Kidney Disease - Chronic Renal Failure

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What is Kidney Disease - Chronic Renal Failure?

Chronic Kidney Disease (CKD, also known as Chronic Renal Failure) is a disease affecting the kidney.

Chronic kidney disease occurs with long-term kidney disease, resulting in a gradual decline in kidney function over time.

There are four major causes of chronic kidney disease:

Glomerular disease (such as glomerulonephritis)
Tubulointerstitial disease (such as prolonged obstruction)
Vascular disease (such as atherosclerosis)
Cystic disease (such as adult polycystic kidney disease)

It is important to understand the anatomy of the kidney so that you know how the diseases affect it. Chronic renal disease affects the two fundamental parts of the kidney called the glomerulus and the tubules. There are millions of glomeruli in each kidney, and these are very small bundles of tiny blood vessels through which blood is pumped. The pressure in this bundle of vessels is very high, and so some of the fluid gets pushed out of them (along with various substances that the body wants to dispose of) and this fluid is collected in the tubules.

The tubules further filter this fluid, removing some substances that the body wants to keep, and disposing of some toxins that it wants to get rid of including urea and creatinine. Much of the water is reabsorbed, leaving a concentrated mix of minerals, salts and other substances that the body wants to get rid of. Usually, protein is reabsorbed and kept in the body.

In chronic kidney disease, this filtration process breaks down and so the glomeruli and tubules do not work as well. Toxins (such as urea) can start to build up and cause problems, and the kidneys can start to 'leak' protein into the urine. All this can lead to some very severe problems with the balance of the chemical environment inside the body.

Who gets Kidney Disease - Chronic Renal Failure?

As many as 2 million Australians may have some form of undiagnosed chronic kidney disease, and 1 in 3 people are at an increased risk of getting it in the future. The incidence of end stage renal disease in men (239/million) is much greater than in women (162/million). It is much higher in Aboriginal Australians (2000-3000/million) than Asians (205/million) or Caucasians (150/million).

Other statistics include that:

1 in 3 people are at risk of developing chronic kidney disease
1 in 7 people, over the age of 25 years, have at least one clinical sign of existing chronic kidney disease
80-90% of cases of chronic kidney disaese may go unrecognised
Chronic kidney disease is the seventh most common cause of death, exceeding diabetes, respiratory disease, and suicide
While Aboriginal Australians represent below 2% of the population, they account for around 10% of people who require kidney replacement therapy, and the disease is increasing at a higher rate than in other populations.

Predisposing Factors

There are lots of risk factors that can cause, or mean you are more likely to get, chronic kidney disease. Some of them include:

Increasing age
Diabetes mellitus
Hypertension
A family history of renal disease
Obesity
Smoking
Aboriginal race

Other factors are actually the cause of initial kidney damage, and so pave the way for chronic renal disease in the future. There are many causes of this, and can be divided up as follows:

General conditions:
- Diabetes mellitus
- Hypertension
Congenital and inherited diseases:
- Polycystic kidney disease
- Medullary cystic disease
- Congenital obstructive uropathy
Primary glomerular diseases such as the glomerulonephritidies
Secondary glomerular diseases such as:
Vascular diseases:
- Renal artery stenosis (constriction of the renal arteries)
- Vasculitis (inflammation of blood vessels)
Tubulointerstitial disease:
- Myeloma nephropathy
- Inflammation of the kidney due to a damaging toxin
- Tuberculosis
- Schistosomiasis
Urinary tract obstruction:
- Renal stones
- Prostate diseases

Progression

Usually, whenever chronic renal disease has begun, it will continue until end stage renal failure is reached, especially once amount of blood the kidney is filtering drops to 80-90% of what it usually is. There are a few reasons for this.

One way (shown below), is that after some of the glomeruli (filters) of the kidney have been damaged, the other glomeruli have to pick up some of the slack and filter more blood. They way they do this is by stopping blood from leaving as easily, leading to an increase in the pressure that is within the little bundle of blood vessels. While this works for a while, eventually the pressure causes the cells to push apart a little and increase the passage of other things that should usually stay in the blood.

One of these things that is allowed through is a larger amount of protein. This protein can actually lodge in the tissue that is around the glomerulus where it can cause inflammation. This inflammation attracts white blood cells and causes the release of inflammatory chemicals that further damage the glomerulus. Some of these chemicals also start the formation of substances that can clog up the glomerulus, making it less effective at filtering blood. The tubules can also become inflamed and change their chemical makeup leading to them being very ineffective at filtering.

The best predictor of decline in renal function is the measurement of a blood chemical called "creatinine" over time, which gives a good indication of renal function. Creatinine is a substance that is created in the body naturally, and usually filtered out by the kidneys. If there is damage to the kidneys however, and they are filtering poorly, then the creatinine in the blood rises. This means that testing the creatinine in the blood can give a good idea as to how the kidneys are functioning. The results may be graphed to determine the time course of progression.

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