Can sacral development as a marker for caudal regression help identify associated urologic anomalies in patients with anorectal malformation?

Background And Aim: The sacral ratio (SR) is a well-established tool to quantify sacral development in patients with anorectal malformations (ARM) and can be used as a predictor of fecal continence. We hypothesized that a lower SR correlated with the presence of urologic and renal malformations.

Methods: We retrospectively reviewed the medical records of patients with ARM treated at our center from 2014 to 2016. We measured the lateral SR as a marker for sacral development and assessed the spine for the presence of tethered cord (TC). Urological and renal anomalies, including single kidney, hydronephrosis, hypospadias, vesicoureteral reflux (VUR), ectopic ureter, and penoscrotal transposition were assessed. Analysis of variance (ANOVA), t-tests, and multivariable linear regression were used to test for differences in SR with consideration of associated urologic malformations and tethered cord.

Results: 283 patients with ARM were included for analysis (156 females). The median age was 39months (10-90). Among these, 178 (55.6%) had 1 or more urologic malformations, and 81 (25.3%) had a TC. Hydronephrosis, high-grade VUR (3-5), solitary kidney, and tethered cord were significantly associated with lower SR (p<0.01). In multivariable regression models, the presence of urologic abnormalities remained significantly associated with lower a SR despite the presence or absence of TC (p<0.001).

Conclusion: SR is a potentially useful indicator of certain urologic anomalies including hydronephrosis, high grade VUR, and solitary kidney in patients with ARM. This association is independent of the presence of TC. A sacral ratio as a part of the VACTERL screening can help the surgeon identify which patients need closer urologic follow up.

Level Of Evidence: IV.