Introduction Adenoma detection and removal is one of the main goals of colonoscopy. Improved adenoma detection has been shown to reduce future risk of colorectal cancer. High definition colonoscopy allows better visualisation of the colonic mucosa and may improve detection of polyps. Previous studies have shown variable results when comparing polyp and adenoma detection between standard definition (SD) and high definition (HD) colonoscopy. The UK bowel cancer screening programme offers colonoscopy to all citizens aged 60–75 years who test positive for faecal occult blood (FOB). We aimed to compare polyp and adenoma detection rates between those patients undergoing SD Colonoscopy and HD colonoscopy in the screening population.
Methods Endoscopy, histopathology and screening database reports were analysed for all BCSP in our institution for the period September 2009 to October 2011. 1020 colonoscopies were performed of which 68 were excluded from further analysis (Incomplete procedure/polyposis syndrome/colitis/unknown definition of endoscope/previous colonic resection). Procedures were divided according to the definition of endoscope used: SD (500 000 pixels) n=421, HD (>500 000 pixels) n=531. Reports were analysed for demographic data, bowel preparation, withdrawal time, and the number, size, morphology, site and histology of all lesions removed.
Results There were no significant differences between the SD and HD groups respectively in percentage male subjects (57% vs 60.0%, p=0.229), mean age (66.47 vs 66.54, p=0.24), percentage with good or adequate bowel preparation (96.1% vs 96.2%, p>0.5), mean withdrawal time (10.9 min vs 10.6 min, p=0.06). In total 1553 lesions were detected: 49 cancers, 1149 adenomas and 335 non-neoplastic polyps. There was no significant difference between the SD and HD in overall polyp detection rate (SD 0.63 vs HD 0.65, p=0.401) and adenoma detection rate (SD 0.59 vs HD 0.59, p=0.516). However a significantly greater number of adenomas per patient (APP) were detected in the HD group (SD 1.20 vs HD 1.34, p=0.016). HD endoscopy detected significantly more diminutive adenomas (1–5 mm) than SD endoscopy (0.87 per pt vs 0.72 per pt, p=0.02), but there was no difference in the rate of detection adenomas >5 mm. More adenomas were detected in the proximal colon in the HD group (0.59 vs 0.44, p=0.03) but there was no significant difference in the distal colon (HD 0.79 vs SD 0.77).
Conclusion Overall adenoma detection rate in this study population was excellent with 59% of patients having one or more adenomas detected. HD endoscopy appears to improve the total number of adenomas detected in the screening population. The main gain of HD endoscopy is in detection of diminutive polyps in the proximal colon.
Competing interests None declared.
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