The importance of clinicopathological correlation in the diagnosis of inflammatory conditions of the colon: histological patterns with clinical implications.

Histological reaction patterns within the colon are not disease-specific but reflect mechanisms of injury and duration of disease. By correlating these patterns with known causes of colonic inflammation, we provide guidelines to enhance the diagnostic value of colonoscopic samples. Normal histological features are reviewed, and the sequence of inflammation and repair is used as the basis for appreciating pathological deviations. The common histological patterns of acute colitis with and without features of pseudomembranous or ischemic colitis and the morphological features of chronic colitis with and without crypt destruction are collated with clinical and endoscopic features to emphasize the importance of dialogue between the pathologist and gastroenterologist. Less common patterns, including eosinophilic colitis, graft-versus-host disease, chronic mucosal prolapse, portal hypertensive colopathy, and nonspecific or idiopathic ulcer, illustrate variations in the basic reaction patterns. Difficulties in differential diagnosis are underscored, and biopsy strategies are suggested.