Blog entry by Meguid El Nahas

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by Meguid El Nahas - Friday, 7 October 2016, 2:21 PM
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J Am Soc Nephrol. 2016 Sep 29. pii: ASN.2016010021. [Epub ahead of print]

Estimating the Risk of Radiocontrast-Associated Nephropathy.

Abstract

Estimates of the incidence of radiocontrast-associated nephropathy vary widely and suffer from misclassification of the cause of AKI and confounding. Using the Nationwide Inpatient Sample, we created multiple estimates of the risk of radiocontrast-associated nephropathy among adult patients hospitalized in the United States in 2009. First, we stratified patients according to the presence or absence of 12 relatively common diagnoses associated with AKI and evaluated the rate of AKI between strata. Next, we created a logistic regression model, controlling for comorbidity and acuity of illness, to estimate the risk of AKI associated with radiocontrast administration within each stratum. Finally, we performed an analysis stratified by the degree of preexisting comorbidity. In general, patients who received radiocontrast did not develop AKI at a clinically significant higher rate. Adjusted only for the complex survey design, patients to whom radiocontrast was and was not administered developed AKI at rates of 5.5% and 5.6%, respectively. After controlling for comorbidity and acuity of illness, radiocontrast administration associated with an odds ratio for AKI of 0.93 (95% confidence interval, 0.88 to 0.97). In conclusion, the risk of radiocontrast-associated nephropathy may be overstated in the literature and overestimated by clinicians. More accurate AKI risk estimates may improve clinical decision-making when attempting to balance the potential benefits of radiocontrast-enhanced imaging and the risk of AKI.

Copyright © 2016 by the American Society of Nephrology.

Commentary

Excellent analysis of the incidence of radiocontrast associated nephropathy (RCN). To start with it is NOT a "Nephropathy" instead most often a transient rise in serum creatinine that is transient and by definition reversible...so to call it a nephropathy is a misnomer as serum creatinine values rise transiently after a number of interventions including a cooked meat meal, ingestion of an H2blocker or some antibiotics...these dont become Meat Associated Nephropathy, or Cimetidine Associated Nephropathy etc...although some have attributed a "Nephropathy" to Warfarin....that is as ill conceived !

Back to the RCN, the strength of the current analysis is the adjustment for comorbidities, and the actual impact of comorbidities themselves on changes in serum creatinine rather than the associated interventions; radiocontrast administration in this publication or warfarin overanticoagulation (INR >3) elsewhere.

Secondly, the definitions of these entities often depend on variable cut off points for changes in the measured parameter, serum creatinine, that defines the "Nephropathy"...mostly arbitrarily chosen with no consideration for clinical severity, reversibility or enhanced morbidity/mortality, and/or the underlying CKD stage.

Finally, RCN has been a fertile ground for research and interventions. Mechanistic research that led to a number of interventions, most of which have shown little advantage over a bag of normal (or half normal) saline before and after the administration of RC material... 

Nephrology has to guard itself from embarking on research for the sake of research, rather than prioritise research that has clinical relevance, clinical impact and ultimately research that benefit patients...

If we ask of RCN whether it fulfils the 5 WHATs, it is unlikely to meet any of the 5 Whats criteriae:

1. What is the clinical relevance of RCN: Negligible!

2. What is the validity of the data supporting this entity: As shown by the publication under discussion, Minimal!

3. What is the Usefulness/Utility of identifying RCN: Optimise Hydration

4. Risk versus Benefit of RCN: too much emphasis, too much research, too much investments for little return: a bag of Saline would do...

5. Cost benefit analysis: same as 4!

So can we conclude from this publication and my commentary that RCN is an irrelevance?

Perhaps not, except that more attention needs to be paid to radiological investigations, specially those that are aggressive and invasive, in patients with significant comorbidities as these are at higher risk of acute on chronic kidney disease...regardless of the coadministration of potentially nephrotoxic agents!

 

 

 
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