Anorectal Physiology Laboratory

The Department's Anorectal Physiology Laboratory offers a valuable service for patients and referring physicians. Located at University Medical Center, this fully-equipped facility enables our colorectal specialists to perform comprehensive anorectal physiology testing, and further distinguishes the quality of care in our colon and rectal surgery program.

Referring physicians are provided a complete, written, fully-interpreted report on the testing that has been performed on their patients. Upon request, a colon and rectal surgeon will also provide a consultation and recommendations.

Anorectal physiology is the study of the function of the anal sphincter mechanism, the anal canal, and the rectum. Indications for requesting physiologic tests include anal and urinary incontinence, pelvic floor descent, constipation that has not been responsive to conventional treatment, chronic anal infections, and anorectal pain. In addition, these tests may be used in the staging of anal and rectal tumors, as well as in the follow-up for cancer recurrence.

Our Anorectal Physiology Laboratory is equipped with state-of-the-art technology. It has advanced ultrasound imaging systems that are not widely available in Suffolk County. The anal manometry and pudendal nerve terminal motor latency testing, described below, is performed on the newest Medtronic Encompass diagnostic system.


The Anorectal Physiology Laboratory offers a range of diagnostic tests that provide important information about the function and anatomy of the anus and rectum. These studies typically take 5-15 minutes to complete. A description of each test follows, with attention to why the test is done, how it is accomplished, and what information is obtained:

Anal Manometry

Anal manometry measures the resting and squeeze pressures in the anal canal. Anorectal reflexes and sensation are tested during the same examination. A narrow, flexible tube is inserted into the anus and rectum. Once the tube is in place, a small balloon at the tip of the tube may be expanded. This test shows how tight the anal sphincter is during rest and squeeze. It also measures the sensitivity and function of the rectum. The test is usually done in cases of loss or bowel control or incontinence, certain types of constipation, and anal pain or spasm.

Pudendal Nerve Terminal Motor Latency Testing

Pudendal nerve terminal motor latency testing measures the delay between an electrical impulse and the muscle contraction. It assesses the functioning of the pudendal nerves, and is useful in evaluating patients with incontinence, constipation, and rectal prolapse. The procedure involves the placement of a gloved finger into the anus. On the glove is a stimulating electrode. Several electrical impulses are delivered and the nerve conduction is determined. Occasionally one may sense the impulse for a few seconds, but any discomfort is very mild.

Anal Ultrasonography

Anal ultrasonography (ultrasound) evaluates the structure of the sphincter muscle and surrounding tissue. Ultrasound is a very useful tool for imaging the anatomy of the internal and external anal sphincters. It is not an x-ray, so there is no radiation exposure. A narrow wand-like probe the size of an index finger is inserted into the anal canal and the rectum. This instrument, which is attached to a computer and video screen, emits sound waves. Using sound waves produced by the probe, images are captured on the screen.

The lab is equipped with the newest 3-D ultrasound technology, which provides 3-D reconstruction of the anal and rectal structures, and gives a more accurate assessment than 2-D ultrasound. Ultrasound may be used to visualize scar and tears in the sphincter muscles, abscess and fistula, and tumors or cysts.

Ultrasound-guided biopsy of suspicious lesions can be performed during this testing. The patient may feel vibration from the probe during the examination, but it should not cause any physical discomfort.

Rectal Ultrasonography

With rectal ultrasound, a rigid instrument is inserted gently into the rectum. The ultrasound probe, with a deflated balloon on the end, is inserted through the scope. The balloon is then inflated and cross-sectional images of the rectum are taken. This test helps to evaluate rectal masses and aids in determining the appropriateness of various surgical alternatives.

For appointments, please call 631-444-3431.