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The Geriatric Cat
Cats have an extraordinary ability to hide signs of illness. This is because in the wild the cat can be either prey or predator and if it shows signs of weakness it may attract attention. Thus, preventive care and routine health checks are even more important in picking up early signs of disease as your cat reaches the mature life stage (7 years old and upwards).
- Annual routine blood pressure monitoring
- Annual health checks
Feline High blood Pressure (hypertension)
Above 7 years of age the risk of hypertension starts to increase and early detection is vital to prevent its effects. Feline hypertension is most commonly reported as a complication of other underlying disease processes (secondary hypertension). These disease processes being chronic kidney (renal) failure and hyperthyroidism (an overactive thyroid gland).
- Eyes; Swelling and detachment of the retina, plus bleeding (haemorrhages) into the eye may result in permanent damage to your cat's vision.
- Kidneys; Hypertension over time damages the kidneys increasing the risk of developing or worsening kidney (renal) disease.
- Heart; Hypertension over time causes the heart to work harder in pumping the blood causing thickening of the muscle of one of the heart chambers (left ventricle). This can lead to the development of hypertrophic cardiomyopathy (HCM) and in very severe cases congestive heart failure.
- Nervous system & Brain; Neurological signs can be seen due to bleeding in this area. These present themselves as odd behaviour, dementia, a wobbly gait, seizures and coma.
As feline hypertension can be a complication of other underlying disease processes, a variety of signs may be seen. In the case of hyperthyroidism, cats may show signs such as weight loss in spite of a ravenous appetite, hyperactivity, increased thirst (polydipsia) and urination (polyuria). Chronic kidney failure, signs such as weight loss, reduced appetite, lethargy, dehydration, mouth ulcers, vomiting, increased thirst and urination may be noticed. In many, no specific clinical signs of hypertension will be observed until the condition advances to spontaneous bleeding into the eye and/or retinal detachment causing a sudden onset of blindness. Although some cats may show a change in their behaviour and appear to be depressed and withdrawn.
To detect hypertension early, regular blood pressure (BP) monitoring in mature cats from the age of 7 onwards is recommended. A doppler flow detector with an inflatable cuff placed around one of the front legs or the tail is used to measure blood pressure which is similar in technique to that used in humans. BP measurements only take a few minutes and are extremely well tolerated by most cats.
- Anti-hypertensive drugs such as amlodipine are used to reduce blood pressure assessed using continued BP monitoring.
- Diagnosis for any underlying disease processes, such as renal disease or hyperthyroidism and relevant therapy.
Kidney (Renal) Failure
When kidney function is no longer able to meet the body's demands this is termed Kidney failure (aka renal failure/ insufficiency).
Normal Kidney Function
Normal cats are born with 2 kidneys (left and right) which are located in the abdomen.
Healthy kidneys are required for many vital functions which include:
- Elimination via the urine of waste products. Such as protein breakdown products (urea and creatinine), hormones and drugs
- Maintaining normal body water content (hydration balance)
- Regulation of blood salt levels (normal electrolytes such as sodium, potassium, calcium and phosphate)
- Regulation of the bodies acidity levels (acid-base balance)
- Activation of vitamin D
- Production of hormones such as erythropoeitin (which stimulates the production of red blood cells by the bone marrow) and renin (important in water and electrolyte control (homeostasis))
Causes of Kidney Failure
Potential causes of renal failure can be divided into 2 main categories:
- Congenital (present at the time of birth) such as;
- Being born with only one kidney
- Renal dysplasia (abnormal development of one or both kidneys)
- Polycystic kidney disease. An inherited cause of kidney failure common in Persian and related breeds. Affected cats are born with small cysts in their kidney tissue which enlarge as they get older and compromise normal kidney function.
- Acquired (normal kidneys at birth, but develop problems in later
life) which include;
- Bacterial and viral infections
- Inflammatory conditions
- Exposure to toxins e.g. Ingesting antifreeze or lilies
- Trauma e.g. Road traffic accident
- Cancer e.g. Adenocarcinoma (tumour of glandular tissues), lymphoma (tumour of white blood cells)
The clinical manifestations of chronic renal failure vary between individual cats and are often non-specific, but commonly include:Clinical Signs
- Weight loss
- Reduced appetite
- Increased thirst (polydipsia)
- Increased urination (polyuria)
- High blood pressure (systemic hypertension)
- Anaemia (low red blood cell count)
- Mouth ulcers associated with bad breath (halitosis)
Kidney failure can be diagnosed through testing blood and urine samples, after an initial health examination. In patients with renal failure the kidneys are unable to excrete waste efficiently causing higher levels of waste products (urea and creatinine) plus altered salt levels (phosphate and potassium) with in the blood. Renal failure also affects the kidneys ability to concentrate urine. Thus, cats with renal failure have more dilute urine and increased blood levels of urea, creatinine (referred to as azotaemia), phosphate (hyperphosphataemia) and decreased blood levels of potassium (hypokalaemia).
