Flexible sigmoidoscopy for pseudomembranous colitis

The diagnosis of pseudomembranous colitis requires direct visualisation of pseudomembranes on bowel mucosa or on microscopic examination of a biopsy sample. 90% of cases can be detected by flexible sigmoidoscopy, although in mild cases pseudomembranes may not be evident macroscopically. The classic sigmoidoscopic appearance of 2 to 10 mm raised yellow nodules are pathognomonic.

An abdominal radiograph may be normal in pseudomembranous colitis, although in severe cases it may show a complicating toxic megacolon. Barium enema and abdominal ultrasound are of no use in confirming or excluding the diagnosis of pseudomembranous colitis, and a positive stool culture for C. difficile toxin would make (rather than exclude) the diagnosis.