The term "chronic kidney failure" suggests that the kidneys have quit working and are not making urine. However, by definition, kidney failure is the inability of the kidneys to remove waste products from the blood. This term can be confusing because kidney failure doesn’t mean the inability to produce urine. Ironically, most dogs in kidney failure produce large quantities of urine, but the body’s wastes are not being effectively eliminated.
The typical form of chronic kidney failure is associated with aging. It may be thought of as a “wearing out” process. The age of onset is often related to the size of the dog. For most small dogs, the early signs occur at about 10-14 years of age. However, large dogs have a shorter age span and may go into kidney failure as early as seven years of age.
The kidneys are blood filters. When aging causes the filtration process to become inefficient and ineffective, blood flow to the kidneys is increased in an attempt to increase filtration. This results in the production of more urine. To keep the dog from becoming dehydrated due to increased fluid loss in the urine, thirst and water consumption is increased. Thus, the early clinical signs of kidney failure are increased water consumption and urination. The clinical signs of more advanced kidney failure include loss of appetite, depression, vomiting, diarrhea, and very bad breath. Occasionally, ulcers will be found in the mouth. When kidney failure is accompanied by these clinical signs, it is called uremia.
The diagnosis of kidney failure is made by determining the level of two waste products in the blood: blood urea nitrogen (BUN) and blood creatinine. A urinalysis is also needed to complete the study of kidney function. A low urine specific gravity (USpG) is the earliest indication of kidney failure.
Although BUN and creatinine levels reflect kidney failure, they do not predict it. A dog with marginal kidney function may have normal blood tests. If that dog is stressed with major illness or surgery, the kidneys may fail, sending the blood test values up quickly.
In some cases, the kidneys are damaged beyond repair and treatment is ineffective. However, with early diagnosis and aggressive treatment, many dogs will live for several months or years.
Treatment occurs in two phases. The first phase is to "restart" the kidneys. Large quantities of intravenous fluids are given to "flush out" the kidneys. This flushing process, called diuresis, helps to stimulate the kidney cells to function again. If enough functional kidney cells remain, they may be able to adequately meet the body’s needs for waste removal. Fluid therapy includes replacement of various electrolytes, especially potassium. Other important aspects of initial treatment include proper nutrition and drugs to control vomiting and diarrhea.
There are three possible outcomes from the first phase of treatment:
Unfortunately, there are no reliable tests that will predict the outcome.
The second phase of treatment is to keep the kidneys functioning as long as possible. This is accomplished with one or more of the following, depending on your pet’s condition:
The prognosis is quite variable depending on response to the initial stage of treatment and your ability to perform the follow-up care. We encourage treatment in most situations because many dogs will respond and maintain a good quality of life for up to four years.
This client information sheet is based on material written by Ernest E. Ward Jr., DVM. © Copyright 2002 Lifelearn Inc. Used with permission under license. May 1, 2018.