Gadolinium-containing contrast agents are associated with a much lower incidence of contrast-induced nephropathy (CIN) than iodinated contrast at doses used for clinical imaging. However, the usage of gadolinium-containing contrast agents can cause other types of renal impairment, such as nephrogenic systemic fibrosis (NSF) . NSF is typically characterized by skin thickening and hyperpigmentation, usually of the extremities and trunk, though in severe cases can lead to contractures and organ fibrosis and may ultimately lead to death. No treatment of NSF exists, other than renal-protective measures, though steroids, hemodialysis, and photopheresis have been described. Factors associated with development of NSF include preexisting renal insufficiency, metabolic acidosis, larger doses of gadolinium, repeated studies, and recent vascular procedures. The FDA requires a boxed warning on all gadolinium-containing contrast agents, stating that the use should be avoided in patients with impaired drug elimination [1, 29, 30].

Studies into alternative contrast agents are ongoing, with attempts at identifying compounds that offer similar opacification and resolution without deleterious side effects. Recently, a review of imaging with ferumoxytol-enhanced magnetic resonance angiography (Fe-MRA) compared images obtained with traditional gadolinium-based contrast agents. Ferumoxytol is an intravenous, ultrasmall, superparamagnetic iron oxide preparation, approved by the FDA in 2009 for treatment of iron-deficient anemia in adults with chronic kidney disease. The compound is well tolerated by patients and is cleared by the reticuloendothelial system, which provides a favorable safety profile for patients with renal insufficiency. No difference was found in the overall quality of the ferumoxytol versus the gadolinium studies, as adjudicated by four independent, experienced vascular surgeons. The reviewers of the studies felt comfortable basing clinical decisions on the images 89% of the time in both the ferumoxytol and gadolinium groups, which demonstrates that there may be alternative contrast agents available for patients with renal insufficiency, possibly obviating the precautions of MR angiography in this group of patients [31].