Introduction Polyp distribution can effect the efficacy and modality of a population screening method. A number of studies in the past demonstrated that a significant proportion of adenomas lie proximal to the splenic flexure,¹however sigmoidoscopy is being increasingly used for screening purposes. We set out to identify distribution and characteristics of colonic polyps in a screening naive population.

Method We conducted a retrospective analysis of 1462 diagnostic and surveillance colonoscopies performed at MDH Malta, between 2012 and 2014. 587 reports contained the term polyp and were further analysed looking at demographics and polyp characteristics.

Results Overall mean age was 60.5 years and 58.7% (n = 341) were males. A total of 1141 polyps were identified with an average of 0.8 polyps per procedure. Overall adenoma detection rate (ADR) was 27.5%. ADR was significantly higher in males (34.4%) than in females (21.4%); Chi-square p = 0.00. 88.2% (n = 1042) of polyps were diminutive (1–5 mm), 3.8% (n = 45) were small (6–9 mm) and the remaining 8.0% (n = 7795) were large (>=10 mm). Table 1demonstrates that whereas adenomas were prevalent throughout the entire colon, hyperplastic polyps were more prevalent distally (p = 0.00). Polyps with advanced histological features were however mostly left sided (p = 0.00); 79.2% and 80.0% of polyps with high grade dysplasia and submucosal invasion respectively. This was also true for large polyps, 78.9% of which (n = 59/95) were distal to the splenic flexure. Polyp size estimation at endoscopy was found to be an overestimate of the pathological specimen measurement (respective means = 8.41 mm and 6.17 mm; paired t-test p = 0.00), and this would have reduced polyp size classification across the 10 mm threshold in 33 instances.

Conclusion Since a large proportion of advanced polyps were situated distal to the splenic flexure, sigmoidoscopy seems to be a plausible alternative to full colonoscopy as a screening alternative. Polyp size estimation at endoscopy resulted in mis-sizing of 33.3% of polyps across the 10 mm threshold and surveillance advice should be based on pathology specimens, when possible.

Disclosure of interest None Declared.

Reference

1. Lemmel GT, Haseman JH, Rex DK, Rahmani E. Neoplasia distal to the splenic flexure in patients with proximal colon cancer. Gastrointest Endosc. 1996 Aug;44(2):109-11