Why did my cat get this?

What causes chronic kidney disease in cats?

Most people arrive at this question for one of two reasons. Either you want to understand what happened, or you're quietly checking whether it was your fault.

If it's the second one, I'll answer that first: almost certainly not. The single largest factor in feline kidney disease is age, and you didn't cause that.

Age, which is most of it

Chronic kidney disease is common in cats over ten and very common in cats over fifteen. Kidneys are working filters with a finite service life, and cats now live long enough to reach the end of it.

That's genuinely most of the explanation. It's also the least satisfying, because there's nothing to blame and nothing to have done differently.

The things that do contribute

Where we can identify something, it's usually one of these.

The dry food question

This one deserves a proper answer because it's where most of the guilt lives.

There's no good evidence that feeding dry food causes kidney disease. Plenty of cats eat kibble their whole lives and never develop it. Plenty of cats eat canned food exclusively and do.

Here's the distinction that gets collapsed, and collapsing it is what generates the guilt:

• Did dry food cause this? No good evidence that it did.
• Is canned better now that she has it? Yes, clearly, because of the water.

Those are two different questions with two different answers, and the internet routinely answers the first one using the evidence for the second. A kidney cat can't concentrate her urine, so she's losing water constantly, and canned food puts some of it back at every meal. That's a management fact, not a causation fact.

So if you're sitting on a decade of dry feeding and feeling responsible: put it down. It isn't yours to carry. What to feed her now is on the kidney diets page.

The vaccine question

I'll give you the real state of this rather than either dismissing it or feeding it.

There is laboratory work showing that some vaccines grown on feline kidney cell lines can prompt cats to produce antibodies against kidney tissue proteins. That's a genuine finding, it was worth publishing, and it's worth further study.

What has never been shown is that this causes clinical kidney disease in cats. Producing an antibody in a lab assay and losing kidney function in a real animal are a long way apart, and the studies that looked for the second thing haven't found it.

Meanwhile the factor with overwhelming evidence behind it is age. So no, vaccinating her on a normal schedule is not why she has this.

What is reasonable, and what I do anyway, is to vaccinate according to actual risk rather than reflex. An indoor-only fifteen-year-old with kidney disease does not need the same schedule as an outdoor three-year-old. That's a conversation worth having with your own vet, and it's a conversation about her, not about a conspiracy.

The ones that come up and don't hold

Tap water. Municipal water isn't causing feline kidney disease. If your water is safe for you it's safe for her, and a filter is a comfort purchase rather than a treatment.

Too much protein over a lifetime. Cats are obligate carnivores built to run on protein. Restricting protein has a role once the disease is established, and even then only moderately. A high-protein life didn't do this.

Stress. It doesn't cause kidney disease, though it can make a cat with kidney disease look worse.

Getting her spayed, microchipped, or anesthetized once years ago. No.

The two things with actual prevention value

Small list, but it's real.

Keep lilies out of the house entirely. Not out of reach: out. All parts of a true lily are severely toxic to cats and a small amount of pollen groomed off a paw can cause devastating kidney injury. This is the single most preventable cause of kidney damage in cats, and it kills healthy cats every year. If somebody sends you a bouquet, check it.

Screen older cats yearly, with blood and urine, from about age eight or ten. Screening doesn't prevent the disease, but SDMA and urine concentration move early, and a cat caught in stage 1 or 2 has far more room than a cat caught in stage 3. This is how most cats on this site got diagnosed while apparently perfectly well.

If you have other cats over ten, that's the practical action item from this page. Not because they can catch it from her, which they can't, but because they share her main risk factor.

What this changes

Practically, not much, and that's worth saying out loud. Knowing the cause wouldn't change her treatment, because the treatment addresses the consequences rather than the origin.

What it changes is the story you tell yourself. And the accurate version of that story is that an old cat's kidneys wore out, you noticed, and you're now doing something about it. That's the whole of it.

The useful next page is either what CKD actually is if you want the mechanism, or the eight practical steps on the start here page if you'd rather get on with it.