The sacral ratio (SR) was proposed by Alberto Peña in 1995 as a reliable tool to evaluate sacral development in anorectal malformations (ARM). The SR is obtained by comparing sacrum size with fixed bony parameters of the pelvis. In previous studies, the average normal SR was calculated to be 0.74 for the anteroposterior view (APSR) and 0.77 for the lateral view (LSR).
