A 59-year-old man presents with abdominal pain. He has a history of small bowel obstruction and diverticulitis. His medical history includes chronic kidney disease (CKD; baseline creatinine, 1.8 mg/dL), hypertension, type 2 diabetes, and depression. He had a colectomy 6 years ago for colon cancer.
He takes the following medications: Semaglutide (1 mg weekly), amlodipine (5 mg once daily), and escitalopram (10 mg once daily). On physical exam his blood pressure is 130/80 mm Hg, his pulse is 90, and his temperature is 37.2 degrees C. He has normal bowel sounds but guarding in the right lower quadrant.
Dr. Douglas S. Paauw
His hemoglobin is 14 g/dL, his blood sodium is 136 mEq/L, his blood potassium is 4.0 mmol/L, his BUN is 26 mg/dL, and his creatinine is 1.9 mg/dL. His kidney, ureter, bladder x-ray is unremarkable.
What imaging would you recommend?
A) CT without contrast
B) CT with contrast
C) MRI
D) Abdominal ultrasound
This patient has several potential causes for his abdominal pain that imaging may clarify. I think a contrast CT scan would be the most likely to provide helpful information. It is likely that if it were ordered, there may be hesitation by the radiologist to perform the scan with contrast because of the patient’s CKD.
Concern for contrast-induced kidney injury has limited diagnostic testing for many years. How strong is the evidence for contrast-induced kidney injury, and should we avoid testing that requires contrast in patients with CKD? McDonald and colleagues performed a meta-analysis with 13 studies meeting inclusion criteria, involving 25,950 patients.1 They found no increased risk of acute kidney injury (AKI) in patients who received contrast medium compared with those who did not receive contrast; relative risk of AKI for those receiving contrast was 0.79 (confidence interval: 0.62-1.02). Importantly, there was no difference in AKI in patients with diabetes or CKD.
Ehmann et al. looked at renal outcomes in patients who received IV contrast when they presented to an emergency department with AKI.2 They found that in patients with AKI, receiving contrast was not associated with persistent AKI at hospital discharge. Hinson and colleagues looked at patients arriving at the emergency department and needing imaging.3 They did a retrospective, cohort analysis of 17,934 patients who had CT with contrast, CT with no contrast, or no CT. Contrast administration was not associated with increased incidence of AKI (odds ratio, 0.96, CI: 0.85-1.08).
Aycock et al. did a meta-analysis of AKI after CT scanning, including 28 studies involving 107,335 patients.4 They found that compared with noncontrast CT, CT scanning with contrast was not associated with AKI (OR, 0.94, CI: 0.83-1.07). Elias and Aronson looked at the risk of AKI after contrast in patients receiving CT scans compared with those who received ventilation/perfusion scans to evaluate for pulmonary embolism.5 There were 44 AKI events (4.5%) in patients exposed to contrast media and 33 events (3.4%) in patients not exposed to contrast media (risk difference: 1.1%, 95% CI: -0.6% to 2.9%; OR, 1.39, CI: 0.86-2.26; P = .18).
Despite multiple studies showing no increased risk, there is still a concern that contrast can cause AKI.6 Animal models have shown iodinated contrast can have a deleterious effect on mitochondria and membrane function.6 Criticisms of the retrospective nature of many of the studies I have shared, and the lack of randomized, controlled trials are that there may be bias in these studies, as the highest-risk patients are the ones most likely not to receive contrast. In a joint guideline from the American College of Radiology and the National Kidney Foundation, this statement was made: “The risk of acute kidney injury developing in patients with reduced kidney function following exposure to intravenous iodinated contrast media has been overstated.”7 Their recommendation was to give contrast if needed in patients with glomerular filtration rates (GFRs) greater than 30.
Myth: Contrast-induced renal injury is a concern.
Clinical impact: For CT scanning, it is OK to give contrast when needed. A conservative cutoff for contrast use would be a GFR less than 30.
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. Contact Dr. Paauw at dpaauw@uw.edu.
References
1. McDonald JS et al. Radiology. 2013:267:119-128.
2. Ehmann MR et al. Intensive Care Med. 2023:49(2):205-215.
3. Hinson JS et al. Ann Emerg Med. 2017;69(5):577-586.
4. Aycock RD et al. Ann Emerg Med. 2018 Jan;71(1):44-53.
5. Elias A, Aronson D. Thromb Haemost. 2021 Jun;121(6):800-807.
6. Weisbord SD, du Cheryon D. Intensive Care Med. 2018;44(1):107-109.
7. Davenport MS et al. Radiology. 2020;294(3):660-668.