Functional ultrasound of the anal canal. The effect of pregnancy and childbirth

Abstract

This thesis is concerned with functional three-dimensional ultrasound of the anal canal. Comparing acquisitions assessed with endoanal- and transvaginal transducers, the transvaginal transducer turned out to be as good as the endovaginal transducer. In addition, the curvatures, position and dimensions of the undisturbed anatomical structures in the anal canal, including the anal mucosa, could be described using the transvaginal acquisitions. The transvaginal technique provided information of how the curvatures, positions and dimensions changed during voluntary squeeze of the pelvic floor. The anal mucosa constitutes 40 % of the structures in the anal canal. Voluntary squeeze caused a distorted mucosa at the ano-rectal junction, increased bowel bend, an increased angle between the anal canal and vagina, and elongation of the canal. These observations could not be studied in acquisitions assessed with the endoanal transducer, which straightened and moved the anal mucosa away during application. Pregnancy affects anal continence, but the natural development of the anal canal during pregnancy and childbirth is not known. The impact of pregnancy was an elongation of the canal and a 20% increase in volume of the anal sphincters and anal mucosa. Much of the effects of voluntary squeeze were maintained.