Defecographic functional evaluation of rectal akinesia

Excerpt

Defecation is a complex and still incompletely understood phenomenon related to several integrated mechanisms. However, improvements over the past few years in our understanding of the process of defecation, along with the increasing use of radiological and anorectal physiology studies, have led to improved treatment results. Segmental and propagated contractions deliver colonic content into the rectum, where sensory mechanisms relay the sense of rectal filling sensation, stimulating rectal emptying. As stool passes through the colon, it is stored in the sigmoid colon until a mass movement empties it into the rectum. Rectosigmoid contractions develop an expulsive force vector directed toward the rectum and the anal canal. A vector is a mathematical representation of a magnitude of force and the direction in which the force is applied. The movement of stool through the colon and rectum can be analyzed by examining the pressure vectors that act upon the stool. When the concept of vector analysis is applied to bowel continence, two major categories of opposing forces appear. Propulsive forces (peristalsis, Valsalva, gravity) are those factors with a pressure vector that would result in the elimination of the stool from the body. Resistive forces are factors that slow or prevent elimination of stools from the body. Resistive forces could be defined as active (primary muscles: puborectalis, internal and external anal sphincter) or passive (including strictures, angulation of the bowel, decreased compliance, poor fixation or the rectosigmoid colon). …