''Causes in west (in order of frequency)''
IBS/functional
Lactose intolerance (or other diet)
Coeliac
Small bowel infection - giardia, bacterial overgrowth, tropical sprue
IBD - Crohns / UC
Pancreatic insufficiency/cancer, cystic fibrosis
Radiation enteritis
Neoplasia / drugs / metabolic / autonomic neuropathy ....

5% adults (M>F) - report loose stool
functional (no pain) or IBS (with pain, 4 per 100 in UK, F more likely to see GP)
Lactose intolerance - adult acquired hypolactasia - mutation occured in NW europe - 10% adults intolerant, 40% SE europe and 90% orientals
Coeliac - 1 in 100 - 1/2 diagnosed as adults
Giardia - tropics, campers, backpackers
IBD - UC 12 and Corhns 24 per 10000
bacterial overgrowth often in elderly with achlorhydria (iatrogenic)
IBS
diet, drugs, psych

''Present with ...''
abdo pain esp IBS - also Crohns and pancreatic disease
weight loss - Crohns and pancreatic disease and neoplasia
vomiting - chronic diarrhoea may occur post acute gastro
steatorrhoea and abdo distention coeliac, pancreatic insufficiency, and giardia
Blood in stool - UC, Crohns, cancer
outlet bleeding (bright red on paper) - exclude IBD and colon ca
 
Urgency is common in chronic diarrhoea
Nocturnal diarrhoea is rarely IBS or functional
 
''Red flags''
age > 50
short history
weight loss
nocturnal Sx
Male
FH colon ca
anaemia
rectal bleeding
recent antibiotic use
 
Drugs - PPI, SSRI, ACE, BB, statins, metformin, mefenamic acid