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The Daily Vet by petMD

The Daily Vet is a blog featuring veterinarians from all walks of life. Every week they will tackle entertaining, interesting, and sometimes difficult topics in the world of animal medicine – all in the hopes that their unique insights and personal experiences will help you to understand your pets.

Feline Kidney Disease: A Vet’s Perspective

One of the veterinary hats that I wear is as an in-home euthanasia provider. It may sound a little bit morbid, but helping pets pass peacefully at home, surrounded by their loved ones, is actually very rewarding (funny that I still feel the need to justify this choice of work, though).


Anyway, I had a notable week awhile back. I saw an unusually high number of cats, and every single one of them was in kidney failure. Statistically, this is probably not too surprising. Kidney disease is the number one killer of older cats, after all, but it still got me thinking, "Why are all these cats dying of kidney disease?"


First a little background. Kidney failure can be divided into two categories: acute and chronic. Acute kidney failure develops quickly, usually as a result of an identifiable problem, such as getting into antifreeze, a kidney infection, low blood pressure during anesthesia, etc. Chronic kidney failure develops more slowly, usually in older cats, and is the result of the gradual loss of nephrons, the functional unit of the kidney (healthy cat kidneys have hundreds of thousands of them).


Nephrons can’t regenerate themselves. Once one is damaged and no longer working, it is gone forever and can’t be replaced. Many things cause the loss of nephrons: a bout of acute kidney failure can knock out a whole bunch at one time, but everyday wear and tear builds up too. Some cats may also be born with fewer nephrons than is normal. So you can see how over time a cat could essentially "run out" of nephrons.


When faced with an owner’s questions about chronic kidney failure, I’ve heard some veterinarians quip that "cat kidneys were designed by committee," but that’s not really the case. They were designed by natural selection, which usually does a great job, on a population level at least, of promoting health. So what’s the deal?


In my opinion, the epidemic of kidney failure in domestic cats is our fault, but not in the way that you might think. I don’t blame inappropriate diets, lifestyle choices, litter box issues, or over-vaccination as some do, I blame excellent husbandry and veterinary care for giving our cats the opportunity to live much longer than they were ever designed to.


Look at the stats. Outdoor cats typically don’t live for more than five to seven years, and truly feral kitties (those that receive no supplemental nutrition, veterinary care, etc.) often only survive to the age of two or so. But even in such a short life, intact males and females can produce many litters, ensuring that their genes are passed on to the next generation… the goal of natural selection.


If all this can be accomplished in just a couple of years, and a cat was likely to die of an infection, be eaten by a predator, or otherwise not make it past the age of five, who needs kidneys that last for 20 years? It’s all about allocation of resources. The energy used to maintain an over-designed kidney has to be taken from somewhere, maybe resulting in weaker muscles, a poorer hunting ability, and fewer offspring.


These days, I think some cats are essentially out-living their kidneys because of their owner’s excellent care. After all, we all have to die of something.



Dr. Jennifer Coates



Image: Julia Shepeleva / Shutterstock



Comments  29

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  • Coincidence or More?
    08/20/2012 06:55pm

    I just came across this article as I'm trying to understand what is happening to my cats. I had 4 cats. One aged 16, one aged 15, one 9 and one 8 years old. On July 23, I took the 15 year old to the ER vet where she was in the advanced stages of kidney failure and ultimately put her down that night. One week later, our 16 year old was exhibiting the same symptoms (lethargic, dehydrated, walking funny). We thought she was depressed because the other kitty had passed but she too was found to be in the advanced stages of kidney failure and we put her down as well. In the last week, we noticed our 3rd cat acting the same and took her to the vet. After receiving the results of her bloodwork, she too was considered to be having very advanced kidney failure and again, we had to put her down. I understand cats get old and I can even understand the first two having this issue. This third cat was old but quite a bit younger than the other two. We have scoured our home looking to see if they may have got into something but have found nothing! I find it very hard to believe this is a coincidence but I can't figure anything else out. We don't work on cars (no antifreeze around), the cats have NEVER been outside, we have not done any home remodeling, no changing of foods, it's just utterly bizarre and quite scary. We have one cat left and she seems to be more than normal (she's a pig actually) and isn't showing any signs but I'm terrified that this is going to happen again. Any suggestions on any other ideas of toxins? We also have NO house plants so that's not an issue. Thank you.

