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Longitudinal Study of Microalbuminuria in Soft-Coated Wheaten Terriers

SUMMARY:

Study shows microalbuminuria increased with age and correlated with progression of kidney disease detected by histopathology.

Microalbuminuria (MA) is a predictor of later development of nephropathy in people with diabetes mellitus or essential hypertension. MA is also found in people with systemic diseases that are associated with glomerular disease. MA has been demonstrated to occur in clinically normal dogs and in dogs with medical problems. However, the predictive value of MA for later onset of renal disease in dogs remains to be determined. The purpose of this longitudinal study was to evaluate urine albumin content in a colony of dogs that are genetically predisposed to the development of glomerular disease.

The study population consisted of 9 soft coated wheaten terriers (SCWT) and 8 SCWTxbeagles. Urinalyses and urine protein:creatinine ratios (UP:C)were evaluated in samples from all dogs every 3 months of life. Aliquots of urine were stored at -70° C at irregular intervals from dogs that were between 3 months and 5.7 years of age. The median number of samples stored per dog was 7 (Q1, 5; Q3, 8). Urine albumin concentrations were measured in stored urine samples using an antigen capture ELISA. To account for varying urine concentrations, results were normalized to a specific gravity of 1.010. MA was defined as urine albumin concentration of 1.0-30.0 mg/dl.

13 of the 17 dogs (76%) had MA detected in one or more samples. Of these 13 dogs, the median percent (Q1, Q3) of samples with MA was 50% (9.1, 50). In all dogs, urine albumin concentrations increased with age (p <0.05). 3 of the 13 dogs with MA developed overt albuminuria (>30.0 mg/dl). Proteinuria (UP:C >0.5) was detected in 3 of 13 dogs (23%) with MA but only 2 of the 3 dogs with overt albuminuria. In these 2 dogs, the age at onset of MA and proteinuria was the same. In the other dog with proteinuria, MA preceded the onset of proteinuria by 1 year.

This preliminary study shows that the prevalence of MA is high in SCWT and SCWT crosses that are genetically predisposed to develop glomerular disease, when compared to other reports of MA in clinically normal dogs or dogs with other medical problems. In this colony of dogs, MA increased with age. More study is needed to determine if the dogs in this study that have MA but did not have proteinuria will progress to develop overt manifestations of glomerular disease.

Reproduced with permission of the Journal of Veterinary Internal Medicine.