What is it?
Chronic Kidney Disease (CKD) in cats is a progressive condition, characterised by a gradual shutdown of the working parts of the kidneys. Sometimes there is a known cause such as, antifreeze poisoning, eating lily’s, slug pellet ingestion, cancer (lymphoma), bacterial infection or kidney stones, but most of the time we are not aware what initially caused the damage . Often by the time it is diagnosed the damage has been done and it is not reversible.
How does it affect my cat?
The effects of CKD are widespread. The most obvious things you will notice are an increased thirst and urination (polydypsia/polyuria) and often a reduced appetite and weight loss.
On top of this there are a lot of other changes occuring in your cat
- Dehydration – This leads to the the increased thirst. This is because of the kidneys inability to concentrate the urine and so the can cannot conserve fluids.
- Increased blood phosphate levels – These lead to problems with calcium within the bone and generally causes a feeling of being unwell.
- Low blood potassium levels – These lead to muscle weakness, and you will often see affected cats walking flat on their back feet and holding their neck bent.
- Nausea – many cats suffer from a build up in gastric acid which can contribute significantly to the poor appetite and weight loss.
- Hypertension – A lot of cats with kidney CKD will develop high blood pressure. This high blood pressure causes further damage to the kidneys, and this can cause further elevations in blood pressure. The high blood pressure will also do damage to other organs, eg eyes, heart and brain, and so it is critical to keep it within normal limits.
- Anaemia – cats are often anaemic because of reduced production of red blood cells (the hormone that stimulates rbc production is produced by the kidney), reduced blood cells lifespan and often chronic loss of blood from small bleeds within the gut (ulceration).
How is it diagnosed?
There are many stages of kidney disease and to have an accurate prognosis and apply correct treatment, there are a range of tests that need to be performed.
- Initially a blood test will tell if the kidneys are able to filter the blood in the way they were designed. However normal kidney function does not mean there is no disease within the kidneys as you have to destroy 70% of the kidneys before the blood levels will start to increase.
- Urine tests – these can give early warning to kidney disease. The loss of the ability to form concentrated urine will happen long before the blood tests become abnormal. Urine tests can detect the presence of protein in the urine which can leak from damaged kidneys, and they are also important to rule out bacterial infections.
- Blood pressure – cats with CKD often suffer from high blood pressure. As well as the other conditions that this can lead to (heart problems, blindness) the high pressures will lead to further damage within the kidneys and potentially then even higher blood pressures.
- Ultrasound – ultrasound examination of the kidneys is helpful to check for any signs of destruction within the kidney(e.g. cancer) or cysts (polycystic kidney disease). It can also pick up signs of stones within the kidney.
- X-rays – occasionally x-rays can help with identifying stones within the kidneys, ureters or bladder.
What treatment will my cat need?
Treatments depend on the stage of the kidney disease and on the results of the tests above.
Stage 1 kidney disease
- Normal blood results
- Dilute urine (specific gravity < 1.025)
- Protein in the urine
- Kidneys feel abnormal, or look abnormal on ultrasound
Stage 2 kidney disease
- Signs of Stage 1, plus mildly elevated kidney values on blood test
Stage 3 kidney disease
- Signs of Stage 2, plus
- Moderately elevated kidney values on blood test
- Elevated blood phosphorus levels
- Often other clinical signs, hypertension, anaemia etc
Stage 4 kidney disease
- Signs of stage 3, with marked elevation of all the kidney values on blood test
- Often present with marked weight loss, dehydration, vomiting etc
The goal of treatment is to
- Slow the progressive loss of renal function
- Reduce the clinical signs
- Maintain adequate weight and hydration
This is achieved through several different means
1)Remove any underlying cause
- Stop any medications that could be potentially harmful to the kidneys
- Treat any bacterial infections
- Correct any dehydration
- Treat hypertension if present
Special renal diets are fairly widespread in both wet and dry forms, and have been proven to improve both survival and quality of life in cats with stage 2-4 kidney disease. It provides a good quality source of protein, important in maintaining weight, along with low phosphorus levels and supplemented with potassium and omega 3 fatty acids. Some cats will prefer one brand over another, so it is worth persevering until you find one that your cat likes.
Some cats that will not eat any renal diets or those whose blood phosphate levels are still elevated despite the renal diet. Both will benefit from being given a phosphate binder. They only work when given with food by ensuring that the dietary phosphate is not absorbed in the gut.
These are tablets which are indicated if your cat is suffering from protein loss in the urine, or hypertension.