The Impact of Obesity on Renal Trauma Outcome: An Analysis of the National Trauma Data Bank from 2013 to 2016

Abstract

Background The obesity paradox has been recently demonstrated in trauma patients, where improved survival was associated with overweight and obese patients compared to patients with normal weight, despite increased morbidity. Little is known whether this effect is mediated by lower injury severity. We aim to explore the association between body mass index (BMI) and renal trauma injury grade, morbidity, and in-hospital mortality. Methods A retrospective cohort of adults with renal trauma was conducted using 2013–2016 National Trauma Data Bank. Multiple regression analyses were used to assess outcomes of interest across BMI categories with normal weight as reference, while adjusting for relevant covariates including kidney injury grade. Results We analyzed 15181 renal injuries. Increasing BMI above normal progressively decreased the risk of high-grade renal trauma (HGRT). Subgroup analysis showed that this relationship was maintained in blunt injury, but there was no association in penetrating injury. Overweight (OR 1.02, CI 0.83–1.25, p = 0.841), class I (OR 0.92, CI 0.71–1.19, p = 0.524), and class II (OR 1.38, CI 0.99–1.91, p = 0.053) obesity were not protective against mortality, whereas class III obesity (OR 1.46, CI 1.03–2.06, p = 0.034) increased mortality odds. Increasing BMI by category was associated with a stepwise increase in odds of acute kidney injury, cardiovascular events, total hospital length of stay (LOS), intensive care unit LOS, and ventilator days. Conclusions Increasing BMI was associated with decreased risk of HGRT in blunt trauma. Overweight and obesity were associated with increased morbidity but not with a protective effect on mortality. The obesity paradox does not exist in kidney trauma when injury grade is accounted for.

Cushioning the blow: role of perirenal fat in renal trauma injury severity

“…Higher BMI potentially reflects more adiposity or more muscularity [9], thus the total effect in a population could be that PFT increases with BMI at a moderate rate. Previously we reported that higher BMI category was associated with lower risk of HGRT in a sample of >15 000 patients [8]. Patients in a higher BMI category are expected to have, on average, more adiposity (including PFT) than those in a lower BMI group.…”

“…We found that increasing PFT was associated with lower risk of HGRT. We had sought to specify and expand on the association between higher BMI and lower HGRT that was previously reported [8]. Anatomically, the kidney is encased by fat and Gerota's fascia in the retroperitoneum, with primary attachments being the renal pedicle and PUJ.…”

“…Several studies have supported a protective role of adiposity in reducing damage in blunt trauma [3][4][5][6][7]. Recently, the risk of HGRT was shown to be associated with body mass index (BMI) in patients sustaining blunt trauma, with higher BMI category conferring lower risk of HGRT in a stepwise manner [8]. BMI has limited ability in quantifying adiposity, especially being unable to differentiate fat tissue from other types of tissue [9].…”

Subcutaneous Adipose Tissue Is Associated with Acute Kidney Injury after Abdominal Trauma Based on the Generalized Propensity Score Approach: A Retrospective Cohort Study

“…Several studies have shown that obesity with body mass index (BMI) ≥30 kg/m 2 increased the risk of AKI following trauma [7, 8]. However, BMI is not a specific measure for adiposity which also depends on lean and fluid mass, and BMI cannot distinguish between visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) [9, 10].…”