Changes in anal anatomy following vaginal delivery revealed by anal endosonography

Objective To investigate changes in anal canal anatomy following vaginal de livery in women without apparent sphincter injury. Prospective controlled o bservational study. Design Setting District general hospital. Population Consecutive parous and nulliparous women attending a gynaecology outpatient clinic. Methods All women were examined using anal endosonography, and parous subje cts without apparent sphincter injury compared with age-matched nulliparous controls to determine any differences in general anal canal morphology. Main outcome measures individual anal canal components were measured at def ined levels and subjects compared with controls. Results Twenty-one of 54 parous women had no anal sphincter scar. Compared with nulliparous women, they had significant anterior sphincter thinning (m ean 3.7 mm vs 4.6 mm, P < 0.01) in association with lateral external sphinc ter thickening (mean 7.0 mm vs 4.4 mm, P < 0.01), and longitudinal muscle t hickening (mean 2.8 mm vs 2.1 mm, P < 0.01). Conclusions Specific changes in anal morphology have been demonstrated foll owing vaginal delivery in women without apparent sphincter injury.