External Anal Sphincter Defects in Patients with Fecal Incontinence: Comparison of Endoanal MR Imaging and Endoanal US

Abstract

To prospectively compare in a multicenter study the agreement between endoanal magnetic resonance (MR) imaging and endoanal ultrasonography (US) in depicting external anal sphincter (EAS) defects in patients with fecal incontinence. The study was approved by the medical ethics committee of all participating centers. A total of 237 consenting patients (214 women, 23 men; mean age, 58.6 years +/- 13 [standard deviation]) with fecal incontinence were examined from 13 different hospitals by using endoanal MR imaging and endoanal US. Patients with an anterior EAS defect depicted on endoanal MR images and/or endoanal US scans underwent anal sphincter repair. Surgical findings were used as the reference standard in the determination of anterior EAS defects. The Cohen kappa statistic and McNemar test were used to calculate agreement and differences between diagnostic techniques. Agreement between endoanal MR imaging and endoanal US was fair for the depiction of sphincter defects (kappa = 0.24 [95% confidence interval: 0.12, 0.36]). At surgery, EAS defects were found in 31 (86%) of 36 patients. There was no significant difference between MR imaging and US in the depiction of sphincter defects (P = .23). Sensitivity and positive predictive value were 81% and 89%, respectively, for endoanal MR imaging and 90% and 85%, respectively, for endoanal US. In the selection of patients for anal sphincter repair, both endoanal MR imaging and endoanal US are sensitive tools for preoperative assessment, and both techniques can be used to depict surgically repairable anterior EAS defects.