Kidney Disease

Symptoms of kidney disease in cats

CatKidneyDiseaseKidney disease is unfortunately very common and will affect about 60% of older cats. Most people think that a thirst is a good thing but if your senior cat is starting to drink more it can be an indicator of an early problem.

Cats come from hot countries where their kidneys have evolved to produce strong urine and conserve as much water as possible. Therefore it is normal to not see your cat drinking much at all. Sometimes in my consultations people worry that their cat is not drinking enough – if your cat is healthy and especially on wet food then I would not worry at all if you didn’t see it drinking – I see it as a sign that the kidneys are working efficiently. It goes without saying that if your cat is showing other signs of being unwell like loosing weight or vomiting then a decreased thirst should be investigated.

There are different causes of kidney disease. By far the commonest cause is called CKD (chronic kidney disease). The exact cause of CKD is unknown but causes the kidneys to show a mixed pattern of scarring and inflammation. It is likely that wear and tear can contribute to this and probably an element of genetic predisposition. Other causes suchCatKidneyDisease2 as infection, toxins, cysts and tumours can add to this pressure on the kidneys and speed up their deterioration.

The kidneys work by filtering the urine and deciding what to keep in the blood and what to pass out in the urine. If the kidneys are starting to age or fail then too much water is lost which the body needs. The body recognises it is becoming short, or mildly dehydrated, and causes your cat to feel thirsty so it can replace what is lost. You, the owner, see this as increased thirst.

In the early stages of increased thirst you might just see very slight signs like the water bowl emptying more quickly than normal or your cat starting to change its drinking habits and drinking from different places eg dogs bowl, a glass of water by your bed or the toilet! As the problem gets worse you may see your cat taking more trips to the bowl or even lying by it. The litter tray may be slightly wetter too or you might find you have to clean it out more regularly.

There are other problems that an increased thirst can tell us too, for example diabetes, liver problems and overactive thyroid.

CatKidneyDisease3Step one in investigating an increased thirst will be urinalysis. This is a simple urine test with an instrument called a refractometer and a dipstick test. The refractometer will tell us the concentration of the urine and the dipstick will tell us if there is any glucose, protein, or blood in the urine and what the pH or acidity is.

How, you may ask, do you get a urine sample from a cat! Some cats are relaxed enough that you can get a shallow container e.g. the lid of a takeaway dish under the bottom when they are passing urine in their tray. We only need about 1 tbsp to be able to test the urine. Other cats are a bit more suspicious and you can get non absorbent cat litter (such as katakor), from the surgery reception. You put this in a clean dry tray and wait…… eventually the cat will usually give in and use it and because it isn’t absorbed you can syringe the sample up with the pipette that’s in the pack. For very stubborn cats (or for some special urine tests) sometimes it is necessary to get a sample directly from the bladder with a small needle. This is called a cystocentesis. This sounds funny but most cats tolerate it very well, with it being only as uncomfortable as a vaccination injection.


A cat that has kidney problems will often have weaker urine than normal and can sometimes have increased levels of protein or even blood. All of which we can detect on an inexpensive urine test. We can also check for diabetes as there would be glucose in the urine if this were present.

Diagnosis and Treatment of Kidney Disease in Cats

CatKidneyDisease3If the urine sample is suggestive of kidney problems then the next step is to take a blood sample to try to work out how severe the problem is. Urine concentration is the best way to catch kidney problems in the early stages. Until at least 60% of the kidney function has been lost the blood test will not usually show a change. This is why it is important to do a urine test as well as a blood test.

Once more than 60-75% of the kidney tissue has stopped working then the bloods will show us some elevations in markers called urea and creatinine. If a blood sample is shown to have higher than normal levels of these markers then we know we need to act quickly to help the kidneys so that they can work as well as possible for as long as possible.

CatKidneyDisease5A blood test will also show us if the cat has elevations of phosphate. Cats get phosphate from the diet and in small amounts it is essential for strong bones and teeth, release of energy and production of some vitamins. If the kidneys are failing to work properly then phosphate will gradually build up too much leading to ‘hyperphosphataemia’. This will actually speed up the progression of the kidney problems and also reduce your cats appetite.

