Diagnosis: Kidney Failure
Chronic renal (kidney) failure is common in the pet population and most prevalent among older pets. In a retrospective study by Bronson, kidney disease was the second most common cause of death for dogs, after cancer. Cases of chronic renal failure can’t be cured, but can be managed with medication, diet, and lots of love and care.
The kidneys are bean shaped organs located inside the abdomen. They are extremely complex, with many active parts. The functioning units of the kidneys are the nephrons. There are thousands of nephrons in each kidney. The glomerulus is the part of the kidney that acts as a filter. The job of the kidney is to actively filter waste products out of the blood and send these waste products to the bladder to be emptied from the body. The nephron is responsible for maintaining water and electrolyte balance within the body. When 75% of the nephrons are damaged, kidney failure becomes clinically evident.
There are numerous causes of kidney failure. Genetics, poisons, medications, infections, inflammation, and cancer are all potential causes of acute and chronic renal failure. Often we may not be able to determine the actual cause or renal failure may simply caused by the aging process.
In early kidney failure, there may not be any symptoms at all. As the disease advances, loss of appetite, increased thirst and urination, loss of muscle mass, and lethargy may indicate that there is a problem. These symptoms are not specific for kidney disease, so veterinary attention is warranted immediately.
Before renal failure as developed, renal insufficiency occurs. This simply means that the kidneys are not working as well as they should, but still are functioning. In pets, the disease process is often not recognized at this stage, unless it is detected by screening labwork. An annual examination including blood and urine tests may detect kidney failure in an early stage. Tests that your veterinarian might discuss with you include: BUN, creatinine, hematocrit or PCV, urine specific gravity, and urine protein level.
BUN, or blood urea nitrogen - elevated above normal in kidney failure. Can also be elevated in cases of dehydration, which can be caused by many different medical conditions.
Creatinine - enzyme that is elevated when kidney failure exists.
Hematocrit or PCV - measure of the concentration of red blood cells. In advanced kidney failure, this is usually low because the kidneys are not producing enough of the hormone erythropoietin to stimulate the bone marrow to produce red blood cells. A low hematocrit indicates anemia.
Urine specific gravity – measure of the concentration of the urine. There is a specific range that indicates that the kidneys are not doing their job to concentrate or dilute the urine. For dogs and cats, this range is 1.010 – 1.012.
Urine protein level – often is elevated. Protein in the urine indicates that the kidneys are not keeping the protein in the blood like they should, the glomerulus is leaking protein.
In advanced kidney disease, elevated phosphorus and calcium in the blood become increasingly difficult to manage.
Once your pet has been diagnosed with kidney failure, immediate treatment is warranted.
Kidney failure is closely tied to other medical issues and patients with the disease must be carefully monitored to keep them feeling as good as they can.
High blood pressure can cause kidney failure or it can be a result of kidney failure. When kidney failure causes high blood pressure, it should be managed with dietary protein, sodium chloride, and phosphorus restriction as well as potentially with medications such as diuretics, ACE inhibitors and vasodilators.
When the kidneys are in failure, they are unable to regulate the body’s pH. The end result is metabolic acidosis. This means that the pH of the blood is lower than normal. Negative effects of metabolic acidosis include loss of appetite and increased breakdown of the protein within the body, including muscle protein. Medications may be used to control the body’s pH.
Nutritional management includes feeding an energy dense formula with very low phosphorus content. For dogs, it is recommended that the phosphorus content be between 0.3% and 0.5% dry matter. For cats, because they require higher protein in their diet, it is not feasible to restrict the phosphorus this much. A target of 0.5% to 0.7% is more realistic. If the phosphorus level in the blood is normal, medications can be administered to bind the phosphorus in the body and keep it at normal levels. Phosphorus has been proven to have adverse effects on the kidney, so phosphorus restriction is very critical. Another important nutritional factor is fat. Dietary fats provide energy to maintain body condition. Omega 3 fatty acids have a protective effect on the kidney by balancing the production of inflammatory mediators and helping dilate the blood vessels to improve blood flow to the kidney. Restricting sodium chloride (salt) helps maintain normal water and salt balance because the damaged kidney has limited ability to maintain the balance in the presence of high levels of salt.
Supplementation of vitamin E, omega-3 fatty acids, arginine, and B vitamins may be recommended. A feeding plan should be developed with the help of your veterinarian to provide the best nutrition for your pet throughout the course of the disease.
Management of a pet with kidney disease can be quite expensive. Regular veterinary visits to monitor blood chemistry values, urinalysis results, and blood pressure are important. Prescriptions may be expensive, including veterinary diets. Make sure you are aware of the costs of follow-up and be prepared as your success in treating your pet will be limited without this critical part of the treatment regimen.
Long-term prognosis is guarded to poor. However, renal failure can be managed for some time with appropriate diet, supplementation, and medication.
Please note that this information does not replace onsite, professional, veterinary care. It is solely for educational purposes. Your pet's medical condition should be evaluated by a veterinarian before any medical decisions are implemented. If there is a potentially life-threatening emergency involving your pet, take your pet to a veterinarian or veterinary facility immediately.
Veterinary Technical Services Department