Relationship between symptoms and disordered continence mechanisms in women with idiopathic faecal incontinence

Abstract

Background and aims: Anal sphincter weakness and rectal sensory disturbances contribute to faecal incontinence (FI). Our aims were to investigate the relationship between symptoms, risk factors, and disordered anorectal and pelvic floor functions in FI.

Methods: In 52 women with "idiopathic" FI and 21 age matched asymptomatic women, we assessed symptoms by standardised questionnaire, anal pressures by manometry, anal sphincter appearance by endoanal ultrasound and magnetic resonance imaging (MRI), pelvic floor motion by dynamic MRI, and rectal compliance and sensation by a barostat.

Results: The prevalence of anal sphincter injury (by imaging), reduced anal resting pressure (35% of FI), and reduced squeeze pressures (73% of FI) was higher in FI compared with controls. Puborectalis atrophy (by MRI) was associated (p<0.05) with FI and with impaired anorectal motion during pelvic floor contraction. Volume and pressure thresholds for the desire to defecate were lower, indicating rectal hypersensitivity, in FI. The rectal volume at maximum tolerated pressure (that is, rectal capacity) was reduced in 25% of FI; this volume was associated with the symptom of urge FI (p<0.01) and rectal hypersensitivity (p = 0.02). A combination of predictors (age, body mass index, symptoms, obstetric history, and anal sphincter appearance) explained a substantial proportion of the interindividual variation in anal squeeze pressure (45%) and rectal capacity (35%).

Conclusions: Idiopathic FI in women is a multifactorial disorder resulting from one or more of the following: a disordered pelvic barrier (anal sphincters and puborectalis), or rectal capacity or sensation.

Figure 1

Endoanal fast spin echo T2 weighted (A) and spin echo T1 weighted (B) magnetic resonance (MR) images demonstrated marked atrophy of the external anal sphincter (arrowheads) in a 75 year old incontinent patient, making the internal anal longitudinal muscle prominent (black arrows). Corresponding endoanal ultrasound images (C) identified patchy thinning of the internal sphincter, also seen on the MR images (white arrows), but not external sphincter atrophy.

Figure 2

Average anal resting (A) and squeeze (B) pressures in controls and faecal incontinence. The shaded area reflects the 5th–95th percentile range of values for controls; 35% and 73% of patients had reduced resting and squeeze anal pressures, respectively.

Figure 3

Endoanal magnetic resonance (MR) images (A, B) in an 88 year old incontinent patient demonstrated a small tear in the anterior external anal sphincter (white arrows) and tear and atrophy of the right puborectalis (white arrowheads). Dynamic MR proctography images obtained during defecation in the coronal (C) and mid sagittal planes (D) demonstrated an anterior and lateral rectocele (large white arrows), corresponding to the sphincter and puborectalis abnormalities, in addition to a large cystocele (small white arrows).

Figure 4

Rectal compliance (pressure at half maximal volume, A) and rectal capacity (maximum volume during compliance curve, B) in faecal incontinence (FI). Compared with normal values (that is, 5th–95th confidence interval) depicted by the shaded area, rectal compliance was normal, reduced (that is, high Pr_half), or increased (that is, low Pr_half) in FI. Rectal capacity, as measured by balloon volume at maximum tolerated pressure during the rectal compliance curve, was also reduced in 25% of incontinent patients.

Figure 5

Relationship between symptoms and rectal compliance (A) and rectal compliance versus hypersensitivity (B) in faecal incontinence (FI). Reduced rectal capacity was associated with urge FI and with rectal hypersensitivity during rectal balloon distension.

Figure 6

Receiver operating characteristic curves demonstrating incremental utility of comprehensive anorectal function assessments for discriminating between controls and faecal incontinence. The proportion of the differences explained by the factors is indicated as a percentage in parentheses. Obstetric-gynaecological (ObGyn) variables included the number of forceps deliveries, number of vaginal deliveries associated with episiotomy, and hysterectomy status. Anal sphincter morphology was graded as normal or abnormal (that is, tear, scar, atrophy, or combination of these abnormalities). Pelvic floor motion was assessed by anorectal angle change during evacuation. BMI, body mass index.