Classification and Etiology

Chronic renal failure (CRF) ensues from the irreversible loss of the metabolic, endocrine and excretory capacities of the kidney. It is a common clinical problem occurring in 2 - 5% of dogs (Bronson, 1982; Lund et al, 1999). Chronic renal failure is considered a leading cause of death in older patients (Figure 1). The 1997 Morris Animal Foundation Animal Health Survey of 2,000 pet owners identified kidney disease as the third leading cause of death in dogs. The mean age of diagnosis in dogs is 6.5 years, with 45% of cases reported over 10 years of age (Polzin, 1989; Polzin et al. 2000). The onset of renal failure tends to be insidious as renal function generally declines over a period of months to years. The uremic syndrome manifests when the residual renal mass is generally less than 25% of normal and compensatory changes fail to meet the metabolic and excretory needs of the body for homeostasis.

Denise ELLIOTT
BVSc (Hons) PhD Dipl ACVIM Dipl ACVN

Denise Elliott graduated from the University of Melbourne with a Bachelor in Veterinary Science with Honors in 1991. After completing an internship in Small Animal Medicine and Surgery at the University of Pennsylvania, Denise moved to the University of California-Davis where she completed a residency in Small Animal Medicine, a fellowship in Renal Medicine and Hemodialysis, and a residency in Small Animal Clinical Nutrition. Denise received board certification with the American College of Veterinary Internal Medicine in 1996 and with the American College of Veterinary Nutrition in 2001. The University of California-Davis awarded a PhD in Nutrition in 2001 for her work on Multifrequency Bioelectrical Impedance Analysis in Healthy Cats and Dogs. Denise is currently the Director of Scientific Communications for Royal Canin USA.

Hervé LEFEBVRE
DVM, PhD, Dipl ECVPT

Hervé Lefebvre graduated from the National Veterinary School of Toulouse in 1988. After completing his doctoral thesis in 1994 he became a Diplomate of the European College of Veterinary Pharmacology and Toxicology in 2000. He is currently Professor of Physiology and he is in charge of the cytotoxicity department of the Pathophysiology and Toxicology Unit at the National Veterinary School of Toulouse. Since 1994, his main research interest has been pharmacokinetics in chronic renal disease, local tolerance to injectable medication and assessment of glomerular filtration and dosage regimen adjustment in dogs. Since 2000, he has been studying the biology of creatinine in dogs and the clinical interpretation of the plasma concentration of creatinine in different canine breeds for the early diagnosis of chronic renal failure in dogs. He has more than 60 publications and papers.

1. Classification and Etiology

Chronic renal failure is caused by replacement of functional nephrons by non-functional scar tissue and inflammatory infiltrates. The precise etiology is however multifactorial: it may be congenital or familial in origin or occur secondary to acquired disease processes that injure the renal glomeruli, tubules, interstitium or vasculature (Table 1) results in entire nephron destruction with ultimate replacement by fibrous scar tissue (Figure 2).

Figure 1. The prevalence of chronic renal in dogs as a function of age.  

Figure 2a. Histopathological images of renal parenchyma in a Cocker Spaniel diagnosed with familial nephropathy. (©A. German). (a: x100 magnification); HE stain. The Bowman spaces are dilated and empty; some of them contain glomerular vascular components and protein deposits, some scattered tubules also contain protein material. Multifocal calcification of Bowman capsules, the tubule basement membrane and the glomeruli are observed.  

Figure 2b. Histopathological images of renal parenchyma in a Cocker Spaniel diagnosed with familial nephropathy. (©A. German). (b: x400 magnification); HE stain. The Bowman spaces are dilated and empty; some of them contain glomerular vascular components and protein deposits, some scattered tubules also contain protein material. Multifocal calcification of Bowman capsules, the tubule basement membrane and the glomeruli are observed.  

A Cocker Spaniel diagnosed with familial nephropathy.