Virtual Colonoscopy Test and Procedure
Overview
Virtual colonoscopy (also called CT colonography) is a modern method in gastroenterology for checking the large intestine using advanced imaging. Instead of a scope, a CT scan makes detailed, cross-sectional images of the colon and rectum. A computer combines these images so doctors can see the inside surface of the colon. Key differences between virtual and traditional colonoscopy:
| Feature | Virtual Colonoscopy | Traditional Colonoscopy |
|---|---|---|
| Tool used | CT scanner | Flexible scope |
| Invasiveness | Less invasive | More invasive |
| Sedation needed | No | Yes, often |
| Bowel prep required | Yes | Yes |
Virtual colonoscopy can spot polyps or signs of cancer, making it a useful option for colon cancer screening. Patients should speak with their provider to understand which screening method fits their needs.
Reasons for Choosing This Test
Doctors often recommend virtual colonoscopy for adults aged 45 and older to check for signs of colon cancer, rectal cancer, or other growths in the colon. People at average risk who want a screening method without anesthesia or recovery time often choose this test.
Those with concerns about the risks of regular colonoscopy, such as possible bleeding or complications, especially if they have conditions making standard procedures more risky, may also benefit. Doctors may suggest a virtual colonoscopy if someone:
- Wishes to drive home after the procedure.
- Prefers to avoid medication that causes sleepiness.
- Has bleeding issues or is taking blood thinners.
- Has a blockage in the bowel.
However, this test does not suit everyone. People with a past history of colon or rectal cancer, a history of colon polyps, or certain long-term bowel diseases like Crohn’s disease or ulcerative colitis usually need other options.
Key Points Table
| Reason for Test | Who Should Get It |
|---|---|
| Cancer screening | People over 45, average risk |
| Less invasive than colonoscopy | Those wishing to avoid sedation |
| Safer for some health issues | People with bleeding or clotting concerns |
The American Cancer Society gives regular updates on colorectal cancer screening guidelines, and virtual colonoscopy is accepted when regular colonoscopy is not the best choice. This test can also spot other problems in the abdomen, sometimes leading to further tests if doctors notice something abnormal outside the colon.
Possible Hazards
Virtual colonoscopy is less invasive than a standard colonoscopy. However, some risks remain.
| Risk | Details |
|---|---|
| Tear/Perforation | Rare, lower chance compared to traditional test |
| Radiation | Very small amount, similar to 2 years’ background |
- Tear (Perforation): Pumping air or carbon dioxide into the large intestine can rarely cause a small tear. The risk is lower than with a regular colonoscopy.
- Radiation Exposure: The test uses a low dose of radiation to create images. The amount matches what a person would get from natural background radiation over two years. This dose is less than what a standard CT scan uses.
Getting Ready
To prepare for a virtual colonoscopy, patients typically follow a bowel cleansing routine. This involves drinking special solutions and taking laxatives to clear the intestines. Only clear liquids—such as water, clear juices, or broth—are usually allowed the day before the scan. Patients should also check with their insurance provider in advance to confirm coverage for the CT scan used in the procedure.
What You Can Expect
Steps to Take Before Your Appointment
To ensure accurate results from a virtual colonoscopy, patients must completely empty the colon. Any remaining stool can interfere with the clarity of the images. The day before the procedure:
- Follow a clear liquid diet—no solid foods. Acceptable fluids include water, broth, and clear sports drinks.
- Do not eat or drink after midnight, as instructed by your provider.
- Take a prescribed laxative the evening before to cleanse the colon.
- Some patients may also need to use a suppository for additional bowel clearing.
- Special medications may be given to highlight any residual stool during the scan.
Inform your healthcare provider about all current medications and supplements. Certain medications may need to be paused to ensure the test is accurate and safe.
What Happens After the Scan
Patients change into a gown and remove all other clothing. Sedation is not required, though providers may give medicine to help relax the colon. The care team begins the procedure with the patient lying on their side on the examination table, knees drawn up. A small, flexible tube is inserted into the rectum.
Through this tube, air or carbon dioxide (CO₂) gas is gently pumped in to inflate the colon. This step helps make polyps or abnormal areas easier to see on the scan. Some patients may feel pressure or slight discomfort from the inflation, but it is usually brief.
Once the colon is inflated, the table moves into the scanner. The patient first lies on their back, then may need to change to their stomach or side. Scans are taken from several angles to create a full view of the colon. The entire process takes about 15–20 minutes.
Key Points During the Scan
- No need for anesthesia.
- Air or CO₂ gas is used to expand the colon.
- Brief discomfort or fullness may happen.
- Multiple body positions are required.
- The procedure is usually quick.
Note: Unlike a traditional colonoscopy, doctors cannot remove polyps during a virtual colonoscopy.
Steps After the Exam
Most people can return to their regular daily routines right after the scan. Some may feel bloated or gassy temporarily as the air or CO₂ exits the body. There are usually no restrictions on eating, drinking, or physical activity after the test.
The care team reviews the images and follows up with the patient to share the results. If any growths or polyps are found, they may recommend a traditional colonoscopy to remove them and conduct further examination.
Post-Test Overview
| Activity | Guidance |
|---|---|
| Resume eating | Allowed, no restrictions |
| Activity | Normal activity is safe |
| Discomfort | Temporary bloating/gas |
| Results | Await provider follow-up |
Test Findings
A virtual colonoscopy can identify polyps, cancer, or other irregularities within the colon. The healthcare provider usually shares results after the exam.
Types of Results
| Result Type | Description | Next Steps |
|---|---|---|
| Negative | No polyps or irregular tissue found | Retest may be needed in 5 years* |
| Positive | Polyps or other concerns are seen | Traditional colonoscopy advised |
| Other Findings | Issues found outside the colon, such as in the liver or kidneys | Further tests may be suggested |
- Accuracy: Virtual colonoscopy detects medium and large polyps with high accuracy.
- Sensitivity: The test detects many cases that require closer attention, with strong results for finding growths that may be cancerous.
- Specificity: It correctly identifies when there are no harmful changes, reducing unnecessary procedures.
If polyps or signs of malignancy appear, doctors may recommend further evaluation right away. Sometimes, the doctor can remove abnormal tissue during the follow-up procedure.
