Why are your kidneys so important?  We can live quite well with only one kidney and indeed, some people live healthily even though born with one missing. Our kidneys are amazing, they play a major role in maintaining your general health and wellbeing but are not usually thought of as essential to a healthy life. But while bones can break, muscles can waste away and the brain can sleep without risk to life, if both kidneys fail, as happens in end stage kidney failure, bone, muscle or brain can not carry on. Without any kidney function our body dies.

What is the role of your kidneys in keeping you healthy?  For organs so small, your kidneys works hard - they have a number of vital roles to play in the daily functions of our body, as they:

• act as filters for your body
• control blood pressure
• make red blood cells, and
• maintain strong and healthy bones

Think of your kidneys as an extremely sophisticated, environmentally friendly, waste disposal system, which sorts non-recyclable waste from recyclable waste, 24 hours a day, 7 days a week, while also cleaning your blood. Every hour your blood supply circulates through the kidneys about 12 times. Each day your kidneys process around 200 litres of blood, with around 1 to 2 litres of waste leaving the body as urine. Much of this waste is produced by the body as it processes the food you eat.

What can go wrong with the kidneys? 

Kidney disease is called a ‘silent disease’ as there are often no warning signs.

• You can lose up to 90 per cent of kidney function without realising it, by which time it is almost impossible to prevent further serious problems.  Refer also Kidney Disease: Are you one in three? 
• People can live a near normal life with as little as 20 percent of their total kidney function.
• When symptoms do occur the initial signs may be general, such as feeling tired or generalised itching. 
• As kidney disease progresses, the symptoms can include changes in the urine (reduced volume, discolouration, blood or pus), nausea and vomiting, and appetite loss.
• Other symptoms include swollen or numb hands and feet (because of water retention), weakness and lethargy, darkened skin and muscle cramps. 

Sometimes kidney failure can happen quickly, caused for example by a sudden loss of large amounts of blood or an accident. A sudden drop in kidney function is called Acute Kidney Failure and is often short lived but can occasionally lead to lasting kidney damage. Refer to our fact sheet on Chronic Kidney Disease. 

More often kidney function worsens over a number of years. This is good news because if kidney disease is found early, medication, dietary and lifestyle changes can increase the life of your kidneys and keep you feeling your best for as long as possible. If you lose over 1/3 of your kidney function for over 3 months, it is called Chronic Kidney Disease (CKD). Sometimes kidney disease leads to Kidney Failure, which requires dialysis or a kidney transplant to keep you alive.

As kidney function decreases, waste begins to build-up in the blood. If symptoms are present, you may start feeling sick, vomit or experience a loss of appetite. Another symptom may be a change in the number of time you need to pass urine and the amount passed. You may also suffer extreme tiredness, shortness of breath, swelling of the hands, face and feet, headaches, high blood pressure and blood in the urine.

These symptoms may worsen gradually as kidney function declines. However, these symptoms are very general and may be caused by other illnesses, so it's a good idea to get your kidneys checked.

This is a simple and very general list of possible symptoms of reduced kidney function:

• High blood pressure
• Changes in the amount and number of times urine is passed, e.g. at night
• Changes in the appearance of urine
• Blood in the urine
• Puffiness e.g. legs and ankles
• Pain in the kidney area
• Tiredness
• Loss of appetite
• Difficulty sleeping
• Headaches
• Lack of concentration
• Itching
• Shortness of breath
• Nausea and vomiting
• Bad breath and a metallic taste in the mouth

Kidney disease is a life-threatening condition and should not be ignored!  Chronic kidney disease is a long term health condition that in many cases is preventable. Early detection and treatment can help prevent kidney failure and the need for dialysis or transplant treatment. Find out more about Chronic Kidney Disease and see how our kidneys work by viewing the animated models which show how healthy kidneys function.

Be aware that you are at high risk if you:

• have diabetes
• have high blood pressure
• smoke
• are over 50 years
• are obese,
• or are of Aboriginal or Torres Strait Islander descent

If you are you at increased risk of kidney disease, ask your doctor for a kidney health check. 

