Effect of vaginal delivery and ageing on the anatomy of the female anal canal assessed by three-dimensional anorectal ultrasonography

Abstract

Aim:  The effect of vaginal delivery was assessed on ageing and the anatomy of the anal canal using three-dimensional anorectal ultrasonography to determine the interobserver reliability.

Method:  118 asymptomatic females without sphincter damage were grouped according to parity and mode of delivery. They were then stratified by age (≤50y vs. >50y). Group I consisted of 35 nulliparous females of mean age 36y [20] and 62 y [15], Group II:of multipara having ≥1 vaginal delivery [43] of mean age 43y [20] and 60y [23] and Group III having Caesarean section [40] of mean age of 41y [20] and 56y [20]. The groups were compared with regard to the length and thickness of the external anal sphincter, internal anal sphincter, posterior external sphincter and puborectalis in all quadrants and the anterior gap. Interobserver variability was assessed.

Results:  In women having vaginal delivery the length of the anterior external sphincter was shorter (p=0.0004) and the gap was longer (p=0.0306). The external sphincter tended to be thinner in individuals having vaginal delivery(p=0.0677) and in those in subjects over 50y having had a vaginal delivery (p=0.0164). In nulliparous women, the internal sphincter was thicker in subjects over 50y (p=0.0229). Intraclass correlation coefficient was in the range 0.755–0.916 for sphincter muscle and gap length and 0.446–0.769 for muscle thickness.

Conclusion:  Vaginal delivery was associated with a shorter anterior external sphincter, a longer gap and thinner anterior external sphincter in asymptomatic females. Age was correlated with sphincter thickness and nulliparous women >50 years had a thicker internal sphincter. Three-dimensional ultrasound was found to be a reliable method for measuring anal structures.

© 2012 The Authors Colorectal Disease © 2012 The Association of Coloproctology of Great Britain and Ireland