Anorectal Manometry: Rectal Ultrasound

Medically reviewed by: Gary H. Hoffman, MD

Anal manometry, defacography, pudendal nerve testing and anal or rectal ultrasound are tests that are utilized to study a number of different conditions, including constipation and fecal incontinence, and are also used to study more severe issues such as anal sphincter disruption and tumors of the anorectum.

Of all gastrointestinal complaints among older adults, constipation is the most common.  60% of elderly outpatients report frequent laxative use. Constipation is medically defined as a decrease in stool frequency to less than three bowel movements per week.

Symptoms of Constipation include:

  • Difficulty or straining when passing feces
  • Hardness of stool
  • Feeling of incomplete bowel evacuation
  • Fecal soiling

Incontinence is less prevalent than constipation, affecting roughly 5% of the general population, and is most common in patients over the age of 65.  Incontinence occurs when there is uncontrollable evacuation of rectal contents.  The leading causes of fecal incontinence among elderly patients include:

  • Impairment of the anal sphincter and puborectal muscle
  • Decreased rectal sensation
  • Fecal impaction
  • Decrease in rectal reservoir capacity
  • Medication related incontinence

Anorectal Manometry

This procedure is a recommended form of evaluation for patients suffering from constipation, fecal incontinence, and injuries to the anal sphincters or a combination of any of these. Your physician may use anorectal manometry to measure the expulsion pressures in the rectum and the constricting abilities or pressures of the anal sphincters.  The sphincters are a set of two muscles, the internal anal sphincter and external anal sphincter.  They help regulate the timing of the acceptable and proper passage of bowel movements. If the anal sphincter muscles tighten or relax at the wrong time, incontinence or constipation will occur.

Anorectal manometry is typically painless and takes about 45 minutes. A small, flexible tube about the size of a thermometer is inserted within the rectum and measures the pressure of the anal sphincters as the patient squeezes, relaxes and then pushes.

There are very few risks associated with this procedure. After this examination you will be able to drive yourself home and resume all normal activities.

Defacography and Sitzmark Testing.

Defacography is generally used to examine patients who experience chronic constipation to identify any possible structural or functional abnormalities of the rectum. This is an x-ray exam conducted using a fluoroscope to watch the movement of barium in the rectum.

During the exam you will be asked to lie on your left side, and approximately 400 cc of barium paste will be inserted gently into your rectum. Barium is a thick paste with a consistency that is close to that of stool.

A fluoroscope is then used to capture internal images of the rectum as the patient is instructed to rest, hold and finally push to evacuate the barium from the rectum. This examination typically takes about 15 minutes total. Side effects and risks associated with this procedure are rare, but do include slight discomfort and minimal exposure to radiation.

The results are useful in determining whether or not a patient has a correctable form of constipation.  Treatment can be in the form of medication or can be surgical, depending on each patient’s findings and diagnosis.

When there is a question as to how fast or how completely food is progressing through the gastrointestinal tract, a sitzmark test is performed.

The patient is asked to swallow a small capsule with metal rings that can be seen under x-ray.  Over the course of five days, x-rays are taken to assess the rate at which these rings pass into the bowel movement.  Depending on the results, treatment may be offered for patients with a delayed transit time.

The test is safe, involves a small amount of radiation and the metal rings pass safely through the system.

Pudendal Nerve Testing

The pudendal nerve innervates the external genitalia of both sexes, as well as sphincters for the bladder and the rectum.  Pudendal nerve pain is also referred to as pudendal neuralgia and is caused by the entrapment or pressure upon the pudendal nerve which is located within the pelvic region. The nerve may be injured during the vaginal delivery of childbirth.

Symptoms of pudendal neuralgia include:

  • Burning
  • Numbness
  • Twisting or Pinching
  • Constipation
  • Sexual dysfunction

During pudendal nerve testing, your physician will measure the amount of time it takes for stimulation of the pudendal nerve to reach the external anal sphincter.

Anal or Rectal Ultrasound

Anal ultrasound is used in the evaluation of anal tumors. Anal ultrasound can also be used to visualize the anal sphincters and look for any injuries or disruption to the sphincters.  Rectal ultrasound is similar to an anal ultrasound but looks higher into the rectum and is primarily used to evaluate rectal tumors.  When evaluating tumors, ultrasound images show the depth of invasion of the tumor (its thickness) and also searches for the presence of any involved or metastatic lymph nodes.

During this procedure your physician will insert an ultrasound probe into the anal canal or rectum to obtain pictures. Ultrasound examinations utilize harmless sound waves.

Ultrasound examinations have no harmful side effects and cause minimal discomfort to the patient during the procedure.

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