Risk Overstated for IV Iodinated Contrast Media Use in Patients with Kidney Disease

The risk of using intravenous iodinated contrast media in CT scans for patients with existing disease has been exaggerated, according to new consensus statements from the American College of Radiology (ACR) and the National Kidney Foundation (NKF).

The statements were published simultaneously in the Jan. 21 issues of Radiology and Kidney Medicine.

Although IV contrast is routinely used to augment the efficacy of CT in evaluating disease and pinpointing the best treatment options, patients with reduced kidney function routinely have contrast withheld or postponed due to the perceived risk of contrast-induced acute kidney injury (CI-AKI) where the contrast directly causes the harm. This frequently results in delayed treatment that causes morbidity or mortality in patients.

This problem largely stems from study design, said lead study author Matthew Davenport, M.D., associate professor of radiology and urology at the University of Michigan in Ann Arbor.

“Most studies looking at the use of contrast in patients with kidney disease have not included a control group of patients not exposed to contrast, so it was assumed that all kidney injuries happening around the time of contrast exposure were caused by the contrast,” he told Diagnostic Imaging. “The overstatement of risk exists because much of the kidney injuries that happen around the time of kidney studies are just coincidental. Patients don’t get a CT scan unless they’re already sick.”

In many cases, cancer, infection, inflammation, or nephrotoxic medication could be responsible for the kidney injury, he said. These instances – where kidney injury can’t be directly attributed to contrast media – are considered contrast-associated acute kidney injury (CA-AKI).

These consensus statements are intended to give both radiologists and nephrologists cross-specialty guidelines for how best to approach using contrast media in this patient population. Following these statements will not only result in more standardized care, but it will also ensure the clearest images and the most informed diagnoses for these patients.

“When doctors at the local level are trying to determine policies for treating patients with reduced kidney function, they now have guidelines approved by both disciplines that they can consult about what they should do,” he said.

Most importantly, although the true risk of CI-AKI remains unclear, the consensus statements do offer several directions:

• Use intravenous normal saline for patients without contraindication, such as heart failure, who have acute kidney injury or an estimated glomerular filtration rate (eGFR) less than 30 mL/min per 1.73 m2 who aren’t undergoing maintenance dialysis.

• In high-risk circumstances, consider prophylaxis in patients with eGFR of 30-44 mL/min/1.73 m2 at the ordering clinician’s discretion.

• Rush dialysis isn’t needed when patients receive a contrast load. Dialysis can proceed at the normal time without acceleration or prescription change.

In addition, the consensus statements warn providers against lowering contrast media dose below a known diagnostic threshold because it decreases diagnostic accuracy. Also, referring clinicians should also withhold nephrotoxic medications in high-risk patients.

Overall, the ACR and NKF drafted 15 recommendations:

• The terms CA-AKI should be used in clinical practice due to the large proportion of AKI events correlated with, but not expressly caused by, contrast media administration.

• CI-AKI is only feasible for diagnosis in the context of a well-matched controlled study.

• Kidney Disease Improving Global Outcomes (KDIGO) AKI criteria are recommended for AKI diagnosis, and KDIGO CKD criteria are recommended for CKD diagnosis.

• CI-AKI risk from intravenous iodinated contrast media is lower than previously thought. Necessary contrast material-enhanced CT without a suitable alternative should not be avoided solely on the basis of CI-AKI risk.

• CI-AKI risk should be determined primarily by using CKD stage and AKI. High-risk patient include those with recent AKI and those with eGFR less than 30 mL/min/1.73m2, including nonanuric patients undergoing maintenance dialysis.

• Kidney function screening should be used to identify patients at high risk for CI-AKI. Personal kidney disease history is the strongest risk factor, pointing to the need for kidney function assessment.

• Radiologist-clinician discussions about risks and benefits of contrast-enhanced imaging can be helpful in patients at high risk for CI-AKI.

• There are no clinically relevant differences in CI-AKI risk between iso-osmolality and low-osmolality iodinated contrast media.

• Prophylaxis with intravenous normal saline is indicated for patients no undergoing dialysis who have eGFR less than 30mL/min/1.73 m2 or AKI. In individual high-risk circumstances, prophylaxis may be considered in patients with eGFR of 30-44 mL/min/1.73m2 at the discretion of the ordering clinician.

• Prophylaxis is not indicated for patients with stable eGFR greater than or equal to 45 mL/min/1.73m2

• Kidney replacement therapy should not be initiated or have the schedule adjusted solely on the basis on contrast media administration.

• The presence of a solitary kidney should not independently influence decision making regarding the risk of CI-AKI.

• In patients at high risk of CI-AKI, ad hoc lowering of contrast media dose below a known diagnostic threshold should be avoided. Rather, the minimum routine clinical diagnostic dose should be used.

• When feasible, nephrotoxic medications should be withheld by the referring clinician in patients at high risk.

• Data on risk of CI-AKI in pediatric patients is extrapolated from data in adult patients. Pediatric-specific research in this area in a major unmet need.