Purpose: To assess the usefulness of infracoccygeal transperineal ultrasonography (US) in differentiation between high- and low-type imperforate anus.
Materials and methods: Infracoccygeal US was prospectively performed with a 7-10-MHz linear-array transducer prior to corrective surgery in 14 neonates with imperforate anus. The approach site was just inferior to the coccyx and posterior to the anus. Transverse images of the anorectal area were obtained. The puborectalis muscle was identified, and the relationship between the puborectalis muscle and the distal rectal pouch was evaluated. US findings were compared with surgical findings.
Results: In 10 neonates, a low-type imperforate anus was correctly diagnosed at infracoccygeal US. In those with low-type imperforate anus, the puborectalis muscle was seen as a hypoechoic U-shaped band (n = 10), and the distal rectal pouch passed through the puborectalis muscle (n = 10). In four neonates with high-type imperforate anus, the puborectalis muscle was not identified (n = 4).
Conclusion: Infracoccygeal transperineal US enables the determination of the type of imperforate anus.