Differentials
Acute diarrhoea
SIGNS / SYMPTOMS
Any infectious agent (bacterial, viral, parasitic) causing gastroenteritis may cause a similar presentation. Cryptosporidium diarrhoea is not usually bloody but co-infections may occur.
INVESTIGATIONS
Stool culture and microscopy or serological tests for bacterial pathogens, other parasites, or gastrointestinal viruses positive according to pathogen.
Chronic diarrhoea
SIGNS / SYMPTOMS
Any infectious agent causing gastroenteritis may cause a similar presentation, but in chronic diarrhoea there may be other contributing non-infectious factors such as intestinal disorders, infiltrative diseases, and iatrogenic causes.
INVESTIGATIONS
Stool culture and microscopy or serological tests for bacterial pathogens, other parasites, or gastrointestinal viruses positive according to pathogen.
Crohn's disease
SIGNS / SYMPTOMS
May present with fatigue, diarrhoea, abdominal pain, weight loss, fever, and rectal bleeding. Other signs may include oral ulcers, perianal skin tags, fistulae, abscesses, and sinus tracts; no mass present on digital rectal examination.
INVESTIGATIONS
Stool culture, microscopy, and antigen testing: negative.
Upper GI and small-bowel series: oedema and ulceration of the mucosa with luminal narrowing and strictures.
CT/MRI abdomen: skip lesions, bowel-wall thickening, surrounding inflammation, abscess, fistulae.
Colonoscopy: aphthous ulcers, hyperaemia, oedema, cobblestoning, skip lesions.
Ulcerative colitis
SIGNS / SYMPTOMS
May present with bloody diarrhoea, history of lower abdominal pain, faecal urgency, presence of extra-intestinal manifestations (e.g., erythema nodosum, acute arthropathy), history of primary sclerosing cholangitis; no mass present on digital rectal examination.
INVESTIGATIONS
Stool culture, microscopy, and antigen testing: negative.
Histology: continuous distal disease, mucin depletion, basal plasmacytosis, diffuse mucosal atrophy, absence of granulomata, and anal sparing.
Colonoscopy: rectal involvement, continuous uniform involvement, loss of vascular marking, diffuse erythema, mucosal granularity, fistulas (rarely seen), normal terminal ileum (or mild 'backwash' ileitis in pancolitis).
Gut acute graft-vs-host disease (aGVHD)
SIGNS / SYMPTOMS
Profuse diarrhoea following bone marrow transplant may be a sign of gut aGVHD.
INVESTIGATIONS
Exclude presence of Cryptosporidium; stool and antigen testing negative for other infectious agents; histological evidence of aGVHD on endoscopic biopsy.
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