Normal ranges for anorectal manometry and sensation in women of reproductive age

To derive a range of normal values for anal sphincter resting and squeeze pressure, and anorectal sensation in healthy women without anorectal disease before and after their first childbirth.

Nulliparous women undergoing anal physiology testing in the third trimester of pregnancy and 12 weeks after delivery. All were asked to undergo anal manometry and anorectal electrosensation testing. Maximum resting pressure, maximum squeeze pressure and anal thresholds to electrical current were assessed at 1 cm intervals down the anal canal. Rectal electrosensitivity thresholds were assessed 10 cm from the anal verge.

A total of 286 women attended for antenatal investigations and 161 (56%) returned postpartum. The anal canal length was 3.9 +/- 0.6 cm antenatally and 3.9 +/- 0.6 cm postnatally. During pregnancy the 95% normal range for anal resting and squeeze pressures, anal and rectal sensation were 29-90 mmHg, 50-163 mmHg, 2-31 mA and 3-33 mA respectively. Post delivery the 95% normal ranges were 27-98 mmHg, 43-156, 2-12 mA and 0.1-34 mA respectively. Both antenatally and postnatally the manometry and sensitivity values were similar in women with and without bowel symptoms.

This study is the largest series of normative data for anal manometry, and anorectal sensation in women before and after their first delivery. The antenatal values can serve to represent ranges for nulliparous women and the postnatal values ranges in primiparous women.