Chronic Kidney Disease in Cats: A Senior Cat Owner's Guide

Chronic kidney disease in cats was the diagnosis I dreaded, and then, over time, learned to live alongside. It is the most common serious illness of old age in cats. It cannot be cured, and it is progressive, which means it slowly advances over months and years. Written down like that it sounds bleak. What the sentence leaves out is that a cat whose kidney disease is found early can often live comfortably for a long time, and that much of what helps is ordinary care you give at home. Biscuit was diagnosed two years ago. She is sixteen now, asleep on the warm end of the sofa as I write this.

This guide is here so the diagnosis feels less like a foreign language. It does not replace your own vet, who can stage your cat's disease and build the plan around her.

What chronic kidney disease actually is

The kidneys filter waste out of the blood and pack it into concentrated urine. They are built from tiny working units, and in chronic kidney disease those units are lost gradually and do not grow back. Waste starts to build up in the blood, and the kidneys lose the knack of concentrating urine, so the body loses water and the cat drinks more to keep up. Cornell's Feline Health Center is blunt about the arc of it: CKD is a progressive disease with no definitive cure, so the goal of treatment is to slow its progression and maintain a good quality of life.

Why it is so common in older cats

Because the machinery wears with age. Cornell puts the numbers at up to 40% of cats over the age of 10 and 80% of cats over the age of 15. There is often no single dramatic cause to point at, which is hard to accept when you want something to blame. It is, more than anything, a disease of getting old. Ten is also the age at which the current guidelines start calling a cat a senior, and the cat age calculator lays out what each life stage asks of you. That figure sits alongside the other senior cat health statistics worth knowing, most of which describe conditions this one travels with.

The signs to watch for

Early on there may be no outward signs at all, which is exactly why it slips past so many of us. As it advances you tend to see increased thirst and urination first, then weight loss, a fading appetite, nausea or the odd vomit, low energy, and a coat that stops looking cared-for.

If your cat is drinking more and losing weight, kidney disease is one of the three usual reasons, alongside an overactive thyroid and diabetes. I wrote a separate piece on what that particular pair of changes can mean and how quickly to act.

How vets diagnose and stage chronic kidney disease

Diagnosis comes from blood and urine together. In the blood, your vet looks at creatinine and at SDMA, a marker that can flag failing kidneys earlier than creatinine alone. In the urine, they check how concentrated it is (are the kidneys still doing their job) and whether protein is leaking through. Blood pressure gets measured too.

From there, most vets use the IRIS staging system. The International Renal Interest Society sorts CKD into four stages based on blood creatinine or SDMA in a stable patient, then sub-stages each cat by how much protein is in the urine and by blood pressure. The stage is not just a label. It is what tells your vet which treatments to start and what to expect, and it gives you a shared language with them.

Is chronic kidney disease treatable?

There is no cure, and there is also a great deal to do. The single most studied intervention is diet. Cornell notes that a therapeutic diet restricted in protein, phosphorus and sodium may prolong life and improve quality of life in cats with CKD. Our quality of life scale is a useful, honest way to score how she is doing as the disease and its treatment unfold. Around that, treatment is built stage by stage:

• Hydration, because dehydration can speed up damage to the kidneys. Wet food, water in more places than one, a fountain if your cat likes moving water, and in later stages fluids given under the skin that your vet can teach you to do at home.
• Controlling phosphorus, through the diet first and a phosphate binder if diet alone is not enough.
• Treating the knock-on problems: high blood pressure, protein loss in the urine (often with a medication such as telmisartan), low potassium (a common cause of weak back legs in a senior cat that supplements can reverse), and, in advanced disease, anemia.
• Keeping her eating, by managing nausea and appetite, because a CKD cat who is eating is almost always doing better than one who is not.

Which of these your cat needs depends entirely on her stage, which is the whole point of staging her.

What you can do at home

The home half of this matters as much as the pharmacy half. Keep water fresh and everywhere, and take extra care in hot weather, when a cat already prone to dehydration has even less to spare. Feed the diet your vet settles on, and guard her appetite fiercely, since going off food is one of the faster ways a CKD cat slides. Weigh her when you can and keep a loose eye on how much she drinks (our water intake calculator gives you a rough daily target to watch against) and what comes out in the litter box. Say yes to the recheck appointments, because the trend across several blood tests tells you far more than any single result. And make the ordinary days soft: a warm bed, a low-sided litter box for stiff old joints, quiet.

What the outlook really is

It depends heavily on how early you caught it. Cats diagnosed in the first stages often have years of good living ahead. Later stages ask more of everyone, and still hold real comfort worth giving. This is a marathon of small, steady care rather than one decisive fix, and cats, it turns out, are good at the long quiet middle of things. Owners who have been given a prognosis and are trying to work out what it means for their own cat will find that unpacked in when to euthanize a cat with kidney disease, including why so many cats outlive the figure they were given.

When to call the vet

Sooner rather than later if she stops eating for a day or more, vomits repeatedly, goes suddenly flat or starts hiding, feels bonier over the spine than she did, or does anything that simply frightens you. You know her baseline better than any chart does.

The day of Biscuit's diagnosis, "incurable" was the only word I heard. It took me a while to hear the rest of it, which is that incurable is not the same as untreatable. The fountain hums, the rechecks come and go, and she is still particular about dinner. Chronic kidney disease in cats is something a great many of them live with for years, gently, not something that takes them in a hurry.

Sources

• Cornell Feline Health Center, Chronic Kidney Disease
• International Renal Interest Society (IRIS), IRIS Staging of CKD