Risk of kidney injury in contrast CT imaging overstated, experts say

Jan. 21 (UPI) -- Two major healthcare professional societies issued consensus statements Tuesday in support of the use of IV-administered contrast solutions during CT scans.

The groups -- the American College of Radiology and the National Kidney Foundation -- highlight the enhanced diagnostic accuracy afforded by the use of contrast in CT, an imaging tool that can spot various cancers and other injuries.

Historically, iodinated contrast solutions, which are delivered intravenously prior to scanning to provide better viewing of key areas of the body, have been linked with side effects -- most notably, reduced kidney function.

"The historical fears of kidney injury from contrast-enhanced CT have led to unmeasured harms related to diagnostic error and diagnostic delay," statement co-author Matthew S. Davenport, an associate professor of radiology and urology at the University of Michigan, said in a press release. "Modern data clarify that this perceived risk has been overstated."

The consensus statements penned by Davenport and his colleagues were published in the journal Radiology.

Iodinated contrast solutions are often used with CT, or computed tomography, to help clinicians evaluate disease and to determine treatment response. Although patients have benefited from their use, they have been administered with caution or even withheld in those with reduced kidney function due to the perceived risks of contrast-induced acute kidney injury.

The consensus statements highlight the differences between contrast-induced acute kidney injury and contrast-associated acute kidney injury. In the former, the authors write, a causal relationship exists between contrast solutions and kidney injury whereas, in the latter, a direct causal relationship has not been demonstrated.

The authors suggest that studies that have not properly distinguished between the two have contributed to the overstatement of the risk associated with the use of contrast. In some cases, they noted, this has hindered timely and accurate diagnosis.

While the risk of contrast-induced acute kidney injury remains unknown, the authors recommend intravenous normal saline for people without certain conditions, like heart failure, who have acute kidney injury or an estimated glomerular filtration rate, or eGFR, less than 30 mL/min per 1.73 m2 and are not on maintenance dialysis. eGFR is a commonly used measure of kidney function.

Having one kidney should not, on its own, influence decisions on risk for contrast-induced acute kidney injury. And lowering the contrast media dose below a known diagnostic threshold should be avoided due to the risk of lowering diagnostic accuracy, they add.

Also, when feasible, medications that are toxic to the kidneys should be withheld by the referring clinician in those at high risk. However, renal replacement therapy should not be started or changed based only on contrast media administration.

Even after clarifying previous practices and concerns, the statement authors say more research is needed on the risk for contrast-induced kidney injury in both adult and pediatric populations.

Said Davenport, "our intent is to provide multi-disciplinary guidance regarding the true risk to patients and how to apply a consideration of that risk to modern clinical practice."