  • 08/21/2012 11:05am

    I'm afraid its impossible for me to determine what might be going on with your cats from afar. My top ruleout would have to be a toxic exposure, particularly if they all eat the same food, treats, etc. Sometimes a full necropsy (the animal equivalent of an autopsy) is necessary to get to the bottom of these things. Hopefully this has just been a terrible coinicidence and your remaining cat will be just fine. It certainly wouldn't hurt to have your veterinarian perform a full wellness check on him (blood work, urinalysis, etc.). Best of luck.

  • kitty died-failed kidneys
    11/05/2012 07:38pm

    Thank you for your article. Reading it helped me. Had to euthanize my 9 yr old siamese kitty, Mimi last week. I am still crying over it. She stopped eating and blood worked showed kidney failure. Had her at vet for 3 days on IV fluids...she did not improve. When we went to be with her, the pupils in her eyes were huge and one had blood behind it. Vet thinks blood pressure and she may have gone blind :( I somehow feel responsible and I cannot relieve myself of guilty feelings. I should have noticed...she was getting thinner, but still acting normal...eating, urinating in proper place, playful...but getting thin. If I had taken her sooner, perhaps I could have saved her? I miss her so much. I have another kitty and he is the same age. Are there any signs I should watch for which may be clues? I don't want to miss something. It's so painful to lose my little furry friends. Thank you

  • 11/07/2012 11:24am

    I'm so sorry for your loss. The "early" signs to look for are increased thirst and urination, "accidents" outside of the litter box, and weight loss - although all of these only develop after significant kidney function has been lost. If you have any concerns, your veterinarian can check your cat's blood levels of BUN and creatinine and urine concentrating ability.

  • 11/07/2012 11:43am

    Thank you for your response Dr. Coates. The symptoms you mention did not appear in my Mimi. The only real sign I saw was that she was getting a little thin. I did notice an increase in drinking...but not signficant and she always urinated in the proper place.

    Can kidney failure happen that suddenly and without warning? I remain heartbroken. :( Toni

  • 11/07/2012 12:32pm

    The disease can occur quickly, but oftentimes it develops over months or even longer, but the cats display no symptoms at all until the majority of their kidney function is lost. This is what makes the disease so heartbreaking.

  • 03/31/2015 09:09am

    It is so heartbreaking when something like this happens. I am going through it right now. It's tearing me apart. You can't take on blame for not noticing the signs. I have been through it with several other cats over the years. Cats are experts at hiding their illnesses. Sometimes changes are very subtle and you just don't see it. Once this disease shows it's face, the best you can do is try to manage it as best you can and I'm sure you did that. I am sorry for your loss. I know how it hurts. It won't be long before I will have to face that terrible day and have to say good-bye to a little kitty that I love with all my heart.

  • 03/21/2013 12:53am

    I'm very sorry for your loss as well. I just received the sad news from my vet this evening that my siamese cat Yogi has acute kidney failure. I'm taking him into the vet tomorrow morning to have him sent back to God. It destroys me when these things happen. My kitties are my kids. I understand what you're going through. It's devastating. I'm so glad I had Yogi for 12 years. Found him on top of a moving van at 1 day old. He was the only one that survived. Thank God he did. He's been the love of my life!

  • 03/21/2013 08:19am

    Dear Kittymom,
    I am so sorry to hear about Yogi and you having to let him go. :( It is one of the hardest and saddest things you have to do. The only thing that helped me get through was having a friend tell me that I was a good Mom and that it was the final act of Love I could do for her. You love your babies so much and in turn, are rewarded with their love and trust. That is what makes it so hard to let go. I know 12 years seems like a long time, but when you love them, it is not nearly enough. Mimi was only 9. It's been 4 months since she died and it seems like a lifetime. I still miss her so much. We have since gotten two more kitties. One Siamese, one Tiger...both shelter rescues. They help fill the hole in my heart...but there will always be a special place for Mimi and I know you will always hold a special place for Yogi. Once again, I'm so sorry. You are in my thoughts and prayers. Reach out to me if you need to "chat." Hugs, Toni

  • Renal Failure
    12/28/2012 10:33pm

    Hi - at what point should you let the cat go? Our cat is 20 years old and has stopped eating and is suffering from chronic renal failure. He is on daily sub-q fluids. I guess we are just about there. Thank you!

