Kidney Disease On Dogs

How do the kidneys work in dogs?

The kidneys have many functions. Their main functions are to remove waste products from the blood, regulate the levels of certain essential minerals (such as potassium and sodium), conserve water, and produce urine.

What is chronic kidney disease in dogs?

Many people think that "chronic kidney failure" or "chronic kidney disease" means that the kidneys have stopped working and are no longer producing urine. This is not the case. By definition, chronic renal failure (CRF) or chronic kidney disease (CKD) is the inability of the kidneys to effectively filter waste products from the blood, not the inability to produce urine. More specifically: most dogs with renal failure produce large amounts of urine, but the body's toxic waste products are not effectively eliminated.

When do cases of chronic kidney disease in dogs occur?

Since kidney tissue cannot regenerate if it is destroyed, the kidneys have a large reserve capacity to perform their various functions. At least 2/3 of the kidneys must be dysfunctional before any clinical symptoms are seen.

In many cases, this means that the damage has been occurring for months to years (chronic) before the malfunction becomes apparent.

In dogs, chronic kidney disease is associated with aging and can simply be thought of as "wear and tear" of the kidney tissue. The age of onset is usually related to the size of the dog. In most small dogs, the early signs of kidney disease occur between the ages of approximately 10 and 14 years. Large dogs, however, have a shorter life span and may develop kidney failure as early as seven years of age.

What are the signs of chronic kidney disease in dogs?

When disease or advanced age causes the filtration process to become inefficient and ineffective, blood flow to the kidneys increases in an attempt to increase filtration. The body must increase the amount of blood flowing through the kidneys because fewer and fewer toxins are being excreted at a time. This results in the production of more urine. To prevent the dog from becoming dehydrated due to increased fluid loss in the urine, thirst and water consumption are increased.

Thus, one of the earliest clinical signs of renal failure is an increase in the amount of water drunk and urine excreted, called compensatory renal failure. After about 2/3 of the kidney tissue has been destroyed, waste products in the blood rapidly increase and severe disease apparently strikes suddenly. Clinical signs of more advanced renal failure include loss of appetite, depression, vomiting, diarrhea, and bad breath. Occasionally, ulcers may be found in the mouth.

How is chronic renal failure diagnosed?

There are two basic tests for kidney function: a complete urine test and a blood test.
A urine test requires a urinalysis to assess kidney function. Low urine specific gravity (USpG) is the earliest sign of kidney failure. An increase in protein in the urine (proteinuria) also indicates a decrease in kidney function.

More often, however, the function of various internal organs is assessed by blood tests. Levels of two main waste products in the blood, urea nitrogen (BUN) and creatinine (CREA), are measured to indicate decreased kidney function. Measurement of blood levels of other substances (such as albumin, globulin, potassium, sodium, phosphorus and calcium) as well as tests for red and white blood cell counts are important to determine the degree of failure and the best treatment options.

Dogs with compensated chronic renal failure have borderline renal function and may have normal urea and creatinine levels but a lower urine specific gravity. In the event of significant stress such as disease or surgery, the kidneys may fail, causing a rapid rise in blood test values. Dogs diagnosed with low urine specific gravity as well as elevated urea and creatinine are said to have azotemia.

How will the veterinarian determine the degree of renal failure in the dog?

The veterinarian will use the IRIS (International Renal Interest Society) staging system. IRIS staging is based on serum creatinine levels, with sub-staging based on the presence of protein in the urine (determined by the urine protein:creatinine ratio [UPC]) and measurement of your dog's blood pressure. By using this staging, your veterinarian can better understand how to proceed with treatment, monitor progress and estimate your pet's prognosis.

How is kidney disease in dogs treated?

Treatment of kidney disease depends on the results of blood tests, and specific treatments are designed to address specific abnormalities. In some cases, the kidneys are beyond repair before diagnosis and medication is ineffective. However, with early diagnosis and aggressive treatment, many dogs will lead normal lifestyles for months or years.
Treatment is usually administered in two phases, first flushing the kidneys and removing accumulated toxins from the bloodstream, and then providing treatment to control the disease and slow its progression.

