One of the most upsetting parts of caring for an elderly cat is the knowledge that there is a very high chance that your feline friend will eventually develop kidney problems; with an incidence of around 80% in geriatric cats, it is less a question of “if” but “when.” And one of the most disheartening parts of being a veterinarian is feeling powerless to prevent or eliminate this inevitable progression in our feline patients. However, a recent article published in Frontiers of Veterinary Science by a group of researchers from the School of Veterinary Medicine & Science at the University of Nottingham, UK, has revealed that a previously overlooked feature of feline urine and kidneys may hold the key to understanding why this species is almost destined to succumb to renal failure, and provide the first meaningful target for the prevention and treatment of this debilitating disease.1
What Is Chronic Kidney Disease?
When we talk about kidney (or renal) disease in cats, we are usually referring to Chronic Kidney Disease (CKD), a progressive condition where the functional units of the kidney, called nephrons, are depleted. The remaining nephrons compensate for this loss for a time, but eventually, even with adjustments to the diet, fluid intake, and electrolyte balance, the kidney loses its ability to adequately remove waste products from the blood. This is known as renal failure. In humans, this is the point at which dialysis and kidney transplants would be implemented, but for cats, this stage of kidney disease is invariably fatal.
Cats can also suffer from acute kidney disease as a result of trauma, dehydration, toxins, infection, or urethral obstruction, and depending on the cause, they can recover from such an illness. However, any form of renal disease is likely to cause a loss of nephrons, which may lead to or speed up the onset of chronic kidney disease.
There have been a number of hypotheses put forward to explain why cats are more susceptible to renal disease than other species, including:
- Cats have fewer nephrons compared with other species2
- As obligate carnivores, cats consume a higher concentration of protein compared to other species, putting a higher strain on the nephrons
- Domestic cats are often fed on dry kibble, predisposing them to chronic, subclinical dehydration
- Due to improved healthcare and husbandry, cats are living longer, making their kidneys more susceptible to the effects of aging
- The selective breeding of cats has led to an increase in congenital and genetic renal dysfunction
some or all of which may be true.
But according to the University of Nottingham researchers, the answers may lie in fat droplets.
Lipid Droplets in Felid Kidneys
Apart from the love of a long nap and a tasty meal, something that humans and cats have in common is that we are both known to exhibit lipid (fat) droplets in the renal tubules and lipiduria (fatty material in the urine). However, unlike in humans, where the presence of these lipid deposits is known to be associated with some severe kidney disease and dysfunction, lipiduria and renal lipid droplets have been historically dismissed as an incidental and inconsequential finding in cats.3 But according to the new study from the University of Nottingham, this assumption may prove to have been a costly one.
In hindsight, the fact that cats producing lipiduria also had significantly reduced renal cortical density (where the nephrons are located) would obviously point to diminished renal function, so why has it taken so long for this link to be confirmed?
It would appear that, until now, the exact properties of the lipid droplets found in feline kidneys had not been discovered. In the University of Nottingham study, several lipidomic approaches, including chromatography, fatty acid characterization, and mass spectrometry, allowed researchers to characterize these lipid droplets more accurately than ever before.
What Are The Implications?
Before we start celebrating the end of kidney disease, that’s not quite what this means. However, in an ongoing quest for greater understanding of the hows and whys of feline CKD, this may prove to be a significant moment. Unlike many of the factors that may contribute to the high incidence of kidney failure in cats, which are largely unchangeable, the early identification of those cats with lipid droplets in the renal tubules could provide vets and scientists with a tangible problem to solve. It might not be a cure, but it would appear to be one step closer to it.
Feature Image Credit: Elpisterra, Shutterstock
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What Is Chronic Kidney Disease?
6 Responses
I have a senior cat. What test so I request the vet do to identify lipid droplets in the renal tubules? If lipid droplets are found what is the treatment?
Hi Donna, this si all very new and your vet might not have heard about this but to identify the lipid deposits highlighted in the University of Nottingham research, the test would be a Urinalysis with a specific focus on Lipiduria (the presence of fat in the urine) along with a High-Resolution Renal Ultrasound. While standard blood work (like SDMA or Creatinine) measures how well the kidneys are currently filtering, an ultrasound can detect changes in renal cortical density, which the study links to the accumulation of these lipid droplets. Essentially, you are looking for structural changes in the "cortex" of the kidney before the filtration numbers actually begin to fail. If lipid droplets are identified, the treatment is not yet a specific "pill," but rather a shift in metabolic and nutritional management designed to reduce renal stress.
Having had a 5 year old die of kidney failure, it is just another question of what the diet should be. She was on wet food. Kidney diet made her loose weight and muscle. This can't be the solution to helping. So I wonder what or how to improve the lipid droplets? This is a long road for me. One cat improved the other died. Same vaccines and same food. Thinking that the one with the worst blood work was also on the same road. She improved and lost so much muscle and weight on the kidney diet. Now I have her back on track and she is doing great. No more blood work that shows kidney failure. A year and a half of heart breaks.
We are incredibly sorry for the loss of your 5-year-old and the emotional rollercoaster we are all familiar with in the feline community; it is devastating to lose a cat so young to a disease usually associated with seniors. Your observation about the "kidney diet" highlights a common struggle: traditional renal diets often restrict protein to ease the kidneys' workload, but this can lead to sarcopenia (muscle wasting) if the cat’s body begins breaking down its own muscle tissue for nutrients. The University of Nottingham study is a major breakthrough, as it suggests that those lipid droplets long dismissed as normal are actually linked to reduced renal cortical density and diminished function. By identifying these lipidomic changes early, we move toward a future where we treat the "how" of kidney damage rather than just managing the "failure" after it happens. Congratulations on getting your survivor’s blood work normalized. She is lucky to have a guardian like you.
Read the article and sent it to friends. So what can we do to Prevent Kidney Disease and failure in older cats? Mine are 12-15 so I am worried! Please write articles on Prevention and helping our cats into their 20s. Thank you for the research.
Thank you for your comment and for reading us Zeus. It is completely natural to feel a bit of "senior cat anxiety" when your companions reach the 12–15 age range, but the good news is that proactive management can significantly slow the progression of Chronic Kidney Disease (CKD). Since kidneys are essentially the body's filtration system, the goal for prevention is to reduce the workload on these organs and maintain maximum hydration. The most critical shift you can make for cats in their teens is moving them toward a high-moisture, high-quality protein diet; while "senior" formulas often lower protein to protect the kidneys, it is actually the phosphorus levels that matter more. High phosphorus can be taxing on aging kidneys, so looking for foods specifically formulated for renal support or those with a low phosphorus-to-protein ratio is key. Because every cat's metabolic needs change as they enter their mid-teens, we recommend a 1:1 consultation with your vet.