Cat Russell at Southampton rehoming centre

Health issues with the older cat

Kidney disease, high blood pressure and hyperthyroidism are all common conditions in older cats. Stay alert for the symptoms and help ensure your cat’s happiness and wellbeing in later years.

Kidney disease in older cats

Why do cats get kidney disease?

Cats are particularly prone to kidney damage and it has a variety of causes. Infections, cancers, exposure to toxins, and malfunction of the immune system may all be responsible for starting a slow process of damage, leading eventually to loss of function and kidney failure.

The original cause is often no longer present at the time of diagnosis and sometimes will never be discovered. The body has more kidney tissue than it needs, so much may be lost before symptoms develop – and before blood tests show changes.

This slow progressive process is referred to as “chronic” kidney disease. Occasionally, previously healthy kidneys suffer sudden and massive damage (acute kidney disease) but this is less common.

What do the kidneys do?

Kidneys filter the blood and take out poisonous by-products produced by the workings of the body. These are added to water to form urine. They also get rid of excess water into urine or, when water is lacking, can concentrate urine to reduce water loss. When they are diseased, the ability to concentrate urine is lost and the animal has to drink more to get rid of the body’s waste products.

The kidney regulates the amount of various salts (sodium and potassium, among others) within the body by moving smaller or larger amounts into the urine. Kidney disease may cause some of these to build up within the circulation making the animal ill and perpetuating the kidney damage.

Other functions of the kidney include the production of chemicals called hormones. One hormone causes the blood vessels to expand or contract – lowering or increasing the blood pressure. Another hormone stimulates the body to make red blood cells so, when the kidney’s hormone production is out of balance, this can sometimes cause anaemia.

How is kidney disease diagnosed?

Diagnosis is reached by a combination of blood and urine tests. An increase in the toxic substances that the kidney normally removes can be measured in the bloodstream.

Looking at the concentration of the urine is also helpful. In kidney disease urine is diluted and also more prone to infection – which can be detected by tests. In some cases, the only way of finding the cause of the disease is by biopsy (removing a piece of kidney for examination). This involves an operation, therefore, it is often not done unless there is a chance that definitive diagnosis could help in the treatment of your cat.

In many cases the damage – which causes the symptoms – cannot be reversed.

What are the symptoms?

Everyone knows that in an animal, drinking lots of water can be a sign of kidney disease, but this can also be a symptom of other illnesses.

Cats are discreet and may be secret drinkers, so early signs of excess thirst may be missed and they may become quite ill before treatment is sought.

As kidney disease advances, other symptoms include weight loss, signs of dehydration, poor appetite, smelly breath, a sore mouth, vomiting and weakness. Eventually there may be twitchiness or even fits. However, these symptoms are common to many illnesses, not just kidney disease.

What is the treatment?

There is no cure. Treatment aims to minimise the symptoms, by reducing toxin production, keeping salt levels normal, and slowing the rate of ongoing damage.

Cats that are unwell and severely dehydrated may benefit from intravenous fluids to re-hydrate and flush out toxins. If improvement does not follow, then kidney damage may be severe, and you should consider the options carefully with your vet.

Home nursing is very important. The toxins produce nausea, loss of appetite and sometimes mouth and stomach ulcers. Tempting food, such as fresh fish or chicken, warmed and given by hand may help.

If loss of appetite is long-term, your cat’s quality of life becomes questionable and should be discussed with your vet.

How long will my cat live?

This varies, depending on the severity of the disease, the underlying cause and the speed at which ongoing kidney damage is occurring – something which only time will reveal.

The most important consideration is the wellbeing and happiness of the patient. Some cats, although thin and drinking lots, stay reasonably well for one to two years or more. Others can be unwell and deteriorate rapidly within weeks.

Long-term treatment

Free access to water is essential, especially in the summer. If the cat is accidentally shut in without water, dehydration and toxin build-up can happen rapidly.

Encourage your cat to drink by placing water bowls in several rooms. Cats prefer dog size bowls, which should be filled to the brim and placed away from feeding places. Some cats prefer running water so consider getting a water fountain.

Many of the toxins come from dietary protein, and there is increasing evidence that low protein diets improve general condition and longevity. Cats can be very reluctant to try new foods, so try to start dietary change at initial diagnosis, when the cat’s appetite may be better. Be prepared to mix new and old diets together for one to two weeks. Warming food may help. However, with a cat that absolutely refuses to eat the diet, maintaining a healthy appetite becomes more important than eating a special diet.

You need to discuss what is best for your animal with your vet. Anabolic steroids may be given in an attempt to improve appetite and reduce weight loss.

Other drugs which are sometimes used include ACE inhibitors. They may preserve function in undamaged parts of the kidney, while anti-nausea drugs, appetite stimulants and anti-ulcer drugs may improve appetite.

