Contrast-induced nephropathy (CIN) is a type of acute renal failure that manifests shortly after exposure to contrast medium. Although the immediate damage is often reversible, there is growing evidence that CIN has long-term deleterious effects. For example, a review of approximately 7000 percutaneous coronary interventions (PCI) at the Mayo Clinic found that patients who experienced CIN after contrast-enhanced PCI had significantly increased risks of myocardial infarction and death over 5 years. Such observational data cannot establish the type of relationship between CIN and long-term adverse events: they may be independent (i.e. patients who experience CIN may in general be more susceptible to poor outcomes) or there may be a causal relationship (i.e. CIN may predispose to later adverse events).