What Is Anorectal Manometry?
Anorectal manometry is a non-invasive diagnostic test that evaluates how well the muscles, nerves, and reflexes in the lower bowel are working. Specifically, it examines the anorectal sphincter — the group of muscles surrounding the rectum and anus — which are responsible for controlling when and how stool is released from the body.
Who May Need Anorectal Manometry?
Your doctor may recommend this test if you have ongoing or unexplained problems with bowel control. A normal bowel movement relies on the synchronized action of specialized muscles and nerves: the sphincter must tighten to hold stool until you are ready, and then relax fully when you push. When any part of this coordination breaks down, problems like leakage or difficulty passing stool arise.
Anorectal manometry is used to evaluate, diagnose, or guide treatment for the following conditions:
Fecal Incontinence (Stool Leakage)
When the anal sphincter muscles are too weak, damaged, or fail to contract quickly enough, stool can leak before you can reach a toilet. Manometry quantifies sphincter weakness and guides decisions about biofeedback therapy, sphincter repair, or other interventions.
Chronic Constipation
When you bear down to pass stool, the sphincter should relax. In pelvic floor dyssynergia (also called anismus), the sphincter paradoxically tightens instead, creating a functional obstruction. Manometry is the key test to identify this treatable pattern.
Hirschsprung's Disease
A congenital condition where nerve cells are absent from a segment of the large intestine, preventing normal muscle relaxation. Anorectal manometry detects the absence of the rectoanal inhibitory reflex (RAIR), which is a hallmark sign of this disease — especially useful in newborns and children.
Irritable Bowel Syndrome (IBS)
IBS often involves altered rectal sensitivity — the rectum may sense stool urgency at much lower volumes than normal (hypersensitivity) or require much higher filling before any urge is felt (hyposensitivity). Manometry helps characterize these sensory abnormalities.
Anorectal Malformations or Injuries
Birth defects affecting the anus or rectum, or injuries from surgery, trauma, or childbirth, can damage nearby muscles and nerves. Manometry provides a baseline map of remaining function and helps determine whether surgical or non-surgical repair is the best path forward.
Rectal Cancer — Post-Treatment Evaluation
Surgery, radiation, or other treatments for rectal cancer can affect the function of the anal and rectal muscles. Anorectal manometry is used to assess bowel function after treatment and to guide rehabilitation strategies.
Manometry can also be combined with a 24-hour pH impedance test to diagnose gastroesophageal reflux disease (GERD). In this context, manometry determines the precise location in the esophagus where the pH probe should be placed for maximum accuracy.
Equipment Used in Anorectal Manometry
Pressure-Sensing Catheter
A thin, flexible, lubricated tube — roughly the diameter of a thermometer — with a small deflated balloon at its tip. Inserted gently into the rectum.
Balloon Inflation Device
A handheld syringe or pneumatic pump connected to the catheter that lets the technician precisely inflate and deflate the rectal balloon with air.
Recording Software
Computer software that receives continuous pressure signals from the catheter sensors and displays them as real-time waveforms for the technician and gastroenterologist to analyze.
In high-resolution anorectal manometry (HR-ARM) — the modern version of the test used at specialized centers — the catheter contains multiple closely spaced sensors that simultaneously map pressure across the entire anal canal length, producing detailed pressure topography plots rather than single-point readings.
Latex allergy note: Some balloon catheters contain latex.
If you have a known latex allergy, inform the nurse or technician before the test so a latex-free catheter can be used.
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