CT (computed tomography) scans, sometimes called a CAT scan, uses x-rays to make detailed pictures of structures within the body. Most parts of the body can be examined using CT.
During the scan, the patient lies on a table attached to the CT scanner, which is a large donut-shaped machine. The CT scanner sends x-rays through the area of the body being studied. Each rotation of the scanner takes less than a second, and provides a picture of a thin slice of the area of interest.
Most CT scans require a patient to have an injection of material we call contrast. It is very important that you tell your technologist and the person booking your appointment if you are allergic to this contrast. There are things we can do to help prepare you for the exam.
Women’s College Hospital provides abdominal, chest, head/neck and musculoskeletal CT scans, as well as colonography (virtual colonoscopy) scans.
Contact Info
76 Grenville St
Floor 2
Toronto, ON M5S 1B2
Hours of Service
Monday to Friday
8:00 a.m. – 5:00 p.m
Virtual Colonoscopy
A Program of the Toronto Joint Department of Medical Imaging: University Health Network, Sinai Health Systems, Women’s College Hospital, and University of Toronto
Virtual Colonoscopy, also known as CT Colonography, is a new method of assessing the large bowel for polyps or colon cancer.
This examination involves having a CT scan of the abdomen, while lying on the back and then on the stomach, and after instilling carbon dioxide into the colon using a small rectal tube. The CT portion takes about 10-20 minutes.
This procedure has been shown to be accurate in detecting colonic polyps and cancers. However, it does not involve polyp removal or biopsy like a conventional colonoscopy. While polyps can be identified by Virtual Colonoscopy, a conventional colonoscopy should follow for confirmation and removal.
More detailed information on Virtual Colonoscopy is available from the website: http://www.virtualcolonoscopy.net
Before the procedure
During the Virtual Colonoscopy, a CT scanner is used to produce two- and three-dimensional images of the entire large bowel, and usually includes a virtual “fly-through”, or map, of the entire colon.
One week prior to your appointment, you will need to go to the hospital to pick up your preparation kit. This kit will include Barium and Omnipaque (two types of oral contrast agents). Barium coats any residual stool, while the Omnipaque coats residual fluid.
You must follow the instructions attached with your appointment letter.
During the procedure
Arrive at the hospital 20 minutes before your scheduled Virtual Colonoscopy appointment. By this point your bowels should be completely cleansed.
The average examination takes approximately 30 minutes. When the procedure begins:
- You will be asked to lie down on the CT scanner;
- The technologist will insert a short rectal catheter into your rectum which releases CO2 to help distend your bowels;
- A muscle relaxant may be injected to avoid bowel spasms;
- You will be asked to lie in different positions to distribute the gas through the entire bowel;
- CT imaging of your abdomen will be taken;
- Once the imaging is complete, the short rectal catheter is removed.
After the procedure
Once the procedure is finished, you may continue with your normal daily routine. The radiologist will analyze the pictures with special software and send the report directly to your referring physician.
In some circumstances we may offer same-day endoscopy if an abnormality is detected during this procedure. This would mean we would ask for your contact details for a two-hour period after the examination. As the bowel needs to remain clean while data is analyzed, you will be asked to continue to refrain from eating.
Most patients feel comfortable enough to return to normal activities (e.g. go to work) after the procedure. You can eat and drink normally.
Due to the Barium, it is normal for your stools to be chalky or white for a few weeks after the test.
You should contact your referring physician to discuss the results of your procedure.
Advantages
- It is a minimally invasive procedure
- It has a markedly lower risk of perforating the colon than conventional colonoscopy
- You can be spared from having to undergo a full colonoscopy
- It uses a short flexible rectal tube rather than a larger less flexible tube to view the bowel walls
- It is an excellent alternative for patients who have clinical factors that increase the risk of complications from conventional colonoscopy (such as treatment with blood thinners or severe breathing problems)
- It is helpful when colonoscopy cannot be completed because the bowel is narrowed or obstructed for any reason, such as by a large tumor
- It provides clearer and more detailed images than a conventional barium enema x-ray examination
- You will not need sedation
- It is a faster exam (10-20 minutes)
- It has reduced risk of complications
- It can examine your entire colon
- The virtual ‘CT Scope’ can look behind folds of the large bowel
Disadvantages
- Full preparation is still needed
- It cannot remove polyps during testing
- Conventional Colonoscopy will be needed if results are abnormal
- There is a small risk of perforation of the colon with air or CO2
- If IV contrast is given, some individuals may have an allergic reaction
- This test is not suitable for pregnant patients because of the use of radiation
Frequently Asked Questions (FAQs)
If you have forgotten to drink your barium at its scheduled time, continue to follow the preparation instructions, and just remember to drink it at the next scheduled time.
No. The size of the rectal catheter for a virtual colonoscopy is approximately half the width of a catheter for a conventional colonoscopy, and about the length of a pinky finger (1.5 inches)
If you cannot pick up your preparation kit yourself the week before your appointment, you are more than welcome to have a family member or friend to pick it up for you at the CT bookings area in the hospital.
