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

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 11 711 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 ≥ 10 mm 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 ≥ 10 mm included: villous adenoma (P = 0.002), polyp ≥ 10 mm (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 ≥ 10 mm (P = 0.031).

Male gender, polyps ≥ 10 mm and villous-preponderant histology at FS were predictors of adenomas < 10 mm and ≥ 10 mm at colonoscopy. Further data are required to assess the role for gender-based stratification of conversion criteria.