By the way, doctor: Are MRI contrast agents harmful?

Most of the contrast agents for MRI scans contain a metal called gadolinium. The gadolinium is attached to other chemicals to keep it from causing any harm. If your kidneys are healthy, you'll excrete the contrast agent before that complex has a chance to break down. But if your kidneys aren't working well, it may break down before it is excreted, so unbound gadolinium persists in the body. When that occurs, it may lead to a complication called nephrogenic systemic fibrosis (NSF), which can thicken the skin and connective tissues throughout the body. While there are reports of NSF as far back as 1997, the association with gadolinium was first identified in Denmark in 2006. Since then, NSF has been recognized as an extremely rare but potentially debilitating complication of giving gadolinium-based contrast agents to patients with poor kidney function. As a result, it's now routine to screen patients for kidney function before giving contrast for an MRI scan. The screening isn't complicated: a simple blood test of creatinine levels is all that's needed. Some MRI centers can measure creatinine on the spot, so the blood sample doesn't need to be sent to an outside lab.