Most cats if they live long enough get some degree of kidney disease. They just seem to be exquisitely prone to it. There are three common types of kidney disease that we will see in cats. Pyelonephritis, acute kidney disease, and chronic kidney disease. The kidneys don't recover well at all from any inflammation or infection. And of course, the kidneys can be prone to cancer.
Pyelonephritis is infection of the kidney, usually caused by a bacterial urinary tract infection that goes untreated for a length of time, but it can also be spread through a blood infection as well. Pyelonephritis is extremely hard to diagnose, and very hard to treat. We will usually make a presumptive diagnosis of pyelonephritis if your cat has a raging bladder infection and a systemically high white count. Antibiotics don't penetrate well into all parts of the kidney, and so once a kidney infection takes hold, it can take 2-6 months of antibiotics to eradicate it, and in some cases antibiotics will never completely clear it. In those cases we will treat on and off with different antibiotics for life to try and avoid resistance. Pyelonephritis can also result in both acute and chronic kidney disease.
Acute kidney disease, or AKD. This usually happens either from ingesting some type of toxin, such as eating lilies, antifreeze, ibuprofen, etc., but it can also happen from pyelonephritis, ureteral or urethral obstruction, or a variety of other causes. Due to a sudden major insult to the kidney, it suddenly becomes almost nonfunctional. Often it will become enlarged and swollen. Early in AKD, blood work can be completely normal, and your cat may act just fine. As it progresses, we can see elevated potassium, and start to see elevated kidney enzymes on blood work. By this time, we already have significant damage to the kidney.
The only treatment for this is copious IV fluids for 1-3 weeks to diurese your cat, and try to reduce the workload on the kidney and give it a break. This requires long term hospitalization of your cat. If available, peritoneal dialysis, or even kidney dialysis is ideal, but most average veterinary clinics, and even many 24 hour veterinary specialty clinics are not able to do this. If caught early enough, and if significant damage has not already occurred, your cat may survive, and live for several more years. Sadly though, by the time we usually find AKD, it is already too late, and we may only be able to buy a few more months of life for your cat, if even that.
Now if money is not an obstacle, which it is for the vast majority of us, you can take your cat to one of about 20 places in the that can perform a kidney transplant. It is from a living donor, you are required to adopt the donor cat, and your cat will need to be on anti-rejection drugs for the rest of their lives. You are looking anywhere from $5000 to $20000 in costs for the surgery and the cost of meds and treatments for the rest of your cat's life, but this has been successfully done many many times now.
1 - acute kidney failure - enlarged kidney
2 - normal kidney
3 - chronic kidney failure - small scarred lumpy kidney
Chronic kidney disease. This is probably the single most common disease that we see in cats. No one knows for sure what causes it, or why cats are so sensitive to CKD. There are a lot of theories, but no one has come up with a definitive provable answer yet. As cats age, we tend to see their kidneys slowly start shrinking and developing scar tissue in various areas of the kidney. This can start at any age. There are some disease that can cause this at younger ages, such as amyloidosis and pyelonephritis, but in most cases, we never know the cause. Eventually the kidney shrinks and scars down to the point that it is nonfunctional. Now, we only need 25% of both kidneys to work to adequately filter the blood. So, we have a long time from when the kidneys drop below 100% up until they drop below 25% function that we can do things to slow down the progression. We can't stop it, but we can slow it down.
The two best ways to assess kidney function are blood work and urinalysis. Once the kidneys start to drop below 100% function, we can start to see lower levels of potassium and phosphorus on blood work. In the urine, we will start to see protein and a reduction in urine specific gravity, which measures the ability of the kidney to concentrate urine. This is one of the many reasons we recommend regular blood and urine screenings once your cat reaches the age of 7 and older.
Once the kidneys drop below 33% function, we will start to see creatinine and urea nitrogen elevate on blood work. We call these kidney enzymes, but they are actually waste products of the body that the kidney removes from the blood and expels into the urine. By looking at the level of creatinine and urea nitrogen, primarily creatinine, we can tell if the kidney is no longer adequately filtering the blood. Once the kidneys drop below 25% function, we will see the creatinine elevate significantly. There is a staging process developed by the International Renal Interest Society that helps us to consistently stage kidney disease. Stage I and II are what we used to call early and late kidney insufficiency. Stage III and IV are what we used to call early and late kidney failure.
In Stage I kidney disease, about the only treatment recommendations that we will make are to increase your cats water consumption, and possibly to supplement potassium.
For Stage II kidney disease, we will also recommend switching to a prescription kidney diet. Now why not just feed your cat a kidney diet from kittenhood on? One of the hallmarks of kidney diets is that they are lower in protein. Protein is converted to ammonia in the GI tract, which is absorbed into the blood stream and converted to urea nitrogen in the liver. This is then filtered out by the kidney and eliminated into the urine. By reducing the protein, we reduce the workload on the kidney. However, protein is needed for a lot of body processes. Lack of protein can eventually lead to lack of muscle mass and other health issues. So, we keep the protein levels high up until we actually see significant damage in the kidney, so as not to cause other issues in other areas of the body. We may also recommend a few supplements and medications that can help slow down the progression of kidney disease in your cat.
In Stage III kidney disease, we get a lot more aggressive. At this point your cat cannot adequately filter the blood. As the toxic enzymes slowly build up in your cat's body, your cat starts to become nauseous, and their appetite drops off. So, we try to help the kidney out by giving subcutaneous fluids under the skin to almost mildly diurese them. The more fluid, the more dilute the blood, and the less hard the kidneys have to work to filter out waster products. At this point, we at All Feline have also had some pretty good luck with anabolic steroids helping your cat's kidney to function better. However anabolic steroids only work for about 50% of cats, and they can have some pretty undesirable side effects. But if they work, they may be able to double the length and quality of life that your cat has left. If you are interested in trying these, talk to your veterinarian. We may also add on anti-nausea medications and appetite stimulants at this point.
In Stage IV kidney disease, we are close to the end. This is end stage kidney failure and your cat does not have long left to live. At this point, our primary concern is to keep your cat's quality of life good. If we can't do that with subcutaneous fluids and medications or with periodic IV fluids to diurese your cat, then we may recommend euthanasia. We don't win with kidney disease. It is a chronic wasting disease and it just plain sucks. The hardest part is knowing when to say when. Cats do not generally die on their own of kidney disease, they die from starvation, or because the toxic waste products are so high that they are basically poisoned by their own body. Neither way is a pleasant way to die. It is much kinder to your cat to have them euthanized when they are suffering. Most people that have had cats for any length of time have lost a cat to kidney disease, or have friends or family that have lost a cat to kidney disease.
Cancer. Just can't escape it. Thankfully kidney cancer is rare, but when we do see it is almost always either lymphoma or transitional cell carcinoma. Lymphoma treatment in the kidneys is about the same as anywhere else, chemo or palliative treatment. Transitional cell carcinoma however has a very good response rate to a non steroidal anti-inflammatory drug that also has anti-tumor effects called piroxicam. While piroxicam is pretty hard on kidneys, it has the potential, not guarantee, but potential to reduce or even cure transitional cell carcinoma. So, if we suspect kidney cancer and taking your cat to a specialty center for a kidney biopsy is not an option, then we may try piroxicam just in case.