Anal vector volume analysis complements endoanal ultrasonographic assessment of postpartum anal sphincter injury

Abstract

Background: The aim of this study was to determine the role of anal vector manometry in the assessment of postpartum anal sphincter injury and to establish the most suitable method of anal vector volume analysis for identifying significant external anal sphincter (EAS) injury in an at-risk parous population.

Methods: A total of 101 consecutive women with a history of instrumental or traumatic vaginal delivery was recruited. Anal ultrasonography and anal vector manometry were performed. Receiver-operator characteristic curves were used to determine the usefulness of anal manometry and anal vector volume analysis in the identification of significant EAS disruption (full thickness, more than one quadrant involved) detected by ultrasonography.

Results: Seventeen women had significant EAS disruption identified by anal ultrasonography. Anal vector manometry provided complementary functional information. Anal vector symmetry index (VSI), determined by analysis of mean maximum squeeze pressure, yielded 100 per cent sensitivity for significant EAS disruption, with a positive predictive value of 61 per cent.

Conclusion: Anal vector manometry complements endoanal ultrasonography. VSI, determined by means of the squeeze pressure profile, correlates best with significant EAS disruption identified at anal ultrasonography.