How can I avoid kidney disease?

Your kidneys look after you, but obesity, high blood pressure, diabetes and smoking contribute to 50 Australians a day dying from, or with, kidney and urinary related disease. Australian Bureau of Statistics *Causes of Death, Australia 2008 - 3303.0

You can reduce your risk of kidney disease by:

• being a non-smoker
• controlling your blood pressure
• staying fit
• maintaining a healthy weight
• eating a healthy diet
• drinking water instead of sugary drinks 
• drinking alcohol moderately (no more than 2 standard glasses a day for men -1 standard glass for women)
•  ensuring your blood glucose is well controlled if you have diabetes

Test results or clinical values can be grouped to show how well your kidneys are working.  These groupings are only a guide and results may be outside these ranges. 

• Stage 1:  A small amount of kidney damage but GFR is often normal.  Kidney function is between 50–100% of normal. A normal GFR is greater than 90 mL/min.
• Stage 2:  Mild kidney damage so there is a slight drop in GFR to between 60–89 mL/min. 
• Stage 3:  Moderate kidney damage so blood pressure increases. Chronic kidney disease can be diagnosed as GFR falls to 30-59 mL/min.
• Stage 4:  Severe kidney damage and GFR is very low at 15-29 mL/min. 
• Stage 5:  Kidney failure occurs and GFR is less than 15 mL/min.

The results of these tests are called clinical values.

Creatinine - a waste product made by the muscles. It is usually removed from the blood by the kidneys and passes out in the urine. When the kidneys aren’t working well, creatinine stays in the blood. The normal level for blood or serum creatinine is less than 120μmol/L for males and 90μmol/L for females. A blood test helps to work out how quickly your kidneys remove or ‘clear’ creatinine from the blood. Creatinine is a good measure of kidney function as it does not change with diet. However it does vary with age, gender and body weight so is not an accurate way of measuring overall kidney function.

Glomerular filtration rate (GFR) - is the best measure of your kidney function and helps decide the stage of kidney disease. It shows how well your kidneys are cleaning the blood. GFR is reported in millilitres per minute. Your GFR is usually worked out from the results of the creatinine blood test with your age and gender. Your GFR helps the doctor plan your treatment. A normal GFR is greater than 90 mL/min. See eGFR fact sheet for more information.

Microalbuminuria - can mean that your kidneys are damaged so albumin, a kind of protein, leaks into the urine in very small or ‘micro’ amounts. Microalbumin in the urine is often an early warning of kidney disease but can also be present for other reasons. The level can be measured by a special urine test either on a single urine sample or timed urine collection. Normal values on this test are less than 15 to 30 mg/l. A microalbumin test should be done at least yearly if you have diabetes.

Proteinuria - occurs when there are abnormal levels of protein in the urine. Normally, protein is not removed when the kidneys filter waste from the blood. However, when the kidneys are damaged protein leaks through the damaged filters and leaves in the urine, along with the waste. The appearance of protein in the urine may be the first sign of an otherwise silent kidney condition.

Urea - is a waste product made by the body as it uses protein from the food you eat such as meat. You need protein for every day growth, building muscles and repairing tissue. If you have lost some kidney function, your kidneys may not be able to remove all the urea from your blood.

Potassium - is a mineral found in many foods. If your kidneys are healthy, they remove extra potassium from the blood. If your kidneys are damaged, the potassium level can rise and affect your heart. A low or high potassium level can cause an irregular heartbeat.

Percent of kidney function - is an estimate of the level that each kidney is working. A GFR of 100 millilitres per minute (mL/min) is in the normal range so it is useful to say that 100 mL/min is about equal to ‘100% kidney function’. A GFR of 30 mL/min could be called ‘30% kidney function’.

Haematuria - or blood in the urine occurs when red blood cells leak into the urine. It can turn urine a red or dark cola colour, which is visible to the eye or may only be found by a urine test, which is called microscopic haematuria. Blood in the urine is a common sign of urinary tract infections but can be the first sign of a problem with the kidneys or the bladder.