  • 12/28/2012 10:47pm

    Hi Mazzy. I'm not a vet, but I have had many cats as part of our family. Recently I lost one to kidney failure. For us, we had no warning at all, so it was such a shock to lose her so quickly. I just wanted to offer my sympathy. I know how hard it is to make this sad decision for your beloved friend. Twenty years is a long time. You must have taken very good care of your cat. As hard as it was, I told myself it was the last loving thing I could do for her and I think she knew it. My thoughts are with you as you go through this difficult process. Toni

  • 12/28/2012 11:04pm

    Hi Toni - thanks so much for your reply. We are discussing the next step. Very difficult to let go....

  • 12/28/2012 11:14pm

    Yes Mazzy, it is. So hard to let go after so many years together. :( I lost my Mimi in October and I still can barely say her name without crying. I understand completely. I'm so sorry.

  • Kitty passed from CKD
    03/09/2014 11:16pm

    Four days ago, our kitty who had been struggling with CKD (complicated by FELV) for several years passed away. We found her when she was about 5 (making her about 12 when she died). She had done well for 3 years on a special kidney diet and sub fluids. Her final turn was rapid and tragic. We brought her to the vet for iv fluids because she wasn't eating, but she developed pulmonary edema. We took her home while she was still alert, and the vet said they could do no more for her. At two in the morning, we made a decision to take her to the ER to have her put down because her breathing had become extremely labored and she was having difficulty staying coherent, but she seized and passed within a minute. I had looked earlier in the day to see if there was a vet locally who would come to our home to euthanize her, as we didn't want her to go in a clinical setting that was unfamiliar and frightening, but there wasn't. I applaud your work, going to people's homes to help them in those final hours, allowing them to both end their loved one's suffering while keeping them at home surrounded by familiar people, smells and objects. I wish we had been able to do that for our kitty. Thank you for the article as well - I'm still reeling, wondering what else I could have done, what I should have done better, but understanding that they are outliving their kidneys helps to relieve the guilt if not the pain.

  • 03/10/2014 01:27pm

    I am so sorry for your loss. You and your kitty are in my thoughts.

  • kidney disease
    03/31/2015 08:58am

    I am going through the kidney disease nightmare right now. My 10 year old cat, Gina, is nearing the end and I am heartbroken. She is still doing all of her usual things, but much more slowly. She is getting fluids and that seems to make her feel better. She can still get up on the bed and she cuddles next to me every night. She doesn't eat as much as she used to, but she does eat enough to maintain her weight. I do not want her to suffer, but that last day will hurt so badly. I think the day you have to say good-bye is the ONLY bad part of owning a pet. They are like children to me.

  • 03/31/2015 04:18pm

    I share your sentiments about your cat, Gina. I know its a difficult time, and I have stood in your shoes. Gina knows that you are doing all you can and she loves you. Each day with her is precious. Just know that one day, you and Gina will be reunited, never to part. I read the book, Do Pets Go To Heaven, by Billy Graham. It was of much comfort.

    Take Care

    03/31/2015 11:33am

    Thank you for the Article about cats Dying from Kidney Disease. About 4 months ago our 18 year old Persian female was diagnosed with End Stage Kidney Disease. The vet suggested the KD wet food for which she did not like so we switched to Wellness No Grain Wet Catfood. She goes for weekly Fluid Therapy at the vet and the fluid therapy really does help her and I am thankful for that. She is doing quite well I might add.

  • Inflammatory Syndrome
    03/31/2015 01:54pm

    These kidneys have Lymphocytic/Plasmacytic (LPs) inflitration in them. Inflammation slowly scars in the cat kidney. Dr Coates is correct that nephrons are do replaceable once they are gone. But we know it is from a glycoprotein antigen host reaction to the high carb feline food. These are formed from the Maillard reaction. When the cell mediated immune reaction is done there is a scarred desert left in the tissue affected. Many of the food manufacturers that sponsor this website have very high carb content food. They are very profitable foods to sell. There is a new test to detect kidney damage at 40% (SDMA) rather than 75% (creatinine). New research is suggesting a high protein/ low carb diet for cat kidney disease! We have too much evidence from how we treat cats for IBD, hepatitis, interstitial nephritis, FORLs (bad teeth), etc. with cyclosporin, rutin, and prednisolone, all anti-inflammatory drugs! All of the listed tissues have LP infiltration! Diet modification helps be once the inflammation starts it is hard to stop. I would suggest feeding a species appropriate diet to cats!

