Urine neutrophil gelatinase‐associated lipocalin to diagnose and characterize acute kidney injury in dogs

BACKGROUND: Urine neutrophil gelatinase‐associated lipocalin (NGAL) is a promising biomarker of acute kidney injury (AKI) in dogs. OBJECTIVES: To evaluate the utility of urinary NGAL for characterizing AKI according to volume responsiveness, presence of inflammation and sepsis, and prognosis. ANIMALS: Dogs with AKI (n = 76) and healthy controls (n = 10). METHODS: Prospective study. Clinical and clinicopathologic data including absolute urine NGAL concentration (uNGAL) and NGAL normalized to urine creatinine concentration (uNGALC) were measured upon admission. Dogs were graded according to International Renal Interest Society (IRIS) AKI guidelines and compared based on AKI features: volume‐responsive (VR‐) AKI vs. intrinsic (I‐) AKI based on IRIS criteria; VR‐AKI and I‐AKI based on urine chemistry; inflammatory versus noninflammatory; septic versus nonseptic; and survivors versus nonsurvivors. Nonparametric statistics were calculated, and significance set at P < .05. RESULTS: Urinary NGAL was significantly higher in dogs with AKI compared to controls, regardless of AKI grade. Urinary NGAL did not differ between dogs with VR‐AKI and I‐AKI based on IRIS criteria, whereas higher uNGALC was recorded in dogs with I‐AKI based on urine chemistry. Urinary NGAL was significantly higher in dogs with inflammatory AKI, whereas no difference with respect to sepsis or outcome was identified. CONCLUSIONS AND CLINICAL IMPORTANCE: Urinary NGAL is a sensitive marker for AKI in dogs, but its specificity is affected by systemic inflammation. Increased urinary NGAL in both I‐AKI and VR‐AKI also suggests the presence of tubular damage in transient AKI. Combining urine chemistry data with IRIS criteria could facilitate AKI characterization in dogs.