PURPOSE:The ability of endorectal ultrasonography (EU) to detect the presence of a malignant focus within rectal villous adenomas was studied.METHODS:Clinical charts were reviewed of 62 consecutive patients undergoing EU of rectal villous adenomas, in whom Histologic confirmation was available.RESULTS:Twelve lesions were found to contain cancer, of which only two demonstrated clinical signs of induration. Positive predictive value of EU for detecting a malignant focus was 66.7 percent, negative predictive value was 88.7 percent, sensitivity was 50 percent, and specificity was 94 percent. There was moderate overall agreement between pathologic and ultrasound staging (kappa statistic, 0.48). When an optimal image was obtained, all cancers that penetrated the submucosa were detected. Sensitivity of the technique was compromised in some large exophytic lesions and those at the level of the anal sphincter because of artefacts produced in the ultrasonographic image.CONCLUSION:A clear EU image can detect a malignant focus within a villous adenoma and direct the surgeon to the appropriate plane of surgical resection. In lesions with an ambiguous image, a malignancy cannot be excluded.