[Computed tomography vs. magnetic resonance in the diagnosis of anorectal anomalies]

Anorectal malformations include a variety of anatomical anomalies which are often difficult to assess. Thirty-four patients (age range: 1 month-19 years) were studied over a 4-year period, 14 of them preoperatively and 20 postoperatively. In addition to inverted lateral plain films, a barred Iopamiro enema was performed in 13 of 14 cases by a Foley's catheter via colostomy. Endocolic pressure could thus be increased, which allowed the detection of rectal fistulas in 11 of 13 cases. Preoperative CT was performed in 9 cases, and MRI in 5. Both CT and axial MR scans provided accurate images of sphincteric muscles: they were well developed in 7 patients and poorly developed in 6; in 1 case the muscles were not identified. Sagittal MR scans only demonstrated the distance between blind pouch and perineum. Sagittal MRI also provided images of the spine (1 patient exhibited tethered cord). In the postoperative management, except for severe sacral anomalies, miscentered puborectal muscle and hypoplastic musculature were observed as the most frequent causes of fecal incontinence in patients treated with abdomino-perineal pull-through of the colon. To select the cases who needed reoperation, most frequently secondary PSARP, 17 patients were studied by CT and 7 by MRI; both techniques were employed in 4 cases. In 6 patients good development of sphincteric musculature and neo-anorectum correctly positioned within were observed. In 4 cases the neo-anorectum was correctly positioned, but sphincteric muscles were too hypoplastic to allow good continence; in 10 patients with incontinence, the neo-anorectum was seen outside sphincteric musculature: in 2 cases the latter was well developed (1 patient had had severe surgical damage to levator ani), while in 8 it appeared to be poorly developed. In our experience, postoperative CT allowed a correct evaluation to be made, whereas MRI failed to yield additional information.