• Rectal endoscopic ultrasound is a test that lets your doctor look at the walls of your lower gastrointestinal tract. This test does not use X-rays or other radiation.
• The doctor uses a thin, lighted tube called an endoscope, or scope, and gently puts the scope into your rectum to the area to be examined and the scope can take pictures of organs and tissues. 
• During the procedure, your doctor can take samples of tissue that can be checked for cancer or other problems.
• Tell your doctor all the medicines, vitamins, supplements, and herbal remedies you take as you need to stop taking certain medications before the procedure.
• Before the test, you will need to stop eating solid foods the day before the procedure and drinks may be limited to clear fluids- plain water, broth, carbonated beverages, and tea and coffee without milk or cream.  
• You may be asked not to eat or drink anything after midnight the night before the procedure. 
• You also will have an enema or take laxatives to empty your lower colon as this will help your doctor to see inside your colon during the test.
• You should be able to return to your normal activities the day after the procedure.
• You may need someone to drive you home.
• After the exam, you may have mild abdominal discomfort or you may feel bloated or pass gas for a few hours as you clear the air from your colon.