Is Contrast Induced Nephropathy really a thing?
Title of Paper:
Risk of Acute Kidney Injury After Intravenous Contrast Media Administration
Journal and Year:
Annals of Emergency Medicine, 2016
Overview of study methods:
- Single centre, retrospective review
- ED patients undergoing CT scan with IV contrast media were compared to both patients having CT without IV contrast and to patients who did not have a CT scan.
- Patients had to have a serum creatinine measurement in the 8 hours preceding the scan, and a repeat measurement in the following 48-72 hours
- Patients were excluded initial creatinine too low (<35 umol/L) or too high (>354 mol/L), had a renal transplant, were on dialysis, had a visit to ED in previous 6 months, had a contrast CT within 72 hours of ED departure or had incomplete data
- Primary outcome measure was the incidence of Acute Kidney Injury, both using published criteria for Contrast Induced Nephropathy and the Acute Kidney Injury Network’s definition ok AKI
- Powered to find difference between groups as low as 1.5%
Summary of Results:
- 17,934 patient visits included overall
- 12,700 patient visits with CT scan performed
- 56.7% received IV contrast
- No difference found in incidence of AKI between the three groups
- Incidence by AKIN definition: Contrast 6.8%, Non-Contrast 8.9%, No CT 8.1%
- Incidence by CIN definition: Contrast 10.6%, Non-Contrast 10.2%, No CT 10.9%
- A well structured, methodical retrospective review with decent attempts to minimise bias
- Authors recognised that the group receiving contrast were likely to be selected by clinical gestalt as less likely to develop AKI in first place, and would be more likely to receive nephroprotective treatment. They used propensity-score-matching adjustment and multiple logistic regression analysis (clever statistical voodoo) to minimise the effect of this bias and other known predictors of AKI and still found no difference between groups.
Clinical Bottom Line:
I don’t see radiology policies changing over this paper but it certainly adds to the body of literature showing that there may not be the causation between contrast administration and AKI that has been presumed from previous publications demonstrating association.
This is probably the best performed study we are going to get on this topic until a prospective RCT is performed.
Other #FOAMed Resources:
- LITFL have a nice summary of Contrast Induced Nephropathy
emDocs give a good written summary of this paper and outline the history of previous studies too