CT scans done with intravenous contrast material did not increase the incidence of death or of contrast-induced kidney damage, even in patients with a pre-existing condition, according to a study published online in Radiology.

Lead researcher Robert J. McDonald, MD, PhD, a radiology resident at the Mayo Clinic in Rochester, Minn., said previous retrospective studies have casually linked the use of iodine-based contrast CTs to kidney damage, or contrast-induced nephropathy, because they lacked adequate controls. For example, wrote McDonald and colleagues, the risk attributed to IV contrast material exposure has been extrapolated from studies that lacked a control population of patients who did not receive contrast material.

As a result of these concerns, the guidelines of the American College of Radiology recommend more restricted use of intravenous contrast material for high-risk patients that have included those with diabetes, heart failure or renal failure.

However, the authors wrote that their single center, retrospective study found that intravenous contrast material administration “was not associated with excess risk” of death, acute kidney injury (AKI), or dialysis, even among patients with pre-existing health conditions that would predispose them to nephrotoxicity.

“For nearly 60 years, physicians have worried about contrast-induced nephropathy when using iodinated contrast material, particularly for patients with impaired kidney function,” McDonald said in a press release. “Emerging evidence now suggests these concerns are likely vastly overestimated.”

About half of the 80 million CT scans performed each year in the U.S. are done using a contrast material, according to McDonald.

Researchers analyzed information on 21,346 patients who underwent abdominal, pelvic and thoracic CT scans at the Mayo Clinic between 2000 and 2010. The group included 10,673 patients who each underwent a contrast-enhanced CT exam and 10,673 patients who underwent a similar CT without contrast.

The two groups of patients were matched by demographics and clinical characteristics, including gender, race and preexisting conditions.

The results for both of the groups were not significantly different for mortality or dialysis, according to the authors.

“Although patients who developed AKI had higher rates of dialysis and mortality, contrast material exposure was not an independent risk factor for either outcome for dialysis,” McDonald and colleagues wrote.