The kidneys contain millions of tiny filters called nephrons. As blood passes through the kidneys, nephrons filter out any excess fluid and waste products that are released from the body as urine. However, if the nephrons become damaged, the kidneys can lose their ability to filter and dangerous levels of fluid and waste products can build up.
Kidney failure occurs when the kidneys have lost around 90% of their filtering ability. Left untreated, the amount of waste products in the blood will build up to a dangerous level, resulting in coma and then death.
A kidney transplant is the ideal treatment for kidney failure. However, many people have to wait several months or years before a suitable donated kidney becomes available so dialysis is used.
Some people are not suitable for a kidney transplant because they have another serious health condition, such as heart failure or cancer. This usually means that it is unlikely they will survive the transplant procedure.
People who aren't suitable for a kidney transplant will require dialysis treatment for the rest of their lives.
Common causes of kidney failure
Common causes of kidney failure include:
- diabetes
- chronic inflammation of the kidneys (glomerulonephritis)
- high blood pressure (hypertension)
These are described below.
Diabetes
Diabetes is a condition where the body either does not produce enough insulin (type 1 diabetes), or does not make effective use of it (type 2 diabetes).
Insulin is vital because it breaks down the glucose in the blood to produce carbohydrate, which provides energy.
If you have diabetes that is not properly controlled, too much glucose can build up in your blood. The excess glucose can damage the tiny filters (nephrons) inside your kidneys.
The damaged nephrons can disrupt your kidney’s ability to filter out waste products and fluids from your blood.
Glomerulonephritis
Glomerulonephritis is a condition where tiny structures inside the kidneys, known as the glomeruli, become inflamed.
The glomeruli are an important part of the nephrons and persistent inflammation of the glomeruli will lead to them scarring. This can disrupt your kidney’s ability to filter and clean the blood of waste products.
Glomerulonephritis can be caused by the immune system (the body’s natural defence against infection and illness) mistaking harmless proteins inside the kidneys as a threat and, as a result, attacking the kidneys, leading to inflammation.
In many cases there is no obvious reason why glomerulonephritis occurs.
High blood pressure
Blood pressure is a measurement of how much pressure is required by your heart to pump blood around your veins and arteries. Too much pressure is known as high blood pressure or hypertension and can damage your body's organs and lead to heart disease.
Hypertension also causes kidney damage by putting strain on the small blood vessels in the kidneys. This prevents the filtering process from working properly.
In 90% of cases of high blood pressure, the causes are unknown. However, there appears to be a strong link between the condition and lifestyle factors, such as being overweight, having a diet that is high in salt, smoking and drinking too much alcohol.
Other causes
Other, less common causes of kidney failure include:
- polycystic kidney disease: a genetic (inherited) condition where cysts (fluid-filled sacs) develop inside the kidneys
- repeated kidney infections
- renal artery disease: a condition where the arteries that supply blood to the kidneys become clogged up with fatty substances known as plaques; a reduced blood supply can damage the kidney’s tissues
