Contrast-Induced Nephropathy: Nephrologist's Opinion

Abstract

Contrast-induced nephropathy (CIN) has become the third leading cause of hospital-acquired acute kidney injury (AKI), due to an increasing number of patients receiving intravascular injection of iodinated contrast media (ICM) every year worldwide.

The risk for patients with predisposing factors, such as advanced age, pre-existing renal disease, congestive heart failure, anterior myocardial infarction, cardiogenic shock, diabetes mellitus and type and volume of contrast, is considerably increased and ranges between approximately 12% and 50%.

Among the contemporary definitions, CIN is characterized by an absolute (= 0.5mg/dL) and relative increase (= 25%) in serum creatinine (sCreat) at 48–72 hours after exposure to a contrast agent compared to baseline sCreat values, when alternative explanations for renal impairment have been excluded.

In patients with acute changes in their glomerular filtration rate (GFR), sCreat is a relatively inaccurate marker, and its alterations are not particularly sensitive or specific for small changes in the GFR. In fact, 25–50% of the increase in creatinine, which is highly predictive for the development of CIN, most often occurs only after 24 hours after administration of ICM.

In the last decade, it has been conducted studies not only for the early detection of biomarkers, but also to assess several therapeutic strategies to prevent CIN.

A widely accepted prophylaxis for CIN after CM application is based on an intravenous volume load with an isotonic saline infusion (0.9%).

Hydration with sodium bicarbonate should provide additional renal protection by alkalinizing renal tubular fluid, with a decreased tubular damage by scavenging oxygen free radicals.

N-acetylcysteine (NAC) has been the most widely studied of all prophylaxis strategies.

Unfortunately, most studies lacked statistical power, used different types of CM, various definitions of CIN and several diverse prophylactic measures. This resulted in the lack of accepted guidelines among radiologists, cardiologists, nephrologists and other involved physicians.

Studies will be designed to clarify the value of these preventive therapies, analysing new indicators of renal function such as NGAL or Cistatin C.