Introduction Individuals with adenomatous polyps are at increased risk of developing further neoplasia and it is recommended that these individuals undergo colonoscopic surveillance at an interval dictated by the size of the adenoma and/or the number of adenomas removed. This study documents the findings at surveillance colonoscopies in individuals within the Bowel Cancer Screening Programme (BCSP).

Methods All patients undergoing surveillance colonoscopies within the BCSP at West London Bowel Cancer Screening Centre (WLBCS) between 1^st January 2009 and 1^st February 2013 were were stratified into four groups according to the findings at the index colonoscopy as follows:

Group A – 3 or more adenomas with at least one = 10 mm

Group B – 5 or more small adenomas all <10 mm

Group C – 1 or 2 adenomas = 10 mm

Group D – 3 or 4 small adenomas all <10 mm

The percentage of adenomas found at surveillance colonoscopy in patients with few adenomas at index colonoscopy was compared to adenoma yield in patients with multiple adenomas at index colonoscopy using Fishers exact test.

Results 242 patients underwent colonoscopies within the study period and a total of 379 adenomas were found in 145 patients. 19 adenomas were greater than 10mm (5.0%) and 3 adenomas showed high grade dysplasia (0.8%). The percentage of patients with adenomas found within the groups A-D is shown in the table below.

Overall the percentage of patients with adenomas was 69.0% in those patients having their surveillance procedure at 1 year and 47.0% in those individuals having their colonoscopy at 3 years. For both surveillance intervals, the group with the largest number of adenomas found at the index procedure had a higher adenoma yield during surveillance. Overall, adenomas were found in 67.8% of patients with multiple adenomas found at the index colonoscopy (groups A, B, D) and in 43.6% of patients with 1 or 2 larger lesions (group C) (p = 0.0004).

Conclusion Adenoma detection at surveillance colonoscopy within the BCSP is high, at both the 1 year and the 3 year interval, suggesting that this is a valuable intervention in reducing future risk of colorectal cancer. The yield of high-risk lesions of a large size or with high-grade dysplasia, however, is low. The yield of adenoma detection is higher in individuals undergoing surveillance for high numbers of diminutive lesions compared to those individuals with 1 or 2 large adenomas. This finding may reflect the presence of a generalised colonic field effect in those individuals with multiple lesions, compared to a more local abnormality in those with small numbers of lesions.

Disclosure of Interest None Declared.