Is pelvic floor muscle contractility an important factor in anal incontinence?

Abstract

Objective: Pelvic floor muscle contractility (PFMC) may contribute to anal continence. The aim of this study was to assess the association between clinical and sonographic measures of PFMC and anal incontinence (AI) symptoms, after controlling for anal sphincter and levator ani muscle (LAM) trauma. Methods: This was a retrospective study of 1383 women assessed at a tertiary center between 2013 and 2016. All patients underwent an interview, including the St Mark's incontinence score (SMIS) in those who reported AI symptoms, a clinical examination, including assessment of PFMC using the modified Oxford scale (MOS), and four-dimensional translabial ultrasound (TLUS). Sonographic measures of PFMC, i.e. cranioventral shift of the bladder neck (BN) and reduction of anteroposterior (AP) diameter of the levator hiatus, were measured offline using ultrasound volumes obtained at rest and on maximum pelvic floor contraction. The reviewer was blinded to all clinical data. Results: Of the 1383 patients assessed during the study period, seven were excluded due to missing imaging data, leaving 1376 for analysis. Mean age of the participating women was 55 years and mean body mass index was 29 kg/m2. AI was reported by 221 (16.1%) women, with a mean SMIS of 11.8. Mean MOS grade was 2.3. On TLUS, mean BN cranioventral shift was 5.9 mm and mean AP diameter reduction was 8.1 mm. LAM avulsion and significant external anal sphincter (EAS) defect were diagnosed in 24.8% and 8.7% patients, respectively. On univariate analysis, sonographic measures of PFMC were not associated with AI. Lower MOS grade was associated with symptoms of AI; however, statistical significance was lost on multivariate analysis. Conclusion: Clinical and sonographic measures of PFMC were not significantly associated with AI symptoms after controlling for EAS and LAM trauma. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.