Introduction The current paradigm of colonoscopic management of polyps is to resect and send for pathologic assessment. Such practice incurs substantial costs for a group of lesions with limited clinical importance. Several studies have proposed a resect and discard approach for smaller polyps. For this to be effective our in vivo assessment of polyp size needs to be accurate. Additionally a high positive predictive value (PPV) of adenomas among polyps resected is essential to ensure patients are correctly risk stratified for surveillance.
Methods All polypectomies performed from 1 January 2010 to 31 December 2010 were identified retrospectively from databases in a dual site teaching hospital and local district general endoscopy units. Polyps removed and retrieved with corresponding histology were identified. Polyp site, endoscopic size and endoscopist specialty were recorded. Carcinomas, adenomas and serrated lesions were determined to be neoplastic. The total number of neoplasms removed divided by the total number of polyps removed was calculated (PPV). Fishers exact test was used to compare the subspecialties of endoscopist (nursing/surgical/medical). In vivo size was analysed for terminal digit preference by the colonoscopist compared to histology measurements using a χ2 goodness of fit test. Calculations of the distribution of error between in vivo estimation and histology measurement and the number of times the size discrepancy crossed the 10 mm value used in planning surveillance colonoscopy were performed.
Results 1212 polyps were included, 864 had in vivo size estimation and subsequent en-bloc histology measurements ≤20 mm. The PPV for neoplastic polyps was 69% (831/1212) with 381 non-neoplastic polyps removed. Nurse endoscopists had the highest PPV, 74% (n=347/486) compared to surgeons (PPV 72%: 143/199) and medics (PPV 64%: 339/527, p<0.02). Considering proximal hyperplastic polyps as neoplastic the overall PPV=73% (879/1212), nurses PPV 75% (364/486); surgeons 74% (147/199); medical 70% (368/527); p<0.1. Size assessment correlated poorly with histology with a significant increase in the use of 5 mm and 10 mm measurements in vivo (χ2=71.3 DF=9 p<0.0001). 290 polyps were estimated smaller in vivo and 302 larger (294 precise) when compared to histology [distribution of error curve: SD=3.22 mm; mean=0.16 mm; median=0]. A discrepancy across the 10 mm size occurred in 96 polyps (11%).
Conclusion Currently a poor PPV for neoplastic polyps and imprecise in vivo size estimation would mean a resect and discard approach would be inaccurate, but current practice removes a large amount of benign pathology and has both patient morbidity and significant cost implications.
Competing interests None declared.
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