CT Colonography Patient Preparations

You have been referred by your physician for a CT colonography exam (also called virtual colonoscopy). This study looks for significant growths, such as polyps, within your rectum and colon. Polyps are growths on the lining of the colon that sometimes grow into cancers. The primary differences between CT colonography and traditional optical colonoscopy are that CT colonography uses a high technology X-ray scanner and advanced computer programs to create detailed images of the tissues inside the colon. It does not require sedation, injections or the insertion of a camera into the colon, and the procedure takes less time than an optical colonoscopy. In addition, you can drive yourself home or return to work immediately following your exam, which is not the case with the traditional optical colonoscopy.

At the S. Mark Taper Foundation Imaging Center, our team of CT colonography experts is led by Mamata Chithriki, MD, chief of Body Ultrasound, and Irene Chen, MD.

Before Arriving for Your Exam

  • You can print and fill out the CT Colonography Questionnaire on the Pre-Registration Questionnaire page before arriving to speed registration.
  • The most important part of any colonography happens before you come to the S. Mark Taper Foundation Imaging Center. To get a good look at the lining of the colon, it is necessary to clean out any traces of food or other material.
  • This cleansing requires a restricted diet the day before your exam, and the taking of medication which will cause the colon to empty. This preparation is required regardless of whether you undergo a CT colonography or an optical colonoscopy.
  • If you have diabetes or have had a previous allergic reaction to an iodinated contrast please contact us before you begin your colon preparation at 310-423-8000, ext 3.
  • If your doctor gave you an order for this study, please bring it.
  • If you have any questions about your procedure, please contact Dr. Richard Sukov or Dr. Ashley Wachsman at 310-423-8000, ext 3.

Insurance Coverage

  • Most insurance plans, including Medicare, do not cover CT colonography for screening purposes.

Preparation Instructions

The following two items you just received in the mail will help you get ready for your procedure.

  • Tagitol V 20 mL bottles (3)
  • Omnipaque 300 30 mL bottle (1)

Before you begin your preparations, you will need to purchase two items from your local pharmacy.

  • Magnesium Citrate Saline Laxative (any flavor) – purchase one (1) 10 oz.  bottle  
  • Dulcolax (bisacodyl 5 mg) purchase 25 count or less – take two (2) tablets

The above four items will get your bowels ready for your procedure.

  • Tagitol V 20 mL bottles (3) – drink one 20 mL bottle with each meal (breakfast, lunch and dinner)
  • Magnesium Citrate (1) – the day before your exam at 5:30pm drink one 10-ounce bottle follow by one full glass of water (8 ounces)
  • Omnipaque 300 30 mL bottle (1) - the day before the exam at 9 p.m., mix the bottle with one full glass of water or clear soda (Sprite or 7-Up) and drink.
  • Dulcolax take two tablets with one full glass of water (8 ounces). Swallow this medication whole. Do not crush, chew or break the tablets.  

Note: A high fluid intake is required for this preparation. Drink at least one full 8-ounce glass of water at each of the times specified. DO NOT USE MILK, CREAM OR NONDAIRY CREAMER.


  • No solid food the day before the procedure.
  • Take clear liquids only (i.e. water, coffee, tea , juices, soda, broth, jello, etc)
  • Try to drink 8 ounces (about one glass), at the least, every hour. (Try never to be thirsty).
  • Complete CT Colonography questionnaire.

Before Your Procedure

Day Before Your Procedure:

Breakfast  (about 8 a.m.)

One (#1) 20 ml bottle of Tagitol V. Shake well.


Clear soup (any broth); strained fruit juices without pulp; flavored Jell-O of any color (do not add extra ingredients); soft drinks, black coffee or plain tea.  One (#2) 20 ml bottle of Tagitol V. Shake well.

1 p.m.

Drink one full 8-ounce glass of water.

2 p.m.

Drink one full 8-ounce glass of water.

3 p.m.

Drink one full 8-ounce glass of water.

4 p.m.

Drink one full 8-ounce glass of water.

5 p.m.

(Dinner) Clear soup (any broth); strained fruit juices without pulp; flavored jello of any color (do not add extra ingredients); soft drinks, black coffee or plain tea.  One (#3) 20 ml bottle of Tagitol V.  Shake well.

5:30 p.m.

Slowly add approximately one half of the contents of the packet of Magnesium Carbonate, Citric Acid, and Potassium Citrate for Oral Solution to 8 ounces of cold water in a large glass (minimum 16-ounce capacity). Stir gently. After effervescence (fizzing) stops slowly add the remaining content of the packet to the glass. Stir gently wait until fizzing stops and drink entire contents of glass. This product generally produces a bowel movement in 30 minutes to six hours.

6 p.m.

Drink one full 8-ounce glass of water.

7 p.m.

Drink one full 8-ounce glass of water.

7:30 p.m.

Peel the backing off the packet of bisacodyl tablets and remove the four enclosed tablets. Take all four (4) with one 8-ounce glass of water. DO NOT CHEW TABLETS. The tablets are to be taken two hours after drinking the white LO SO Prep.

8 p.m.

Drink one full 8-ounce glass of water.

9 p.m.

Mix the 30 mL bottle of Omnipaque with a glass of water or other clear liquid (7-Up or Sprite) and drink. Do not eat after 9 p.m.

Warning: Omnipaque should not be taken if you have a history of prior allergy to an imaging contrast containing iodine.

Day of Procedure
  • Newborn to 4 years old: no preparation
  • 4-16 years: clear liquid dinner the day before the procedure; clear liquids only on the day of exam

*If a referring physician requests a prep, contact radiology at 310-423-2723 and ask to speak to a GI radiologist.

If your doctor gave you an order, please bring it with you.

During Your Exam

  • A radiology nurse or technologist will ask you a few questions regarding your medical history. You will be asked questions such as: Why are you having the exam? Have you had prior colon surgery?
  • This procedure should not be performed if you are or might be pregnant.
  • While positioning you on the exam table, a technologist will explain your procedure and answer any questions you may have.
  • You will be asked to lie on your side and a small flexible tube will be inserted into your rectum. We use a special system to pump carbon dioxide into your colon through this tube. This gas will make the colon expand and will reduce the natural folds and wrinkles on the walls of your colon enabling a more accurate study. We use carbon dioxide instead of air because it absorbs into the bloodstream faster and reduces the bloated feeling many experience when air is used.
  • The table you are on will slide into the scanner. The scanner is open at the back and the front, allowing you to see out. The technologist will always be able to see and hear you during your exam.
  • You will be asked to hold very still and at times to hold your breath for about 15 seconds.
  • Two sets of images will be taken, the first while you are positioned on your back and the second on your stomach.
  • After the scan is complete, you will want to go to the bathroom to expel the remaining gas.
  • While the procedure takes about 15 minutes, you should expect to be at the center for approximately one hour.

After Your Exam

  • There are no restrictions placed on you after this procedure. You may drive yourself home and resume your normal schedule.
  • Your study will be read by an imaging physician who has been specially trained in the interpretation of CT colonography scans. The results will be sent to your physician, usually within 48 hours.
  • Your physician will discuss these results with you and explain what they mean in relation to your health.

If you are not currently scheduled for CT colonography, and have questions, you may contact an imaging specialist at 310-423-8000, ext. 3.

For more information or to schedule an appointment