Kidney Disease ~ Chronic Renal Failure

The kidneys perform very important life functions that are classified into three categories. First, they excrete wastes, which are by-products of protein breakdown. Secondly, the kidneys regulate the body’s water balance as well as the balance of sodium and chloride in the bloodstream. Thirdly, the kidneys produce hormones that regulate blood pressure, affect the production of red blood cells, and control the balance of calcium and phosphorus within the body.  Because of these functions, it is easy to understand why disease of the kidneys can cause significant illness.

The kidneys must lose 2/3 to 3/4 of their functional tissue before toxins build up in the blood stream and animals start showing signs of kidney disease.  We all know that we can donate a kidney and live happily with 1/2 the amount of kidney tissue given to us at birth.  But once the loss of functional kidney, usually the result of aging, reaches the 2/3 to 3/4  degree, affected animals will start to show signs that a problem is occurring. Initially most pets increase their water intake, and then eventually over time, lose interest in food, lose weight and become lethargic.  Prior to this level of loss of normal kidney tissue, the animal will act normal, making early diagnoses of kidney disease difficult.

Chronic renal failure (CRF) is the most common form of kidney disease. CRF most often affects middle aged to elderly animals and can lead to a progressive loss of kidney function. In most cases, the cause of kidney failure is due to the replacement of normal kidney tissue with non-functioning scar tissue. Why this happens is usually unknown. Sometimes however, we can blame the kidney failure on bacterial infections, kidney stones, cancer, or deposit of protein (amyloid) in the kidney’s filtering system. In most cases it is not possible to cure the disease and CRF gradually worsens over a period of weeks, months, or even years. It is difficult or impossible to determine whether an individual’s disease will progress slowly or rapidly.

A diagnosis of CRF is made on the basis of clinical signs, physical exam findings, and laboratory evaluation. Clinical features of CRF include drinking and urinating excessively, weight loss, vomiting, bad breath, poor appetite and weakness. Diagnosis requires blood work and an analysis of the urine. Changes in blood work include elevated toxins (BUN and creatinine), elevated phosphorus levels and anemia (low red blood cell count). Urine abnormalities include poor concentration and an excess amount of protein. As kidney disease progresses, animals may stop drinking and eating altogether and become more depressed. On-going weight loss and increased vomiting may also occur as kidney disease worsens.  As well, the patient’s blood pressure may rise.

Treatment of kidney failure involves correcting dehydration and blood chemistry imbalances. One of the most important measures of therapy is to keep the patient well hydrated. This may involve a period of hospitalization to treat with intravenous (IV) fluids. Fluid therapy improves clearance of toxins, corrects dehydration and also treats electrolyte and acid/base imbalances.  Medicines are also used to control the high phosphorus values and blood pressure measurements, as well combat the nausea associated with kidney disease

Once stable and depending on patient size and disposition, some owners are able to administer subcutaneous (under the skin) fluids as part of the follow up at-home therapy. This can be of great benefit since maintaining hydration and assisting the removal of toxins is paramount in minimizing the signs and progression of kidney disease.

In addition to fluid therapy, long term treatment of kidney disease with a protein restricted diet has been a cornerstone of therapy and remains an important measure for managing CRF. This helps decrease blood toxins which are by-products of excess dietary protein. To accomplish this goal, it is ideal to utilize a prescription food made especially for kidney disease, such as Purina NF and Hill’s k/d diets. Specially prepared homemade diets are an acceptable alternative to prescription food.

Elevated blood phosphorus often accompanies kidney disease due to a complex process that involves increased parathyroid hormone. Treatment involves reducing the phosphorus content in the diet, another important feature of prescription kidney diets. If dietary phosphorus restriction alone is not effective, then medicine that binds phosphorus is given at mealtime to prevent phosphorus absorption.

Since high blood pressure is common with kidney disease, a salt restricted diet is beneficial. Vitamins tend to be lost in patients with ailing kidneys; therefore, supplementation is another therapeutic feature. Restricting protein, salt and phosphorus, as well as adding more vitamins should all be taken into account for maximum patient benefits.

The elevated levels of toxins associated with kidney disease cause nausea, an increase in stomach acids, and may even lead to ulcers in the mouth and stomach of some patients. These problems are addressed by administering antacids and anti-nausea medications.

Dialysis and kidney transplants have limited availability. We are fortunate, however, that there is a feline renal transplant program at North Carolina State University. The patient and his/her owner must meet narrow enrollment guidelines for acceptance. The cost of transplant therapy can run several thousand dollars and owners must also adopt the donor cat. Even if limited, it is reassuring to know this form of therapy is available.

The specific treatment method used is tailored to each individual patient and their owner’s desires. Even though CRF cannot be cured, many of our kidney disease patients live with an extended quality of life and continue to bring happiness to their homes.