Rectal Ultrasound is a test done to assess the extent of tumors, trauma or infection of the rectum or anus. A special form of rectal ultrasound called “transrectal ultrasound” can be used to assess tumors of the prostate gland (refer to our links on prostate volumetrics and prostate brachytherapy.)
Your doctor will prescribe the preparation he feels is necessary for this test. Usually, the only requirement is that the rectum be empty, so an enema is taken at home just before you come to the hospital or just after you arrive for your test.
During the rectal ultrasound study a proctoscope (about ¾” in diameter) is passed through the anus into the rectum. The doctor can then directly look at the tumor or injury. He then inserts an ultrasound probe through the proctoscope and takes ultrasound pictures of the rectum and the tissues surrounding it. Ultrasound pictures are made using high-frequency sound waves to create images of tissue layers beneath the surface. A physician who has special training in ultrasound exams performs the exam. He will have an assistant who also has special training for this procedure. The entire procedure usually takes less than 15 minutes. The doctor will discuss the result with you before you leave.
The doctor may decide to take biopsies during the procedure. To do this he uses a special instrument to take a snip or two of rectal tissue. There will be no pain, but you may feel some pressure or tugging. There may be a small amount of bleeding from your rectum, but if you notice more than a tablespoon of blood call the physician immediately.
The pressure of the proctoscope and ultrasound probe can be uncomfortable if you are not relaxed. Most people handle this without any difficulty, but you may wish to speak to your doctor about this if you feel that you may not be able to relax enough for the test.