Background and aims Colonoscopy is the current reference standard for the detection of colorectal neoplasia, but nevertheless adenomas remain undetected. The Endocuff, an endoscopic cap with plastic projections, may improve colonic visualisation and adenoma detection. The aim of this study was to compare the mean number of adenomas per patient (MAP) and the adenoma detection rate (ADR) between Endocuff-assisted colonoscopy (EAC) and conventional colonoscopy (CC).

Methods We performed a multicentre, randomised controlled trial in five hospitals and included fecal immonochemical test (FIT)-positive screening participants as well as symptomatic patients (>45 years). Consenting patients were randomised 1:1 to EAC or CC. All colonoscopies were performed by experienced colonoscopists (≥500 colonoscopies) who were trained in EAC. All colonoscopy quality indicators were prospectively recorded.

Findings Of the 1063 included patients (52% male, median age 65 years), 530 were allocated to EAC and 533 to CC. More adenomas were detected with EAC, 722 vs 621, but the gain in MAP was not significant: on average 1.36 per patient in the EAC group versus 1.17 in the CC group (p=0.08). In a per-protocol analysis, the gain was 1.44 vs 1.19 (p=0.02), respectively. In the EAC group, 275 patients (52%) had one or more adenomas detected versus 278 in the CC group (52%; p=0.92). For advanced adenomas these numbers were 109 (21%) vs 117 (22%). The adjusted caecal intubation rate was lower with EAC (94% vs 99%; p<0.001), however when allowing crossover from EAC to CC, they were similar in both groups (98% vs 99%; p value=0.25).

Interpretation Though more adenomas are detected with EAC, the routine use of Endocuff does not translate in a higher number of patients with one or more adenomas detected. Whether increased detection ultimately results in a lower rate of interval carcinomas is not yet known.

Trial registration number http://www.trialregister.nl Dutch Trial Register: NTR3962.