Prevention of acute renal failure

Prospective evaluation of 5 urinary biomarkers as predictors of acute kidney injury in nonazotemic, hospitalized dogs

BACKGROUND

Early recognition of acute kidney injury (AKI) is hindered by current definitions and use of traditional, insensitive markers.

HYPOTHESIS/OBJECTIVES

Urinary (u) activity of γ-glutamyl transpeptidase (GGT) and alkaline phosphatase (ALP), and concentrations of heat-shock protein 70 (HSP70) and interleukins (ILs) -6 and -18, are predictive biomarkers for AKI and survival.

ANIMALS

Nonazotemic, hospitalized dogs (n = 118) and healthy controls (n = 20).

METHODS

A prospective observational study. Nonazotemic dogs at risk of AKI were recruited and their urinary biomarker concentrations were measured at presentation. Serum creatinine (sCr) and symmetric dimethylarginine (sSDMA) were measured daily until discharge/death.

RESULTS

The overall case fatality rate was 18.6%. Fifteen dogs (12.7%) developed AKI, which was associated with death (relative risk, 3.2; 95% confidence interval [CI], 1.57-6.55). All 5 urinary biomarkers were significantly higher in hospitalized dogs compared to controls, with minimal overlap. uHSP70/uCr, uGGT/uCr, and uIL-6/uCr at presentation were higher in dogs which later developed AKI. Areas under the receiver operator characteristic curve (AUROC) (95% CI) for the 3 biomarkers as predictors of AKI were 0.67 (0.51-0.83), 0.68 (0.55-0.81), and 0.78 (0.65-0.91), respectively. When they were categorically classified as elevated/normal, each additional elevated biomarker increased the odds for AKI (OR, 2.83; 95% CI, 1.23-6.52, P = .01). Agreement between sCr and sSDMA was poor (Cohen's kappa = .071). The AUROC of SDMA at presentation for AKI prediction was 0.73 (0.51-0.95).

CONCLUSIONS AND CLINICAL IMPORTANCE

Kidney injury was common, irrespective of subsequent worsening of azotemia or death. The predictive value of individual urinary biomarkers was reduced by moderate sensitivities and specificities. SDMA showed moderate discriminatory utility for AKI prediction, and often displayed discordant results with sCr.

The kidney in critically ill small animals

Critically ill animals may have preexisting renal disease or develop acute kidney injury as a consequence of their presenting complaint. Age, concurrent medical therapy, electrolyte and fluid imbalances, and exposure to potential nephrotoxicants are factors that predispose to acute kidney injury. Many risk factors are correctable or manageable, and these should be addressed whenever possible. Measurement of serum creatinine is insensitive for the detection of acute kidney injury, and clinicians should consider assessment of other parameters such as urine output, urinalysis, and urine chemistry results. A stepwise approach for management of acute kidney injury in small animal patients is outlined.

Characterization of primary rat proximal tubular cells by gene expression analysis

The kidney plays a major role in excretory and reabsorptive processes. The kidney cortex consists primarily of proximal tubular cells, which are epithelial cells that are often involved in the induction and progression of various kidney diseases. Therefore primary proximal tubular cells are widely used as a renal cell model. To further characterize this kidney in vitro model different time points in culture after isolation of the cells were compared to the cortex in vivo using gene expression analysis based on microarrays. This study revealed that many metabolic pathways and some kidney-specific functions are lacking in the in vitro model. Furthermore genes involved in RNA and protein synthesis, intracellular transport, extracellular matrix and cytoskeletal organization were upregulated in culture compared to in vivo, indicating proliferation of the cells and differentiation into a cell culture phenotype. The data represented here may help to evaluate the in vivo relevance of results obtained with this in vitro model.

Acute Renal Failure in Dogs After the Ingestion of Grapes or Raisins: A Retrospective Evaluation of 43 Dogs (1992-2002)

A review of records from the AnTox database of the American Society for the Prevention of Cruelty to Animals Animal Poison Control Center identified 43 dogs that developed increased blood urea nitrogen concentration, serum creatinine concentration, or both as well as clinical signs after ingesting grapes, raisins, or both. Clinical findings, laboratory findings, histopathological findings, treatments performed, and outcome were evaluated. All dogs vomited, and lethargy, anorexia, and diarrhea were other common clinical signs. Decreased urine output, ataxia, or weakness were associated with a negative outcome. High calcium x phosphorus product (Ca x P), hyperphosphatemia, and hypercalcemia were present in 95%, 90%, and 62% of the dogs in which these variables were evaluated. Extremely high initial total calcium concentration, peak total calcium concentration, initial Ca x P, and peak Ca x P were negative prognostic indicators. Proximal renal tubular necrosis was the most consistent finding in dogs for which histopathology was evaluated. Fifty-three percent of the 43 dogs survived, with 15 of these 23 having a complete resolution of clinical signs and azotemia. Although the mechanism of renal injury from grapes and raisins remains unclear, the findings of this study contribute to an understanding of the clinical course of acute renal failure that can occur after ingestion of grapes or raisins in dogs.

Strategies for management of acute renal failure

Acute renal failure (ARF) is often defined as the sudden inability of the kidneys to regulate water and solute balance. ARF may be more broadly defined as rapid deterioration of renal function resulting in the accumulation of nitrogenous wastes such as urea and creatinine. Clinically, oliguria is defined as urine flow of less than 2 mL/kg/h and anuria has no measurable urine production. In animals, the most common cause of ARF is nephrotoxicity; ischemia ranks second, with interstitial and glomerular diseases following.

[Influence of dose regimen on gentamycin nephrotoxicity in rats]

The acute renal failure (ARF), that still presents a right mortality rate (50%) can be defined as an abrupt decline of the glomerular filtration, resultant of ischemic or toxicity event. The drugs nephrotoxicity is one of the most frequent cause (27%) of ARF and it is suggested that the interval of administration of the drug can interfere in this side effect, however the best administration regimen is not very well established. This study evaluated the renal function of rats that received gentamicin (100 mg/kg) in one dose or in two doses (2 x 50 mg/kg), by intraperitoneal infusion. The results obtained in this research, indicated that the single infusion of gentamicin determined smaller nephrotoxicity by the reduction of serum concentration of this drug in 24 hours, decreasing the intracellular accumulation of this gentamicin, which is one of the main cellular mechanisms of this renal injury. The single dose treatment regime, otherwise, shows advantages not only related to the nephrotoxicity effect, but also it is relevant to the cost and safety, which can be rationable factors in the administration of this drug.