Disease and Illnesses of dogs – Canine kidney failure
What is kidney failure?
Kidney or Renal failure occurs when the kidneys stop working effectively and they can no longer remove the waste products from the blood. These waste products build up and cause the symptoms seen with kidney failure which are discussed in detail below. Kidney failure is less common in dogs than it is in cats.
Kidney failure can either come on suddenly, called acute kidney failure or have a more gradual onset, called chronic kidney failure. There are many possible underlying causes of kidney failure.
Age: A lot of the cases of chronic renal disease in dogs happen in older animals and sometimes no obvious underlying cause is found. In these cases it is put down to wear and tear of the kidneys over the years.
Infection: Infection in the kidneys, such as glomerulonephritis or pylonephritis can lead to a compromise in their function and sometimes renal failure.
Poisoning: Some toxins such as antifreeze (ethylene glycol) can cause acute kidney failure and these are often very difficult to treat.
Obstruction: An obstruction of the lower urinary tract, for instance a bladder stone, can cause urine to back up into the kidneys and cause renal failure.
Shock: If a dog does not have a normal volume of blood, for example of they were bleeding severely from a wound, the kidneys would not receive enough blood and therefore oxygen and would start to fail.
Heart failure: This condition again may result in poor perfusion of the kidneys as the heart will not be working as efficiently as it should.
Congenital: This refers to developmental abnormalities in the kidneys which are present from birth and mean the kidneys cannot function normally. This results in kidney failure in younger dogs.
What are the symptoms of kidney failure in dogs?
The symptoms of renal failure are caused by the build up of toxins in the blood as the kidneys are not filtering them out. This build up of toxins doesn’t occur until there is only 25% of the kidney left functioning so the kidney does have huge reserves to withstand damage. The waste products that we measure to assess kidney function are called Urea and Creatinine and when they are both raised in kidney failure is it called azotaemia.
The symptoms caused by this azotaemia include the following:
- Weight loss
- Increased Urination (polyuria)
- Increased thirst (polydipsia)
- Ulcers in the mouth caused by increased urea in the blood
No urine production in end stage renal failure
The increased urination is because a failing kidney loses the ability to concentrate urine so the affected dog will produce large volumes of very dilute urine, this leads to an increase in thirst to try and compensate for the lost water in the urine but it is often not enough and the dog will end up being dehydrated. This increased urination changes to no urine production in end stage kidney failure as the kidneys shut down altogether.
A number of these symptoms, if present in the history or examination of an unwell dog will make your vet suspicious of kidney disease.
How is kidney failure diagnosed in dogs?
The first step in diagnosis is a thorough history and clinical examination which will show up some or even all of the symptoms listed above. If your vet suspects kidney failure as the cause of your dog’s illness, they will need a blood test to confirm it.
The blood test will show higher than normal levels of Urea and Creatinine, the waste products usually filtered out by the kidneys. In cases of chronic kidney failure, blood tests may also show an increased level of phosphate in the blood as this is also usually eliminated by the kidneys. Animals with kidney failure may also be slightly anaemic as the hormone that stimulates red blood production is made in the kidneys and is reduced in kidney failure. The next test that is very useful is a urine sample. This can be tested to see if the kidneys are still able to concentrate urine as failing kidneys are not.
In some cases, depending on the suspected underlying cause of the kidney failure, your vet may want to do some imaging of the kidneys which may include x-rays or ultrasound.
How is kidney failure treated in dogs?
The important thing to realise about kidney failure is that it cannot be cured but it can be managed to try and slow the progression of the disease and to make sure that affected dogs have a good quality of life.
· Diet is very important. Dogs with renal disease benefit from reduced salt in their diet as well as small quantities of protein although it should be good quality. Restricted phosphorous is also beneficial. There are prescription diets that have been specially formulated for dogs with kidney disease such as Hills k/d and Royal Canin renal diet.
· Fluids can be required in some cases to correct dehydration and to reduce the levels of urea and creatinine in the blood. This can involve being on a drip and having fluids directly into the vein or in some cases fluids can be given under the skin.
· Phosphate binders are medications that can be added to the food to reduce the high levels of phosphate found in the blood of dogs with renal disease
· Angiotensin Converting Enzyme inhibitors (ACEI), such as Fortekor, are drugs that can be very beneficial in cases of kidney disease. These drugs treat high blood pressure that can accompany kidney disease which is useful as high blood pressure can further damage the kidneys. ACEI’s also increase the blood flow to the kidneys which can help them function more effectively.
Your vet may advise some or all of these measures depending on the severity of disease or the suspected underlying cause.