Sonographic determination of the type in imperforate anus: Infracoccygeal approach

Technique of infracoccygeal approach. We developed an infracoccygeal approach with transperineal US to identify the anal sphincter complex and levator ani muscle, and to determine the type in patients with imperforate anus. We modified the transperineal US technique to use infracoccygeal approach to obtain transverse images. The babies were placed in the supine position, both legs were drawn up to the chest, and the buttocks were accordingly lifted up. The approach site for infracoccygeal US was just inferior to the coccyx and posterior to the anus. Scanning was performed to obtain transverse images of the anorectal area. US images were rotated vertically to correspond to the usual orientation on computed tomographic or MR images. Infracoccygeal US revealed the internal anal sphincter(IAS) and external anal sphincter(EAS) in the lower part of anal canal and the puborectal muscle in the upper part of anorectal region.