Anorectal Physiology Laboratory

Anorectal Physiology Laboratory

Anorectal Physiology Laboratory

Here, you can learn more about our Anorectal Physiology Laboratory service!

Bangkok-Phuket Colorectal Disease Institute is the first in the nation to offer international standard anorectal physiology testing including endorectal ultrasonography, endoanal ultrasonography, defecography (both conventional and ecchodefecography), anorectal manometry, pudendal nerve terminal motor latency (PNTML), anal sphincter electromyography (EMG), and biofeedback therapy. These sophisticated tests are essential for the best practice in treating colorectal-disease conditions.

Endorectal and Endoanal Ultrasonography

Anorectal ultrasound is ultrasonographic examination of the anus and the rectum. It is a painless, quick and simple out-patient tests which does not require any sedation during the procedures. The ultrasound probe is about the same size as a finger and is inserted into the anus, and occasionally rectal balloon is used. This tests is usually recommended to evaluate the patients who are complaining of

  • Fecal incontinence
  • Rectal prolapsed
  • Constipation
  • Obstructed defecation

Furthermore the test is also very useful for preoperative staging of anorectal cancer, anorectal abscess, and anorectal fistula. On order to study some fistulas, it may be necessary to use a diluted hydrogen peroxide contrast to better define the tract. In addition, anorectal ultrasound can be used to assess the extrarectal masses, and follow-up for recurrence of these diseases following treatment.

Anorectal manometry

Anorectal manometry is a test used to assess patients with constipation or fecal incontinence. This test performed to measure the pressures of the anal sphincter muscles, the sensation in the rectum, real compliance, and the neural reflexes that are needed for normal bowel movements.

Anorectal manometry is a safe, painless and low-risk procedure. Prior to the study, one or two Fleet® enemas are given. The patient then lies on his or her left side. A small, flexible tube, about the size of a thermometer, with a balloon at the end is inserted into the rectum. The catheter is connected to a machine that measures the pressure. During the test, the small balloon attached to the catheter may be inflated in the rectum to assess the normal reflex pathways. The nurse or technician may also ask the person to squeeze, relax, and push at various times.


Defecography is a radiological test that allows the doctor to visualize what occurs when you are emptying your rectum. Before the test, the anal canal is lubricated and a soft plastic tip is inserted through the anal canal into the rectum. The rectum and anal canal are filled with barium paste and the tip is removed. X-ray dye is also placed in the vagina. This test may be awkward but provides valuable information that will aid in diagnosing the problem. Defecography provides important information on how the rectum empties and if there are any structural abnormalties such as

  • Intussusception (falling inside itself ) of the rectum
  • Rectal prolapse (protrusion of the rectum)
  • Rectocele (bulging in the rectum)
  • Enterocele (falling of the bowels during evacuation)

Defecography is also used to gather more information about a patient’s condition and/or confirm the diagnosis of constipation, diarrhea, and Solitary Rectal Ulcer syndrome (SRU), obstructed defecation, and, anismus (inappropriate spasm of the anal sphincter).

Electromyography (EMG)

Anal sphincter electromyography (EMG) is performed using superficial electrodes placed around and within the anal canal. The patient is asked to relax, squeeze and push (as if having a bowel movement) at different times. The anal sphincter muscle (the muscle valve at the opening of the rectum) electrical activity is recorded and displayed on a computer screen.
Anal sphincter EMG confirms the proper muscle contractions during squeezing and muscle relaxation during pushing. This provides information as to whether the muscle is squeezing and relaxing properly as it should, which aids in a better understanding of what might be behind your defecation symptoms. In people who paradoxically contract the sphincter and pelvic floor muscles, the tracing of electrical activity increases, instead of decreasing, during bearing down to simulate a bowel movement (defecation). Normal anal EMG activity with low anal squeeze pressures on manometry may indicate a torn sphincter muscle that could be repaired.

Pudendal Nerve Terminal Motor Latency (PNTML)

Pudendal Nerve Terminal Motor Latency (PNTML) is the test evaluates the nerve that controls the anal sphincter muscle (pudendal nerve). Pudendal nerve latency is in fact the measurement of the time from stimulation of the pudendal nerve at the ischial spine to the response of the external anal sphincter. The doctor does a rectal exam with a small electrode located at the index finger. The nerve inside the rectum is then stimulated with a low electrical current. This should cause the sphincter muscle to contract. A computer measures how long it takes for the muscle to contract after the nerve is stimulated. Some people do not feel the stimulus. Others may feel it only slightly. It is not painful and takes only a few minutes to complete. It is useful as a diagnostic tool in fecal incontinence. It has also been used as a predictive factor in sphincteroplasty repairs.

Biofeedback Therapy

Bangkok Hospital Phuket is the only medical center in the region to provide biofeedback therapy using anal manometry and special exercises of the pelvic floor muscles which can strengthen the muscles and improve sensation. This technique can help treat fecal incontinence.

There are many causes of constipation, however in some patients with constipation, 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 biofeedback techniques using anal manometry.