Contrast-induced nephropathy may be less common than previously reported

1. In a retrospective review of over 2200 patients undergoing contrast-enhanced computed tomography scans, there were no significant differences between the incidence of contrast-induced nephropathy immediately after or 48 hours after contrast administration.

2. The overall incidence of acute kidney injury attributable to contrast administration was less than 1% in all patients, with a statistically insignificant risk of dialysis due to contrast nephropathy.

Evidence Rating Level: 2 (Good)

Study Rundown: Contrast-induced nephropathy is a reversible type of acute kidney injury (AKI) in patients who undergo contrast-enhanced computed tomography (CT) scans. Patients with contrast-induced nephropathy most commonly demonstrate oliguria and an elevation in serum creatinine immediately after the administration of radiocontrast dye. The incidence of contrast-induced nephropathy is not well-characterized with current definitions of this condition attributing all kidney injury occurring after imaging to contrast administration. Researchers in the current study sought to more accurately characterize the incidence of contrast-induced nephropathy. The study retrospectively analyzed the laboratory studies of over 2200 patients who underwent contrast-enhanced CT scans and compared the incidence of AKI in the time interval between the immediate post-scan period (0-48 hours) and a delayed (48-96 hours) post-scan period. The incidence of AKI attributable to contrast administration was defined as the difference in incidence between the immediate and delayed periods. At the conclusion of the trial, the incidence of AKI was similar across patients with mild to moderate renal insufficiency; however, there is a trend to increased nephropathy in patients with end-stage renal failure. The results of this study support the hypothesis that the overall risk of contrast induced nephropathy is small, which may lead to increased diagnostic capacity for contrast-enhanced CTs, particularly in patients with mild renal dysfunction. The study was limited by retrospective design and the inability to control for residual confounders. Furthermore, given the small sample size of patients with moderate to severe renal dysfunction, there was significant variance in the confidence intervals and thus the results may not be generalizable to this population. Additional large, prospective trials are needed to confirm the low incidence of this condition.

Click to read the study in AJR

Relevant Reading: Incidence of CT Contrast Agent-Induced Nephropathy: Toward a More Accurate Estimation

In-Depth [retrospective cohort]: This retrospective review included patients who underwent a contrast-enhanced CT scan from January 2006 to May 2013. Exclusion criteria included patients without serum creatinine levels, patients receiving long-term dialysis, and patients without relevant demographic information. The primary outcomes were serial serum creatinine levels: 0-12 hours before scan, 0-48 hours, and 48-72 hours after scan. The level of AKI was defined by the Acute Kidney Injury Network stages. The presence of AKI was determined by the serum creatinine difference of adjacent time intervals (immediate: 0-48 hours post scan minus 0-12 hours before scan; delayed: 48-96 hours after scan minus 0-48 hours after scan) in an attempt to reduce confounding from episodes of AKI unrelated to contrast administration. The difference between the incidence of immediate and delayed post-CT AKI was assumed to be the risk of AKI attributable to the imaging study. At the conclusion of the study, the incidences of contrast induced nephropathy were 0.5% (95% CI: -0.4%-1.4%) for patients with GFR > 60 mL/min/1.73m2 and 2.4% (95% CI: -0.7%-5.6%) for GFR 30-59 mL/min/1.73m2. There was significant variance due to small sample size for patients with GFR < 30 mL/min/1.73m2.

Image: PD

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