PREOPERATIVE MRI OF ANORECTAL ANOMALIES IN THE NEWBORN PERIOD

Nine infants (six boys, three girls) with anorectal anomalies were exa mined in the immediate newborn period, prior to corrective surgery, wi th MRI. Three high, one intermediate and five low anomalies were found at MRI - one patient with a ''low'' lesion was subsequently found at surgery 2 months later to have a high anorectal anomaly, This infant h ad passed meconium per urethram soon after the MRI study, prompting th e need for a protective colostomy and stressing the importance of a th orough clinical examination of babies with anorectal malformations. Th e MRI results and findings at surgery were in agreement in all other p atients (n = 8). Hydronephrosis was evident in two and renal agenesis in one patient. Sacrococcygeal hypoplasia was found in two and two hem ivertebrae in one infant. No spinal cord lesion was identified. One fi stula was evident on MRI but four were later found at surgery. Uniform ly hyperintense T1 signal meconium was seen in all nine newborns, allo wing for easy differentiation of rectal contents from rectal wall and the adjacent musculature. MRI can provide useful information regarding the development of the puborectal and external anal sphincter muscles , can help guide the pull-through procedure and help predict future co ntinence pre-operatively in the newborn period.