Clinical presentation:
25 year old male who had recently received a course of ampicillin for upper respiratory tract infection. Now has blood and mucus in the stool.

The colon is immobile and outlines with gas from hepatic flexure to distal descending colon. There is loss of the usual colonic haustral pattern and ill-defined areas of mucosal thickening are present.

Clinical presentation:
Another adult male with previous broad-spectrum antibiotic with bloody diarrhoea.

There is massive thickening of the walls (mucosa?) of the ascending colon.

a case with less conclusive clinical detail:
47 year old male with sudden onset of blood and mucus per rectum.

The colon shows massive mucosal thickening with typical "thumb printing" appearance. This haemorrhagic colitis was thought antibiotic related, but this pattern could also be ischaemic. There was no evidence of systemic arterial disease and no evidence of bacterial endocarditis or myocardial infarction.