biopsy:
several stages of development of the parasite
Cystoisospora belli
History
self-limiting in immunocompetent people, but chronic cases have been seen; diarrhoea, steatorrhoea, abdominal pain, nausea and vomiting, fever, malaise, volume depletion, and weight loss; in immunocompromised people: chronic diarrhoea, can relapse after treatment; severe watery diarrhoea and weight loss
Exam
usually normal; fever, abdominal tenderness, signs of volume depletion, weight loss, and wasting
1st investigation
- stool ova and parasites:
Cystoisospora oocyst
More
Other investigations
- FBC:
high eosinophils
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Klebsiella oxytoca
History
has been associated with some cases of Clostridioides difficile-negative antibiotic-associated haemorrhagic colitis
Exam
signs of mild volume depletion; may be hypotensive, hypothermic, or have high fever; diffuse abdominal tenderness, abdominal distension, and absent bowel sounds in severe cases
1st investigation
- stool culture:
positive
Other investigations
Bowel ischaemia
History
history of coronary artery disease, aorto-iliac surgery, cardiopulmonary bypass, cardiac embolism, myocardial infarction, atrial fibrillation, haemodialysis, mesenteric vein thrombosis, mechanical injury, or patient presenting with shock or cardiopulmonary compromise; abdominal pain, passage of bloody loose stool
Exam
initial phase: minimal abdominal tenderness over affected side; discrepancy between degree of abdominal pain described by patient and abdominal examination; progresses to abdominal distension, severe abdominal tenderness, and absent bowel sounds; severe cases: volume depletion, shock
1st investigation
- CT scan of abdomen with contrast/CT angiogram:
bowel thickening, bowel dilation, pneumatosis intestinalis, portal venous gas, occlusion of the mesenteric vasculature, bowel wall thickening with thumbprinting sign suggestive of submucosal oedema or haemorrhage
More - WBC:
raised
More - liver function tests:
may be raised
More - arterial blood gas and serum lactate:
acidosis
More
Other investigations
- abdominal x-ray:
bowel distension and pneumatosis
More - sigmoidoscopy or colonoscopy:
pale mucosa and petechial bleeding, bluish haemorrhagic nodule, and mucosal ulceration
More - mesenteric angiography:
proximal defect of a mesenteric vessel or vasoconstriction of all mesenteric arcades
More - amylase:
may be raised
More
Radiation injury
History
history of radiation to the abdominal region for different reasons (e.g., prostate cancer); abdominal pain, nausea, vomiting, and diarrhoea; intestinal obstruction and/or intestinal stricture; might present with new lactose intolerance
Exam
usually normal; some might present with mild abdominal tenderness, abdominal distension, and increased bowel sounds; might present with signs of bowel obstruction
1st investigation
- upper gastrointestinal series:
stricture and the extent of the injury
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