Anorectal manometry is a diagnostic procedure that evaluates the function of the muscles and nerves controlling bowel movements. It assesses the rectum and anus, providing detailed information on how these structures work together. This test helps medical professionals understand the physical mechanisms contributing to various bowel-related symptoms.
Why the Test is Performed
This test is often recommended for individuals experiencing chronic constipation, fecal incontinence, or other difficulties with bowel control. It identifies issues like weak or uncoordinated anal sphincter muscles, impaired rectal sensation, or problems with stool expulsion. For example, weak sphincter muscles can cause fecal incontinence, while muscles tightening instead of relaxing during a bowel movement can contribute to constipation. The test also evaluates muscle function after injury or surgery, or assesses conditions like Hirschsprung disease.
How the Procedure Works
Anorectal manometry involves inserting a thin, flexible catheter, roughly the size of a thermometer, into the rectum and anus. This catheter contains pressure sensors that record readings from different depths within the anal canal and rectum. A small, deflated balloon attached to the catheter’s tip can be inflated to assess rectal sensation and reflexes.
Resting pressure assesses the internal anal sphincter, while squeeze pressure evaluates the strength of the external anal sphincter when a patient voluntarily contracts these muscles. The technician may inflate the balloon inside the rectum to different sizes, asking the patient if they feel the urge to defecate, which assesses rectal sensation. Patients are also asked to perform actions like coughing, squeezing, relaxing, and pushing, allowing the device to record muscle responses and coordination. A balloon expulsion test, where the patient attempts to expel an inflated balloon, provides information on the ability to coordinate defecation.
Preparing for and Undergoing the Test
Preparation for anorectal manometry involves ensuring the rectum is clear. Patients are usually advised to use one or two enemas at home, with specific instructions provided by the healthcare provider. Patients may also be asked to refrain from eating solid food for several hours before the test, though regular medications can usually be taken with small sips of water.
During the procedure, the patient typically lies on their side with knees bent. A brief digital rectal examination might be performed before the lubricated catheter is gently inserted. The test usually takes about 30 minutes, and patients remain unsedated because their active cooperation is required for various maneuvers. Patients might experience mild pressure or the sensation of needing to have a bowel movement as the balloon is inflated or during specific actions. After the test, most individuals can resume their normal activities immediately, with any mild discomfort usually resolving quickly.
Understanding Your Results
The results of an anorectal manometry test are interpreted by a healthcare professional, often a gastroenterologist. The data from the pressure sensors and balloon tests provide a detailed profile of muscle strength, coordination, and nerve function. Normal findings indicate well-coordinated muscle contractions, appropriate relaxation, and typical rectal sensation.
Abnormal findings can point to various issues, such as weak sphincter muscles, impaired rectal sensation (where the rectum doesn’t adequately signal the need to defecate), or dyssynergic defecation, where muscles contract instead of relaxing during a bowel movement. These results are integrated with a patient’s symptoms and other clinical information to form a comprehensive diagnosis. The findings then guide the development of an individualized treatment plan, which might include biofeedback therapy or other interventions.