Blood pressure and kidney disease

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

Yes. And of everything on this site, this is the test I'd least want you to skip, because the cost of missing it is the most sudden and the most permanent.

Between one in five and one in three cats with kidney disease has high blood pressure. It produces no symptom you would ever notice at home. Then one morning she walks into the coffee table, and she's blind.

That sequence is why I'll spend a paragraph nagging about a test that takes four minutes.

Why the two travel together

They feed each other, which is part of what makes it worth breaking the cycle.

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 a daily tablet interrupts it. That's why controlling pressure is one of the three things in this disease that genuinely slow progression rather than just making her comfortable, alongside controlling phosphorus and treating protein loss.

The numbers

Blood pressure in cats is quoted as systolic pressure, in mmHg, and the bands are worth knowing because they set what happens next.

What it costs her when it's missed

Her eyes, most commonly. 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. If that happens, it's an emergency the same day: caught within a day or two the retina can sometimes be reattached and sight saved. Left longer, it's usually permanent.

Her kidneys, silently, by grinding down the vessels that remain.

Her heart, which thickens over time from pushing against the pressure.

Her brain, less commonly, showing up as disorientation, unusual vocalizing, wobbliness, or in bad cases seizures.

How it's measured, and whether stress ruins it

A small inflatable cuff goes around a front leg or the base of the tail, and a Doppler probe or an oscillometric machine reads the pressure. It takes a few minutes and most cats find it boring rather than distressing. No sedation, no needles.

The white-coat effect is real in cats, and a good measurement accounts for it. That means letting her settle in the room for five or ten minutes first, taking several readings, discarding the first one or two, and using the lowest consistent values. Quiet room, minimal handling, ideally the same person each time.

So a single high reading isn't a diagnosis, and any vet worth their license will say so. But repeated readings above 160, or any reading at 180 or above, get treated as real. Dismissing a genuinely hypertensive cat as merely nervous is how retinas detach, and the more common error by a distance is under-treating rather than over-treating.

One useful thing your vet can do at the same visit: look at the back of her eyes. Changes visible in the retinal vessels confirm that a high reading is doing real damage rather than reflecting nerves.

How it's treated

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. Stopping removes the protection from her eyes and her kidneys, usually without any warning sign until something has already gone.

What to ask for at her next visit

If blood pressure isn't on the list, ask for it. If she's never had it done, ask why not. And if she's stage 3 or 4, or on a kidney diet with numbers that are drifting, treat it as standard rather than optional.

The other test in the same category, also skipped, also treatment-changing, is the urine protein ratio. Those two together are what IRIS calls substaging, and a stage without them is only half an answer, which is covered on the IRIS stages page.

What a complete recheck looks like, including both, is on the recheck page.