Background and aims: Anal sphincter weakness and rectal sensory disturbances c ontribute to faecal incontinence (FI). Our aims were to investigate the relation ship between sym- ptoms,risk factors, and disordered anorectal and pelvic floor functions in FI. Methods: In 52 women with “idiopa- thic" FI and 21 age matched asymptomatic women, we assessed symptoms by standa rdised questionnaire, anal pr- essures by manometry, anal sphincter appearance by endoanal ultrasound and mag netic resonance imaging (MRI), pelvic floor motion by dynamic MRI,and rectal com pliance and sensation by a barostat. Results: The prevalence of anal sphincter i njury (by imaging), reduced anal resting pressure (35%of FI), and reduced squee ze pressures(73%of FI) was higher in FI compared with controls. Puborectalis at rophy (by MRI) was associated (p<0.05) with FI and with impaired anorectal motio n during pelvic floor contraction.Volume and pressure thresholds for the desire to defecate were lower, indicating rectal hypersensitivity, in FI. The rectal vo lume 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 squ eeze pressure (45%) and rectal capacity (35%). Conclusions:Idiopathic FI in wo men is a multifactorial disorder resulting fromone ormore of the following: a di sordered pelvic barrier (anal sphincters and puborectalis), or rectal capacity o r sensation.
