Why Feline Kidney Insufficiency is Still Tricky to Treat

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Gary Norsworthy, DVM, Dipl. ABVP (Feline), owner of Alamo Feline Health Center in San Antonio, believes veterinarians should be careful when using the term “kidney failure” in talking to cat owners.

To determine kidney function, creatinine and BUN (blood urea nitrogen) tests are conducted. Kidney failure occurs in a dog in which the creatinine value from blood tests is over 2.5 mg/dl, giving a dog a month or two to live.

A creatinine number over 2.4 signals kidney trouble for a cat, yet actual kidney failure for a cat doesn’t start until that number reaches 5.0 or 5.5 mg/dl, Dr. Norsworthy said.

Poor word choice can come into play when a veterinarian gets blood test results back with a creatinine value over 2.4 for a cat, he said.

“Many cats are diagnosed with kidney failure that don’t have failure,” he said.


Norsworthy said that in such cases he advises practitioners to use the term “kidney insufficiency,” a phrase he considers more accurate to describe cats in this range.

“That’s an important distinction,” he said. “If you use the term ‘failure,’ owners wonder if their cat’s about to die. So cats often get euthanized when they shouldn’t.”

With proper treatment, Norsworthy said, cats with kidney insufficiency frequently live for one to three years before kidney failure and death, and they can live a fairly normal life.

When Norsworthy treats cats with kidney inefficiency he pays close attention to two electrolytes: the phosphorous and the potassium levels.

The phosphorous level can get too high, so it must be brought down, while the potassium can get too low and must be brought up, he said.

“Managing the electrolytes is part of the treatment,” Norsworthy said.

Christopher G. Byers, DVM, Dipl. American College of Veterinary Emergency and Critical Care, Dipl. ACVIM (small animal internal medicine), believes every veterinarian should be familiar with the staging system for chronic kidney disease developed by the International Renal Interest Society.

IRIS staging is undertaken following the diagnosis of chronic kidney disease to facilitate appropriate treatment and monitoring of the patient, and is based initially on fasting blood creatinine assessed on at least two occasions in a stable patient.

The patient is then substaged based on proteinuria and systemic blood pressure, according to IRIS guidelines.

“Use of the IRIS staging system yields prognostic information and helps identify consequences of CKD for which veterinarians can prescribe interventions,” said Dr. Byers, a faculty criticalist/internist at Midwest Veterinary Specialty Hospital in Omaha.

“Simply stated, universal application of this staging system could enhance our understanding of CKD in dogs and cats and allow veterinarians to identify optimal therapies.”

Byers said he would like veterinarians to appreciate the incidence of renal secondary hyperparathyroidism and the renoprotective role of calcitriol therapy in patients with chronic kidney disease.

He said a previous study (Polzin et al, J Vet Intern Med, 2005) confirmed that calcitriol prescribed to treat renal secondary hyperparathyroidism caused a 68 percent reduction in mortality.

“Extrapolation from dogs to cats suggests the benefits should be similar in cats with CKD,” Byers said.

A common oversight by veterinarians that Byers sees is failure to obtain concurrent urine samples when evaluating blood renal values.

“If a clinician wants to satisfactorily assess renal function, both blood and urine must be analyzed,” he said. “Failure to properly perform a complete urinalysis can lead to misdiagnoses and inadequate therapeutic interventions.”

Cats Living Longer

Cats are living longer today – and that has implications where chronic kidney disease is concerned, the experts said.

In 1983, 26 percent of cats were older than age 6, and by 1996 47 percent of cats were 6 or older, according to surveys from the American Veterinary Medical Association. A 1999 survey of primary care practices in the U.S. showed that 20 percent of cats were older age 10 years and 5 percent were older than 15.

Byers pointed to these statistics to make his case that the cat population has grown in age due to better veterinary care, among other factors.

“The cause of this increased longevity is unquestionably multi-faceted, and I suspect increased awareness by owners of advanced medical and surgical interventions available for their pets, as well as the phenomenal veterinary care provided to these pets are the major contributors these statistics,” Byers said.

It is because cats are living longer – and because they can continue to live a normal life if diagnosed early and treated property – that Norsworthy recommends that veterinarians actively look for cats entering the kidney insufficiency stage by ordering a senior blood panel for their cat patients age 10 and up.

“That will allow you to find it early and treat them,” he said.

Since chronic kidney disease is common in elderly cats, the importance of screening cannot be overstated, said Jessica Quimby, DVM, Ph.D., a faculty member in small animal internal medicine at Colorado State University Veterinary Teaching Hospital.

