VISUAL DISAPPEARING PHENOMENON CAN RELIABLY PREDICT THE NONADENOMATOUS NATURE OF RECTAL AND RECTOSIGMOID DIMINUTIVE POLYPS AT ENDOSCOPY

Previous studies have failed to differentiate adenomatous from nonaden omatous diminutive polyps according to their gross macroscopic feature s at endoscopy. We prospectively evaluated the prevalence, distributio n, and predictive value of a recently described morphologic feature-th e ''disappearing phenomenon''-in diminutive polyps of the distal 20 cm of the large bowel by studying 218 polyps in 90 consecutive patients. Disappearance was graded as complete, incomplete, or absent. Overall, complete disappearance was noted in 93 (43.1%) polyps, with a signifi cantly higher prevalence in the middle and lower rectum (p < .05) and among smaller, paler, and smooth-surface polyps (p < .001). Incomplete disappearance was detected in both nonadenomas (23.1%) and adenomas ( 15.8%), but, more importantly, complete disappearance occurred in none of the 19 observed adenomas compared with 93 of 199 nonadenomas. Mult iple logistic regression analysis revealed that disappearance was the strongest predictor (p < .001) of nonadenomatous histology among consi dered morphologic criteria. When complete disappearance was used to pr edict histologic type of diminutive polyps, its sensitivity was 100% a nd its specificity was 46.7%. In conclusion, the disappearing phenomen on represents a reliable visual marker for identifying nonadenomatous rectal and rectosigmoidal diminutive polyps at endoscopy. Diminutive p olyps that disappear completely upon insufflation are invariably nonad enomatous and should not require endoscopic biopsy or removal.