[Anal sphincter function and recto-anal continence]

Recto-anal continence results from a complex interplay of motor, sensory and anatomical continence mechanisms. Accordingly, fecal incontinence may be due to motor defects, sensory defects, neurological defects, or defects of the reservoir function of the ano-rectum. In a study in 16 patients with fecal incontinence and 16 continent controls the question was examined, to which extent disturbances of the motor function of the internal and external anal sphincter contribute to the pathogenesis of fecal incontinence. Basal and squeeze anal sphincter pressures were not different in incontinent and continent patients. However, 8/16 incontinent patients showed no or only an insufficient increase of external anal sphincter function while squeezing. It is concluded that disturbances of the motor function of the anal sphincters contribute to fecal incontinence in only about one half of the patients. In addition, the pressure increase of the sphincters during squeezing is of more importance for recto-anal continence than the absolute height of the muscular force of the anal sphincters.