“Early diagnosis has been associated with longer survival,” said Dr. Quimby, a member of the American Association of Feline Practitioners.

“Just knowing that a cat has CKD will encourage a higher level of monitoring at home, more frequent vet visits, more care with procedures, drugs and anesthesia. Regular monitoring for metabolic complications of disease will allow them to be addressed in a timely manner with the goal of slowing disease progression.”

Quimby has seen a higher incidence of chronic kidney disease in cats in recent years, and she attributes this to better care and better medicine.

“We do feel that cats are living longer than they did 20 years ago, and I’d like to think that we are better at diagnosing them early and helping manage the disease rather than seeing them in late stage disease in a uremic crisis,” she said.


A changing view of the best diet is a key development in the treatment of chronic kidney insufficiency, Nortsworthy said.

In the past, the approach was a low-protein diet. Now the practice is to put such a cat on a high-protein diet, he said.

There are several reasons for this switch in thinking, particularly to keep the cat from losing too much weight and muscle. Muscle wasting is a common problem in senior cats, Norsworthy noted. Their spines and hips become very prominent because they have lost muscle mass. This occurs due to protein deprivation.

“The low-protein diet really hasn’t done the good that we thought it was doing,” Norsworthy said, adding that its benefits to kidney function “are minimal to nil” and that many older cats on a low-protein diet will begin to lose muscle and get thin.

Despite this change in thinking, many manufacturers continue to make low-protein diets that are officially labeled for the kidney disease, he said.

“I don’t even use those official kidney diets anymore,” Norsworthy said. Instead he recommends foods made for diabetes patients because they are low in carbohydrates, which is in excess amounts in many cat foods, and the food makers have replaced the carbs with mostly proteins.

Norsworthy noted that creatinine is artificially lowered when a cat loses a lot of weight, and muscle mass is needed to make creatinine.

“In a very thin cat, the creatinine will not be a true reflection of the kidney function,” he said.

That means the creatinine measurement is not reliable in a thin cat, and on the other hand the BUN measurement is falsely elevated in a cat that’s dehydrated. “Therefore, you have to consider body condition and hydration status when interpreting creatinine and BUN values,” he said.

High protein diets will elevate the BUN measurement, but that doesn’t mean the kidney function is down, he said. “It just means the cat’s on a high-protein diet.”

A picky appetite is one of the most common concerns Quimby hears about patients with chronic kidney disease

“Appetite should be actively addressed, as poor body condition is linked to a poor prognosis,” she said.

Treating complications of the disease, like hypertension, dehydration and anemia, will help maintain appetite, Quimby said, but feeding tubes, appetite stimulants and anti-nausea medications should be considered to manage nutrition.


Byers is excited by a potential breakthrough in diagnosing chronic kidney disease may come from any of the various studies that have confirmed that symmetric dimethylarginine – a byproduct of protein methylation that is eliminated by the kidneys – is a precise biomarker for calculating estimated glomerular filtration rate in humans, and is more sensitive than serum creatinine for assessing renal dysfunction.

Studies have shown that measuring SDMA levels allowed earlier detection of chronic kidney disease in cats compared with serum creatinine, Byers said.

“These results are encouraging, as early recognition of CKD will empower veterinarians with invaluable information about initiating renoprotective therapies that could slow CKD progression,” Byers said.

Quimby believes there haven’t been enough breakthroughs in treating or understanding more about this disease.

“One of the most discouraging things about CKD is that despite its prevalence, we still have very little idea what causes it or why it is so common in elderly cats,” Quimby said.

However, she is encouraged by the emergence of recent studies focusing on exploring etiology of the disease and possible treatment options.

“A new focus of several research groups has been to better understand the pathophysiology of feline chronic kidney disease to direct us in the development of novel therapies,” Quimby said. “Although this information is not currently available, it is a very important area and provides hope for the future.”

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34 thoughts on “Why Feline Kidney Insufficiency is Still Tricky to Treat

  1. I had a cat that was diagnosed with kidney disease at 4 years of age. The vet wanted us to feed him a very low protein diet and give him fluids. we said no to both , as he hated the fluids with the needle so we were willing to let him go instead of torturing him., I felt he needed high protein. She told us we were killing him as she screamed at us. Needless to say I left that vet, found a holistic veterinarian in Tucson Az who put Dakota on Chinese herbs. The vet studies and travels to China getting her herbs. Dakota lived 12 years with the disease to the age of 16 if that tells you anything.

