The term “chronic kidney failure” suggests that the kidneys have stopped functioning and are, therefore, not making urine. However, by definition, kidney failure is the inability of the kidneys to remove waste products from the blood. This definition can occasionally create confusion because some will equate kidney failure with failure to make urine. Kidney failure is NOT the inability to make urine. Ironically, most dogs in kidney failure are actually producing large quantities of urine, but the body’s wastes are not being effectively eliminated.
The typical form of chronic kidney failure is the result of ageing; it is simply a “wearing out” process. The age of onset is 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 7 years of age. In some breeds, there is a genetic predisposition to kidney failure.
The kidneys are nothing more than filters. When ageing 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 is increased; this results in more water consumption. Thus, the early clinical signs of kidney failure are increased water consumption and increased urine production. The clinical signs of more advanced kidney failure include loss of appetite, depression, vomiting, diarrhoea, and very bad breath. Occasionally, ulcers will be found in the mouth. When kidney failure is accompanied by these clinical signs, it is called uraemia.
The diagnosis of kidney failure is made by determining the level of either of two waste products in the blood: blood urea and/or blood creatinine and by confirming a concurrent inability to modify urine concentration.
Although urea and creatinine levels reflect kidney failure, they do not predict it. A dog with marginal kidney function may have normal blood levels. If that dog is stressed with major illness or surgery, the kidneys may fail, sending the urea and creatinine values up quickly.
In some cases, the kidneys are worn out so that they cannot be revived. However, with appropriate treatment, some dogs will live for several more 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 diarrhoea.
There are three possible outcomes from the first phase of treatment:
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 the situation:
The prognosis is quite variable depending on the response to the initial stage of treatment, your ability to perform the follow-up care and your dog’s willingness to eat the special diet. Treatment can be effective. Many dogs will have a good quality of life for months or even years.