Evaluation of Predictors of the Development of Azotemia in Cats

Abstract

Background: Chronic kidney disease (CKD) is a common condition in geriatric cats. Diagnosis is based on the development of persistent azotemia with inadequate urine concentrating ability. Biomarkers are sought for early identification.Hypothesis: Clinical variables, urine concentrating ability, proteinuria, and N‐acetyl‐β‐d‐glucosaminidase (NAG) index will be predictive of cats at risk of developing azotemia within 12 months.Animals: Client‐owned nonazotemic geriatric (≥9 years) cats.Methods: Prospective longitudinal cohort study monitoring a population of healthy nonazotemic geriatric cats every 6 months until development of azotemia, death, or the study end point (September 30, 2007). Multivariable logistic regression analysis was used to assess baseline clinical, biochemical, and urinalysis variables, urine protein to creatinine ratio (UP/C), urine albumin to creatinine (UA/C) ratio, and urinary NAG index as predictors of development of azotemia.Results: One hundred and eighteen cats were recruited with a median age of 13 years. Ninety‐five cats (80.5%) had been followed or reached the study end point by 12 months of which 30.5% (29/95) developed azotemia. Age, systolic blood pressure, plasma creatinine concentration, urine specific gravity, UP/C, UA/C, and NAG index were significantly associated with development of azotemia in the univariable analysis (P≤ .05). However, in the multivariable analysis, only plasma creatinine concentration with either UP/C (Model 1) or UA/C (Model 2) remained significant.Conclusions and Clinical Importance: This study demonstrates a high incidence of azotemia in a population of previously healthy geriatric cats. Proteinuria at presentation was significantly associated with development of azotemia although causal association cannot be inferred. Evaluation of NAG index offered no additional benefit.

Current Understanding of the Pathogenesis of Progressive Chronic Kidney Disease in Cats

“…The cats in these studies diagnosed with systemic hypertension however, were always treated with the calcium channel blocker, amlodipine besylate, and therefore the true effect of systemic hypertension on the development and/or progression of CKD may have been masked. [38][39][40]  Diabetes mellitus: Unlike in human medicine, to date no association has been identified between diabetes mellitus and CKD in cats or the development of a diabetic nephropathy, although it remains possible that this reflects the relatively shorter life expectancy of diabetic cats compared to diabetic humans. 23,41  Hyperthyroidism: Hyperthyroidism is a common condition in the older cat and therefore is often diagnosed concurrently with CKD.…”

“…40 Epidemiological studies have evaluated factors associated with the development of azotemia, survival of cats with CKD and also demonstrating a more progressive phenotype of CKD. 24,[38][39][40][115][116][117] From the experimental and human literature there are a number of key pathophysiological mechanisms which have been implicated in both the development and progression of CKD. An understanding of these mechanisms is important not only because many may be applicable and translated to feline CKD but also because they provide potential targets for therapy in order to slow disease progression.…”

Management of Proteinuria in Dogs and Cats with Chronic Kidney Disease

“…When nonazotemic cats were prospectively and longitudinally evaluated, proteinuria was found to be significantly associated with the development of azotemia by 12 months (Jepson et al, 2009). Both proteinuria and serum creatinine were related to shortened survival in cats with chronic kidney disease (Syme et al, 2006;King et al, 2007).…”

“…The kidney is one of the target organs for hypertensive damage and sustained hypertension may lead to an increased magnitude of proteinuria, rate of decline of renal function, frequency of uremic crises and mortality (Jepson et al, 2009, Finco et al, 2004Brown et al, 2007). The goal of antihypertensive therapy is to reduce the blood pressure so that the risk of continued target organ damage is minimized (Table 4).…”

Effect of common storage temperatures and container types on urine protein : creatinine ratios in urine samples of proteinuric dogs

“…Studies in humans and other animals suggest an association between persistent renal proteinuria and rate of progression of chronic kidney disease 1, 2, 3, 4, 5. In dogs, a positive correlation between magnitude of proteinuria and time to uremic crisis or death has been reported 5.…”