Vet 101: Understanding Kidney Disease in Cats

vet 101-kidney-cat

Kidney disease is the number one killer of older cats. Merlin, pictured above was diagnosed two years ago with CKD or chronic kidney disease. Our Vet 101 guest post is by Veterinarian Dr. Letrisa Miller who has a feline-only practice in Connecticut. This is the first in a three part-series on Kidney Disease.

Understanding Kidney Disease in Cats -1

Hearing a diagnosis of kidney disease from your veterinarian can be a frightening thing. Most people have had or know someone who had a cat that died of kidney failure and are naturally worried that this will happen to their cat. The good news is that for many cats the future is actually quite bright. A diagnosis of kidney disease doesn’t mean your cat is destined to go down the road of kidney failure!
  • Kidney disease comes in two main types: acute and chronic. Acute kidney disease, which usually presents as kidney failure, arises suddenly over a period of a few hours to a few days. Two common causes of acute kidney disease are lily toxicosis and antifreeze poisoning. Chronic kidney disease, CKD progresses slowly as kidney function decreases gradually, usually because of small insults such as infection, inflammation, cystic disease, or (more rarely) small blood clots. This post focuses on chronic kidney disease.
To understand what happens in cats with kidney disease, it helps to know what the kidneys do. Kidneys have numerous functions, so I’m going to touch only on the ones that are most important for understanding kidney disease.
  • One of the most important roles is to keep water in the body when it is needed and to secrete it in the urine when it is not. If the kidneys aren’t functioning properly, a cat can become severely dehydrated even when it is spending most of its time drinking. The kidneys simply can’t retain the water and it just goes right out as dilute urine. In almost all cases, this is a symptom of chronic kidney disease.
With acute kidney disease (kidney failure), a cat may literally drown in its own fluids because the kidneys aren’t able to secrete water fast enough. This rarely happens with chronic kidney disease.
  • Kidneys also make sure that the right electrolytes are conserved or excreted. When the kidneys aren’t functioning properly, cats can have problems with potassium deficiency or retention, B vitamin deficiencies, and calcium and phosphorus imbalances. Any imbalance in this group can cause heart, digestive, or musculoskeletal malfunction. Severe imbalances can cause death.
One of the lesser-known functions of the kidney is production of the hormone erythropoietin. This hormone is responsible for signaling to the bone marrow to make red blood cells. In late kidney disease, the hormone may need to be supplemented with injections to treat anemia.
  • Four stages of kidney disease have been defined by the International Renal Interest Society, or IRIS. These are based on measures of how much work the kidneys can do. One way to think of this: A healthy kidney can do more than 100% of the work it is “assigned” (such as removing toxins from the body and conserving water). Once a cat reaches stage 4 kidney disease, the kidneys may be able to do only 10% of that work.
  • The first three stages are kidney insufficiency stages, and the first two of them have very few detectable symptoms or signs. They are are also easily managed. The third stage is more symptomatic and requires more treatment.
In times past many veterinarians labeled all kidney disease as kidney failure, which paints too bleak a picture of what the future might hold. We now understand kidney disease much better, and survival times in cats diagnosed with stages 1–3 are typically counted in years not months if the cats receive well-managed care.
  • The fourth stage is failure and usually requires intensive treatment. However, even stage 4 can often be well managed to give a cat a good quality of life for an extended period of time.
How the stages are defined and what each stage means for your cat will be the topics of my next two blog posts. If you’d like to jump ahead and get more in-depth information now, you can find a lot of good information on the Internet, but I find the following two pages to be especially helpful:
Next time: Kidney insufficiency, IRIS stages 1 and 2.
Dr. Letrisa Miller DVM


Connecticut Feline Medicine and Surgery


27 thoughts on “Vet 101: Understanding Kidney Disease in Cats”

  1. I just heard the most horrible news that My Beautiful Siamese Cat, Akeim’s kidney are failing. I thought, I was going to die. Sure he’s gotten thin but, everyone said: he’s an older cat. He is 19 though, so I didn’t think much until, he wouldn’t eat his regular food. I got him an appt. & I thought she was gonna say: he’s a spoiled brat & send us home! I never even considered the fact that he actually has something wrong with him? I’m still trying to wrap my head this–she said: 6 mons……
    I have hope that he will live, I’m praying for a few more yrs….. All I can do is is have faith!!!

    1. When our Siamese was diagnosed with CKD at 16, he lived another five years but it was a lot of work, frequent vet visits and expense. Prevention is always easier than a cure. 19 is an amazing age and if you’re willing to do sub-q fluids and follow your vet’s advice, who knows. What’s important is to know what to look for as a cat ages, for signs of pain or discomfort. Making their final months or years comfortable is a blessing.

  2. Unca Caleb had this – and we wish we had known the signs to watch for – we caught it when he was stage 4 we think. Not much we could do to help him – he was almost 20, though, and had the kitty version of ALS (could not swallow and was being hand fed).

    Now we’ll read and learn and be ready in future years as the kids age.

  3. Thanks for this. My guys both have kidney disease, as well as a host of other medical issues. Even having worked at a veterinarian’s office for several years, some of this information was new to me. Fascinating and always helpful!

  4. Thanks so much for this – I’ve had one cat die, who was and always will be the apple of my eye: Lulu-Cat, a 1/2 African Wild Cat. Which got me to wondering, if wild cats, too, suffer from CRF but we just ‘don’t know’….

  5. .We’ll be interested in reading this. We had a cat that lived many years with chronic kidney disease and another that died quickly from the acute form, but it wasn’t from antifreeze or poisons. We’re not sure what caused it.

  6. Great Post!
    Hissy Old Licorice had Kidney disease for the last 4 years of his life. It is something that all owners of older cats should be aware of.
    Nellie and Mommy

  7. Continued health to Merlin! I’ve been reviewing my articles about Cookie last year, when she was in end-stage renal failure. I’ve seen it often enough in my geriatric cats it’s just not all that frightening any more.

  8. Lots of very useful information here. Several of my cats developed kidney disease but lived to a good age with medication. They were all the same family, mother and sister who lived to 23 and 24 years old, and 3 sons who lived to 18, 19 and 21 years old.Kitty YumBum was the daughter of the sister cat and only lived to 15 years old.

  9. Thank you for this very easily explained article on kidney disease in our older cats. There was a lot of good information which will be very helpful to anyone who is going through this with their own kitties.

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  10. merlin…dood…..thanx for de post…N heerez ta several mor qualitee yeerz for ya buddy….

    this nastee dizease iz what took me cross de bridge near five yeerz ago…..

    dude K

  11. My Siamese, Indi, was diagnosed and lived 5 more years. She died at 19.5. We only did SubQs the last year and a half. She was a great patient once she learned that they helped her. I’m not sure if she felt better because it countered her dehydration, or if my perpetually cold cat just liked all that warm water in her. She would just sit there with the most contented look on her face.

    1. Thanks for adding Tanya’s site. Some of your concerns will be addressed in other parts of this series. Our vet, Dr. Rich Goldstein who treats Merlin does advocate supplements. Merlin is on Renal K and RenAvast with positive results.

  12. So glad you posted this, Layla. So very glad.

    Well wishes to Merlin.

    Emma died at 20, but I don’t know the cause. She went downhill over the last four years of her life. Quietly.

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