Norm of Rectal Motility Test (Rectal Manometry)
Adult: 40–120 mm Hg. Distention of the rectum produces relaxation of the internal sphincter and contraction of the external sphincter.
Usage of Rectal Motility Test (Rectal Manometry)
Assists in the diagnosis of colonic dilation, constipation, diarrhea, external sphincter disorders (hypothyroidism, myasthenia gravis, myotonic dystrophy, polymyositis), Hirschsprung's disease, incontinence, and internal sphincter disorders (scleroderma); detection of anal achalasia; and evaluation of intrinsic ganglionic innervation of the internal sphincter of the rectum.
Crohn's disease. Decreased anal squeeze pressure and/or rectal motility and/or rectal sensation: Hyperglycemia, irritable bowel syndrome, post anorectal repair or microscopic surgery, post irradiation of the prostate, multiple sclerosis, proctalgia fugax, severe idiopathic chronic constipation, and ulcerative colitis.
Description of Rectal Motility Test (Rectal Manometry)
This test measures the pressures within the rectum and provides an evaluation of the strength and function of the internal and external anal sphincters. The anal canal length is 5 cm, with a functional length of 3–5 cm. Functional length is determined by the extent of pressure generated by the involuntary internal and voluntary external anal sphincter muscles within the anal canal. Increasing rectal distention from filling produces progressive increasing electromechanical activity in the surrounding tissue accompanied by increasing proximal pressure and decreasing distal pressure along the rectal canal until the contents are expelled. This test is a more sensitive indicator of short segments of anal achalasia than barium enema. A small, thin, flexible balloon catheter with four sensing ports is introduced into the proximal portion of the rectum. The catheter is connected to three pressure transducers. Pressure readings of the rectum and sphincter are measured and recorded onto a graph or computer.
Professional Considerations of Rectal Motility Test (Rectal Manometry)
Consent form NOT required.
- The client should disrobe below the waist.
- If a large amount of stool is present, a Fleet enema is given, and the examination is performed 1 hour after rectal evacuation.
- a. The client is placed in the left lateral position.
- b. A small, thin, flexible balloon catheter with four sensing ports is introduced into the proximal portion of the rectum.
- c. The catheter is inserted 8–10 cm above the mucocutaneous level, with the balloon portion in the proximal portion of the rectum and the sensing ports in the anal canal.
- d. The catheter is connected to three pressure transducers.
- e. The rectum is distended with an inflated balloon for 7–12 seconds until resistance to balloon distention is demonstrated by passive movement of a syringe. Usually 30–50 mL of air is required and is dependent on the client's age, the balloon size, and rectal dilation capacity.
- f. The amount of air required for the client to feel resistance is recorded as the internal anal sphincter response.
- g. Air is withdrawn in 5- to 10-mL amounts until distention is no longer felt. This smallest volume reflects the threshold of rectal sensation. Most people have relaxation of the internal sphincter with a distention volume of 15 mL.
- h. The client is asked to squeeze the external sphincter tightly for 2 seconds and then relax.
- Anal canal pressures are measured at eight points, in 0.5- to 1.0-cm increments, with the highest resting and voluntary squeeze pressures recorded at each point.
- j. Pressure readings of the rectum and sphincters are recorded onto graph paper, or images are configured on a computer.
- k. The catheter is removed.
- a. The same procedure as that described previously for adults is used with the following changes: The catheter is inserted 5 cm above the mucocutaneous level, and the child may be sedated to prevent unnecessary movements and crying.
- Cleanse the anal area.
Client and Family Teaching
- Once home, call your doctor if rectal bleeding or discharge occurs.
Factors That Affect Results
- Rectal stool decreases pressure readings.
- Insufficient rectal distention results in decreased pressure readings.
- Improper placement of the anal balloon or equipment malfunction.
- Rectal manometry has not been demonstrated to be reliable in the newborn.
- To avoid bacterial growth, store the equipment tubing dry. To detect bacterial growth, perform regular water quality testing.