    1. Hi Dee,
      I would be interested in hearing more about the diet you fed your cat and the Chinese herbs you gave him. My cat was just diagnosed today with the early stages of kidney disease and I am being told by the vet to feed him a kidney diet which is low in protein. This goes against everything I believe. Currently, my cats are on a high-protein raw food diet, which I believe is the best for them. Any information you can share with me I would greatly appreciate.

      Thank you!

      1. For many years a product Rubenol was on the market (French manufacture). Chinese rhubarb basically. Two companies were offering products and Ruben makers were pushed aside from an Italian maker. We had two of our boys on Rubenol for years. Their kidney values improved to normal range – meaning that the kidney tissue was actually regenerating. We only fed them a mix of raw freeze dried and high quality protein canned food. One of them lived to be twenty years – and half his life with kidney disease (he died of something unrelated). Wish they would start making this product again as it helps so much.

      2. The reason why vets and doctors suggest low protein diets in those with kidney disease is because protein increases the pressure on the kidneys… if you aren’t of medical background, it can get a little complicated.. but basically protein is hard on the kidneys. For Dee above, it probably wasn’t a great experience to have a vet screaming at you, but technically the vet is correct in telling them that high protein can worsen kidney function. Her cat probably would have lived to 12 regardless (or maybe longer had it not gotten a ton of protein). My parents had a cat that died of chronic kidney disease… we fed her whatever she wanted. She lived to 21 years old! My current cat refuses to eat the low protein diets/kidney diets, so I also just feed her whatever she wants. She has always been low in weight, so I’d rather that she have nutrition and not lose more mass, than to be strict on her kidney diet. You have to weigh the pros and cons–they are present with every medical decision we make!

      3. Hi guys,

        Try Porus One. My cat’s blood renal panel improved after just using it for a week. Frkm 2.9, became 2.6, after 1 month, 2.6- became 2.3. All other greatly improved Bun- 37, Phosphorus 4.1, etc
        Bad thing- you can buy only in UK OR Germany. I asked my brother to ship them me. This is cheaper than having your cats uremic symptoms and toxins in her body. Google it, they also has FB.

    2. My 15-year-old Siamese cat was just diagnosed this week with stage 4 kidney disease and I would love to hear about what Chinese herbs you used and any other supplements? I have been feeding him raw food since he was a kitten and I don’t want to give him one of those low protein diets the vet recommended.

    3. Hi Dee, can you PLEASE share the diet and chinese herbs you gave your baby? Im desperate and my little one is also getting so thin on this “kidney disease” diet.

      1. My 12 year old kitty was just diagnosed with early stage CKD. We’ve been seeing a wonderful holistic vet who put him on Chinese herbs Strengthen Water and Kidney Works. He’s just at 2.3 and she’s very encouraged that it can be reversed.

      2. Please check with your veterinarian surgeon as to the safety of these herbs. There are a lot of toxic ones out there. To point out- whilst herbal remedies have their place in naturopathic medicine, there is little evidence for some on its use. With animals with compromised kidney issues- you need to be very careful about what you are giving them. Like anything, there are side effects of each. The low protein diet from the vets is a very high quality and easily digestible protein, which means less of it is required to provide the same results. Although by concentration it is lower, by digestibility it is much higher.
        Good luck in your quest to help, but please always refer back to your vet before supplementing.

        1. Delores, I respectfully disagree with your choice of foods. All of the kidney special diets are the lowest quality protein and causes cats to start wasting. I researched for months and found a food that is lightly cooked, low phosphorus chicken and my cat loves it and has actually gained weight. It’s called My perfect pet. It is quite expensive but worth every penny because it doesn’t have fillers, additives, meal and unnecessary ingredients. So far my ckd kitty is doing quite well with adding Omega 3 oil and probiotics to her meals.

      3. Go to cat info.com and get him high protein, low carb for. This vet is awesome and researched the TRUE nutritional value of nearly EVERY cat food out there. aloha from Hawaii(My fur baby is 16:)

      4. Please see my comment above… have you taken your cat to the vet? I think they would say, as my vet did, that nutrition is really important and if your cat is not eating the “kidney disease” diet, then you should feed it whatever it will eat. You will die of malnutrition before you die of CKD (chronic kidney disease).

    4. That is an awesome story. My 12-year-old cat’s recent blood work and urinalysis came up with unusual values. I love my vet. She is doing a culture to see if Molly might have a kidney infection versus kidney failure. But could you provide more information about the veterinarian and the Chinese herbs in case I need the info? Thanks very much!

