Geographic differences in the prevalence and distribution of large-bowel polyps--colonoscopic findings.

The large-bowel polyp pattern in two widely separated geographic regions of Sweden, Bollnäs in the central part and Trelleborg in the south, was studied prospectively by colonoscopic polypectomy. In Bollnäs 11.8% of 1,153 patients had neoplastic, and 3.8% hyperplastic, polyps. In Trelleborg 29% of 1,040 patients had neoplastic, and 17.3% hyperplastic, polyps. Furthermore, the Trelleborg patients had, on average, more polyps per patients than their Bollnäs counterparts: 2.0 versus 1.5 neoplastic, and 2.1 versus 1.7 hyperplastic, polyps. There was a marked difference in the anatomic location of the polyps between the two regions: in Trelleborg 55.4% of the neoplastic, and 40.5% of the hyperplastic polyps were distributed above the rectosigmoid, compared with 20.9% and 26.4%, respectively, in Bollnäs. The findings offer an explanation of the fact that the incidence of colorectal carcinoma in the Malmö region, close to the Trelleborg area, is the highest in Sweden.