Transperineal sonography of the anal sphincter complex in neonates and infants: differentiation of anteriorly displaced anus from low-type imperforate anus with perineal fistula.

PURPOSE: To evaluate the usefulness of transperineal sonography of the anal sphincter complex for differentiating between an anteriorly displaced anus, which is a normal anatomical variant, and a low-type imperforate anus with perineal fistula, which is a pathological developmental abnormality requiring surgical repair.
MATERIALS AND METHODS: Transperineal sonography was performed with a 13-MHz linear-array transducer on 8 infants (1 day-5.3 months old) who were considered on clinical grounds to have an anteriorly displaced anus and on 9 infants (0-8 months old) with a low-type imperforate anus and perineal fistula confirmed at surgery. The anal sphincter complex was identified and the relationship between the anal canal and the anal sphincter complex was evaluated.
RESULTS: Transperineal sonography was feasible for all children without any specific preparation. An anal canal running within an intact sphincter complex was identified in all infants with an anteriorly displaced anus (n = 8). In 8 of 9 infants with a low-type imperforate anus, a perineal fistula running outside the anal sphincter complex was correctly diagnosed by transperineal sonography. In one infant with a low-type imperforate anus, transperineal sonography revealed a deficient anal sphincter complex.
CONCLUSION: Transperineal sonography appears to be a useful non-invasive imaging technique for assessing congenital anorectal abnormalities in neonates and infants, allowing the surgeon to select infants who would benefit from surgical repair.