How to perform a digital rectal exam

The digital rectal exam (also referred to as the DRE) is used to evaluate the anus, distal rectum, pelvis, and prostate. More specifically, it is used to inspect for anal tumors, obtain fecal samples for a fecal occult blood test, assess the function of the anal sphincters, evaluate for the cause of rectal bleeding (such as hemorrhoids), and evaluate the prostate gland.

To understand how to perform a DRE, a brief review of anorectal anatomy is pertinent. The anus is the most distal portion of the large intestine. The anorectal junction is about 5 cm superior to the anal verge (e.g., the anal orifice). The anal verge is the most distal portion seen externally.

The anal canal is the lumen located between the anal verge and the rectum. The dentate line (e.g., the pectinate line) is about 2 cm superior to the anal verge and is in the transitional zone.

The dentate line is the division between the ectoderm and endoderm mucosa, which is important because of their embryological origins. Above the dentate line, the mucosa is endoderm, has splanchnic innervation, and is insensitive to pain. Below the dentate line, the mucosa is ectoderm, has somatic innervation through the inferior rectal nerve, and is sensitive to pain.

The internal anal sphincter surrounds the upper two-thirds of the anal canal. It is formed from a thickening of the involuntary circular smooth muscle in the bowel wall. The external anal sphincter surrounds the lower two-thirds of the anal canal and is a voluntary muscle.

Start by communicating with the patient about why a DRE is necessary, what is involved, and how the exam will be performed. Prepare the patient for a little bit of discomfort with the exam.

If possible, have the patient lay on their side in the left lateral decubitus position (e.g., with their right side up). A standing rectal exam can also be performed, but it may not be as comfortable for some patients. Usually, a standing exam is only performed for a prostate examination.

To perform a DRE, put on gloves, and perform these five steps:

1. Visually inspect the anus
2. Palpate the anal sphincters
3. Palpate the rectal wall
4. Palpate the prostate (in males)
5. Collect a fecal sample if indicated

Step 1: Visually inspect the anus

First, inspect the anus. Look for any external hemorrhoids, skin tags, anal fissures, discharge, drainage, and any other abnormalities.

Step 2: Palpate the anal sphincters

Use your index finger of your dominant hand and place some lubricant jelly on it. Ask the patient to take a deep breath in, exhale, and relax. Insert your index finger into the anus, with the finger facing anteriorly, which we will refer to as the six o’clock position.

Note the external anal sphincter tone. Ask the patient to bear down and feel for tightening of the sphincter against your finger.

Step 3: Palpate the rectal wall

Palpate the rectal wall for masses, nodules, and tenderness. From the six o'clock position (e.g., the anterior direction), rotate your finger clockwise to the twelve o'clock position (now in a posterior direction), and then return to the six o'clock position.

Step 4: Palpate the prostate

In males, the prostate gland lies anteriorly at the six o’clock position. Palpate the prostate gland and note the approximate size. Feel the prostate gland for tenderness, nodules, or masses.

Step 5: Collect a fecal sample if indicated

If the patient has any signs or symptoms of anemia or unintended weight loss, then a guaiac kit to test fecal matter for occult blood is indicated.

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