- Patients in whom there are contraindications to the administration of intravenous contrast material (as detailed in out Department of Radiology intravenous contrast material use guidelines), including renal contraindications (such as a University of Michigan laboratory record of most recent serum creatinine concentration of >1.5 mg/dl or an estimated glomerular filtration rate (EGFR) <60 ml/min); if no serum creatinine is available, patients will be receive contrast material based on departmental guidelines