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Diarrhoea

Introduction: definition

Increased stool water: increased amounts of loose stool (> 300 g /day)

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Differential diagnosis

Common
Acute
- food poisoning
- pseudomembranous colitis
- colitis
- CRC

Chronic
- colitis
- Coeliac disease
- giardiasis
- IBS
- drugs

Osmotic
Na⁺ ions
- laxatives

Bile salts
- Crohn’s
- ileal resection
- bacterial overgrowth
- chronic pancreatitis

CHO
- disaccharidase deficiency
- lactase deficiency

Secretory
Endotoxins
- E. coli
- Vibrio cholerae

Neoplastic
- villous adenoma
- neurohormones (VIP, gastrin, 5-HT...)

Drugs
- EtOH
- PPI (proton pump inhibitors)
- digoxin
- beta-blockers

Exudative
Infective
- viral
- bacterial
- parasitic

Ischaemic
- ischaemic colitis

Inflammatory
- Crohn’s
- Ulcerative colitis
- vasculitis

Gut motility
Functional
- IBS

Endocrine
- thyroid (hyper)

Neurological
- autonomic neuropathy

Overflow
Constipation
- CRC...

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Differential diagnosis: bloody diarrhoea

Infective
- Clostridium difficile

- Campylobacter spp.
- Shigella spp.
- Escherichia coli 0157 (HUS: haemolytic uraemic syndrome)

- Yersinia enterocolitica
- Entamoeba histolytica (amoebic dysentery)

Other colitides
- UC
- Crohn’s colitis

- ischaemic colitis (elderly patients in AF)
- radiation proctitis

- microscopic colitis

Pseudomembranous colitis
- Clostridium difficile toxin-related diarrhoea
- Occurs 2–30 days after broad-spectrum antibiotics, esp. cephalosporins
- Management = metronidazole (PO) / vancomycin (PO)

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Investigation

Stool
- frequency charts
- MC & S (microscopy, culture and sensitivity)
- CDT assay

Bloods
- effects (FBC, U+Es, CRP, ESR, albumin, LFTs)

Potential causes
- also do: TFTs, EMAs

Special
- AXR
- flexible sigmoidoscopy

- Barium enema
- Barium follow-through
- Barium small bowel enema

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Management

Rehydration
- oral
- IV N saline with K⁺
- Drugs: codeine phosphate
- Treat cause

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