What it is
The kidneys filter the blood: they get rid of waste, hold on to water and salts, and help control blood pressure and the making of red blood cells. In chronic disease the working units of the kidneys keep dwindling, and the ones left do the work of all of them until they can no longer keep up. The first signs only show once a large part of the kidneys has already stopped working.
When the kidneys can no longer concentrate urine, the cat passes more of it and makes up for the loss by drinking. As waste builds up in the blood, the cat feels sick, loses its appetite and its breath may smell. The disease can raise blood pressure, which harms the eyes, the heart and the kidneys themselves.
Chronic kidney disease is a disease of older cats, although a younger cat can have it too. Blood and urine tests at a routine check-up can show changes before you notice anything at home, and the water bowl and the litter box are the best everyday gauges.
Signs you may notice
A cat drinks and urinates more, the litter box has bigger clumps, and it slowly loses weight and eats less. Later there may be vomiting, bad breath and an untidy coat.
When to see a vet
Book a visit if your cat has started drinking or urinating more, is losing weight or eating less. If it has eaten nothing for a day or more, keeps vomiting or has become very listless, contact a vet the same day.
This is general information, not veterinary advice. For your own cat's health, tests and treatment, see a vet.