CT contrast not tied to poor outcomes, even in at-risk patients

The use of intravenous contrast before CT imaging is safe for most patients, according to a large study published online on Tuesday in Radiology. Researchers from the Mayo Clinic in Rochester, MN, found no difference in complication rates between patients who received contrast and those who did not.

Half of the 80 million CT scans performed in the U.S. each year are preceded by the injection of iodine-based contrast material. Despite rare reports of acute kidney injury, there is scant evidence that the practice is harming patients, wrote lead author Dr. Robert McDonald, PhD, and colleagues (Radiology, September 9, 2014).

The risky reputation comes mostly from prior uncontrolled studies suggesting that patients who develop contrast-induced nephropathy (CIN) have increased risk of dialysis and death com­pared with patients who do not develop CIN. Those with pre-existing renal function concerns, particularly acute renal failure, chronic renal failure, or diabetes mellitus, are thought to be at the greatest risk, the authors wrote.

In their retrospective study, the researchers sought to assess the risk of emergent dialysis and short-term mortality after the use of intravenous iodinated contrast material.

McDonald and colleagues looked at all contrast-enhanced and unenhanced abdominal, pelvic, and chest CT scans from 2000 to 2010, and they identified patients with pre-existing diabetes mellitus, congestive heart failure, or chronic or acute renal failure.

The researchers documented the effects of contrast on acute kidney injury, defined as serum creatinine levels more than 0.5 mg/dL (44.2 mmol/L) above baseline within 24 to 72 hours of contrast exposure, and dialysis or death within 30 days of exposure using odds ratios (ORs) and hazard ratios (HRs).

Among the 21,346 patients,10,673 had received contrast and 10,673 had not, according to the authors.

Risk of complications after CT contrast administration
Complication type OR p-value
Acute kidney injury 0.94 0.38
Emergent dialysis 0.96 0.89
30-day mortality 0.97 0.45

Patients who developed acute kidney injury had higher rates of dialysis and mortality, but contrast material exposure was not an independent risk factor for either outcome. For dialysis, the odds ratio was 0.89 (95% confidence interval: 0.40-2.01, p = 0.78), and for mortality, the hazard ratio was 1.03 (95% confidence interval: 0.82-1.32, p = 0.63).

The results were the same among patients with compromised kidney function and comorbidities such as congestive heart failure and diabetes, which are assumed to predispose a patient to acute kidney injury.

"These results challenge long-held assumptions regarding the presumed nephrotoxic risk of intravenous contrast material," McDonald said in a statement. "We hope that our findings will help refine the safety profile of these contrast agents."

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