Defecography uses an X-ray to look at the shape and position of the rectum as it empties. The anal canal is lubricated and a soft plastic tip is inserted through the anal canal into the rectum. The rectum and anal canal are filled with barium paste and the tip is removed.
X-ray dye is placed in the urinary bladder and the vagina. The person drinks barium about one hour before the test so the small intestine shows up. This way everything in the pelvis can be seen when the person strains.
The person sits on a toilet-like seat, called a defecography chair, which is attached to the X-ray table. The table is tilted into the upright position. The person puts their elbows on their knees. The person is asked to squeeze, to push and to empty the rectum. The X-ray of these maneuvers is recorded on videotape.
Defecography shows the rectum as it empties. Defecography reveals rectoceles and signs of rectal descent. In women with rectal descent, there is more rectal length down in the bottom three inches of the pelvis.
A normal rectum should empty in just a few seconds. In rectal descent it may take 30, 60 or even 90 seconds to empty, and the rectum may not empty completely. The lower end of the rectum may close before the upper rectum is empty (flap valving).
People with a tight internal anal sphincter have a big bowl-shaped rectum that empties slowly through a narrow, short anal opening that never opens up.
People with non-relaxing puborectalis muscles have rectums that do not empty because the pelvic floor muscles do not relax.
Defecography findings of rectal descent are:
- Horizontal rectum during push
- Delayed or incomplete rectal emptying
- Delayed or incomplete rectocele emptying
- Rectum protruding into anal canal
- Long rectum in the bottom three inches of the pelvis