One of the changes in a dog’s behavior that is really important for owners to notice is a change in the dog’s thirst (and need to urinate). If you see any changes in your dog’s behavior, please remember to discuss them with our doctors at the Animal Clinic at Thorndale. If your dog has been asking to go out to urinate more than normal, or perhaps has had accidents in the house, and/or it seems to be hanging around the water bowl more than in the past, there may be a significant health problem. The “big two” are diabetes and kidney disease, but there are numerous others that could be causing this change. The doctors at the Animal Clinic at Thorndale categorize kidney disease three ways. It is usually diagnosed as acute (sudden onset) or chronic (gradually changing) and acute on chronic (a known case of chronic kidney disease that suddenly became worse).

Acute, or sudden onset, of kidney failure is generally due to toxin ingestion, whether from poisonings, antifreeze ingestion, spoiled or contaminated foods, plant materials, NSAIDs and other human medications, toxic foods (grapes). These dogs may drink and urinate large quantities in the initial phases, and then stop producing urine all together.

Obstruction of the urinary outflow tract, such as can occur when bladder stones pass through the urethra from the bladder, can result in kidney failure in a matter of a day. Unlike chronic kidney disease, where dogs drink and urinate a lot, when the outflow tract is blocked, these dogs will be straining to urinate without success.

Almost all cases of acute kidney disease in dogs are medical emergencies. The body does not have time to adjust to a rapid deterioration of kidney function.

Chronic kidney disease is a relatively common disorder in dogs, especially geriatric dogs, although it can occur in young dogs. It occurs when the kidneys are no longer able to perform their normal function of removing waste products from the blood. This is not the same as the inability to make urine. In fact, most dogs with chronic renal disease are producing large volumes of urine. This disparity between the large volume of urine produced and declining kidney function are often a source of confusion for owners.

Typically, chronic kidney disease comes about as the kidneys undergo aging changes and begin to “wear out.” It is a process which develops over months to years. Initially, there may be no apparent signs and the dog’s bloodwork is normal. However, there are irreversible microscopic changes underway in the aging kidney. Eventually, the kidneys will begin to shrink because of scar tissue and will become small and hard. By this time, there are usually signs of progressive kidney disease and the labwork will indicate associated changes.

The kidneys function mainly as filters which selectively keep certain compounds in the blood, while allowing unnecessary waste products to escape into the urine. When aging causes the filtration process to become progressively less effective, blood flow to the kidneys increases in an attempt to improve filtration. This is the reason that the dog with kidney disease is producing a large volume of urine. Because of the loss of excessive fluid through the urine, the dog is obligated to drink more water to avoid becoming dehydrated. This is called a compensatory change.

Thus, the early clinical signs of kidney disease are increased water consumption (polydipsia) and increased urine production (polyuria).

Contributing Factors

Infection in the urinary tract, toxic substances, and kidney stones can be a primary cause of kidney disease or can lead to deterioration of function in previously diseased kidneys. However, in many cases of advanced chronic kidney disease, the underlying disease cannot be determined.

Prevalence

Various clinical studies have evaluated the prevalence of renal disease in dogs. For most dogs, onset of clinical signs begins anywhere from 7-12 years of age. However, the prevalence of overt kidney disease is highest in dogs older than twelve years of age. One study found that approximately 30% of dogs over 12 years of age had chronic renal disease.

The frequency of renal disease in male dogs is essentially the same as for female dogs.

Renal disease in young dogs is most likely due to a congenital defect in the structure of the kidneys. A number of breeds are at risk for juvenile kidney disease; these include the Shih Tzu, Samoyed, Doberman pinscher, Shar Pei, Lhasa Apso, and Basenji.

Causes/Transmission

In most cases, a specific cause cannot be identified. A number of infectious, inflammatory, or neoplastic (cancerous) conditions can lead to kidney disease in the dog. Toxins and inappropriate use of human medications can also lead to kidney disease. Certain human foods (grapes) can lead to acute sudden kidney failure.

Clinical Signs

As described above, the classic signs of chronic and non-obstructed acute kidney disease are increased urine output and a compensatory increase in water intake (thirst). The clinical signs of more advanced kidney disease include loss of appetite, weight loss, depression, vomiting, diarrhea, and very bad breath. Occasionally, ulcers will be found in the mouth. When kidney disease is accompanied by these clinical signs, it is called “uremia.” In effect, this means “urine in the blood.” High blood pressure (hypertension) occurs in a large number of dogs with chronic renal disease. This can only be diagnosed with measurement of the dog’s blood pressure.

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 develop kidney disease as early as 7 years of age. For dogs with congenital kidney disease, signs usually occur by 2 years of age.

Diagnosis

The diagnosis of kidney disease is primarily made by determining the level of two waste products in the blood, blood urea nitrogen (BUN) and creatinine, along with a urinalysis to determine how well the kidneys can concentrate the urine. Besides BUN and creatinine, other blood values may also be abnormal in kidney disease. Blood protein and albumin levels may be decreased, especially if protein is leaking out of the kidney. Calcium and phosphorus levels may be abnormal. Anemia will develop in long standing cases.

