It is most conveniently diagnosed by a radiopaque-marker method that assesses mean colonic transit time. There are two commonly used variations of this method. The first method involves ingestion of 24 radiopaque markers in a soluble medication capsule on four successive days and plain abdominal radiography on day 5. Normally, there should be fewer than five markers remaining in the colon. In all patients with delayed colonic transit, the possibility of outlet obstruction to defecation or a pangastrointestinal motility disorder must be ruled out.
Treatment consists of increasing dietary bulk and giving osmotic and stimulant laxatives.
A careful clinical history is useful in identifying failure of evacuation and the need for digital disimpaction of the rectum or digital pressure on the posterior wall of the vagina to expel stool. Enemas may not be emptied. The rectal examination identifies an immobile perineum during the process of straining and a tight, unyielding puborectalis sling muscle abutting the rectum posteriorly that persists during attempts to evacuate. In rare instances, the anal sphincter itself is spastic or the entire perineum balloons or herniates down as a result of years of straining, which weakens the ligaments and muscles that normally support the pelvic floor and rectoanal angle. Occasionally, outlet obstruction is caused by an anatomic defect such as a rectocele or rectal internal mucosal prolapse.