Kidney Disease
Kidney, or more correctly, renal failure, occurs in any animal when approximately 75% of the animal’s kidneys cease to function. There are essentially two types of kidney failure:
1. Acute kidney failure. This results from an abrupt or rapid decline in the kidney function to a degree that is incompatible with life if the condition is prolonged. The kidneys are susceptible to the effects of certain antibiotics, heavy metals (e.g. lead), poisons (e.g. pesticides) and various other chemicals (e.g. snake venom). Acute failure is not commonly seen and if treated quickly can be reversed.
2. Chronic kidney failure. This develops from the inability of the kidneys to perform their normal functions as a result of gradual but progressive loss of kidney tissue over a long period of time (months to years). Certain breeds of cats (e.g. Persians) and dogs (e.g. Bull Terrier) have an inherited form but in most cases the cause may never be known though congenital abnormalities, kidney infections, kidney stones, diabetes and certain forms of cancer can be responsible. Chronic kidney failure is the most common form seen. All breeds of dogs and cats can be affected. It is seen most commonly in dogs over seven years of age and cats over nine.
What actually happens in kidney failure?
In the body the kidneys act like a very complex filter. Blood passes through them and is filtered. The blood cells and large molecules such as protein remain on one side of the filter while the fluid part of blood which contains glucose, sodium and water as well as the by-products of the body’s metabolism pass on the other side of the filter. The normal kidney should reabsorb most of the water (thus concentrating the urine), salts and glucose and allow the by-products to pass into the urine. With kidney failure the kidney loses the ability to concentrate the urine and so the volume of urine that is produced is much greater. If severe enough the animal will become dehydrated because it can’t drink enough water to replace that lost in the urine. In addition to the loss of water, certain by-products are not excreted and so they accumulate in the body. As the kidney failure worsens protein and glucose is lost in the urine resulting in weight loss.
What are the signs of chronic renal failure?
The severity of the signs seen in animals will depend directly on the amount of kidney function the animal has remaining. These signs include:
- urinating more than normal
- drinking more than normal
- anorexia
- lethargy
- vomiting
- weight loss
- diarrhoea
- bad breath due to bad dental disease (particularly in cats)
How is kidney disease diagnosed?
A diagnosis of kidney failure is made on the basis of:
1. The animal’s symptoms
2. The results of blood tests that measure certain chemicals that are normally excreted by the kidneys. If these levels are elevated then it suggests the kidneys are not working as well as they should be.
3. The results of urine tests. These tests involve measuring how concentrated the urine is and if there is any protein or glucose present in the urine.
4. Ultrasound. In certain cases the ultrasound machine can be used to examine the structure of the kidneys. This can reveal if the kidneys are smaller, abnormally shaped, the presence of kidney stones and if the kidney is being invaded by cancer.
How is kidney failure treated?
Unfortunately there is no cure for kidney failure but in its early stages it can be managed so as to slow its progression. If the animal is dehydrated it may need to go on a drip. A change in the animal’s diet may be required. This involves reducing the amount of protein, phosphorus and sodium in the diet so as the kidneys do not have to work as hard to remove these chemicals’ by-products. Such diet change is easiest achieved by using one of the specially made diets that are available such as Hill’s K/D or Waltham Low Protein diet. There are also a number of specific drugs, such as anabolic steroids which can help maintain body weight and appetitie, that can be used depending on the severity of the signs and the results of the blood tests. If the animal’s teeth are in poor condition they should be scaled and polished - this won’t help the kidney failure but it will make your pet a lot more comfortable. Because of the kidney failure it may be necessary to put the animal on a drip during the procedure.