Colography

Colography

Colography, also known as colonography, is a medical imaging technique used to visualize the interior of the colon (large intestine) and rectum. It is primarily used for the detection of colorectal polyps and colorectal cancer. Colography can be performed using different imaging modalities, including computed tomography (CT) and magnetic resonance imaging (MRI).

History

The development of colography began in the late 20th century as a non-invasive alternative to traditional colonoscopy. The first clinical trials of CT colography, also known as virtual colonoscopy, were conducted in the 1990s. Since then, advancements in imaging technology and software have improved the accuracy and reliability of this technique.

Techniques

CT Colography

CT colography involves the use of computed tomography to obtain detailed images of the colon. The procedure typically requires bowel preparation to clear the colon of fecal matter. During the scan, the colon is inflated with air or carbon dioxide to enhance visualization. The CT scanner then takes multiple cross-sectional images, which are reconstructed into a 3D model of the colon.

MRI Colography

MRI colography uses magnetic resonance imaging to visualize the colon. This technique is less commonly used than CT colography due to longer scan times and higher costs. However, it offers the advantage of avoiding ionizing radiation. MRI colography is particularly useful in patients with contraindications to CT, such as those with renal insufficiency or allergies to iodinated contrast media.

Indications

Colography is indicated for:

• Screening for colorectal cancer in asymptomatic individuals.
• Evaluation of patients with symptoms suggestive of colorectal disease, such as rectal bleeding or unexplained anemia.
• Surveillance in patients with a history of colorectal polyps or cancer.

Advantages and Limitations

Advantages

• Non-invasive: Unlike traditional colonoscopy, colography does not require the insertion of a scope into the colon.
• No sedation: Patients do not require sedation, allowing for a quicker recovery and return to normal activities.
• Visualization of extracolonic structures: CT colography can also provide information about structures outside the colon, such as the liver and kidneys.

Limitations

• Radiation exposure: CT colography involves exposure to ionizing radiation, which may be a concern for some patients.
• Incomplete visualization: Small polyps or flat lesions may be missed, and if abnormalities are detected, a follow-up colonoscopy may still be necessary.
• Bowel preparation: Patients must undergo bowel preparation, which can be uncomfortable and inconvenient.

Comparison with Colonoscopy

While colography offers a less invasive alternative to colonoscopy, it is not a replacement for all patients. Colonoscopy remains the gold standard for colorectal cancer screening due to its ability to directly visualize and remove polyps during the procedure. However, colography is a valuable option for patients who are unable or unwilling to undergo colonoscopy.

Also see

• Colonoscopy
• Computed tomography
• Magnetic resonance imaging
• Colorectal cancer