The Anatomical Distribution of Colorectal Polyps at Colonoscopy

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Abstract
Colorectal carcinoma is one of the most common causes of cancer-related deaths in Australia. The distribution of polyps in the colon may effect the efficacy of a screening modality. The aim of this study was to determine the age-matched anatomic location and histologic type of colorectal polyps observed at colonoscopy over a 10-year period at our endoscopy unit. Endoscopy reports on 2,578 patients were reviewed; polyp/lesion histology and location (left, right, or both) were determined in 2,553. Of all polyps observed, 1,310 (51%) cases were left-sided, 510 (20%) were right-sided, and 733 (29%) were synchronous. Adenomas were present in 1,659 cases (65%); of these, 734 (44%) were left-sided only and 405 (24.5%) were right-sided only. Carcinoma was observed in 189 (7%) cases, of which 71 (37.5%) were left-sided only. There was an increased right-sided prevalence of adenoma or carcinoma with age (p = 0.0029). This was not a screening study, but it has shown that a significant number of adenomas and carcinomas lie proximal to the splenic flexure. Thus, in the absence of left-sided lesions, it is expected that examination of the colon limited to the splenic flexure would miss 23% of such lesions. The increasing right-sided prevalence of these lesions with age suggests that evaluation of the proximal bowel is particularly important in older people.