Defecating proctography, fecogram, and defecography all refer to a study in which the rectum is filled with a semi-solid paste with a consistency of soft stool containing contrast. The individual sits on a commode within an x-ray machine and is then asked to relax, to squeeze, to tense the abdomen and to evacuate the material. X-ray films and video are taken during each phase. The study is then analyzed for anatomic defects such as internal or complete rectal prolapse, enterocele or rectocele, anorectal angles and function of the puborectalis muscle and emptying. This study is particularly useful when evaluating complaints of constipation and difficult evacuation.
Manometry tests the anal canal and provides information about the strength of the anal sphincter muscles. The test measures the pressures in the rectum and in the anal canal and is helpful in defining the strength or weakness of the anal muscles and the sensation and reflex activity of the rectum. It helps to identify the nature of anorectal disorders such as incontinence, constipation and pain. The test is performed with the individual lying comfortably on an examination table on his or her left side. The test takes about 30 minutes and is well tolerated by most people.
Balloon capacity and compliance
A balloon capacity and compliance test studies the function of the rectum and its ability to expand and contract. The test takes about 45 minutes and is performed with the individual on his or her left side on an examination table. An empty, soft, latex balloon attached to a thin plastic catheter is lubricated and gently placed through the anus into the rectum. The balloon is slowly filled with warm water while measurements of volume and pressure are recorded.
Balloon evacuation study
A balloon evacuation study tests pelvic floor relaxation and opening of the anal canal. It is useful in determining how easy or difficult it is to pass a bowel movement. A thin catheter with a small balloon is placed in the rectum. The balloon is gently blown up to different small volumes and the patient is asked to push the balloon out. The maximal volume balloon able to be evacuated is determined.
Pudendal nerve terminal motor latency
Pudendal nerve terminal motor latency tests the pudendal nerves, which are the main bundles of nerve fibers going to the anal sphincter muscles. These nerves may be injured by direct trauma, by age, by stretching during childbirth, or during prolonged straining during bowel movements.A specially designed probe with stimulating and recording electrodes is mounted on the physician's gloved finger which is then placed into the rectum. A very small current is used to stimulate the nerve through the rectal wall. The response of the muscle is recorded and the time from stimulation to response is calculated.
Electromyography (EMG) tests the electrical activity in the anal sphincter and pelvic floor muscles. The electrode reads the electrical activity produced by the muscles and amplifies it.
Ultrasound is an imaging technique that allows parts of the body beneath the skin to be "seen" without the use of radiation such as x-rays. Sound waves are beamed through the tissues, and the waves bounced back are read and displayed. Imaging of the rectum looks for lesions such as rectal polyps. Ultrasonography of the anal sphincters may be used to search for defects and injuries of these muscles.
Adapted from IFFGD Publication: Rectocele by Bruce A. Orkin, MD, Professor of Surgery; Director, Division of Colon and Rectal Surgery and Director, Colorectal Physiology Laboratory at the George Washington University in Washington, DC.