Poster (15W210)

Can We believe our eyes on Endoscopy polyp size?

Author(s)

Doherty J, Nolan B, Rea J, Cullen G, Doherty G, Sheahan K, Buckley M

Department(s)/Institutions

Centre for Colorectal Disease St Vincent's University Hospital

Introduction

Surveillance colonoscopy intervals following polypectomy are guided by polyp size and quantity. Individuals with larger polyps may be at greater risk of developing colorectal cancer. When the excised polyp is ≥10mm, (20mm in patients referred through the Bowelscreen programme) a surveillance procedure is scheduled for 3 years. The microscopic measurement is the ‘yardstick’ used.

Aims/Background

Most endoscopists estimate polyp size prior to excision. Ideally polyps are excised and retrieved in one piece. This is not always feasible, either due to piecemeal excision or fragmentation. Size is then determined by the endoscopist. As this measurement dictates follow-up intervals, we reviewed polypectomies performed to determine accuracy of endoscopic sizing.

Method

We undertook a retrospective analysis of all patients referred to the Bowelscreen programme from January 2014 to July 2015. Any patient whose polyp size was not estimated at endoscopy was not included. 355 polyps were measured endoscopically and excised. Of these 278 had a microscopic measurement(78%, remainder not assesible). Endoscopic measurement was based on visual assessment only. Size variation was defined as (endoscopic size–microscopic size/microscopic size). Clinical mis-sizing was defined as a size variation of >33%.(1). The percentage of polyps on endoscopy within 2mm of the microscopic size was assessed as an alternative measurement of accuracy. (2)

Results

Included for analysis were 165 patients who underwent colonoscopy by one of three Consultant Gastroenterologists. A total of 278 polyps met the inclusion criteria. The median age was 68 years(62-72) and 67%(110/165) were male. A total of 128 polyps were mis-sized(46%), of these 106 were over-estimated and 22 underestimated. The mean variation between the endoscopic and microscopic size was 40%. Of the 278 polyps, 207 were within 2mm of microscopic size compared to endoscopic estimation(74.46%). 90/278 polyps were 1cm or greater, 80 of these were microscopically measured(88.88%) Of these 31 polyps were missized( 38.75%). 28 were overestimated, 3 underestimated. 38/80 were within 2mm of the microscopic size(47.5%).

Conclusions

Endoscopic estimation of polyp size consistently overestimated the size of the polyp. This was particularly the case in polyps ≥10mm. Some of this difference may be attributable to polyp damage during excision or retrieval. The endoscopic assay is two dimensional, histological three dimensional. While in this study 46% of polyps were mis-sized, 74.46% were within 2mm of the histological measurement. A recent comparative study cites 65% and 46% respectively(2). Our figures concur with previous studies showing a greater discrepancy in sizing larger polyps. However overall, careful assessment of polyp size by experienced endoscopists accurately reflects polyp size in 74% of polypectomy specimens, with the closest concordance occurring in polyps less than 10mm.