When to Order a Contrast-Enhanced CT.

Family physicians often must determine the most appropriate diagnostic tests to order for their patients. It is essential to know the types of contrast agents, their risks, contraindications, and common clinical scenarios in which contrast-enhanced computed tomography is appropriate. Many types of contrast agents can be used in computed tomography: oral, intravenous, rectal, and intrathecal. The choice of contrast agent depends on route of administration, desired tissue differentiation, and suspected diagnosis. Possible contraindications for using intravenous contrast agents during computed tomography include a history of reactions to contrast agents, pregnancy, radioactive iodine treatment for thyroid disease, metformin use, and chronic or acutely worsening renal disease. The American College of Radiology Appropriateness Criteria is a useful online resource. Clear communication between the physician and radiologist is essential for obtaining the most appropriate study at the lowest cost and risk to the patient.