Kidney role and structure
The kidneys are 2 highly vascularised organs located beneath the spinal column of the animal, close to the lumbar vertebra. They are bean shaped in dogs and round shaped in cats and weigh about 0.5 to 1% of the total weight of the pet. They produce urine, from the filtration of blood, which is collected in the bladder.
Dog's kidney
The kidneys perform multiple functions:
- Excretory function: elimination of waste products of metabolism, toxins and drugs.
- Regulatory function: maintenance of fluid and electrolyte balance.
- Biosynthetic functions: formation of a variety of regulatory hormones that have important local and systemic functions.
The excretory function of the kidney is carried out by many functional units called nephrons. There are approximately 200 000 in normal cat's kidney and 400 000 in dog's. They filter the blood of to produce urine which is then collected in the bladder. The filtration process is mainly mechanical, the larger molecules (red and white cells, large size proteins) remain within the blood whereas the smaller ones enter into the nephron. The filtration process takes place in the glomerulus.
Albumin is a medium sized molecule which should stay in the blood, but may go into the urine in case of some renal dysfunction.
Chronic Renal Failure :
frequency and symptoms in dogs and cats
Chronic Renal Failure may also be referred to as Chronic Kidney Failure. Failure is defined as an inability to perform.
Due to the very difficult diagnosis of the disease, the current figures are very likely to be widely underestimated
In cats
The disease occurs in 10% of the total population and more commonly affects older cats (12 years or more). A cat with CRF can leave for many years. Adequate treatment can dramatically increase its life expectancy.
The main symptoms are:
1. Anorexia, lethargy, weight loss
2. Increased drinking and excessive thirst, mouth ulcers
3. Vomiting
In dogs
Because the diagnosis of CRF in dogs is only possible in the latter stages of the disease, only 1-2% of the population are affected. Once diagnosed, dogs with CRF only live for months rather than years.
The main symptoms are:
1. Increased drinking and excessive thirst
2. Vomiting, diarrhoea, weight loss.
Chronic Renal Failure : underlying causes and progression of the disease
Chronic renal failure is an inherently progressive disease. It usually starts with an initial lesion which, in most cases, remains unnoticed. Its progression either results from continuing renal damage induced by a nephropathy or from mechanisms independent of the initiating lesion and responsible for the spontaneous self perpetuation of the disease.
The initial lesions may have many causes: infection, hypertension, a lesion in the kidney parenchyma or in the kidney glomerulus.
Whatever the cause, the result is often the same: the death of nephrons, which is accelerated due to inherent mechanisms. Although the kidney has a huge reserve capacity of nephrons, when two third of the initial nephron population have disappeared, the kidney can no more get rid of the nitrogenous wastes and the symptoms become apparent.
