Rectal involvement by prostatic carcinoma: barium enema findings.

A retrospective study was performed to determine the radiographic features of prostatic carcinoma invading the rectum on double-contrast barium enemas. In 11 such patients, these examinations revealed localized narrowing and/or speculation of the rectum (four cases); a smooth, extrinsic mass impression on the rectosigmoid colon (two cases); an umbilicated submucosal mass in the rectosigmoid colon (one case); and rectosigmoid narrowing with spiculated, pleated mucosal folds in the narrowed segment of bowel (four cases). Thus, most patients (64%) had localized involvement of the rectosigmoid colon with sparing of the distal rectum. The anatomic-pathologic basis for the localized spread of prostatic carcinoma to the rectosigmoid colon is illustrated on MR scans. Thus, prostatic carcinoma invading the rectum may be manifested on double-contrast barium enema by a spectrum of radiographic findings, and most patients have localized rectosigmoid involvement with sparing of the distal rectum.