Staging rectal cancer by MR and CT.

Sixteen patients with known rectal cancer were evaluated and staged with CT and MR, and at surgery. Detailed evaluation of the pathologic specimens was performed and correlated with CT and MR to determine the accuracy of staging. Most of the cases were advanced stages, and both CT and MR were equally effective in staging. Prone positioning using an air-distension technique was equally important for CT and MR examinations. Because of a positive contrast material (iodine), adequate CT examinations could be performed without prior bowel preparation; however, bowel cleansing was necessary for MR examinations. Both techniques could identify the primary tumor and invasion into perirectal fat and local organs. Neither CT nor MR were able to assess the extent of bowel-wall infiltration or tumor spread to normal size perirectal lymph nodes.