Rectal biopsy in clindamycin-associated colitis. An analysis of 23 cases.

The findings on rectal biopsy and proctoscopic examination in 23 cases of clindamycin-associated pseudomembranous colitis are summarized. On proctoscopic examination, discrete 2- to 5-mm raised plaques are seen adherent ot an edematous, friable mucosa. Rectal biopsy shows pseudomembrane formation and inflammation of the underlying rectal mucosa. Necrosis of the surface epithelium is a frequent finding; however, true ulcers were not observed. Vasculitis or thrombosis is not a feature of any of the cases. Frequently, the pseudomembrane is observed to be dislodged from the mucosal surface. In five of 23 cases, characteristic pseudomembranes are not present in the biopsy specimen in spite of the fact that they are evident proctoscopically.