Prevalence and characteristics of incidental colorectal polyps in patients undergoing colonoscopy at a South African tertiary institution

Abstract

Background. There is a lack of data on the frequency and pattern of colorectal adenomas in sub-Saharan Africa to guide diagnostic and preventive strategies for colorectal cancer (CRC) in the region.

Objectives. To describe polyp characteristics and adenoma frequency in patients at average risk of CRC, who are undergoing colonoscopy for bowel symptoms at a tertiary hospital in South Africa (SA).

Methods. Colonoscopy records from the prospective endoscopy database at Groote Schuur Hospital, Cape Town, SA, from August 2014 to February 2017, were retrieved. The presence of polyps, and their morphology, size, site and number in relation to ethnicity, symptoms and colonoscopy quality indicators were analysed. The histological type and grade were obtained from laboratory records and analysed. The primary endpoint was the adenoma detection rate (ADR). Age, gender, ethnicity, symptoms, bowel preparation and caecal intubation rates were also compared between patients with adenomas and those without.

Results. Of 1 334 colonoscopies, 342 were performed in patients at increased risk of premalignant lesions; these were excluded from the analysis. Polyps were identified in 172 of the remaining 992 patients (17.3%), whose self-declared ethnicity was mixed race (76%), white (12%), black African (11%) or Asian (1%). The quality of bowel preparation and caecal intubation rate were similar between patients with polyps and those without. Patients with polyps were older than those without polyps (mean age 61.5 (standard deviation 12.9) v. 56.3 (17.4) years; p<0.002). On histological examination of these polyps, 119 were adenomas, 26 were hyperplastic and 27 were normal. The majority of the adenomas were tubular (80%), and there were only 6% with high-grade dysplasia. Half (51%) of the adenomas were in the proximal colon, and the overall ADR was 12%. The ADR (prevalence) was highest in white and Asian South Africans (18% each), followed by that in persons of mixed race (13%), but much lower in black Africans (5%).

Conclusions. This study provides a benchmark ADR for our catchment population and potentially across Africa. There is evidence of a continuing differential colorectal neoplasia risk according to ethnicity, with fewer adenomas being detected in black South Africans.