Management & Treatment
Current treatment options involve predominantly supportive measures aimed at improving the quality of life of affected cats by employing a variety of medical treatments tailored to the individual's needs. Damaged kidneys will not recover and will get progressively worse with time, but treatment can make an enormous difference to the cat's quality and length of life.
- Dietary management: Specific kidney diets (Hill's k/d and Royal Canin Renal) have been shown to dramatically improve the quality of life and survival of cats with chronic renal failure. These diets restrict the level of phosphate which may build up in cats with kidney failure contributing to their feeling unwell. Restrict levels of high quality protein which limits the amount of protein breakdown waste products. Reduce the levels of sodium which may help to reduce the risk of developing systemic hypertension. Increase the amount of potassium and B vitamins which cause a loss of appetite and muscle weakness. They also contain increased numbers of calories which helps maintain a normal body weight.
- Maintaining hydration: Inadequate water intake in chronic renal failure is common and is associated with dehydration, causing further impairment of renal function. In the early stages following diagnosis intravenous fluid therapy may be indicated. Also, maintaining adequate fluid intake at home is of prime importance via moist diets, water fountains, and adding water to feed. Ensure that water supplies are easily accessible and plentiful. Avoid offering salty broths (fish in brine) and milk as the former may increase the risk of hypertension and the latter contains high levels of phosphate.
- ACE (angiotensin converting enzyme) inhibitors: Clinical trials have indicated that cats with kidney failure receiving benazepril have a better quality of life, increased appetite and help to reduce blood pressure.
- Phosphate binders: Cats that will not eat the prescription kidney diets or do not respond to dietary therapy will require a prescribed drug that limits the phosphate absorbed by the bowel. These phosphate binders can be added to food.
For further information on kidney failure, we recommend the book written by Dr Sarah Caney titled 'Caring for a cat with kidney failure'.
Hyperthyroidism (over-active thyroid gland)
This is a common disorder seen in older cats. It is caused by an increase in the production of thyroid hormones from the thyroid glands, which are located on each side of the cat's trachea (wind wipe) in the neck.
1; Normal thyroid gland, 2; parathyroid gland, 3; parathyroid gland & 4; enlarged thyroid gland
Thyroid hormones have an important role in controlling the body's metabolic rate, hence cats with hyperthyroidism tend to burn up energy too quickly and suffer from weight loss despite having a ravenous appetite with increased food intake. They also increase blood pressure, heart rate, body temperature and gut motility.
These are usually quite subtle at first, but as the disease progresses they become more severe. These commonly include;
- Weight loss
- Increased appetite (polyphagia)
- Increased thirst (polydipsia) and urination (polyuria)
- Increased irritability and restlessness
- Unkempt coat
- Mild to moderate diarrhoea and/or vomiting
- Hypertension is a potential complication of hyperthyroidism causing damage to the kidneys, heart, eyes and brain.
- Thyroid hormones cause an increased heart rate and stronger heart muscle contraction. This overtime causes thickening and enlargement of the muscle of one of the heart chambers (left ventricle). This can lead to the development of hypertrophic cardiomyopathy (HCM) and in very severe cases congestive heart failure.
- Kidney (Renal) failure does not occur as a direct effect of hyperthyroidism, but these diseases can be seen together. Hyperthyroidism increases the blood supply to the kidneys which may improve their function, hence masking the severity and extent of the renal failure.
After an initial health examination, hyperthyroidism can be diagnosed via a blood test. The blood test looks at the thyroid hormone thyroxine (T4) concentrations and other organ parameters such as liver enzymes which are commonly increased secondary to hyperthyroidism, urea and creatinine which are usually elevated in renal failure. Blood pressure should also be checked due to the potential complication of hypertension and if indicated an ECG (electrocardiogram), ultrasound or chest x-ray if secondary heart disease is suspected.
- Dietary Treatment: A vital element required to produce thyroxine is iodine. By using a diet with a restricted iodine content, the thyroid gland's thyroxine production can be limited to normal levels. Hills y-d is a specially formulated diet with very carefully controlled iodine levels. If a cat is fed Hills y-d and nothing else, it will return to normal thyroxine levels. Unfortunately, cats have a habit of eating other things as well and if this happens, the control of the iodine levels in the diet is lost.
- Medical management: Methimazole (Felimazole) and Carbimazole (Vidalta) are anti-thyroid tablets that act by reducing the production and release of thyroid hormone from the thyroid gland. They do not provide a cure for the condition, just control. Monitoring of the T4 levels are required whilst on medication via blood sampling.
- Surgical Thyroidectomy: This is surgical removal of the affected thyroid tissue (thyroidectomy) which may produce a long-term cure. Although, hyperthyroidism can develop again at a later date in previously unaffected thyroid tissue. It is always recommended that patients are initially stabilised with anti-thyroid medication for 3 to 4 weeks before surgery to reduce anaesthetic and surgical complications.
- Radioactive Iodine Therapy: Radioactive iodine (I 131) is administered under the skin and taken up by the abnormal thyroid tissue. The radiation destroys the affected abnormal thyroid tissue.
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