Background-Propensity to colonic neoplasia diVers between the right and left colon. Aims-To examine whether this difference may be related to regional diVerences in epithelial apoptosis, in expression of a proapoptotic regulatory protein, Bak, and in proliferation. This suggests that colonocytes may be lost by methods other than apoptosis in the right colon. (Gut 1999;45:45-50) Keywords: programmed cell death; Bcl-2; cell cycle; cell proliferation; colon carcinogenesisThe human colon develops embryologically from the primitive midgut and hindgut. The midgut gives rise to the ascending and proximal transverse colon whereas the distal transverse, descending, and sigmoid colon, and the rectum are derivatives of the hindgut. The junction between the midgut and the hindgut is proximal to the splenic flexure, approximately one third of the way along the transverse colon, and the right colon is conventionally defined as the area proximal to the splenic flexure.

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