Obstructive Defecation

What is obstructed defecation?
Obstructed defecation is a common cause of constipation or difficulty passing stool.

The lower part of the rectum is encircled by the pelvic floor muscles. These muscles are different than the anal sphincter muscles (the muscles that can be tightened to hold in a bowel movement). The pelvic floor muscles are not muscles that people can usually consciously control. During a bowel movement, the pelvic floor muscles relax to let stool pass, then contract again after the bowel movement is completed to prevent additional stool from passing. In some people these muscles fail to relax when it is time for a bowel movement, and the symptoms of obstructed defecation occur.

What are the symptoms of obstructed defecation?
Symptoms commonly reported by persons with obstructed defecation include:

  • feeling like stool is “right there” (just inside the anus) but being unable to have a bowel movement
  • needing to change position or apply pressure around the anal opening to have a bowel movement
  • needing to strain excessively to have a bowel movement
  • passing only small amounts of stool or oddly-shaped stools
  • feeling pressure inside the rectum or like the rectum has not emptied completely after a bowel movement
  • needing to return to the bathroom soon after a bowel movement to have another bowel movement
  • seepage of stool after a bowel movement       

Why does obstructed defecation happen?
Sometimes, obstructed defecation can be triggered by a traumatic or painful occurrence in the anal area, such as an anal fissure or thrombosed hemorrhoid. Other times obstructed defecation can occur without an obvious cause.

How is obstructed defecation diagnosed?
It is usually best to start with a visit to a colon and rectal surgeon. The surgeon will ask you questions about your symptoms and perform a physical exam. Often, the diagnosis will be suspected after this visit, but usually testing at the Pelvic Floor Center® is performed to confirm the diagnosis. These tests may include:

  • Anal manometry and sensory testing, where a thin sensor is placed within the anus and used to measure the strength of the anal sphincter muscles
  • EMG, where sensors are used to see if the muscles of the pelvic floor are relaxing and contracting at the proper times
  • Defecography, where xrays are taken while a patient passes contrast material as if having a bowel movement. This determines whether the pelvic floor muscles are relaxing to allow a bowel movement to occur, and whether there are any other factors blocking the exit of stool

How is obstructed defecation treated?
If the pelvic floor muscles are found to not be coordinating well to allow a bowel movement, biofeedback is usually recommended. The biofeedback therapist will work with the patient to retrain the muscles to relax and contract at the proper times and empty the rectum of stool more effectively.