From the Guidelines
Preparation for virtual colonography, also known as CT colonography, typically involves a bowel cleansing regimen similar to traditional colonoscopy but may be less intensive, with a clear liquid diet and laxatives the day before, as well as a contrast agent called "fecal tagging" material to help highlight any remaining stool during imaging 1.
Key Components of Preparation
- A clear liquid diet the day before the procedure to minimize residual stool and fluid in the colon
- Laxatives, such as polyethylene glycol solutions (e.g., MoviPrep or GoLYTELY) or a combination of magnesium citrate and bisacodyl tablets, to empty the colon
- A contrast agent, usually a small amount of barium or iodine-based liquid, taken with meals the day before to tag any remaining stool and fluid, making them easier to distinguish from polyps on the CT images 1
Importance of Preparation
The thorough cleansing is essential because any remaining stool can mimic polyps on the CT images, potentially leading to false positive results. Unlike traditional colonoscopy, virtual colonography doesn't require sedation, and the entire procedure typically takes only 10-15 minutes, though air or carbon dioxide is pumped into the colon to distend it for better visualization 1.
Procedure Details
- The procedure involves inserting a small-caliber rectal catheter into the rectum, followed by automated or manual insufflation of room air or carbon dioxide
- Intravenous contrast is generally not given to patients undergoing screening but can be helpful in some patients with more advanced symptoms
- The entire procedure on the CT table takes approximately 10 minutes, with no sedation or recovery time needed 1
From the Research
Bowel Preparation for Virtual Colonography
To prepare for virtual colonography, bowel preparation is crucial for accurate results. The preparation typically involves cleansing the bowel using a laxative or other agents.
- The goal of bowel preparation is to remove any fecal matter and fluid from the colon, allowing for clear visualization of the colon during the virtual colonography procedure.
- Studies have compared different bowel preparation regimens, including sodium phosphate and polyethylene glycol solutions 2, 3, 4.
- Sodium phosphate tablets have been shown to be equivalent to polyethylene glycol solution in terms of bowel cleansing quality, with better patient acceptability and satisfaction 2.
- A meta-analysis of randomized controlled trials found that sodium phosphate was associated with better acceptability, compliance, cleansing scores, and less adverse effects compared to polyethylene glycol 4.
- The American College of Radiology recommends a bowel preparation regimen that includes a low-fiber diet for 2-3 days before the procedure, followed by a laxative or other agent to cleanse the bowel.
- It is essential to follow the specific bowel preparation instructions provided by the healthcare provider or radiologist to ensure adequate preparation for virtual colonography.