Lateral distant view for improved accuracy in locating rectal tumors.

The lateral distant view of the rectum is proposed for more precise identification of sites of rectal tumors for preoperative planning and to increase the number of sphincter-saving operations. In a prospective study of 39 patients with rectal tumors, radiologic and rectoscopic measurements of tumor levels were compared with each other and with the actual tumor site. Radiologic measurement on the lateral distant view showed that tumors usually are located much higher (2-11 cm) than is suggested by rectoscopic evaluation. Unlike rectoscopy, the lateral distant view also can be used for measuring the length of the anal canal. This measurement is important for evaluating the distance between the tumor and the inner end of the anal canal and reflects the width of a possibly tumor-free margin. Sphincter-saving operations could be predicted much better by the lateral distant view than by rectoscopy.