Acute Kidney Injury Risk Linked to Adiposity

PUERTO RICO—Excessive body fat in trauma patients as quantified using computed tomography (CT) scans may be associated with an increased risk of acute kidney injury (AKI), data suggest.

In a prospective study of 49 trauma patients presented at the Society for Critical Care Medicine's 2013 annual meeting, researchers found that AKI risk rises rapidly in patients with large amounts of visceral or subcutaneous abdominal adiposity on CT scans. For example, trauma patients in the 75th percentile for  visceral fat area have a 18% probability of developing AKI, whereas those in the 95th percentile have a 54% chance of developing AKI.  For subcutaneous fat, those in the 75th percentile have an 18% risk for AKI and those in the 95th percentile have a 39% risk for AKI.

The researchers noted that excess adipose tissue causes a chronic inflammatory state, and proinflammatory cytokines have been implicated in AKI pathophysiology.

“The intent of the study was not to create a predictive model,” lead investigator Michael Shashaty, MD, MS, of the Perelman School of Medicine at the University of Pennsylvania in Philadelphia, told Renal & Urology News. “Instead, it highlights both the potential feasibility of directly studying the amount of adipose tissue – as opposed to the less-specific BMI [body mass index]-- in the trauma population, and how probing the mechanisms underlying the obesity-AKI association may, ultimately, lead to a better understanding of AKI pathophysiology.”

CT is used routinely for critically ill trauma patients and can be used to quantitate visceral and subcutaneous adipose tissue accurately, Dr. Shashaty's group noted.

Dr. Shashaty and his colleagues performed the study to build on earlier research showing an association between increased AKI risk and higher BMI in critically ill patients. Using a prospective cohort of trauma patients with an Injury Severity Score of at least 16, and who had stayed in the intensive care unit for more than one day, they retrieved abdominal CT images to quantify adipose tissue.

Among the 49 patients with usable abdominal CT images, those who developed AKI had a significantly higher median area of visceral adipose tissue than those who did not develop AKI (111 vs. 42 cm2). They also had significantly larger areas of subcutaneous fat (245 vs. 152 cm2).

“Right now, we are focused on expanding this study to a larger sample within our trauma cohort in order to improve generalizability and to adjust the association of adipose tissue with AKI for several potential cofounders,” Dr. Shashaty said. “Depending on our findings, studies examining the potential mechanistic pathways by which adipose tissue might predispose critically ill patients to AKI may be warranted.”

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