Introduction
Chronic renal failure (CRF) in dogs is caused by primary kidney (renal) disease that has persisted for months to years, resulting in inadequately concentrated urine and abnormally elevated levels of urea nitrogen in the dog’s blood. CRF can be present without overt clinical signs; this form usually is called renal insufficiency rather than failure. Overt CRF, with clinical signs, reflects uremia and severe, irreversible kidney damage.
Causes of Canine Chronic Renal Failure
The precise causes of most cases of CRF are never determined; thus, the condition is often referred to as “chronic generalized nephropathy”. Certainly, there are risk factors for this disease, the most important of which is advancing age. The average age of dogs diagnosed with CRF is 7 years, although it is important to remember that dogs of any age can be affected. Genetics appear to play a role as well, with a predisposition for familial inheritance reported in the following breeds: Basenjis, Beagles, Bedlington terriers, Bernese mountain dogs, Bull terriers, Cairn terriers, Chows, Cocker spaniels, Doberman pinschers, German shepherds, Golden retrievers, Keeshonds, Lhasa apsos, Miniature schnauzers, Newfoundlands, Norwegian elkhounds, Pembroke Welsh corgis, Rottweilers, Samoyeds, Shar-peis, Shih-tzus, Soft-coated Wheaten terriers and Standard poodles. Again, any age, breed or gender can develop chronic renal failure.
A number of other things can cause or contribute to CRF. Contributing factors include exposure to poisons or nephrotoxins (nephrotoxicity means that something is destructive to kidney cells), congenital kidney disorders, prior episodes of acute renal failure, chronic urinary tract obstruction (narrow urethra, chronic infection, or kidney or bladder stones), nephrotoxicity caused by drugs, polycystic kidney disease (a common congenital defect of the kidneys), lymphoma, possibly diabetes mellitus and then a number of kidney-specific disorders that your veterinarian can discuss with you if they pertain to your pet (glomerulonephritis, pyelonephritis, tubulonephrosis, amyloidosis, tubulointerstitial nephritis, etc.).
Regardless of the specific cause, CRF is the end result of serious insults to the kidneys. Once approximately 70% of functional kidney tissue has been damaged, the affected kidney can no longer concentrate the urine so as to remove nitrogenous waste products from the blood. As these waste products rise in circulation (instead of being excreted normally in the urine), they cause a number of serious medical and clinical consequences. Because veterinarians frequently are unable to identify a specific “cause” of chronic renal failure, owners may struggle with the thought that perhaps they could have done something to prevent the disease. This should not happen. The majority of chronic renal failure cases cannot be prevented, and most of them are not particularly responsive to treatment. At this time, most canine CRF cases can be managed, but not cured. Aging dogs should receive an annual veterinary examination with blood screening to assess kidney function and the health of other vital organs. While chronic renal failure can not be prevented, early diagnosis and supportive care can delay progression of the disease.