Patient with CKD: Contrast or no contrast?

A 67-year-old man with stage 3 chronic kidney disease (CKD) develops abdominal pain over 24 hours. He has had low grade fevers and nausea. He has a history of colon cancer and had a resection four years ago. Abdominal exam reveals tenderness to palpation, including rebound tenderness in his right lower quadrant. Labs: hemoglobin: 13; hematocrit: 39; white blood cells: 18,000; platelets: 333; blood urea nitrogen: 28; creatinine: 1.8 (estimated glomerular filtration rate: 37); sodium: 136; potassium: 3.9; bicarbonate: 24; chlorine: 105; and lipase: 10.

Dr. Douglas S. Paauw

What testing would you recommend?

A) Ultrasound

B) Non contrast computed tomography (CT)

C) Contrast CT

D) MRI without gadolinium

The correct answer here is to get a contrast CT scan, as it will give you the most appropriate diagnostic information.

For years, we have hesitated to order contrast studies in our patients with CKD, for fear of causing contrast-induced nephrotoxicity. We might choose less helpful studies that avoid contrast, or might not obtain imaging that is needed. Over the years I have especially seen this in the case of avoiding computed tomography angiography (CTA) for evaluation of pulmonary embolus and choosing the much less useful ventilation/perfusion scan. The problem arises with the fact that patients with CKD are more likely to develop worsening renal function when they get sick.

The assumption had been that when kidney injury occurred after contrast that it was due to the contrast. Many recent studies refute this assumption. Lee and colleagues performed an analysis of six retrospective studies involving a total of 55,963 participants. They found that patients with CKD receiving contrast material did not have an increased risk of deteriorating renal function compared with those without CKD (odds ratio, 1.07; 95% confidence interval, 0.98-1.17).¹

The early studies reporting contrast-induced renal disease were in patients who received high osmolality contrast agents.² Most patients now receive low osmolality agents, with less nephrotoxicity.³

Key points of guidelines

This year, the American College of Radiology and the National Kidney Foundation put out joint guidelines that helped clarify why there is a diminished concern for contrast-induced kidney disease in the modern era.⁴ Below are some of the key points of these guidelines:

• The risk of contrast-induced acute kidney injury (AKI) 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 contrast-induced chronic kidney insufficiency risk.
• Contrast-induced AKI risk should be determined primarily by using CKD stage and AKI.
• Patients at high risk for contrast-induced kidney injury include those with recent AKI and those with estimated glomerular filtration rate (eGFR) less than 30 mL/min per 1.73 m².

Data supporting guidelines

The data from several studies used to support these recommendations were impressive, showing just how low the risk for contrast-induced AKI is in most patients. In these studies, the risk of contrast-induced AKI has been estimated to be near 0% for patients with an eGFR greater than or equal to 45 and 0%-2% for patients with an eGFR of 30-44.^5-7 This information and recommendations make imaging much easier. In most of our patients, we can get contrast studies when we need them. The group to be concerned about are patients with eGFRs less than 30. The guidelines single out this group as the patients where risk/benefit needs to be calculated before proceeding with the study, and to use prophylactic saline hydration in patients not undergoing dialysis.

Myth: Contrast-induced renal disease is common.

Dr. Paauw is professor of medicine in the division of general internal medicine at the University of Washington, Seattle, and he serves as third-year medical student clerkship director at the University of Washington. He is a member of the editorial advisory board of Internal Medicine News. Dr. Paauw has no conflicts to disclose. Contact him at imnews@mdedge.com.

References

1. Lee YC et al. Contrast-induced acute kidney injury among patients with chronic kidney disease undergoing imaging studies: A meta-analysis. Am J Roentgenol. 2019 Oct;213(4):728-35.

2. Luk L et al. Intravenous contrast-induced nephropathy: The rise and fall of a threatening idea. Adv Chronic Kidney Dis. 2017 May;24(3):169-75.

3. Goldfarb S et al. Low-osmolality contrast media and the risk of contrast-associated nephrotoxicity. Invest Radiol. 1993;28(Suppl 5):7-10.

4. Davenport MS, et al. Use of intravenous iodinated contrast media in patients with kidney disease: Consensus statements from the American College of Radiology and the National Kidney Foundation. Kidney Med. 2020 Jan 22;2(1):85-93.

5. Davenport MS et al. Contrast material–induced nephrotoxicity and intravenous low-osmolality iodinated contrast material. Radiology. 2013;267(1):94-105.

6. McDonald RJ et al. Intravenous contrast material–induced nephropathy: Causal or coincident phenomenon? Radiology. 2013;267(1):106-18.

7. McDonald JS et al. Risk of intravenous contrast material–mediated acute kidney injury: A propensity scorematched study stratified by baseline-estimated glomerular filtration rate. Radiology. 2014;271(1):65-73.