Study Contradicts Consensus on Women’s Risk of Kidney Injury Following Surgery

A new study disputes the generally held consensus that female sex is an independent risk factor for the development of cardiothoracic surgery–associated acute kidney injury (CSAKI).

“This finding was surprising insofar as it contradicted accepted dogma,” said lead study author Joel Neugarten, MD, in the Renal Division at Montefiore Medical Center in the Bronx, New York.

Female sex is a well-established risk factor for the development of CSAKI, the researchers said. “In striking contrast, women are less likely to develop AKI associated with noncardiac surgical procedures than men. In an attempt to ascertain why being a woman might be protective for ischemic AKI after general surgery but deleterious in patients undergoing cardiothoracic surgery, we examined [CSAKI] in greater detail.”

The researchers performed a systematic review and meta-analysis of CSAKI studies published between January 1978 and December 2015 to further explore the relationship between sex and CSAKI. They identified 64 studies that provided sex-specific data regarding the incidence of CSAKI among 1,057,412 subjects.
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Utilizing univariate analysis, the researchers found that women were more likely than men to develop AKI postoperatively. However, when the investigators restricted the analysis to the 120,464 subjects reported in 29 studies that utilized Acute Kidney Injury Network (AKIN); Risk, Injury, Failure, Loss, End Stage (RIFLE); or Kidney Disease: Improving Global Outcomes (KDIGO) criteria to define AKI, they found no significant sex-related difference in risk.

Seventeen studies utilized multivariate analysis to assess risk factors for CSAKI and provided sex-specific odds ratios. Among the 1,587,181 individuals included in these studies, the risk of developing CSAKI was not significantly associated with sex. However, when they restricted the analysis to the 5106 subjects reported in 4 studies that utilized AKIN criteria to define AKI, the risk of developing AKI was significantly lower in women compared with men.

“These disparate results may merely reflect different definitions of CSAKI,” the researchers concluded. “However, this simple explanation may mask more complex interactions between sex and cardiovascular surgery. We believe that factors related to but not inherent in one’s gender may be responsible and may reflect a greater burden of comorbidities in women undergoing cardiovascular surgery due to disparities in health care delivery or due to a more aggressive course of cardiovascular disease in women.”

Animal models of AKI show female animals are protected from kidney damage, said Dr Neugarten, noting that they will continue research in this area by examining whether women are similarly protected from AKI acquired in a hospital setting. “We hypothesize that female sex hormones are renoprotective and confer protection from acute kidney injury.”

—Mike Bederka

Reference:

Neugarten J, Sandilya S, Singh B, Golestaneh L. Sex and the risk of AKI following cardio-thoracic surgery: a meta-analysis [published online October 20, 2016]. Clin J Am Soc Nephrol. doi:10.2215/CJN.03340316.