Blood pressure and kidney disease

Does my cat with kidney disease need her blood pressure checked?

If your vet has the equipment, yes. It's useful information, it's the ideal, and I'd take it if I could get it.

I'll be straight with you, because you deserve that: I don't have the equipment at my clinic, and a lot of other clinics don't either. That isn't a confession of doing this badly. It's how a great deal of good feline medicine is practiced, and cats with kidney disease are managed well without a pressure reading every day of the week.

So take this page as what it is. Blood pressure is one useful piece of information. It is not the thing your cat's whole plan rests on.

Why the two travel together

They feed each other, which is part of what makes it worth knowing about.

Damaged kidneys mishandle fluid balance and the hormone systems that set blood pressure, so kidney disease pushes pressure up. High pressure then damages the tiny vessels inside the kidney, which costs more function, which pushes pressure up further.

It's a loop, and where it's found, a daily tablet interrupts it.

The numbers

If she does get measured, the number is quoted as systolic pressure in mmHg, and the bands are worth knowing because they set what happens next.

Why the reading is harder to get right than it sounds

This is the part that rarely gets said out loud, and it's the reason I'm not going to tell you your vet is failing you if there's no machine in the building.

Cats are small. The cuff has to be sized to the limb or the tail, and a cuff that's slightly too big reads low while one that's slightly too small reads high. On a leg the width of a marker pen, "slightly" is not much room to work with.

Then there's the machine itself. The oscillometric units, the ones that give you a number on a screen, are noticeably less reliable in cats than in dogs or people. Doppler gives better numbers in cats but it takes a trained ear, a quiet room, and time, and the unit is a few thousand dollars sitting on a shelf for a practice that may use it a few times a week.

And then there's the cat. White-coat effect in cats is not a minor footnote. A cat who has just been in a carrier, in a car, in a waiting room with a dog in it, will give you a number that says hypertensive and means frightened. Doing it properly means letting her settle for five or ten minutes, taking a run of readings, throwing out the first ones, and using the lowest consistent values. The same cat can read thirty points apart on two visits with nothing having changed inside her.

None of that makes the test worthless. It does mean a single number is worth less than people think, and it means a practice can reasonably decide the money is better spent elsewhere.

What genuinely can't be missed

Here is the part I'd underline if I could only keep one paragraph of this page.

Her eyes. High pressure can detach the retina, and the resulting blindness arrives suddenly, sometimes overnight. The tell owners notice is pupils that are wide and stay wide, or a cat suddenly navigating badly, misjudging jumps, bumping into things.

This one doesn't need a machine to catch. It needs you, looking at her.

High pressure costs her elsewhere too, more slowly. Her kidneys, silently, by grinding down the vessels that remain. Her heart, which thickens over time from pushing against it. Her brain, less commonly, showing up as disorientation, unusual vocalizing, wobbliness, or in bad cases seizures.

If your vet can't measure it

Most of what changes how your cat feels and how long she has doesn't run through a blood pressure cuff. Phosphorus, hydration, diet, appetite and potassium are the heavy lifting, and all of them are managed on bloodwork and on what you see at home.

What I'd do in your position:

Watch her eyes, and take a sudden change seriously the same day. That's the one that's time-critical, and it costs nothing.

Mention any of the odd neurological things. Disorientation, walking into a room and seeming lost, unusual night vocalizing, a wobble that's new. These have other explanations too, but they're worth saying out loud.

Ask where it can be done, if you want the number. Plenty of practices have a Doppler, and a referral or a one-off visit somewhere that does is a perfectly reasonable thing to ask your vet to arrange. Ask especially if she's stage 3 or 4, or if her numbers have jumped without an obvious reason.

Don't let it become the thing you worry about. I've seen owners spend more energy on a test they can't get than on the daily things that actually move the needle.

How it's treated

If she is measured and she's hypertensive, treatment is straightforward and it works.

Amlodipine is the standard, a small tablet once daily, and cats respond to it well. It's inexpensive as a generic and most cats take it without much drama.

Telmisartan is the other option, and it's often preferred if she's also losing protein in her urine, because it treats both problems with one tablet. If her UPC is above 0.4, ask about that specifically.

Two practical points. It's dose-found, not dose-known, so the first dose is a reasonable estimate and the recheck one to two weeks later is what turns it into the right dose. And don't stop it because she seems well. Seeming well is what treated hypertension looks like.

What to ask for at her next visit

If your vet has a machine, ask for a reading, particularly if she's stage 3 or 4 or her numbers have moved without explanation. If they don't have one, ask what they'd want you to watch for instead, and ask where you could get it done if you want it.

The other test worth asking about, and the one I'd chase first of the two, is the urine protein ratio. It's widely available, it's cheap, and it changes treatment. Both of those together are what IRIS calls substaging, covered on the IRIS stages page.

What a complete recheck looks like is on the recheck page.