Omnipaque, also known as iohexol, is a contrast agent used in X-ray imaging and computed tomography (CT) scans to help doctors diagnose conditions Omnipaque is a clear, colorless, iodine-based liquid that can be administered orally, intravenously, or into a body cavity. It helps doctors see abnormalities and define different structures in the body, such as arteries, veins, ventricles of the brain, the urinary system, and joints.