  • 03/31/2015 03:45pm

    As a cat owner of many years, having had cats with kidney disease, I have listened to both "sides of the fence". I have come to the conclusion that for Daisy that presents with End Stage Kidney Disease, she needs protein in her diet, which increases the blood flow and blood volume to repair the damage to the kidney cells. These cells cannot be repaired without protein.

    Wellness Cat Food reigns above the rest and believe me, I have tried many, in the course of my kitties, is the most nutritious with real meat and no meat by products, no grain, preservatives, the nasty stuff fillers other cat foods contain. Daisy is 18 years old and is quite impressive at any rate. She is doing wonderfully thanks with the help of our vet and her bi weekly fluid therapy.

  • 03/31/2015 04:14pm

    I, too have a kitty that has kidney disease. I got her from the Human Society, and we don't really know how old she is, but I'm thinking she's about 6 or 7 now. About a year ago she was diagnosed with kidney disease. I put her on Prescription Diet k/d. Although she was eating it with no problem, she now has developed a dislike for it. I have two other cats and feed them Science Diet sensitive skin and stomach formula. Now she is eating only that food, and so far, so good. She's thriving and doesn't look sick. The vets have all told me limited protein, as it affects the kidneys. I don't believe that it makes that much of a difference, and will continue to feed her what I am now. I'm glad to hear Daisy is doing well.

  • 03/31/2015 04:26pm

    When Daisy was on the Science Diet K/D, she looked at me, like, "is this it?
    So, I put her back on the Wellness that she was on before the KD. So I know she is happy that I did not buy anymore of the KD stuff. You just go by what your kitty wants and likes. That is something.

  • 03/31/2015 04:50pm

    Just wanted to add one more thing. Each cat that is diagnosed with Kidney Disease, or like mine with End Stage, each cat's regimen is different.

    My vet said I could give her 1 fourth tablet of Pepcid (Famotidine 10 mg) with her evening meal, crushed in the wet food. That is helping too.
    Every other day, I give Daisy a probiotic, one half capsule and that is helping her to receive nourishment from the food she eats. Probiotics are good for cats who have vomiting, hairballs, constipation, diarrhea, etc.

    Daisy tends to get constipated and the friendly flora in probiotics helps her in this way. Also good for cats that have been on antibiotics, as it restores the balance to their digestive system. Am told that constipation is also a part of the kidney disease. Always consult your vet about these things though.

  • 03/31/2015 06:30pm

    I am very happy to hear your cat is doing well on Wellness canned cat food, Natural Planet chicken or turkey is another good carnivore choice. Stella and Chewies freeze dried chicken or turkey is another. We are monitoring some subtle changes to Wellness canned cat for over the last year. We have recommended Wellness canned chicken and turkey formulas for a decade but I am not sure they are still less than 5% carbs. The pet food industry is very competitive. Good carnivore protein costs money!

  • 03/31/2015 10:29pm

    Just the thought of anything dry or freeze dried is totally unhealthy. Plus the "shelf life" preservatives alone makes it indigestible. Cats need protein and high moisture. Personally it would make me gag, if I were a cat.

    I would rather use real chicken meat and home cook for my cats then what you suggest as in the recipes Dr Pitcairn uses.

  • 04/01/2015 12:06pm

    The freeze dried is a complete and balanced safe raw product. It is 99% meat that is high pressure processed to destroy bacteria at 34 degrees and the meat is not heat damaged. It must be hydrated with warm water to feed it. The product is relatively new for cats. It is getting increasingly difficult to find decent canned cat foods.

  • 04/01/2015 12:56pm


    Has anyone thought about chlorinated water as causitive for kidney disease?
    Thank you

  • 04/01/2015 02:35pm

    Good Point.

  • What a Sadistic Viewpoint
    02/26/2016 11:45am

    To say that cats should only live a couple years because they get kidney disease is so incredibly sad, mean, and painful, I am SO thankful you are not my vet. Oh my goodness, do all your patients and their owners know what you think when you treat them for kidney disease? Why not kill all cats above 5 years old to eliminate kidney disease altogether? How ridiculous is that, yet THAT is exactly what you are saying.

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