Preoperative staging of rectal carcinoma with MR imaging: surgical and histopathologic correlation.

Twenty-nine patients with rectal carcinoma were examined with magnetic resonance (MR) imaging at 1.0 T. In most patients a Helmholtz coil was used and a bowel distention obtained with a barium enema balloon tip. The MR findings were graded according to the modified Astler-Coller staging classification and correlated with the surgical or histopathologic results. Correct diagnosis was made in nine of the 12 patients with stage A and B1 tumors. Overestimation occurred in the other three patients, who had previously undergone radiation therapy or surgery. Local stage was correctly assessed in 11 patients with stage B2 carcinoma and in six patients with stage B3 tumors. Enlarged lymph nodes were detected in four of seven patients with nodes containing carcinoma. In two other patients with enlarged nodes, no carcinoma was identified at histologic examination. MR imaging may enable correct staging of local extent of rectal carcinoma, particularly in patients who have not previously undergone radiation therapy or surgery. However, evaluation of lymph nodes is less accurate.