Anorectal malformations: Role of MRI in preoperative evaluation

PURPOSE: To evaluate the spectrum of magnetic resonance imaging (MRI) findings in pediatric patients with anorectal malformation (ARM) and compare the accuracy of MRI and distal cologram (DC) findings using surgery as reference standard. MATERIALS AND METHODS: Thirty pediatric patients of age less than 14 years (19 boys and 11 girls) with ARM underwent preoperative MRI. MRI images were evaluated for the level of rectal pouch in relation to the pelvic floor, fistula, and development of sphincter muscle complex (SMC). Associated spinal and other anomalies in lumbar region and pelvis were also evaluated. DC was done in 26 patients who underwent colostomy. Ultrasound of abdomen and pelvis was also done for associated anomalies. RESULTS: Overall accuracy of MRI and DC to detect the exact level of rectal pouch including cloacal malformation was 93.33% and 76.9% respectively. MRI and DC could correctly identify presence or absence of fistula in 76.6% and 76.9% cases respectively. MRI and DC correctly identified the anatomy of fistula in 76% and 65% cases respectively. On MRI, correlation of development of levator ani and puborectalis with the level of rectal pouch as found on surgery was significant (P = 0.008; 0.024 respectively). Subjective assessment of sphincter muscle development on MRI correlated well with the surgical assessment [P = 0.019 and 0.016 for puborectalis and external anal sphincter (EAS) respectively]. Lumbosacral spine anomalies were present in 33.3% of patients and were most common in high type of ARM. Vesicoureteric reflux and renal agenesis were the most common renal and urinary tract anomalies and were present in 40% of cases. CONCLUSION: MRI allows reliable preoperative evaluation of ARM and should be considered as a complementary imaging modality for preoperative imaging in ARM.