Anal canal coronal-sagittal ratio: a novel parameter for diagnosing pelvic floor injury in 2-dimensional transanal ultrasound

Abstract

Purpose: Pelvic floor injury diagnosis using 3-dimensional (3D) pelvic floor ultrasound or magnetic resonance imaging is unfeasible in many clinics. We assessed the efficacy of a novel diagnostic parameter, the anal canal coronal-sagittal (CS) ratio, for pelvic floor injury on 2D transanal ultrasound. Methods: This retrospective study analyzed the data of 126 female patients who underwent 3D pelvic floor ultrasound (including 2D transanal ultrasound) at a pelvic floor center between August and December 2020. The anal canal CS ratio on 2D transanal ultrasound and pelvic floor avulsion injury measurements were recorded for all patients. Results: A cutoff anal canal CS ratio of 1.15 was obtained using receiver operating characteristic analysis (sensitivity, 0.820; specificity, 0.763; and area under the curve, 0.838). Patients were categorized into the anal canal CS ratio ≥1.15 and the anal canal CS ratio < 1.15 groups. Bilateral pelvic floor avulsion was more common in the anal canal CS ratio ≥1.15 group (n = 35, 56.5%), and the incidence of pelvic floor avulsion was significantly different between the 2 groups (P = 0.001). Existing parameters of pelvic floor injury, including minimal levator hiatus (P = 0.001), levator plate descent angle (P = 0.001), and levator ani deficiency score (P = 0.001), were statistically different between the 2 groups. Conclusion: The anal canal CS ratio was an efficient novel parameter that indirectly detected pelvic floor injury in 2D transanal ultrasound. It is a potential alternative indicator for pelvic floor injury on the widely popular 2D transanal ultrasound.