Proteinuria in Apparently Healthy Elderly Dogs: Persistency and Comparison Between Free Catch and Cystocentesis Urine.

BACKGROUND: Up to 25% of elderly humans have proteinuria, often associated with underlying lesions. Data concerning the presence of proteinuria in elderly dogs is scarce. OBJECTIVES: To describe the presence and persistence of proteinuria and to compare urinary protein : creatinine ratio (UPC) between free catch and cystocentesis urine samples in apparently healthy elderly dogs. ANIMALS: Hundred apparently healthy elderly dogs. METHODS: Prospective study. Owners of 100 elderly dogs were asked to collect 2 free catch urine samples. Dogs were considered healthy based on owner's perception and an age chart, based on ideal bodyweight, was used to define dogs as senior or geriatric. UPC of urine collected by free catch and cystocentesis were compared. Overt proteinuria and borderline proteinuria were defined as UPC >0.5 and between 0.2 and 0.5, respectively, if examination of sediment did not explain proteinuria. Proteinuria was considered persistent if present at both sampling times. RESULTS: At baseline, 71 owners succeeded in collecting urine. Eleven percent of dogs had overt proteinuria, 14% were borderline proteinuric, and 75% nonproteinuric. Thirty-seven repeated urine samples, with a median time interval of 31 days (range 10-90), were available. Nineteen percent of dogs had a persistently increased UPC (>0.2), with persistent overt proteinuria present in 8%. A strong correlation (ρ = 0.88) was found between UPC of urine collected by free catch and cystocentesis. CONCLUSIONS AND CLINICAL IMPORTANCE: As 19% of study dogs had persistent proteinuria, our findings emphasize that measurement of proteinuria should be part of geriatric health screening. For UPC in dogs, free catch urine provides a good alternative to cystocentesis.

Long-term follow-up of renal function in dogs after treatment for ACTH-dependent hyperadrenocorticism.

BACKGROUND: Systemic hypertension and proteinuria are frequent complications in dogs with Cushing's syndrome and do not always resolve after treatment of hypercortisolism. Therefore, dogs with Cushing's syndrome may be at risk for renal dysfunction before and after treatment. HYPOTHESIS/OBJECTIVES: To assess renal function in dogs with ACTH-dependent hyperadrenocorticism (ADHAC) before and after treatment. ANIMALS: A total of 19 dogs with ADHAC and 12 control dogs. METHODS: Renal function was assessed before and at 1, 3, 6, and 12 months after treatment. Twelve dogs were treated with trilostane and 7 dogs by transsphenoidal hypophysectomy. Routine renal markers were measured and urinary albumin (uALB), immunoglobulin G (uIgG), and retinol-binding protein (uRBP) were assessed by ELISA. Urinary N-acetyl-ß-D-glucosaminidase (uNAG) was determined colorimetrically. All urinary markers were indexed to urinary creatinine concentration (c). Plasma clearance of creatinine (Cl(creat)), exo-iohexol (Cl(exo)), and endo-iohexol (Cl(endo)) was used to measure glomerular filtration rate (GFR). Data were analyzed using a general linear model. RESULTS: Serum creatinine and urea concentrations increased post-treatment, but remained within reference ranges. Plasma Cl(creat) and Cl(endo) were significantly lower post-treatment, whereas Cl(exo) was not different. Urinary protein-to-creatinine ratio (UPC), uALB/c, uIgG/c, and uRBP/c were decreased post-treatment, but at 12 months 5/13 dogs remained proteinuric. Urinary NAG/c did not change significantly. CONCLUSIONS AND CLINICAL IMPORTANCE: A decrease in GFR and persistent proteinuria post-treatment may warrant the clinician's attention. Future research including renal histopathology of dogs with persistent proteinuria or low GFR is needed to further assess renal outcome.

Hypercortisolism affects glomerular and tubular function in dogs.

Renal function was assessed in 25 dogs with Cushing's syndrome and in 12 healthy controls. Routine renal parameters and glomerular filtration rate (GFR) were measured and urinary biomarkers such as urinary albumin (uALB), urinary immunoglobulin G (uIgG), and urinary retinol-binding protein (uRBP) were assessed by ELISA. Urinary N-acetyl-ß-D-glucosaminidase activity (uNAG) was determined colorimetrically. All urinary markers were indexed to urinary creatinine concentration (c). Plasma exo- (Cl(exo)) and endo-iohexol (Cl(endo)) clearance were used to measure GFR. Based on a Mann-Whitney U test, urea and Cl(exo) did not differ, sCr was significantly lower, and UPC, uALB/c, uIgG/c, uRBP/c, uNAG/c and Cl(endo) were higher in the dogs with Cushing's syndrome when compared with controls. The findings indicate that glomerular and tubular function are both altered in dogs with Cushing's syndrome. Further longitudinal studies will be required to elucidate the pathogenesis of the changes in GFR.

Urinary markers in healthy young and aged dogs and dogs with chronic kidney disease.

BACKGROUND: Blood urea nitrogen and serum creatinine concentrations only detect a decrease of > 75% of renal functional mass. Therefore, there is a need for markers that allow early detection and localization of renal damage. HYPOTHESIS: Urinary albumin (uALB), C-reactive protein (uCRP), retinol binding protein (uRBP), and N-acetyl-beta-D-glucosaminidase (uNAG) concentrations are increased in dogs with chronic kidney disease (CKD) compared with healthy controls and in healthy older dogs compared with young dogs. ANIMALS: Ten dogs with CKD, 10 healthy young dogs (age 1-3 years), and 10 healthy older dogs (age > 7 years) without clinically relevant abnormalities on physical examination, hematology, biochemistry, and urinalysis. METHODS: Urinary markers were determined using an ELISA (uALB, uCRP, and uRBP) or a colorimetric test (uNAG). Results were related to urinary creatinine (c). The fixed effects model or the Wilcoxon rank sum test were used to compare the different groups of dogs. RESULTS: uALB/c, uRBP/c, and uNAG/c were significantly higher in CKD dogs than in healthy dogs. No significant difference was found for uCRP, which was not detectable in the healthy dogs and only in 3 of the CKD dogs. Between the healthy young and older dogs, no significant difference was detected for any of the markers. CONCLUSION: The urinary markers uALB/c, uRBP/c, and uNAG/c were significantly increased in dogs with CKD compared with healthy controls. Additional studies are needed to evaluate the ability of these markers to detect renal disease before the onset of azotemia.