What is the role of contrast in Computed Tomography (CT) colonography?

From the Guidelines

Intravenous contrast is not typically used in Computed Tomography (CT) colonography for screening purposes, but it may be helpful in certain situations, such as characterizing solid organs or distinguishing polyps from stool.

Role of Contrast in CT Colonography

• The use of intravenous contrast in CT colonography is generally reserved for situations where characterization of solid organs is necessary, such as evaluating a potentially significant extracolonic finding or staging an obstructing colon cancer 1.
• In these circumstances, normal dose settings are also appropriate so that the attenuation of colonic lesions can be accurately assessed 1.
• The American College of Radiology practice guidelines for CT colonography recommend a kVp of 120 kV and a tube current of 100 mAs for routine CT colonography examinations in adult patients, but do not typically include the use of intravenous contrast 1.
• However, some studies have demonstrated the usefulness of CT colonography with intravenous contrast in individuals who have undergone incomplete colonoscopy, particularly in detecting lesions 6 mm or larger 1.
• In these cases, the use of intravenous contrast may help to improve the accuracy of CT colonography in detecting colorectal cancer and adenomatous polyps 1.

Key Points

• Intravenous contrast is not typically used in CT colonography for screening purposes.
• Intravenous contrast may be helpful in certain situations, such as characterizing solid organs or distinguishing polyps from stool.
• The use of intravenous contrast in CT colonography should be guided by the specific clinical situation and the recommendations of relevant professional organizations, such as the American College of Radiology 1.

From the Research

Role of Contrast in CT Colonography

The use of contrast in Computed Tomography (CT) colonography plays a significant role in improving the diagnostic accuracy of the procedure.

• The administration of intravenous contrast material has been shown to enhance bowel wall conspicuity and reader confidence for examining the colon 2.
• It also aids in differentiating true colonic masses from pseudolesions such as residual stool, and improves the depiction of enhancing masses that might otherwise be obscured by residual colonic fluid 3.
• The addition of contrast material can help distinguish between the bowel wall and mural abnormalities from luminal contents, which is essential for accurate diagnosis 2.

Benefits of Contrast-Enhanced CT Colonography

The benefits of using contrast in CT colonography include:

• Improved diagnostic accuracy for the detection of medium and large polyps 2.
• Enhanced visualization of the colon, allowing for better detection of colorectal cancer 3.
• The ability to differentiate between true colonic masses and pseudolesions, reducing the risk of false positives 3.

Variations in Contrast Administration

Different studies have explored the use of various contrast agents and administration methods in CT colonography, including:

• Intravenous contrast material 2, 3.
• Oral contrast agents, such as fecal tagging 4.
• The use of low-dose protocols to minimize radiation exposure 5.