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Anorectal Manometry with Paradoxical EMG

Anorectal manometry (ARM) with paradoxical EMG is performed to evaluate patients with constipation and/or fecal incontinence and is a basic study of anorectal function.  The anal and rectal area contain specialized muscles that are helpful in regulating the proper passage of bowel movements.  Anorectal manometry with paradoxical EMG will provide useful information regarding the pathophysiology of these disorders.  Anorectal manometry with paradoxical EMG studies anorectal pressures and muscle tone at rest, during sphincter muscle contraction, and during emulation of a bowel movement (push).  The test also provides important information about the coordination between the rectum and anal sphincter muscles.

  • Constipation is an acute or chronic condition in which bowel movements occur less often than usual or consist of hard, dry stools that are painful or difficult to pass.  Bowel habits vary, but an adult who has not had a bowel movement in three days or a child who has not had a bowel movement in four days is considered constipated.  In some patients the anal sphincter muscles do not relax appropriately when bearing down or pushing to have a bowel movement.  This abnormal muscle function may cause a functional type of obstruction.  Muscles that do not relax with bearing down can be retrained with pelvic muscle rehabilitation techniques.  Constipation is more common in women than in men and while this condition is rarely serious it can lead to:

  • Bowel Obstruction
  • Chronic Constipation
  • Hemorrhoids—a mass of dilated veins in swollen tissue around the anus
  • Hernia—a protrusion of an organ through a tear in the muscle wall
  • Irritable Bowel Syndrome (Spastic Colitis)—a condition characterized by alternating periods of diarrhea and constipation
  • Laxative Dependency

  • Fecal incontinence is the inability to control bowel movements, causing stool (feces) to leak unexpectedly from the rectum.  Fecal continence is maintained by the resting muscle tone and muscle reflex of the internal and external anal sphincters in conjunction with the muscles of the pelvic floor. Normally when the stool enters the rectum the anal sphincter muscles tighten to prevent the passage of stool at an inconvenient time.  Also called bowel incontinence, fecal incontinence ranges from an occasional leakage of stool while passing gas to a complete loss of bowel control.  There are many causes of fecal incontinence.  Weak anal sphincter muscles or poor sensation in the rectum can contribute to fecal incontinence.  If these abnormalities are present, they can be treated.  Pelvic muscle rehabilitation techniques in conjunction with special exercise of the pelvic floor muscles can strengthen the muscles and improve sensation.

  • EMG (Electromyography) is one of the principal techniques to evaluate the internal and external sphincters as well as the pelvic floor muscles.  Paradoxical EMG (Electromyography) is used to assess the role of the paradoxical puborectalis contraction during defecation.  This study is performed noninvasively by either using EMG (Electromyography) surface electrodes or a rectal sensor placed in the anal canal.  If using surface electrodes, the active electrodes are placed in a clock-like fashion around the perineum and the ground electrode on a convenient neutral area.  The patient is usually placed in the left lateral position.  To evaluate anal sphincter muscle activity, the patient is asked to:  1) Rest; 2) Squeeze and; 3) Push at different times.  The anal sphincter muscle activity is recorded and displayed on a computer screen. This paradigm confirms the proper muscle contractions during squeezing and muscle relaxation during pushing.  In patients who paradoxically contract the sphincter and pelvic floor muscles, the tracing of EMG (Electromyography) activity increases, instead of decreasing, during bearing down to simulate a bowel movement (defecation).  Normal EMG (Electromyography) accompanied by low anorectal manometry squeeze pressures may indicate a torn sphincter muscle that could be repaired.

  • Anorectal Manometry (ARM) evaluates a number of important parameters: 1) Maximum voluntary squeeze pressure in conjunction with rest/relax pressures; 2) Internal anal sphincter inhibitory reflex to rectal distension (RAIR); 3) Rectal volume sensory thresholds; 4) Sphincter length to include the high pressure zone (HPZ) and; 5) Defecation dynamics (balloon expulsion study).  As with the EMG study, the patient is placed in the left lateral position.  Bowel preparation is recommended.  A four channel manometry catheter with a compliant balloon at the end is inserted to 6cm for pressure monitoring and measurements are taken at every 1cm interval.

  • Maximum voluntary squeeze pressure is obtained by having the patient squeeze as hard as possible for 10-20 seconds and then repeat the squeeze once or twice with intervals of rest/relax at 10—20 seconds intervals for each 1cm of depth.
  • Internal anal sphincter inhibitor reflex to rectal distension (RAIR) is the relaxation of the proximal internal anal sphincter in response to rectal distension.  This is performed by inflating the compliant balloon through the rectal lumen and observing the resting anal pressure.  A drop in the resting anal pressure of at least 50% in one of the four channels of manometry is considered a positive reflex.
  • Rectal volume sensory thresholds or rectal sensation measurements consist of a progressive distension of the rectum by increasingly inflating the compliant balloon in conjunction with the patient’s feedback on rectal sensation.  This provides information on rectal capacity and the urge to defecate.  Rectal compliance reflects the capacity and ability to distend the rectum and is measured from the data obtained during the rectal volume sensory thresholds.
  • Defecation dynamics (balloon expulsion study) may be performed to simulate defecation once the maximum capacity of the rectal volume study is obtained.  The ability to expel the compliant balloon and/or the time needed to expel is recorded.  Prolonged balloon expulsion suggests a dysfunction in the anorectal area.

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