Histologic spectrum of diversion colitis.

Biopsy specimens taken from six patients with diversion colitis, an inflammatory process that occurs in the bypassed colonic segment after diversion of the fecal stream, showed a spectrum of histologic changes ranging from mild colitis to those seen in severe active chronic ulcerative colitis. Histologic abnormalities included aphthous ulcers, crypt distortion, atrophy and abscesses, a villous colonic surface, and a mixed acute and chronic inflammatory infiltrate with patchy lymphoid hyperplasia. Accurate pathologic diagnosis is dependent on clinical history, comparison of histologic morphology in both colonic segments, and response to therapy with local application of short chain fatty acids.