The use of computerized tomography to evaluate anorectal anomalies.

Computerized tomography (CT) was applied to various types of anorectal anomalies to directly image the anal sphincters. In normal cases and low type anomalies, CT demonstrated clear images of the puborectal muscle and external sphincters. Among high type anomalies, the distribution of sphincter muscle in patients with rectovesical fistula is totally different from that seen in patients with rectourethral fistula. In the latter, the puborectal muscle is attached not only around urethra, but also around the distal part of the blind rectum; external sphincters are present as a mass beneath the perineum. In the rectovesical fistula, however, the puborectal muscle cannot be identified and the external sphincters exist only as a string-like structure. CT done postoperatively identified two different causes for incontinence. In one type, the pull-through colon missed the sphincteric musculature, and in the other, sphincters were markedly hypoplastic. CT, therefore, provides adequate imaging to determine the type of operation needed to correct the abnormality.