Faecal Incontinence: Obstetric Causality

Abstract

Introduction Faecal incontinence is more common in parous women who havehad a difficult vaginal delivery. However, the pathophysiology of the injuryresulting in faecal incontinence in such women is incompletely understood.This study therefore aimed to compare anal canal and pelvic floor parametersbetween continent and incontinent women and measure these duringpregnancy and after delivery in order to more fully understand the initial insult tothe pelvic floor.Methods Anal manometry and fatigue (using a water-filled microballoon) andpelvic floor strength and fatigue (using an air-filled vaginal probe connected to aPeritron) were measured in 30 primiparous women at booking, end ofpregnancy and 6 months post partum. Ten of these women also underwentmeasurement of pelvis size using ultrasound. A further 61 women, 39incontinent and 22 continent, also underwent these measurements in order tocompare pelvic floor parameters between continent and incontinent women.Results Voluntary contraction of the external anal sphincter (EAS) wassignificantly lower 11 weeks post partum than antenatal values (106.5 ± 43.6cmH2O antenatally vs 75.5 ± 45.6 cmH2O post partum, p < 0.001) but there wasno significant difference between antenatal values and those measured 6months post partum (p = 0.24). Anal fatigue rate was significantly slower 11weeks post partum (p = 0.001), but by six months post partum the difference isno longer significant (p = 0.053). Pelvic floor muscle (PFM) strength fell with ageand was significantly lower in incontinent women (8.97 ± 12.88 cmH2O) than incontinent women (27.17 ± 18.16 cmH2O; p < 0.001). PFM fatigue rate was alsosignificantly slower in incontinent women (p = 0.01). The PFM strength wassignificantly higher in nulliparous than parous women (p = 0.002) and fatiguerate was faster (p = 0.022). PFM strength (p = 0.006) and fatigue rate (p =0.004) were significantly lower six months post partum when compared withantenatal values. It was shown that pelvis size can be measured usingultrasound and was found to be repeatable, but inaccurate when compared withmagnetic resonance imaging. Insufficient numbers were studied to show aneffect on pelvic floor function.Conclusion Vaginal delivery causes impairment of EAS voluntary contractionwhich appears to have recovered by six months post partum. It also causesimpairment of PFM contraction which is persistent at six months post partum.The reduced PFM function seen post partum also occurs in incontinent women,adding to the evidence that childbirth causes the initial insult to the pelvic floorwhich results in faecal incontinence, either immediately or some years later.

Date of Award	1 Aug 2012
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Edward Kiff (Supervisor)