Time for some more information about disease in older cats. Kidney disease or renal failure is another of the big 3 diseases that we worry about in older cats. The kidneys are one of the organs, along with the liver, that helps us to "clean" our blood of toxins. They are also important in maintaining fluid levels, blood pressure, red blood cell production and a variety of other tasks. The kidneys are extremely important in maintaining our overall health and wellbeing. And the output of the kidneys? Urine of course!
Kidneys are made up of millions of little structures called nephrons. These nephrons are not replaceable so once they are damaged they cannot be replicated. However, the nephrons that are left have an amazing ability to increase their workload to make up for loss. While that is great news if there is damage to the kidney it can make it difficult to diagnose problems with the kidneys. By the time we can diagnose kidney disease we are down to less than 1/3 of our normal kidney function (ie 2/3's of the kidney's are no longer working). This makes it very important that we identify kidney disease as early as we can. There are some great new treatments that can improve both quality and quantity of life. But they work best with early intervention.
Diagnosis involves collecting a blood sample and a urine sample. Both samples are necessary to identify kidney problems. We look at levels of several compounds in the blood in combination with the concentration of the urine to determine if there is kidney disease present. If you are working with your vet on diagnosing or treating kidney disease you will talk about BUN (blood urea nitrogen), creatinine, phosphorus and calcium levels as well as the urine specific gravity which is a measure of concentration. At a minimum, yearly blood work in geriatric cats should be done to increase our chance of catching this disease as early as possible.
You may also notice some signs at home that would suggest that your cat should be checked. These signs can look a lot like other older age diseases and should never be ignored. These signs include increased vomiting (more than 1x per week), increased thirst, increased urination frequency and/or volume, weight loss, exercise intolerance and lethargy. Increased thirst occurs because the cat is urinating more frequently. Increased urination occurs because as nephrons are lost the kidney becomes less able to conserve water and so there is more water lost into the urine (it becomes less concentrated).
Treatment for cats with kidney disease has come a long way recently. We do recommend some nutritional changes to account for the abnormal retention and loss of various nutrients that occurs with a poorly functioning kidney. This will likely involve the recommendation to switch your cat to one of a variety of prescription diets available commercially. It is also very important to provide easy access to fresh water. Cats often prefer moving water so this would be a good time to check out one of those automatic waterers or cat water fountains.
Your veterinarian may also recommend a medication called calcitriol. Calcitriol is the active form of Vitamin D. It plays many roles in the body. Its primary use in renal disease is to lower levels of parathyroid hormone (PTH). PTH is toxic at elevated levels leading to increased loss of kidney function, inappetance, depression, anemia and increased risk of infection. Calcitriol is made naturally in the body in the kidney cells. As kidney cells are lost there is less calcitriol made resulting in higher levels of PTH. Higher levels of PTH lead to more loss of kidney cells, lower calcitriol production and the cycle continues. Calcitriol given early in kidney disease has been proven to slow the progression of kidney disease. It also tends to make animals that are experiencing subtle symptoms to feel better. Owners will often comment after starting calcitriol that they were surprised at how "kitten-like" their cat becomes as they begin to feel better. Even if kidney disease is diagnosed later in its course, calcitriol can still be very helpful to reduce symptoms and support the remaining kidney function.
Other treatments may include subcutaneous fluids, phosphorus binders, antacids and potassium supplements. The use of these medications will be dependent on the specific circumstances of the cat, other diseases that may be present and the ability of the cat and owner to cooperate in terms of giving multiple medications.
Kidney disease is a chronic disease that we cannot reverse or cure. But it is no longer the immediately terminal diagnosis that it used to be. With early diagnosis and intervention you can make your cat feel good and happy with life for several years despite living with kidney disease.
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