[Un- classifiable types of ulcerative colitis].

10-15% of cases of non-specific inflammatory bowel disease cannot be classified. In a retrospective study of 35 colectomy specimens during a ten-year period, we observed 5 such cases. These cases of so-called "unclassified colitis" or "indeterminate colitis" nearly always follow, a fulminating course and require urgent surgery. On macroscopic examination there is marked dilatation of the colon with perforations. The colon is continuously involved, the right colon sometimes more so. Microscopically there is transmural inflammation with acute fissuring and extensive ulcerations. No specific criteria of ulcerative colitis or Crohn's disease are present. "Unclassified colitis" is not a definitive diagnosis. Followup studies sometimes serve for final classification of a case.