What is involved in the first phase of treatment in dogs?

In the first phase, high doses of intravenous fluids are given to "flush" the kidneys and blood. This flushing process, called diuresis, helps mildly damaged kidney cells function again by removing toxic metabolites and creating a healthier environment for healing.

If enough functional kidney cells are retained, they may be able to adequately meet the body's need for filtration and waste removal. Fluid therapy includes replacement of various electrolytes, especially potassium. Other important aspects of initial therapy include proper nutrition and medications to control vomiting and diarrhea (if present). Your dog will usually begin to feel better soon after this phase of treatment begins.

What can my dog expect from Phase I treatment?

There are three possible outcomes from the first phase of treatment.
1. The kidneys will regain function and continue to function for several weeks to years.
2. The kidneys will regain function during treatment, but once treatment is stopped, the kidneys will fail again, usually within three to fourteen days.
3. Kidney function is not restored.
Unfortunately, there is no reliable test to predict the outcome. Each case should be treated aggressively and monitored closely. Even dogs with severe renal failure may respond positively to treatment and return to a normal quality of life after treatment.

What needs to be done after the first phase of treatment in dogs is successful?

The second phase of treatment is to help keep the kidneys functioning as long and as normally as possible. This is usually accomplished through one or more of the following, depending on your pet's condition.

Special diet - Nutrition is one of the cornerstones of effective treatment for dogs with chronic renal failure. The ideal diet for dogs in the advanced stages of renal failure is one that is low in protein, low in phosphorus and not acidified. This type of diet helps reduce the amount of protein waste or metabolic toxins that can make your pet feel nauseous and lethargic. In advanced kidney disease, a reduced protein diet will also reduce the workload of the kidneys.
Nutritionists have developed commercial therapeutic diets designed to treat all stages of chronic kidney disease. Your veterinarian will recommend the most appropriate diet for your dog, which contains the necessary quantity and quality of nutrients.

Phosphate Binders - Phosphorus is removed from the body through the kidneys. Once the filtration process is impaired, phosphorus begins to accumulate in the blood. Elevated blood phosphorus levels can also lead to drowsiness and loss of appetite. Some drugs bind excess phosphate in the intestine, so they are not absorbed into the bloodstream.
so they are not absorbed into the bloodstream, resulting in lower phosphorus levels in the blood.

Home fluid therapy - Once your dog is stabilized, you can provide your dog with maintenance levels of subcutaneous (under the skin) fluids at home. This helps prevent dehydration, helps to continually flush toxins from the kidneys and provides additional levels of electrolytes. This is done from twice a day to once a week depending on the degree of your dog's kidney failure. Most dogs do best when they receive a small amount of fluid each day. Once the dog becomes stable, the frequency of treatment may decrease. Although home fluid therapy may not sound like something you can do, you will be surprised at how easy the technique is and how well most dogs tolerate it.

Treatment of Protein in Urine (Proteinuria) - Dogs with protein in the urine are at increased risk for CKD progression. Angiotensin-converting enzyme inhibitors (blood pressure medications) will help reduce renal pressure, thereby reducing the extent of proteinuria.

A drug that regulates parathyroid and calcium levels - The ratio of calcium to phosphorus in the blood must be maintained at approximately two to one (2:1). Elevated blood phosphorus levels secondary to renal failure stimulate the parathyroid glands to increase blood calcium levels by removing them from the bones. This helps to normalize the calcium to phosphorus ratio, but it can make bones brittle and prone to fracture. Calcitriol can be used to decrease parathyroid function and increase intestinal absorption of calcium. This drug is needed if there is evidence of abnormal parathyroid function.

A drug that stimulates the bone marrow to produce new red blood cells - The kidneys produce a hormone (erythropoietin) that stimulates the bone marrow to produce red blood cells. As a result, many dogs with renal failure will not produce erythropoietin and develop anemia or low red blood cell counts. Synthetic erythropoietin stimulates the bone marrow to produce red blood cells and corrects the anemia in most dogs. Unfortunately, for some dogs, this drug cannot be used long-term because the immune system develops antibodies against the drug. If your dog has persistent anemia, this treatment may be recommended.