Characterization of acute kidney injury in hospitalized dogs and evaluation of a veterinary acute kidney injury staging system

Objective - To retrospectively apply standards characterizing acute kidney injury (AKI) used in human medicine to a population of critically ill hospitalized dogs in order to identify dogs with potential AKI based on subtle increases in plasma creatinine concentration. Design - Retrospective study. Setting - University Veterinary Medical Teaching Hospital. Animals - One hundred and sixty-four client-owned dogs admitted to the intensive care unit. Interventions - None. Measurements and Main Results - Medical records of 164 dogs meeting the study inclusion criteria were reviewed to identify age, results of creatinine measurements, discharge status, length of stay, performance of general anesthesia, number of diagnoses, and calculated survival prediction index scores (SPI2). A veterinary AKI (VAKI) staging system was retrospectively applied to classify dogs based on increase in creatinine concentration from baseline as follows: stage 0 (S0; < 150%), stage 1 (S1; 150-199% or >= 26.5 mu mol/L [>= 0.3 mg/dL]), stage 2 (S2; 200-299%), or stage 3 (S3; >= 300%). Of the dogs evaluated, 140/164 were VAKI stage S0, 19/164 were classified as S1, 3/164 as S2, and 2/164 were S3. Mortality rate was greater for S1-3 (13/24; 54.2%) compared to S0 dogs (22/140; 15.7%) (P < 0.0001). Length of stay, general anesthesia, and number of diagnoses were not associated with survival. In a logistic regression model, stage and age were jointly, significantly associated with mortality (P = 0.0002 and P = 0.0330, respectively). Mean SPI2 scores were not different between S0 (0.52) and S1 (0.59) dogs (P = 0.23). Only 4/19 (21%) of S1 dogs had a peak plasma creatinine concentration above the laboratory reference interval. Conclusions - Dogs meeting VAKI stage 1-3 criteria were less likely to survive to discharge. Small increases in plasma creatinine concentration may be clinically relevant even when absolute values are within reference intervals.