Anaemia can develop secondary to kidney disease due to accumulation of toxins affecting the bone marrow and slowing the production of new red blood cells.
Some cats with kidney disease can develop low blood potassium levels. This can cause weakness and pickiness with feeding.

CatKidneyDisease6The main way that we can slow the progression of chronic kidney disease is by special diets. Royal canin is the range we stock and they do a range of different wet and dry in different textures and flavours. They also have a very good taste guarantee so if you buy a bag (of any of their foods) and your cat will not eat it at all then bring it back to the surgery and you will get a refund.

The special renal foods work in a few ways:

  • They have restricted protein – any excess protein in the diet is broken down into energy with the production of a toxin (urea) as a by product. If the kidneys are not working properly then this toxin accumulates in the blood and basically poisons the body – initially causing inappetance and pickiness, but then progressing onto vomiting and sometimes even getting into the brain and causing seizures. The toxins can also poison the bone marrow and cause anaemia. By feeding a restricted protein food the level of this toxin increases much more slowly.
  • The have restricted phosphate – phosphate also accumulates in the body if the kidneys are not working well, by restricting it in the diet this can help to protect the kidneys from further damage.
  • It is important to remember that the benefits of these diets will be cancelled out if you add other foods to them especially things high in protein like chicken or tuna.

CatKidneyDisease7Of course cats don’t like change! Unfortunately protein and salt give food a much tastier character and these are things that we have to try and reduce if we are to help the kidneys. Often as kidney disease progresses then the cat will be pickier anyway (due to toxins irritating the stomach and causing mild nausea) so it is important to change the diet as early in the diagnosis of things as possible if we are to get the full benefits.

Changing diets

  1. Make the change slowly and gradually, start with adding a small amount and increase slowly over a few weeks if possible.
  2. Warm the food up – this increases the smell and makes it more palatable.
  3. Some cats can be persuaded to change by just putting the new food in a different bowl. Initially just get them used to looking and sniffing at it and maybe trying a little but still have the old food in another bowl so they don’t feel pressurised into eating it. Then after a week or so slowly decrease the amount of the old food so the cat should start to eat more of the new food!
  4. Some cats can benefit from some medications that can increase the appetite – speak to your vet about this.

A blood test will also show if your cat is anaemic. Anaemia is where you have low levels of red blood cells. These are the cells that carry oxygen around the body. If your cat doesn’t have enough then they will become tired and weak. In more severe cases of kidney problems the toxins that accumulate can cause anaemia by poisoning the baby red blood cells. There is the possibility of giving injections of hormones to stimulate more blood cells to be produced, but this is expensive and not without risk, so a good chat with your vet is essential before you decide if this is going to be considered useful.

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It is also very important to control blood pressure. With kidney disease the blood pressure tends to increase. High blood pressure or ‘hypertension’ can cause some very serious problems such as strokes and blindness, as well as further damaging the kidneys. To find out more about hypertension click here.

Other Medications:

  • Sickness and nausea cause the appetite to be reduced. There are some medications, such as ranitidine and famotidine, which can help reduce the nausea and encourage the cat to keep eating.
  • ACE inhibitors are drugs that are normally used for heart problems but they can be used in some cases of renal problems. They help encourage a good blood supply to the kidneys and also reduce the loss of protein in the urine that can cause weight loss.
  • Potassium supplements – low potassium can occur with kidney problems. It causes weakness and can contribute to inappetance. By supplementing your cat with potassium if it is low, you can make them feel a lot better.

To summarise, urine and blood tests are used to help work out if kidney problems are present and how bad they are. From this information the we can then advise on the appropriate medication and management to slow the kidney disease as much as possible. If we can catch and slow the kidney disease as early as possible then you cat will have not just a longer life, but more importantly, a happier more comfortable life.

To book an appointment with our team of animal experts, call our Lancaster surgery on 01524 32696, our Morecambe surgery on 01524 410867 or our Milnthorpe surgery on 01539 562770. Alternatively, send us an email to and we will get back to you within 24 hours.