Post-operative serum uric acid and acute kidney injury

Background: We hypothesized that post-operative serum uric acid (SUA) may be associated with acute kidney injury (AKI). Methods: In this prospective, observational study, the relationships between SUA, urine neutrophil gelatin-ase-associated lipocalin (uNGAL) and interleukin-18 (uIL-18), serum monocyte chemoattractant protein-1 (sMCP-1) and tumor necrosis factor-alpha (sTNF-al-pha), and incidence of AKI were determined. SUA were divided into tertiles and their association with AKI investigated. Results: A total of 100 cardiac surgery patients were included for analyses. The 1 ^st, 2 ^nd, and 3 ^rd SUA tertiles were associated with 15.1%, 11.7%, and 54.5% incidence of AKI, respectively. The 3 ^rd SUA tertile, compared to the referent 1 ^st tertile, was associated with an eightfold (OR 8.38, CI _95% 2.13-33.05, p=0.002) increased risk for AKI. Patients with AKI on post-operative day 1 (n=11) were then excluded for the purpose of determining the predictive value of SUA to diagnose AKI on postoperative day 2 and during hospital stay. In comparison to the referent 1 ^st tertile, the 3 ^rd tertile SUA was associated with an eightfold increased risk for AKI on post-operative day 2 (adjusted OR 7.94, CI _95% 1.50-42.08, P=.015) and a five-fold increased risk for AKI during hospital stay (OR 4.83, CI _95% 1.21-19.20, P=.025), respectively. SUA (Area Under Curve, AUC 0.77 (CI _95% 0.66-0.88, P<.001), serum creatinine (0.73, CI _95% 0.62-0.84, P<.001) and sTNF-alpha (0.76, CI _95% 0.65-0.87, P<.001) had the best diagnostic performance measured by the Receiver Operating Characteristics curves. Conclusions: We conclude that post-operative SUA is associated with an increased risk for AKI and compares well to conventional markers of AKI.