What chronic kidney disease actually is

What is chronic kidney disease in cats?

You've probably already found ten different explanations of this, most of them either three words long or written for veterinary students. Here's the version I'd give you in the room.

Your cat's kidneys are filters. Blood goes in, waste and surplus water come out as urine, and the things she needs stay in. Chronic kidney disease means a good number of those filters have stopped working and won't be coming back.

That's the whole idea. Everything else on this site is a consequence of it.

What the kidneys were doing for her

Filtering waste is the job everyone knows about. The kidneys do four more things that matter just as much once they start failing, and each one explains a symptom you'll meet later.

Why she looked perfectly well until last week

This is the part that makes people feel they missed something, so let me deal with it directly. You almost certainly didn't.

Kidneys are built with enormous spare capacity. A cat can lose something in the region of two thirds of her total kidney function before her blood values move outside the normal range at all. She spends that whole period compensating, quietly and effectively, by drinking more and passing more urine.

So by the time a routine senior panel catches it, or by the time you notice she's at the water bowl more, the process has been running for a long while. She wasn't well last month and ill this month. She was compensating last month, and she's run out of margin now.

The two earliest signs are drinking more and urinating more, and both are genuinely easy to miss. A cat with a covered litter box, a cat who goes outside, a cat in a house with three other cats, a cat who drinks from the bath tap when nobody's watching. Nobody spots those reliably. Vets don't either, which is why we screen with bloodwork instead of asking you to watch.

Why it can't be reversed

The filtering units are called nephrons, and each kidney has a few hundred thousand of them. When a nephron dies it isn't replaced. There's no mechanism in a cat, or in us, for growing new ones.

The surviving nephrons take on more work, which keeps things looking normal for a long time and is exactly why the disease is so quiet early on. It also means that as more are lost, the remaining ones are running harder, which is part of why the disease tends to accelerate rather than hold still.

So there's no treatment on this site, or anywhere, that grows kidney tissue back. Anything you read that claims otherwise is selling something.

What we can genuinely change is two things, and they're worth more than they sound:

• How she feels. Nausea, dehydration, high phosphorus, low potassium, high blood pressure and anemia are all treatable, and they're what make a kidney cat miserable.
• How fast she loses the rest. Controlling phosphorus and treating protein loss and hypertension slow the decline. That's not a small win. That's years, in some cats.

Chronic or acute, and why your vet keeps asking

These are two different problems that can look similar on a lab sheet.

Acute kidney injury happens over hours or days. A lily chewed in the kitchen, antifreeze, a urinary blockage, a bad drop in blood pressure, certain medications. It's an emergency, and because the tissue may be stunned rather than dead, some of it can genuinely recover.

Chronic kidney disease has been building quietly for months or years. It doesn't recover.

Your vet cares which one she's dealing with because the urgency and the outlook differ enormously. And a cat can absolutely have both at once: a chronic kidney cat who then gets dehydrated, or picks up a kidney infection, or eats something she shouldn't. That combination is common, it looks like a sudden collapse, and the acute part is often fixable. Which is why a cat who suddenly gets much worse deserves a proper workup rather than a shrug.

There's more on that on the crisis page.

Is it my fault, and is it hereditary?

Almost certainly not your fault. In most cats we never identify a single cause, and age is the biggest factor by a distance. Persians and a few related breeds carry a genuine inherited kidney condition, and past urinary blockages, infections, toxins and high blood pressure all contribute in individual cats.

The food she ate is very unlikely to be the reason, and vaccinating her on a normal schedule is not the reason either. That whole question is worth its own page, and it has one: why did my cat get this.

What "manageable" actually means

I use that word carefully, so here's what I mean by it.

It doesn't mean cured, and it doesn't mean she'll be exactly as she was. It means most kidney cats can be kept comfortable, eating, and interested in their own lives for a long stretch, using things you can do at home: the right food where she'll accept it, water, a phosphorus binder, nausea control, and fluids under the skin if it comes to that.

It also means the work is mostly unglamorous and mostly yours. Weighing her weekly. Giving a tablet at the same time each day. Noticing on a Tuesday that she's eaten less for three days running and phoning about it instead of waiting for the recheck.

That's the job. It's tedious and it's genuinely effective, and the fact that you're reading this at all is the strongest predictor I know that she'll do well.

Where to go from here

If you've just been handed the diagnosis, the useful next step isn't more reading about the disease itself. It's the eight practical things, in order, on the start here page.

If you want to understand her particular situation, the two pages that do that are her IRIS stage and her bloodwork, translated.