Signs of kidney failure don’t appear until at least 70% of kidney function is lost. The kidneys remove waste products from the blood stream, regulate fluid
and electrolyte balance, maintain the 
acid-base balance of the body and
remove toxins and drugs. They also help maintain blood pressure and
stimulate blood cell production.
Kidney damage accumulates for years before we see any signs. Even then the early signs of kidney failure - increased thirst and urine production - are not easy to pinpoint in our feline friends.
You may notice an increasingly wet litter tray if your cat is only indoors. However if you have other cats you may not pick up increased urine production in a particular cat.
Cats often drink from multiple water sources making it difficult to recognise increased consumption.
Other signs of kidney failure such as weight loss and poor coat quality are even more insidious.
Sometimes the first thing we see is a cat off her food, vomiting, depressed and dehydrated. The kidneys are already badly affected by this stage.
We diagnose and stage kidney failure with blood tests for the two waste products, urea and creatinine and a urine analysis to measure the kidneys ability to concentrate urine. We also check the urine for protein loss or a urinary tract infection.
Tests for other substances like potassium, phosphorus and calcium as well as blood cell counts help us decide on the best course of treatment.
Annual blood and urine tests, as well as regular body weight checks, help pick kidney failure up as early as possible. If urine concentrating ability is deteriorating, your cat is losing weight or the creatinine is trending up we slow the progression of the disease with a special kidney protective diet. Many cats in the early stages of kidney disease live for years on the right diet and with regular checks.
