Rules of thumb

The following guidelines may help in the differential diagnosis of diarrhoea:

• copious watery diarrhoea suggests an organic aetiology
• nocturnal diarrhoea suggests an organic aetiology - patient wakes up in the night needing to open bowels
• frequent passage of small amounts of faeces suggests functional bowel disease, e.g. irritable bowel syndrome
• bloody diarrhoea implies colonic disease, often inflammatory bowel disease or carcinoma, or an invasive infective diarrhoea, e.g. Campylobacter jejuni
• acute diarrhoea often has an infective aetiology