Fractional excretion of electrolytes in volume‐responsive and intrinsic acute kidney injury in dogs: Diagnostic and prognostic implications

Abstract

BackgroundThe value of fractional excretion (FE) of electrolytes to characterize and prognosticate acute kidney injury (AKI) is poorly documented in dogs.ObjectivesTo evaluate the diagnostic and prognostic roles of FE of electrolytes in dogs with AKI.AnimalsDogs (n = 135) with AKI treated with standard care (February 2014‐December 2016).MethodsProspective study. Clinical and laboratory variables including FE of electrolytes, were measured upon admission. Dogs were graded according to the AKI‐IRIS guidelines and grouped according to AKI features (volume‐responsive, VR‐AKI; intrinsic, I‐AKI) and outcome (survivors/non‐survivors). Group comparison and regression analyses with hazard ratios (HR) evaluation for I‐AKI and mortality were performed. P < .05 was considered significant.ResultsFifty‐two of 135 (39%) dogs had VR‐AKI, 69/135 (51%) I‐AKI and 14/135 (10%) were unclassified. I‐AKI dogs had significantly higher FE of electrolytes, for example, FE of sodium (FENa, %) 2.39 (range 0.04‐75.81) than VR‐AKI ones 0.24 (range 0.01‐2.21; P < .001). Overall, case fatality was 41% (55/135). Increased FE of electrolytes were detected in nonsurvivors, for example, FENa 1.60 (range 0.03‐75.81) compared with survivors 0.60 (range 0.01‐50.45; P = .004). Several risk factors for death were identified, including AKI‐IRIS grade (HR = 1.39, P = .002), FE of electrolytes, for example, FENa (HR = 1.03, P < .001), and urinary output (HR = 5.06, P < .001).Conclusions and Clinical ImportanceFractional excretion of electrolytes performed well in the early differentiation between VR‐AKI and I‐AKI, were related to outcome, and could be useful tools to manage AKI dogs in clinical practice.

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

“…Volume‐responsive AKI generally is thought to reflect a less severe form of renal insult compared to the intrinsic form. This is supported by evidence of a lower increase in markers of kidney function (sCr) and tubular injury (FE of electrolytes) in human medical and veterinary studies . Increases in uNGAL are detected in people with transient VR‐AKI compared to healthy subjects, indicating that transient AKI reflects mild renal injury rather than a completely functional form of AKI with no cellular damage.…”

“…Our study was a prospective, observational case‐control study performed at the Veterinary University Hospital (VUH) of the University of Bologna between February 2014 and December 2016. The subset of dogs included in the present study was part of an extended investigation on AKI in dogs …”

“…Inclusion criteria were acute onset of clinical signs (<7 days) with history, and clinical, clinicopathological and imaging findings suggestive of AKI. Specifically, the diagnosis of AKI was based on sCr >1.6 mg/dL (azotemic AKI) or a progressive non‐azotemic >0.3 mg/dL increase in sCr from baseline within 48 hours, persistent oliguria or anuria (urine output <1 mL/kg/h) over 6 hours, or both criteria, as previously reported …”

“…Conversely, I‐AKI was defined as persistent azotemia over 48 hours with or without oliguria or anuria (<1 mL/kg/h) despite appropriate fluid therapy, once euvolemia was achieved. Based on the results of a previous study, the cutoffs identified for the fractional excretion of sodium (FENa) and for the urinary creatinine (uCr) to sCr ratio (uCr/sCr) to differentiate dogs with VR‐AKI and I‐AKI were used for further grouping . Thus, dogs were defined as volume‐responsive based on urine biochemistry (VR‐AKIchem) if they had FENa ≤0.9%, uCr/sCr ≥33% or both, whereas they were considered affected by I‐AKI based on urine chemistry (I‐AKIchem) if they had FENa >0.9% and uCr/sCr <33%.…”

“…The growing interest in refining AKI recognition and characterization in veterinary medicine has led to development of the AKI‐International Renal Interest Society (IRIS) grading system, which proposes standardized criteria to diagnose and classify AKI based on clinical and clinicopathological data and response to treatment . Both sCr and UO criteria increasingly have been used to diagnose and grade AKI in recent veterinary studies, with emphasis on the recognition of volume‐responsive AKI (VR‐AKI) and intrinsic AKI (I‐AKI) as a continuum of renal injury of increasing severity …”