Magnetic Resonance (MR) Defecography

Magnetic resonance (MR) defecography is a noninvasive test that uses magnetic resonance imaging to obtain images at various stages of defecation to evaluate how well the pelvic muscles are working and provide insight into rectal function. It is used to help determine the cause of fecal incontinence, constipation, and other conditions such as pelvic organ prolapse that may interfere with a person's ability to pass stool.

What are some common uses of the procedure?

Physicians use MR defecography to:

• obtain information about how well the pelvic muscles are working during a bowel movement.
• provide insight into rectal function.
• determine the cause of accidental or involuntary bowel motion/passage of feces or the inability to control the passage of waste material from the body.
• determine the cause of constipation, or difficulty passing waste material from the body.
• diagnose and evaluate diseases affecting rectal function and pelvic floor disorders (also called pelvic floor dysfunction), such as hernia, pelvic organ prolapse or rectal prolapse, a condition where part or all of the rectum wall slides out of place.
• provide information for surgical and treatment planning.

• How is the procedure performed?

  MRI exams may be done on an outpatient basis.
  You will be asked to drink water during a period of 30 minutes prior to the exam. Your rectum will be filled with a soft substance that is similar to the consistency of feces and contains a contrast material. A towel will be placed underneath you to absorb any urine or feces that may leak out during the exam.
  If your exam is being performed in a traditional MRI unit, you will be positioned on a moveable examination table lying on your back with your knees bent. Straps and bolsters may be used to help you remain still and maintain the correct position during imaging. If your exam is being performed in an open MRI unit, you will be seated on an adjustable chair within the unit between two large magnets.
  A device that contains coils capable of sending and receiving radio waves will be strapped around your pelvis in a traditional MRI unit or placed on the seat beneath you in an open MRI unit.
  The examination will be performed by a radiologist working at a computer outside of the room.
  Images will be obtained as you contract your muscles as you would during a bowel movement including squeezing, straining and defecating. Images will also be taken while your muscles are relaxed. The technologist will give you instructions during the exam.
  The MR defecography exam typically includes two or more sets of images and is usually completed in 30 minutes to an hour.