Changing distribution of carcinoma of the colon and rectum.

The anatomic distribution of carcinoma of the colon and rectum in patients operated upon at this institution over a 30 year period was studied. All patients with recently diagnosed adenocarcinoma of the colon and rectum were placed into one of three groups: right colon, left colon or transverse colon. An analysis of the distribution of tumors over four time periods--1945 to 1949, 1956 to 1957, 1966 to 1969 and 1976 to 1978--revealed an increase in the percentage of tumors of the right colon with time that was most significant in the last time period studied. Various explanations for the recent increased incidence of tumors of the right colon found were discussed.