Ultrasound in preoperative staging of rectal tumours.

A dynamic ultrasound sector scanner with 5.0 and 7.5 MHz transducers was used for examination of resected bowel specimens with rectal carcinoma. Pathologic structures, i.e. tumour extension into or beyond the bowel wall, and perirectal lymph nodes, were marked. Corresponding parts of the tissue were embedded in paraffin and a detailed comparison between the findings at ultrasound and those in the histopathological sections was made. There was a good accordance between the histopathologic and ultrasonic findings which makes it possible to perform an exact preoperative staging of rectal carcinomas with ultrasound. Twenty patients with primary tumours of the rectum preoperatively underwent ultrasonography with a prototype transrectal probe with the same type of crystals and frequencies. In the 14 cases, however, where ultrasound findings could be compared with the histopathologic findings only six (43%) were correctly staged at ultrasonography. Certain difficulties were encountered in the preoperative examinations with a rigid probe as used in this study.