    5. I’ll be polite and say….yeah sure. Folks if you can’t see the woefully contrived nature of this comment you’re in for a long hard life.

      This comment is no different than that of an antiVaxxer. It’s ideologically driven and it’s purpose is to make you believe not to inform. It’s also dangerous as fooling around with holistic treatments does nothing but delay essential treatment for the number 1 killer of cats in the USA. And the proof is in the pudding. Note that may people ask the name of this miracle vet…..no answer. There are only 3 such hospital in Tucson. Shouldn’t be hard to remember which it was. Call all 3. None will verify this.

      Holism and CAM are not the same thing but hustlers and anti-conventional treatment ideologues often confuse and conflate the two. If CAM ( Chinese Alternative Medicine..something the Chinese shun ) worked it would be employed in alopathic treatments. It doesn’t so it’s not.

      Note the ridiculous claims. “vet yelled at her”. I doubt that. The nonsense lay quantity of protein argument when it’s bioavialbiliy and quality that matter. “she felt the cat needed high protein” which is nothing but resisting treatment like all anti-medicine folks do.

      If your cat is experiencing declining kidney function don’t play with goofy notions. Seek veterinary care. This is YOUR Cat not someone else’s and it needs vet care not control by a lay person with an uninformed agenda.

      The world is not constrained by this person’s experiences. Even if this stuff were true it would not be universally so. Your cat is not her cat. Get help.

  2. My 14 year old cat was also just diagnosed with early chronic kidney disease as well as IBD. I would also appreciate any information that you can share. Thank you! Ann

    1. Hi Ann,

      Our cat, Sylvie was also diagnosed with IBD. We used a PEMF mat and CBD tincture every other day and it has disappeared. She has elevated creatinine as well but since the rest of her values are normal, we are giving her Azodyl and trying out Mature Cat from Young Again pet foods.

  3. My very healthy 3 year old Siamese was poisoned and went into severe kidney failure and was hospitalized for over a week. His levels are coming down from BUN 141 and Creats 11.

    They are now at 62 and 2.7 . The kidneys are damaged but they want me to still do fluids and low protein diet. He hates both! I would like to learn more about the Chinese herbs you gave him. The treatment he is on has been helping to lower these levels but we cannot keep at this for a lifetime. Thank you, Mary and my baby Phil

  4. I have/had 3 cats, 13/11/10 one of them started getting sick, we took her to the vet and took the other 2 for a check-up. The one aged 11 (Male) has urinary problems and living on a monthly preventation meds. They all have been eating Urinary S/O for the past 5 yrs and 3 months ago, we added Urinary Care to the mix (50% each food). 1.5 month ago, soon after the 13yr old cat showed symptoms, she died. At the same time the other 2 were also tested with high creatnine/bun/uric acid … They been taking treatment for 40 days now and the levels are getting higher and higher. They seemed totaly fine before all of that, after the treatment they are so sick … The vet dosent know why it keeps elevating.

    1. Since all 3 cats were eating the same food and all are getting sick I would start with checking the food. Maybe you have gotten a bad bag. I am sorry to hear about your loss. I hope the other 2 are getting better.

    2. go too catinfo.org and RESEARCH all the info she (a vet) placed there on cat food INGREDIENTS. she spent hundreds of hours going over which foods have good protein and low carb–NO to low protein! no no no! THE BIGGEST CAUSE F AL OF THIS IS KIBBLE FOOD DIETS, high carb, low quality plant protein (NO!) and HIGH fat. The grain free ones are now showing heart disease problems–why? THEY ARE HIGH CARB, low quality plant protein, pea flour, sweet potatoes and potatoes (ha ha grain free traded for CHEAP ass carbs)

      EDUCATE yourselves please! This website is AWESOME.

  5. I wish we would also study the effects of water sources on cats’ urinary system and kidneys. Though my older cat is have kidney problems currently, our cats quit getting UTIs when I began giving them bottled spring water over our city source, treated with chlorine. Cats can often spend their whole life drinking from one spicket.

  6. I wish this vet, or any other, would address Azodyl as a very viable treatment for kidney dysfunction/disease. This non-prescription supplement is composed of three probiotic organisms that settle in the large intestine and feed on the nitrogenous waste that the kidneys aren’t able to excrete. My cat’s creatinine decreased form 3.2 to 2.6, In its human counterpoint drug, Renadyl, many people are able to delay dialysis when on this. Years ago, when I had an elderly cat with CKD, my vet never told me about this, and I suspect many vets still don’t know abut it, or just haven’t used it. I’m thrilled with the results. Check it out online. It also seems to have minimal and innocuous side effects. I’d love t osee a RECENT scholarly article on this.

