Virtual colonography (VC), or Computerized Tomographic Colonography (CTC), produces 2-D and 3-D images of the colon (large intestine) from the lowest part, the rectum, all the way to the lower end of the small intestine. Using X-rays and computers, VC provides your doctor information to diagnose colon bowel disease, including polyps, diverticulosis, and cancer. VC is performed with computed tomography (CT), sometimes called a CAT scan.

What should I expect during my virtual colonography exam?

VC takes place in our Diagnostic Imaging Department. The exam lasts about 30-40 minutes and you can resume normal activity after the procedure. The scanning procedure is done with you lying on your back, your stomach, and again on your left and/ or right side.

First, the CT technologist will ask you to lie on your side on the CT table. A thin tube will be inserted into your rectum. Air will be pumped through the tube to inflate the colon for better viewing.

The table moves through the scanner to produce a series of 2-D cross-sections along the length of the colon. We will ask you to hold your breath during the actual scan to avoid distorting images. A computer program assembles these images into a 3-D picture viewable on screen.

After the examination, the information from the scanner must be processed to create the computer picture or image of your colon. A radiologist evaluates the results to identify any abnormalities

How do I prepare for my virtual colonography exam?

The prep for a virtual colonography requires a full day to clean out the bowel and prepare you for the procedure.

  • At least two days before your VC: Pick up a prep kit from the Diagnostic Imaging Department Broadway Location.

The prep kit includes laxatives and a type of imaging contrast in a liquid form. When you come to pick up the prep kit, a technologist can go over the instructions with you. Kits can be picked up at the other imaging sites with advance notice.

Scheduling and Authorization

If your provider orders a CT exam, we will contact you to schedule your appointment.

CT exams require a pre-authorization form from your insurance company. If you elect to have the CT exam without this pre-authorization, there will be a deposit required at the time of study. You may be responsible for the full balance after your insurance has been billed. If you have questions regarding your insurance coverage or benefits, please contact your insurance company directly.

  • For general questions about CT scans at The Polyclinic, please call 206-329-1760.


The Polyclinic's CT Department is proud to be recognized as an Accredited CT Facility by the American College of Radiology.mri