Although BUN and creatinine levels reflect kidney disease, 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. Some of these earlier cases may be detected by changing ability of the kidneys to concentrate urine, as reflected in a value called urine specific gravity.

Treatment

When patients are detected early in kidney disease, hospitalization may be avoided. Routine screening of blood and urine values can aid greatly in early diagnosis and thus early treatment. Most of these patients can be monitored at home and treated with appropriate dietary and supplement management. Phase 2 below describes many of the treatments that may be required at home. Each patient’s case will be unique, so that not all the listed treatments will be correct at a given stage of the disease. Careful sequential monitoring of blood and urine allows treatment to be adjusted over time.

If a cause of kidney failure can be identified, the underlying cause is treated. This may involve placing a urinary catheter to allow urination in an outflow obstruction, removing toxins or access to toxins, or if available antidotes to toxins. When patients are ill with their kidney disease, treatment occurs in two phases. In severe acute kidney disease in dogs, specific injectable medications may also be warranted to help “reopen” kidney function. Both acute and chronically ill dogs will need hospitalization for Phase 1.

Phase 1 – Diuresis.

In the first phase of treatment, large volumes of intravenous fluids are given in an attempt to flush toxins from the body. This flushing process, called diuresis, is designed to maximize the function of all remaining kidney tissue. If enough functional kidney cells remain, they may be able to adequately meet the body’s needs for waste removal, with the help of this additional fluid. Also, the fluid therapy helps to replace various electrolytes, especially potassium. Other important aspects of initial treatment include proper nutrition and drugs to control vomiting and diarrhea.

Unfortunately, there are no reliable tests that will predict the outcome of this first phase of treatment. We hope that intensive fluid therapy will substantially decrease the blood levels of BUN and creatinine. If there is no improvement after 3+ days of fluid therapy, the prognosis is more guarded than for dogs who show significantly decreased values.

Dogs who improve on intravenous fluid diuresis are weaned off the intravenous fluids and Phase 2 begins. It is important that the dogs can remain stable at home using Phase 2 medical management. Depending on how well the dog is doing we will need to schedule follow up blood work and urinalysis after a few days at home, then likely at 3 and 6 month intervals.

Phase 2 – Ongoing medical therapy.

The second phase of treatment is designed to maximize the remaining function of the diseased kidneys. This is accomplished with one or more of the following, depending on the situation:

1. A low protein, low phosphorous, low sodium diet. This helps to keep the blood tests as close to normal as possible. This improvement in the bloodwork often correlates with improvement in the way the dog feels. We can recommend foods that have the low quantity and high quality of protein needed by your dog. The new diet should be introduced gradually over a few weeks because of the lowered sodium content. We generally send home samples of several prescription diets designed for kidney disease so that we can find one that your dog likes.
2. A phosphate binder. As the filtering ability of the kidneys declines, phosphorous begins to accumulate in the blood. High serum phosphorous contributes to depression and anorexia. Certain drugs will bind excess dietary phosphorous in the intestine so that less is available for absorption. Blood levels of phosphorous can be monitored to help tailor the drug dosage. High phosphorus levels in the blood are a negative prognostic indicator. Pets in which an elevated phosphorus can be brought back into the normal range generally do better. There are a number of aluminum hydroxide antacids available over the counter that can help lower blood phosphorus.
3. B vitamin supplements, such as Pettinic, help replace the water soluble vitamins that are being washed out of the body with the excessive water losses.
4. Fluids given at home. After your dog has completed a course of intravenous fluid therapy in the hospital, subcutaneous (under the skin) fluids can be given at home. This serves to continually “restart” the kidneys as their function continues to decline. This is done once daily to once weekly, depending on the severity of kidney disease. This technique is easily mastered by most owners so don’t be afraid to consider this very helpful option.
5. A drug to regulate the parathyroid gland and calcium levels. Calcium and phosphorus must remain at about a 2:1 ratio in the blood. The increase in blood phosphorus level, as mentioned above, stimulates the parathyroid gland to increase the blood calcium level by removing it from bones. This can be helpful for the sake of the normalizing calcium:phosphorus ratio, but it can make the bones brittle and easily broken. Calcitriol can be used to reduce the function of the parathyroid gland and to increase calcium absorption from the intestinal tract.
6. A drug to stimulate the bone marrow to produce new red blood cells. The kidneys produce erythropoietin, a hormone that stimulates the bone marrow to make red blood cells. Therefore, many dogs with kidney disease have a low red blood cell count, anemia. Epogen, a synthetic form of erythropoietin, will correct the anemia in most dogs. Unfortunately Epogen is a human product. For some dogs, the drug cannot be used long term because the immune system recognizes the drug as “foreign” and will make antibodies (immune proteins) against it.
7. For dogs with confirmed high blood pressure (hypertension), medication may need to be administered.
8. Stressful situations, such as boarding, should be avoided as these can precipitate a crisis with declining kidney function.

Prognosis

The prognosis is quite variable depending on response to the initial stage of treatment and your ability to perform the follow-up care. However, we encourage treatment in most situations because many dogs will respond and have good quality life for up to 4 years.

Prevention

For the most part, kidney disease is not a preventable disease. It occurs as a consequence of aging. Early recognition and treatment are key to delaying the effects of fading kidney function.