Computed tomography in carcinoma of the rectum.

A total of 11 cases of untreated carcinoma of the rectosigmoid colon and 56 cases of recurrent rectosigmoid carcinoma have been investigated by computed tomography. A tumor size of more than 2 cm in diameter is easily demonstrated within the rectosigmoid wall. Invasion of the pararectal fatty planes and the neighboring structures and organs is conclusively diagnosed when obliteration of the demarcating fat planes is demonstrated. Enlargement of the regional lymph nodes of more than 15 mm diameter indicates malignant metastatic spread. Local malignant recurrence following complete resection of the rectum is recognized when the tumor size has reached 2 cm or more. Fine-needle aspiration biopsy may be necessary to conclusively identify malignant tissue within the postoperative cavity.