    1. maria,
      You are confusing causation and correlation. Just because you added in one drug, does not mean that drug caused the change. Secondly, humans and animals have very different pharmacokinetics, whilst this works well in humans and there may be minimal side effects in humans, there may be very different, detrimental effects in animals. In the veterinary profession we are constantly assessing new drugs and those that are working in human medicine, the reason none of your vets are using it, and that there are no recent scholarly articles is possibly because it didn’t pass through the strict regulations governing its use in animals. Hopefully with future trials we can start proving that there are minimal side effects and that it may be beneficial- but without field safety data, it should not be used. For example, NSAIDs although working similarly for humans and animals are 100x more potent in cats and dogs, than their human counterparts.
      Your best bet is to contact pharmaceutical companies regarding the application of this drug to veterinary medicine, they can provide you with further information.

    2. maria,
      You are confusing causation and correlation. Just because you added in one drug, does not mean that drug caused the change. Secondly, humans and animals have very different pharmacokinetics, whilst this works well in humans and there may be minimal side effects in humans, there may be very different, detrimental effects in animals. In the veterinary profession we are constantly assessing new drugs and those that are working in human medicine, the reason none of your vets are using it, and that there are no recent scholarly articles is possibly because it didn’t pass through the strict regulations governing its use in animals. Hopefully with future trials we can start proving that there are minimal side effects and that it may be beneficial- but without field safety data, it should not be used. For example, NSAIDs although working similarly for humans and animals are 100x more potent in cats and dogs, than their human counterparts.
      Your best bet is to contact pharmaceutical companies regarding the application of this drug to veterinary medicine, they can provide you with further information.

  7. Hi. I worked with a vet for many years so please bear with me. If you love animals, please stay away from any Chinese meds. Most require killing or maiming wild animals to take their parts – very sad. Anyway, my cat is 17
    He had hyperthyroidism for years until I had his thyroid gland irradiated to basically “kill, it. He also has kidney disease – stage 4 – and has had it for years
    He was so thin, his coat dry, he never washed, all the symptoms. He takes mirtazipine, a human antidepressant, once every 3 days for appetite and now weighs 16+lbs. He eats Hill’s m/d dry to help his diabetes. Yes, he’s been diabetic for many years and requires insulin twice daily along with subQ fluids. No, he doesn’t like getting fluids, but they are essential for his kidneys and his diabetes. Don’t be concerned if your cat doesn’t like getting fluids. I hate the dentist but I go and I’m better for it. And recent studies are showing that a diet high in protein can keep a cat with kidney disease from getting too thin. Talk with your vet. Go online and learn (or print out) normal blood test values for a CBC and an SMA. Then ask your vet for copies of your cat’s lab work. Your vet should be willing to explain what the BUN and creatinine levels mean and how you can best help your cat. But please, stay away from Chinese quackery – your cat will do best with proven vet care. Good luck to you and your cat and don’t be afraid of needles – no matter how big they are. Cats don’t remember and they forgive easily.

  8. I used Azodyl with my cat for years when she suffered from severe kidney problems. I firmly believe using this supplement gave us at least 3 yrs before she succumbed right before her 19th birthday. I highly recommend the use of Azodyl.

  9. My luvie was just dx’d with stage 1-2 kidney disease. He has been on kd dry for about 5 ys along with high quality wet food. Would appreciate any help from you guys

    1. Patti check out Facebook group Feline Chronic Kidney Disease. It’s been a lifesaver for me and my cat, literally. It’s got thousands of members and awesome admins with the experience to really give helpful advice. Tanya’s CKD site online is also helpful and often referenced on the site

  10. My male Ragdoll is Twelve years old. He just had a blood test and his Urea Nitrogen level reads 194. His Creatinine Level is 13.6.How bad are these results?

  11. My cat was recently diagnosed with kidney disease. BUN is now 77 and creatinine 5.8. She is a picky eater & snubbed so many low protein diets until my vet said to let her eat whatever she want, to get food in her and not starve. She is on an Adventi supplement for kidney support. This week she took a liking to Blue Buffalo K+M dry food. Kidney canned food is still a challenge to get her to eat though. She purrs while I give her daily fluids and she lets me know when she is done (normally 150mls is her threshold). I am interested in whatever protein/low phosphorous/low carb recipes/diets that worked for your cats to improve their kidney issues and values that you can share as well any additional articles. Thank you! Roz