Excessive potassium loss due to failing kidneys may lead to weakness, therefore potassium powder or tablets may be prescribed. Phosphates may build up in the circulation of patients with kidney problems, worsening the kidney damage, so your vet may prescribe medicine to reduce your cat’s intake of phosphates, especially if your cat is not eating a special low protein diet.

A blood pressure check may be suggested. High blood pressure worsens kidney damage and unfortunately, kidney disease can also cause high blood pressure – working in a vicious circle. In advanced cases of anaemia, there are treatments to stimulate red blood cell production, but these are expensive, only work short-term and are not suitable in all cases.

Your vet will discuss with you what is best for your cat. In summary, kidney disease cannot be cured, but there are treatments that may make your pet feel better.

High blood pressure in older cats

What is blood pressure?

Imagine a hose pipe connected to a tap. If the tap is turned on slightly, the hose will be soft because the pressure inside is low. If the tap is full on, or if a hose of smaller diameter is used, it will feel hard as the pressure in it is high. The same principles apply to blood in the blood vessels.

Kidney disease and high blood pressure are connected because failing kidneys produce chemicals that contract the blood vessels and so raises blood pressure. In addition, they cannot eliminate excess salt, which then leads to retention of water in the circulation. This increases blood volume, which further raises the blood pressure.

Blood pressure can also rise in hyperthyroidism (see below) – sometimes for no apparent reason.

What effect does high blood pressure have on cats?

It often damages the eyesight. Tiny blood vessels cross the visual layer (the retina) in the back of the eye. High pressure can rupture these and the leaked blood covers the retina, sometimes obscuring vision. In some cases, high blood pressure may also cause retinal detachment.

High blood pressure may also accelerate kidney damage. The heart has to work harder to circulate the blood when blood pressure is high. This reduces its efficiency, and eventually causes heart disease and heart failure.

High blood pressure may cause rupture of the tiny vessels in the brain leading to changes in the personality, seizures, collapse or other nervous symptoms.

What is the treatment for high blood pressure in cats?

Drugs may be given to relax the blood vessels, so they widen and the pressure drops. A low salt diet may help. Regular check-ups with your vet are needed for monitoring.

Hyperthyroidism in older cats

The term hyperthyroid means “too much thyroid hormone”. This chemical, manufactured by the thyroid glands in the neck, sets the running speed of the body. Levels of this hormone can be measured by a blood test. If too much thyroid hormone is being produced, all the body functions (the metabolism) speed up.

A pet with hyperthyroidism will eat lots but still lose weight and the cat may also be active, or even aggressive. Their heart rate will be rapid and permanent heart damage may result. Blood pressure can go up too.

Vomiting and diarrhoea (including toileting outside the litter tray) are common symptoms, although hyperthyroidism is not necessarily the only cause. The underlying reason for hyperthyroidism is unknown.

What is the treatment for hyperthyroidism?

There are two common options – tablets or surgery. However, even if surgery is chosen, tablets are used in the first instance, to stabilise your pet's condition ready for an anaesthetic. T

ablets do not cure the condition, but block the excessive production of thyroid hormone, and need to be given lifelong, usually two or three times daily, at regularly spaced intervals (eg first thing in the morning, early afternoon and last thing at night).

Surgery may provide a cure. As all animals have two thyroid glands, the size of both are inspected at surgery, then one or both removed if they are enlarged. If both are removed, either together or in two separate operations, this may carry an increased risk of post-surgical complications. If one gland is left, it may later start producing an excess of thyroid hormone. There is no rule on whether both glands should be removed together or in separate procedures, and your vet will advise you on the best option for your cat.

A third option is radioactive iodine therapy, but this is only available at some specialist centres and is expensive. It usually destroys all abnormal thyroid tissue, but does mean that the cat has to be hospitalised for three to six weeks.

When is a cat too old for surgery?

With modern anaesthetics the risks are minimal. Many thyroid patients are at least middle aged so thyroid operations on elderly animals are common.

Surgery can be advantageous if the administration of tablets is difficult, or if they do not seem to be working well. Some caution is needed.

Excess thyroid hormone can mask other problems, especially kidney damage. In this case, high blood pressure can force toxins out of the system even whilst the kidney’s filtering mechanism is failing (although it eventually causes kidney damage). Blood tests to check kidney function are often recommended prior to surgery.

In summary, with hyperthyroidism:

  • your pet can be treated with tablets, but surgery may be a better option
  • the condition may recur if both glands are not removed
  • your cat may also have kidney problems and therefore need more careful management. A skinny ravenous cat that is messing in the house may have hyperthyroidism and be treatable.
— Page last updated 30/05/2023