Virtual Colonoscopy Using Omnipaque as a Contrast Agent

CT colonography (CTC) is a validated screening exam for colorectal cancer. The diagnostic accuracy of CTC depends on the quality of the bowel cleansing and contrast tagging of residual stool and fluid. New bowel preparation media for CTC should be assessed for their efficacy and for patient satisfaction. Iohexol is currently approved by the FDA for oral use for imaging of the gastrointestinal tract. A potential advantage of using iohexol for CTC is that low-and iso-osmolar oral contrast agents have fewer risks than hyperosmolar contrast agents, which make them ideal for use in all patients, especially those who are frail and/or have multiple co-morbidities. For example, hyperosmolar contrast agents that are accidentally aspirated into the lungs during ingestion may result in life-threatening acute pulmonary edema and severe chemical pneumonitis, which is not the case for low- and iso-osmolar contrast agents. It may even be safer to use low- or iso-osmolar contrast agents for patients undergoing CTC on the same day as their incomplete colonoscopy, since they are at risk for aspiration from being sedated for their colonoscopy. Additionally, unlike hyperosmolar contrast agents, low- and iso-osmolar contrast agents do not cause sudden and massive fluid shifts, thus eliminating the risk of dangerous electrolyte imbalances.