Video Link from The Cornell University College of Veterinary Medicine: Cat owners guide to kidney disease. Includes tests used to diagnose it, what it is, medications used to manage it and instructions on giving fluids under the skin (subcutaneous fluids).
Kidney disease implies that one or both of the kidneys are not working as they should. It can go undetected until the disease is severe enough to cause clinical signs or changes in blood and urine tests. Other terms used include renal or kidney failure. Kidney disease can be acute (recently occurred and may be reversible) or chronic (has been occurring and progressing for a long time and is not reversible). Sometimes it can be a combination where a patient with stable chronic kidney disease has an acute worsening of kidney function, termed acute on chronic kidney disease.
The kidneys are important for daily function as they eliminate the waste the body produces, make sure electrolytes and water balance and they produce a variety of important hormones including one that helps prevent anemia. Luckily the kidney is made with plenty of “back-up” help. 66% of the kidneys must be damaged to lose the ability to concentrate urine and 75% of the kidneys must be damaged to see elevations in levels of wastes the body clears from the blood. This is why people and animals can donate one kidney and continue to live a normal life, as both kidneys are not necessary if they are completely healthy. One disadvantage is that the “back-up” help makes it difficult to detect kidney disease early on.
The goal of identifying kidney disease early is to attempt to slow its progression. How can you tell at home if your cat may have kidney disease? Early on, your cat will appear normal and healthy. Once 66% of the kidneys are damaged, concentration of the urine (a way the body conserves water) is not possible. A sign of this is that your cat begins to drink more water and urinate more often. You may notice that your cat is always at the water bowl or that you fill it more often than usual. You may also notice that your cat is using the litter box more often or that you are scooping the litter box more frequently.
As the disease becomes more advanced your cat will lose weight, have a poor hair coat and may not eat as well. As the kidney damage progresses body wastes are not eliminated properly and they accumulate in the blood and body. This elevation of toxins can be measured with blood work and when these levels are increased the condition is called uremia which literally means urine in the blood. Signs of uremia include loss of appetite, vomiting, ulcers in the mouth, weakness and bad breath due to the accumulation of ammonia.
Other abnormalities that can occur include anemia (the kidney produces a hormone called erythropoietin that is responsible for making red blood cells), and high blood pressure. The anemia makes the weakness and loss of appetite worse. High blood pressure can cause blindness, stroke-like signs such as changes to behavior or seizures, injury to the heart and worsening of the kidney disease itself.
So how can you identify this disease earlier rather than when your cat is sick? This is where the importance of yearly urine and blood tests during your senior cat’s annual visit comes in. A urine sample will show whether the kidneys can concentrate it appropriately (remember loss of this ability is one of the first indicators of kidney disease). If the kidney is damaged enough or there is high blood pressure proteins will also accumulate in the urine and this can be detected as well. Sometimes, urinary tract infections can affect the kidneys and a urine test can also identify if this is present. A complete blood test is important to monitor not only for two main indicators of toxin accumulation in the body (BUN and creatinine) but also to make sure that anemia is not present. A blood test can also identify electrolyte abnormalities which may require special supplements to correct.
Other tests that should be done during your senior cat’s exam should include a blood pressure. Once kidney disease is identified x-rays and ultrasound are needed to evaluate the kidneys. This evaluation is important in identifying possible kidney stones, abnormalities in size and shape of the kidneys.
Although chronic kidney disease is irreversible, for most cats treatment can “assist” the kidneys and allow a good quality of life for months or years. There is no single treatment for kidney disease. Your veterinarian will tailor make a plan for your cat based on the severity of the changes in the blood work and the signs that your cat is experiencing. Treatments include a “kidney friendly” diet, hydration therapy by giving fluids under the skin, supplements and medications to vomiting, nausea, poor appetite and high blood pressure. If your cat becomes anemic injections of the hormone erythropoietin may be recommended.
Your veterinarian will formulate a schedule for exams that will include re-checking blood work, urine tests and blood pressure. This will assist in making adjustments to the treatment plan.
In humans chronic kidney disease is sometimes managed with hemodialysis (where a machine acts like a kidney and cleanses the blood of wastes) or by kidney transplant, both of which are available for cats but usually not a realistic option for the general cat population due to limits in availability, costs and specific criteria to be an ideal candidate. It is important to remember that hemodialysis is not a cure and those receiving kidney transplants require long-term medication administration to try and avoid rejection of the donated kidney.
Remember, just because your cat seems healthy at home, it is important to see your veterinarian at least yearly for younger cats, every 6 months for senior cats (>7 years old) and that blood work and urine tests be performed in senior patients to try and spot changes before your cat is actually sick!
