A CT scan after a colonoscopy might seem unexpected, as many patients anticipate the colonoscopy to be the final diagnostic step. However, healthcare providers order this additional imaging for several medically sound reasons. A CT scan can offer further insights not always available from the colonoscopy alone, ensuring a comprehensive understanding of your health.
Reasons for a CT Scan After a Colonoscopy
A colonoscopy provides a direct visual examination of the large intestine, but it has limitations that a CT scan can address. One common reason for a CT scan is to further investigate findings observed during the colonoscopy. For instance, if the colonoscopy reveals polyps, masses, or other areas of concern, a CT scan can provide more detailed information about their size, exact location, and whether they extend beyond the colon wall. This is particularly relevant when assessing potential colorectal cancer, as CT can help characterize the extent of the disease within the bowel wall.
A CT scan is also frequently used to evaluate potential complications that may arise from a colonoscopy. Although rare, a colonoscopy carries a small risk of complications such as a perforation or significant bleeding. A CT scan can precisely identify the location and extent of these complications, aiding in prompt and appropriate management. The perforation rate for diagnostic colonoscopy is approximately 0.1%, while for therapeutic colonoscopy it ranges around 0.2%.
When colorectal cancer has already been diagnosed or is strongly suspected based on colonoscopy findings and biopsy results, a CT scan is often performed for “staging.” This process determines if the cancer has spread to other organs, such as the liver or lungs, or to nearby lymph nodes. A CT scan of the chest, abdomen, and pelvis is a standard part of this staging process, providing a comprehensive view of potential spread.
In some situations, a colonoscopy might be incomplete. This can occur due to anatomical challenges like a fixed colon or sharp angulations. In such cases, a CT colonography, also known as a virtual colonoscopy, can be performed to visualize the unexamined segments of the colon and detect any missed polyps or cancers. Additionally, if surgery is being considered based on the colonoscopy findings, a CT scan provides detailed anatomical information, including the vascular structures, which is important for surgical planning.
What to Expect During the CT Scan
A CT scan is a quick and painless procedure that creates detailed cross-sectional images of your internal organs, bones, and soft tissues. You will lie on a narrow table that slides into a large, donut-shaped scanner. The table will move through the center of this machine while the X-ray tube rotates around you, capturing images from various angles.
To enhance image clarity, a contrast material may be administered orally or intravenously through a vein in your arm. When receiving intravenous contrast, you might experience a temporary feeling of warmth or a metallic taste in your mouth. The scanning process takes only a few minutes, though the total appointment time may be around 15 to 30 minutes. Throughout the scan, a technologist will be in an adjacent room, communicating with you through an intercom, and may ask you to hold your breath briefly to ensure clear images.
What Happens After the CT Scan
Once your CT scan is complete, you can resume your normal activities immediately, unless your doctor provides specific instructions. If a contrast dye was used, you might be advised to drink plenty of water. The images acquired during your scan are then sent to a radiologist for interpretation.
The radiologist reviews the images and compiles a detailed report. This report is then sent to the healthcare provider who ordered your CT scan within 24 to 48 hours for routine scans. Your referring doctor will interpret these CT scan results in conjunction with your colonoscopy findings, medical history, and any other relevant tests. This comprehensive assessment helps determine the next appropriate steps in your care, which could include further diagnostic tests, specific treatment plans, or ongoing monitoring.