Relationship of Anatomy and Function: External Anal Sphincter on Transperineal Ultrasound and Anal Incontinence

The aim of this study was to investigate the association of the anatomic integrity of the external anal sphincter (EAS) detected on transperineal ultrasound (TPUS) with symptoms of anal incontinence (AI) as measured by St Mark's Incontinence Score (SMIS) and the visual analog scale (VAS).

This is an observational, cross-sectional analysis of 486 women who presented to a tertiary urogynecological center between May 2013 and August 2014. They underwent a standardized interview and an examination that involved 3-dimensional/4-dimensional TPUS. The SMIS and VAS were administered if they answered positively to a question on AI. The association between defects of the EAS and symptoms of AI was evaluated using bivariate tests, as well as adjusting for pertinent covariates using multiple linear regression modeling.

Of the included patients, 17.1% reported AI, and 15.2% had significant EAS defects (≥4 slices) on TPUS imaging. A significant sonographic defect was diagnosed in 23% of women with AI versus 14% of those without (P = 0.033). Women with symptoms of AI were more likely to have a significant defect on TPUS (odds ratio, 1.878; 95% confidence interval, 1.05-3.37). No significant findings were seen when analyzing SMIS, its components, and VAS against sonographic EAS defects.

The symptom of AI is associated with significant EAS defects detected on TPUS. However, this study failed to show an association between significant EAS defects and the SMIS and VAS.