Kidneys are important organs and are extremely fragile.
They handle a large amount of work, such as:
- maintaining the balance of chemicals in the blood
- filtering out and excrete toxins from the body through the urine
- regulating blood pressure
- regulating production of calcium
- regulating phosphorus metabolism
- producing a hormone that stimulates red-blood-cell production
Healthy kidneys conserve water and concentrate toxins into a smaller amount of liquid to be urinated away.
Kidney failure is defined as the inability of the kidneys to remove toxins from the blood, causing toxin build-up in the body.
Canine kidney failure can be acute (one that appears suddenly) or chronic (one that comes on gradually over a period of time):
Canine Acute Renal Failure (ARF)
Acute kidney failure in dogs is usually caused by poisoning, especially antifreeze. Other possible causes include:
- Congestive heart failure
- Complete urinary tract obstruction
- Shock (causing inadequate blood flow to the kidneys)
- Bacterial infections (such as lyme disease, leptospirosis)
Acute kidney failure is very dangerous and highly fatal.
Symptoms such as dehydration can come on rather suddenly. You will notice the dog standing with an arched back because of the pain in the kidneys. Immediate veterinary treatment with intensive fluid therapy and hospitalization is necessary.
Canine Chronic Renal Failure (CRF)
Chronic kidney failure in dogs is usually caused by one of the following:
Inflammation of the Kidney (Nephritis)
This is caused by some form of infectious diseases, such as canine hepatitis, canine systemic lupus, chronic pancreatitis, and others.
Kidney Tissue Degeneration (Nephrosis)
This can be due to toxins and poisons or due to inadequate blood flow to the kidneys.
Some medications can cause this condition, such as aspirin, ibuprofen, butazolidin, as well as certain antibiotics when used long-term, such as polymyxin B, gentamicin, amphotericin B, and kanamycin.
A poor-quality or unbalanced diet can also result in nephrosis. In particular, too much phosphorus in the food is problematic – especially for dogs with pre-existing kidney disease.
Additionally, if there is excessive phosphorus AND insufficient quantity of usable calcium in the diet, the kidneys cannot eliminate the phosphorus effectively, resulting in kidney stone formation or kidney tissue degeneration. This will eventually lead to kidney failure.
Symptoms of Chronic Kidney Failure
The kidneys have a very large reserve capacity, and dogs with chronic kidney failure do not show any signs until about 75% of the kidney tissue is not functioning.
The first signs of chronic kidney failure in dogs are increased water intake and frequent urination.
This is because when the kidneys are damaged, they become less able to concentrate the urine.
This results in a large urine output and, because a large amount of water is lost in the urine, the dog becomes thirsty all the time. This can subsequently lead to dehydration.
As kidney functions continue to decline, other signs of canine kidney failure occur, such as:
- Appetite loss
- Weight loss
- Dry haircoat
- An ammonia-like odor to the breath
- A brownish discoloration to the surface of the tongue
- Uclers in the mouth
The above symptoms are the result of a build-up of chemicals, wastes and toxins (such as ammonia, nitrogen, acids) in the blood and tissues.
At this stage, the dog will actually urinate less frequently than normal.
At the end stages of canine kidney failure, the dog falls into a coma.
Diagnosis of Canine Kidney Failure
To diagnose dog renal failure and to determine the severity of the disease, blood tests and urinalysis are necessary.
From the blood test, the values of blood urea nitrogen (BUN) and creatinine are obtained and analyzed.
BUN is produced when the body is digesting protein and, since it is a waste product, it is normally excreted and eliminated by the kidneys.
However, if the kidneys are not functioning properly, waste products such as BUN cannot be eliminated and they accumulate in the blood, causing the BUN value to increase.
Creatinine is a by-product of muscle energy use in the body and is also of no use to the body.
Creatinine is also eliminated and excreted by the kidneys in healthy animals, but if the kidneys are not working effectively, creatinine will build up to higher than normal levels.
In dogs, normal BUN is about 10-25 mg/dl and normal creatinine level is about 1-2 mg/dl.
In addition, exploratory surgery and biopsy of the kidneys may also be performed to make an exact diagnosis to see if the kidney failure is treatable, and if so, to determine the most appropriate treatment.
Treatment of Canine Kidney Failure
Some forms of mild acute kidney failure are curable using medication.
In most other cases of acute kidney failure, a complete recovery is not possible and the dogs usually will have some renal function deficit for the rest of their lives.
For chronic kidney failure, there is no cure since the disease involves the death of kidney cells and replacement by scar tissue.
Chronic kidney failure in dogs must be controlled and monitored carefully for the rest of the dog’s life.