Kidney disease in cats What it is, what to watch for, and how we help

What kidney disease in cats actually is

Each kidney has a few hundred thousand tiny filtering units called nephrons. When one dies, it isn't replaced, in a cat or in you or me. The ones left take on extra work, which keeps things looking normal for a long time, and that's exactly why the disease is so quiet early on.

Kidneys carry a lot of spare capacity. A cat can lose something like two thirds of her kidney function before her blood values move out of the normal range at all, so she wasn't well last month and sick this month. She was quietly compensating, mostly by drinking more, and now she's run out of margin. Nobody reliably spots that at home, and vets don't spot it by looking either.

In most cats we never find a single cause, and age does most of it. Persians and a few related breeds carry an inherited kidney condition, and past urinary blockages, infections, toxins and high blood pressure can all play a part in a particular cat. If you'd like the longer explanation, I wrote it up on my free site for owners of kidney cats: kidney disease in cats, from the day of the diagnosis onward.

Signs of kidney disease in cats

The two earliest signs are easy to miss: she drinks more, and she urinates more. You might notice bigger clumps in the litter box, or that she's at the water bowl more than she used to be. A covered box, a cat who goes outside, or three other cats in the house can hide both.

As the disease moves along, the waste her kidneys can't clear starts to make her feel sick. You may see:

• a smaller appetite, or eating less than normal for a day
• weight loss, even a quarter of a pound on a ten-pound cat
• nausea or vomiting
• a cat who seems dull, weak, or less interested in her own life

None of that is anybody missing something. Cats are very good at hiding how they feel, and that's why I'd rather screen older cats with blood and urine than ask you to watch for symptoms. For a fuller walk-through of what changes and why, see signs of kidney disease in cats.

What I do at the clinic

Lab work: blood and urine together

On the blood panel I look at creatinine and SDMA, the two waste products her stage is based on. SDMA often moves first, partly because muscle loss affects it less, and that's why it's so often the value that catches kidney disease on a routine senior panel. I also look at phosphorus, which drives how sick she feels, and potassium, which drives how strong she feels.

I want urine with the blood every time. Urine concentration often slips before any blood value moves, and a UPC, the urine protein to creatinine ratio, tells me whether her filters are leaking protein. Leaking protein makes the disease run faster, and it has its own treatment, so a stage without a UPC is only half the picture. Together, those numbers give her an IRIS stage, from 1 to 4, which tells us what to do next rather than what happens next.

One thing that confuses almost everyone: a cat who's dehydrated on the day of the draw can look worse on paper than she really is. Dehydration, a hidden infection or constipation can all lift a panel for a week, so I'll recheck once she's settled and well hydrated before anyone reads too much into one sheet.

The kidney diet

A therapeutic kidney diet is the one food change with good evidence behind it, and it works mainly by lowering phosphorus, not by cutting protein hard. Canned beats dry, because roughly three quarters of a can is water and a kidney cat loses water all day. We carry the prescription diets from Hill's and Royal Canin, and I'll help you switch slowly so she doesn't refuse it. If she won't eat it, tell me. A cat eating an ordinary food beats a cat refusing the right one, and there are fallbacks. More on that in my guide to the kidney diet for cats.

Fluids under the skin

When her kidneys can't hold onto water, giving fluids under the loose skin between her shoulder blades is the most useful thing most owners learn to do at home. We'll show you how, and we'll set the amount and how often for her size and stage. It looks impossible the first time, and it's routine by about the fourth. If you want to read up before your lesson, here's my step-by-step guide to subcutaneous fluids for cats. Please don't change the amount yourself, because too much fluid is a real risk in a cat with heart disease or high blood pressure.

Rechecks

There isn't one schedule for every cat. A stable stage 2 cat is often fine at three to six months, stage 3 at two to three months, and a stage 4 cat, or any cat whose treatment just changed, usually needs to come back in two to four weeks. Anything newly started, especially fluids, gets a check within a week or two. A full recheck is her weight, blood and urine. If money is tight, tell me. I'd much rather trim the panel than have you quietly stop coming.

Screening older cats

Screening doesn't prevent kidney disease, but a cat caught in stage 1 or 2 has a lot more room than one caught in stage 3. I'd check blood and urine every year from about age seven, and twice a year once she's past ten. That's how most kidney cats I see get diagnosed while they still look perfectly well. Our senior bloodwork page explains what's on the panel and why.

When to call us

Call Hearthstone the same day, not Monday, if she:

• has eaten far less than normal for a day (a few licks of gravy doesn't count)
• is vomiting repeatedly, or can't keep water down
• has yellow gums or yellow in the whites of her eyes
• is weak or wobbly, or restless and can't settle
• has lost more than about five percent of her weight in a month

Go to an emergency clinic now, and call on the way if you can, if her ears and paws feel cold, her gums are pale, she's collapsed, she's breathing hard or with her mouth open, or she's straining in the litter box. In a male cat, straining is a blockage until proven otherwise. Our emergency page lists the after-hours hospitals we trust.

If she's just stopped eating, our page on a cat who isn't eating explains why that can't wait long in cats.