Colonoscopy conversion after flexible sigmoidoscopy screening: results from the UK Bowel Scope Screening Programme.

Abstract

In the UK Bowel Scope Screening Programme (BSSP), patients progress to colonoscopy based on high-risk features on flexible sigmoidoscopy (FS). We aim to assess the practice of colonoscopy conversion and predictors of detection of additional adenomas on colonoscopy. The Bowel Cancer Screening database was interrogated and collated with endoscopic and histological findings from patients undergoing colonoscopy following FS between August 2013 and August 2016. Multivariate analysis was performed to identify predictors of new adenomas. FS was performed on 11711 patients, with an adenoma detection rate (ADR) of 8.5% and conversion to colonoscopy in 421 (3.6%). The additional ADR at colonoscopy was 35.2%, with one additional malignant diagnosis (0.26%). The adenoma miss rate was 3.6%. On multivariate analysis, a polyp ≥10mm was the only high-risk indication associated with additional ADR at colonoscopy (OR 3.68, 95% CI 1.51-3.65, P<0.001), in addition to male gender (OR 2.36, 95% CI 1.46-3.83, P<0.001). Predictors of detection of a new adenoma ≥10mm included: villous adenoma (P=0.002), polyp ≥10mm (P=0.007) and male gender (P=0.039). The presence of any conversion criterion was associated with the detection of any proximal adenoma (P<0.001) and adenoma ≥10mm (P=0.031). Male gender, polyps ≥10mm and villous-preponderant histology at FS were predictors of adenomas <10mm and ≥10mm at colonoscopy. Further data are required to assess the role for gender-based stratification of conversion criteria.