Validity of Transperineal Ultrasound in Infants with Imperforate Anus

Optimal surgical management of the neonate with imperforate anus depends on accurate determination of the level of the rectal pouch. The use of ultrasound to determine the pouch level has been previously described, but has not become widely accepted. The goal of this study is to determine the validity of this measurement according to final surgical findings in patients with anorectal malformation. In a cross sectional study,23 children with imperfo-rated anus were evaluated by transperineal ultrasound with a 7.5 MHz sector transducer in the supine and lithotomic positions to determine the pouch level and pouch to perineum (P-P) distance. In all cases, the level of the distal pouch was confirmed by definitive surgery or distal colostogram. The agreement between sonography and surgery or colostogram as gold standard was obtained by weighted kappa test. In five children, the pouch to perineum (P-P) distance was less than 10mm. All of these low lesions were safely treated by a simple perineal anoplasty (minimal posterior sagittal anorectoplasty; i.e. minimal PSARP) and were confirmed as low type. Seven children had P-P distance of 10-15 mm. In the follow up definitive surgery, 5 cases were intermediate and two cases were high. Eleven children had a P-P distance of more than 15 mm, of which ten cases were high lesions and had colostomy at birth. During follow up, 8 cases underwent definitive surgery of PSARP and two of these high cases were confirmed by distal colostogram and one case was categorized as intermediate by definitive PSARP. Measure of agreement (Kappa) was calculated to be 0.791 (P = 0.001) Therefore, Ultrasound correctly predicted the level of the distal pouch in 20 of 23 patients. Transperineal ultrasound can be confidently used prior to surgical decision in children with imperforate anus in addition to physical exam.