For the best results your bowels must be cleansed. In doing this you must take a laxative. There are several types of laxatives, however, for virtual colonoscopy, the laxative you will need to orally ingest would be Pico Salax.
Many of your other medications could have caused this. For instance, pain medications such as Fentanyl can cause adverse effects such as constipation. In this situation, we will have to reschedule your virtual colonoscopy and request you to follow a three-day preparation with a low residue diet. This will help you cleanse your bowels while taking your needed medications.
Other options available for detecting colon cancer and/or polyps include fecal occult blood testing, air contrast barium enema, flexible sigmoidoscopy, and fiber optic colonoscopy.
A lot of bowel preparations leave a residue in the colon which can interfere with the quality of the CT. We therefore prefer that you use our bowel preparation. However, if you have specific medical reasons, we would be happy to speak with you.
Yes. However, please advise us in advance in order to facilitate the proper accommodation for the day.
Please inform us if you are usually constipated. In this case we would advise you to follow the Low Residue Diet Bowel Preparation.
No, continue to take all medication as you normally would.
If you have diabetes, please call your doctor to discuss how your diabetes medicine (oral diabetes pills and/or insulin) doses should change before the VC. Test your blood sugar more often the day before this test. Also check your blood sugar the morning of your test. If your blood sugar level is low (less than 70 mg/dl) or if you have symptoms, take some glucose tablets or drink 4 ounces of a clear liquid that contains sugar. Always recheck your blood sugar level to make sure it stays above 70. We may still be able to do the VC unless you need to eat solid food to keep your blood sugar at a normal level. If the blood sugar ever gets too high or too low and you can’t bring it back to normal, call your primary care or diabetes doctor.
If you have significant cardiac problems including congestive cardiac failure or renal (kidney) problems that have resulted in impaired kidney function you may need to take an alternate bowel preparation regime. Please let our scheduler know at the time of booking your appointment so that a radiologist may be consulted for alternate methods.
A referral from a physician is required.
Electronic Referrals
The Joint Department of Medical Imaging is now accepting referrals through Ocean eReferral to help everyone save time and to increase efficiency.
Ocean Network eReferral benefits for providers include:
- Accelerates appointment booking by improving communication between providers with secure bidirectional messaging
- Easy to use – integrates with top EMRs such as Telus PSS, Accuro and Oscar
- User friendly web-based portal
- Keeps you and your patients informed of referral status with automated email notifications and EMR status updates
- Patients can confirm appointment electronically
Ocean eReferral Network: For more information about eReferral can be found here.
Fax Referrals
The MRI Request Form (.pdf) is PDF writeable enabling external referring physicians to type directly into the form, print, sign and fax to Women’s College Hospital.
Typed requisitions will improve overall legibility and completeness of the forms we receive. Please note this electronic version cannot be populated and saved, but must be printed, signed and faxed to the appropriate number indicated on top of the form.
Learn more about our medical imaging services and how to prepare:
I’m having an abdomen/pelvis CT
You may be asked to not eat for four hours before the exam, while continuing to drink plenty of fluids. Your referring physician or our booking office will inform you of these instructions.
CT scans do not cause any pain. If you are having a dye (contrast) injection, this injection may cause you to feel warm.
The length of the exam depends on the type of scan. If an oral contrast is taken, it takes approximately 45 minutes to one hour for the contrast to move through the digestive tract. While you are drinking this oral contrast you will be in the waiting room. If there is no oral contrast, the exam can take 15 to 30 minutes.
If no contrast is used, there are no specific instructions to follow. If intravenous contrast or oral contrast is used, drink water throughout the day to help eliminate the contrast. Watch for and report any delayed reaction to contrast.
A report will be sent to your doctor within 10 days.
I’m having a chest CT
You may be asked to not eat for three hours before the exam, while continuing to drink plenty of fluids. Your referring physician or our booking office will inform you of these instructions.
CT scans do not cause any pain.
Approximately 15-30 minutes.
If no contrast is used, there are no specific instructions to follow. If intravenous contrast is used, drink water throughout the day to help eliminate the contrast.
A report will be sent to your doctor within 10 days.
I’m having a CT colonography (virtual colonoscopy)
Please refer to your preparation sheets that will be given to you together with the preparation kit.
This examination involves having a CT scan of the abdomen after filling your colon with carbon dioxide using a small rectal tube. Following this, the CT scan will be performed, first with you lying on your back then on your stomach.
The exam will last 30 minutes.
If intravenous contrast is used, drink water throughout the day to help eliminate the contrast.
A report will be sent to your doctor within 10 days
What do I need to do to prepare?
You may be asked to not eat for three hours before the exam, while continuing to drink plenty of fluids. Your referring physician or our booking office will inform you of these instructions.
What will I feel during the scan?
CT scans do not cause any pain.
How long will the exam last?
Approximately 15-30 minutes.
What am I supposed to do after my exam?
If no contrast is used, there are no specific instructions to follow. If intravenous contrast is used, drink water throughout the day to help eliminate the contrast.
When can I expect results?
A report will be sent to your doctor within 10 days.