The kidneys are blood waste filters, activators of vitamin D, and controllers of blood pressure.  Kidney failure can cause a backup of blood waste products, an inability to activate vitamin D, and high blood pressure.  Damage to the kidneys can accumulate without signs or symptoms until more than 75% of the total volume of both kidneys cannot work, then signs of disease become evident.  Chronic kidney failure is one of the 3 most common causes of death in dogs.

Causes of Kidney Failure

In chronic kidney failure, the cause (or causes) is usually unknown.  Insults to the kidneys may have accumulated over years, and the causes may have varied.  Known potential forms of damage to the kidneys include chronic infection (nephritis and pyelonephritis), immune system disorders that injure the filters (glomeruli) in the kidney, chronic partial obstruction to the outflow of urine, inherited malformed kidneys, ingestion of kidney poisons (such as antifreeze), and some cancers.

Signs of Kidney Failure

The development of kidney failure has traditionally been divided into 4 stages.  The first 2 stages cause few to no signs.  Laboratory test abnormalities in the blood or urine may be detected in the early stages.  The latter 2 stages usually do not appear until after 5 years of age.  By the 3rd stage, excessive thirst and urination become obvious.  These are compensatory signs, In other words, the excessive thirst and urination are ESSENTIAL to prevent waste products from accumulating to dangerous levels.  NO attempt should be made to curtail the excessive thirst or urination.  Withholding or restricting drinking water in a dog with Stage 3 Kidney Failure, even for a short period, could cause rapid rise in blood wastes and death.

In Stage 4, waste products in the blood have reached a concentration that suppresses appetite and causes depression, vomiting, and weight loss.  Other signs can include anemia, loose teeth, soft bones, and problems related to high blood pressure such as nose bleeding or hemorrhage in the eye.   

Diagnosis

Your veterinarian can determine the presence of failure, the stage of development, and prescribe the appropriate treatment for the cause and stage of disease after a physical examination and examination of the dog’s blood and urine samples.

Treatment

Dogs can survive with only 5% of their total kidney volume functioning properly, if properly managed.  Special diets that are low in phosphorus and have high quality, low quantity protein will reduce some of the blood wastes that could accumulate and suppress appetite, weaken bone, and raise blood pressure.  Special diets will not stop renal failure but, in some cases, they can promote better quality of remaining life.  Dogs with advanced kidney failure sometime benefit from phosphorus binders, antacids, high blood pressure control medications, or hormones to stimulate the production of red blood cells.  Dialysis or kidney transplant are possible in a few U.S. locations, but the costs are high, and so far, the results are marginal.

Prevention Measures

C.B. Chastain, DVM
Professor, University of Missouri
College of Veterinary Medicine