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High Resolution Anoscopy

What it is

High resolution anoscopy is a procedure that is used to examine the anus for abnormal cells that have a high likelihood of turning into cancer.
The procedure is performed on an outpatient basis. Total time of the procedure is about 20-30 minutes.

How to prepare

Patients do not need to do anything special in order to prepare for high resolution anoscopy.
Some medications and supplements can cause a risk of increased bleeding, such as aspirin, ibuprofen, vitamin E and certain herbs. If you are taking any of these, please call your doctor ahead of time for guidance. 
Starting 24 hours before your exam, avoid using any douches, enemas or creams that are applied to the anal canal. It is also important to avoid anal sex.

What to expect

During an anal anoscopy, you will be asked to lie on your side with your knees drawn up slightly toward your chest.
An thin hollow tube called an anoscope will be coated with an anesthetic cream and inserted about two inches into the anus. 
Next, a cotton swab covered with acetic acid will be inserted through the anoscope and into the anus. The anoscope will be removed, leaving the cotton swab behind. The acetic acid on the cotton swab will cause any abnormal cells to turn white. 
After a few minutes, the cotton swab will be removed. The anoscope will then be reinserted. A high-resolution colposcope is used to examine the interior of the anus. 
The colposcope provides magnification of up to 40 times. With it, the colorectal surgeon performing the exam can detect any abnormal cells that have been turned white by the acetic acid.
If any such cells are detected, the surgeon can take a biopsy right during the exam. A local anesthetic will be used prior to the biopsy to help minimize any discomfort. The cells removed during the biopsy will then be sent to a pathologist for further examination.

After your exam

If a biopsy is required, some bleeding should be expected for one to two days. If bleeding is heavy or you have a fever of 101 or above, please call your doctor.
Nothing should be inserted into your anus until all bleeding has completely stopped.
The following guidelines should be followed for 3 days after your high resolution anoscopy:
  • Avoid heavy exercise. Walking is allowed.
  • Wear loose clothing.
  • Avoid prolonged sitting or standing.
  • Drink plenty of fluids to help prevent constipation.
  • Avoid tobacco and second-hand smoke.
  • Do not swim or take baths. Showering is allowed.


At the University of Rochester Medical Center, high resolution anoscopy is performed by a team of specialists including fellowship trained colorectal surgeons. The doctor who performs your exam is a specialist who also performs the most advanced colorectal surgeries.
When a biopsy is performed during high resolution anoscopy, the tissues are sent to a pathologist who specializes in colorectal pathology. The University of Rochester Medical Center has the only pathologists in the region who specialize in colorectal pathology.