Correlation between magnetic resonance imaging findings after posterior sagittal anorectoplasty for anorectal malformations and the clinical outcome: Preliminary report.

BACKGROUND/PURPOSE: To assess the anatomical results after posterior sagittal anorectoplasty (PSARP) by magnetic resonance imaging (MRI) and to evaluate the correlation of these findings with clinical outcomes.

METHODS: Patients followed-up at our center after PSARP, being at least 6year old, with neither evidence of sacral abnormalities nor spinal dysraphisms were prospectively included. Complex ARMs were excluded. MRI was performed on a 1.5T unit. T1- and T2-weighted sequences were acquired, in orthogonal planes, according to the anal canal orientation. The degree of anorectal centering in the muscle complex (DARC), the pelvic floor symmetry, the rectal maximum diameter, the fat tissue interposition, and the presence of fibrosis were evaluated. A clinical questionnaire (Rintala score) was filled in by the parents. MRI findings were compared to the clinical outcomes assessed by the Rintala score. For statistical analysis the Spearman rho correlation coefficient was calculated and the Wilcoxon rank-sum test was performed.

RESULTS: We recruited 11 patients (mean age 12years, range 6-19) with MRI. DARC (range 252-360°) was strongly correlated with the degree of fecal incontinence (rho=0.70), mildly with the ability to hold back defecation (rho=0.58), constipation (rho=0.46) and total Rintala score (rho=0.41). Pelvic floor symmetry correlated with the frequency of defecation (rho=0.58). Rectal maximum diameter negatively correlated with the ability to feel the urge to defecate (rho=-0.60). Patients with fibrosis were slightly more constipated (p=0.056) and presented more social impairment (p=0.04). Fat tissue interposition had no correlation with the clinical outcome.

CONCLUSIONS: Thanks to soft tissue definition, multiplanar imaging, and lack of ionizing radiation, MRI is a valuable tool in the postoperative anatomical evaluation of patients with ARM. Our preliminary results show that abnormal anatomical findings can correlate to a nonoptimal functional outcome, thus helping in understanding the clinical course. The degree of anorectal centering in the muscle complex (DARC) seems to have the better correlation with the outcome, especially in terms of fecal continence.

TYPE OF STUDY: Prognosis study.

LEVEL OF EVIDENCE: level IV.