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Kidney stones

This factsheet is for people who develop kidney stones and those who want to know more about them.

Kidney stones are hard, stone-like masses that can form in one or both kidneys. They are usually painless when in the kidney but can cause severe pain as they travel from the kidneys to the bladder. An attack of this pain is called renal or uteric colic.

What are kidney stones?

Most people have two kidneys, which "clean" the blood. They filter out water and waste products, making urine.

Kidney stones are small, solid masses that form when salts or minerals normally found in urine become solid crystals (crystallise) inside the kidney. In most cases, the crystals are too tiny to be noticed, and pass harmlessly out of your body. However, they can build up inside your kidney and form much larger stones.

If a stone becomes large enough, it may begin to move out of your kidney and progress through the ureters - the tubes that carry urine from the kidney to your bladder.

If it gets stuck in the ureter, this can cause an infection which can lead to permanent kidney damage.

Depending on where they are located, kidney stones are also known as renal calculi, urinary calculi, urinary tract stone disease, nephrolithiasis, urolithiasis and ureterolithiasis.

Illustration of the urinary system

Illustration of the urinary system

What are the symptoms?

Many kidney stones don't move and are too small to cause any symptoms. However, if a kidney stone causes a blockage, or moves into the ureter, it may cause some of the following symptoms:

These can also be symptoms of a urinary tract infection, or cystitis, which is much more common than kidney stones in young women. If you have one or more of these symptoms you should seek medical advice.

Kidney stones are usually passed out of the body within 48 hours, but attacks can sometimes last for over 30 days.

What causes kidney stones?

In most people the underlying cause isn't known. Some people with kidney stones have lower levels of citrate in their urine, which usually stops the stones forming.

Different kinds of kidney stones form from different salts in the urine.

Calcium stones are the most common type of kidney stone. They are either spiky or large and smooth, and are made up of calcium oxalate or calcium phosphate.

Calcium stones are more common in people who have excess levels of vitamin D or who have an overactive parathyroid gland. People who have medical conditions such as cancer, some kidney diseases, or a disease called sarcoidosis are also more likely to develop calcium stones.

Uric acid stones are smooth, brown and soft. Excess amounts of uric acid can be caused by eating a lot of meat. Conditions such as gout and treatments such as chemotherapy can also increase the risk of getting uric acid stones.

Struvite stones (infection stones) are usually large and have a horn-like shape. They develop when there is too much ammonia in the urine. This can happen if you have a urinary tract infection (UTI), because the bacteria that cause these infections can generate ammonia. This kind of kidney stone is most often found in women.

Cystine stones are yellow and crystalline. They develop if you have high levels of cystine in your urine, which happens if you have a hereditary disorder called cystinuria. Only one in a hundred kidney stones are caused by this condition. Cystine stones tend to develop earlier in life than other kidney stones, usually between the ages of 10 and 30 years.

Who gets kidney stones?

Men are more prone than women, and around half of all people who have previously had a kidney stone will develop another one within five years.

Other risk factors include:

How are kidney stones diagnosed?

Doctors can usually diagnose kidney stones by asking about your symptoms and examining you. Further tests may be done to confirm the diagnosis and to reveal the size, location and type of stone. These include:

How are kidney stones treated?

Treatment depends on the type and cause of the stone. Most stones can be treated without surgery. Drinking lots of water (two and a half to three litres per day) and staying physically active are often enough to move stones smaller than about five millimetres out of your body. You may be prescribed paracetamol or codeine to reduce the pain.

Your doctor may ask you to catch the kidney stone by passing your urine through filter paper or a tea strainer. The stone can then be analysed to find out what type it is to help guide your treatment.

However, if there is an infection, a blockage, or a risk of kidney damage, you will receive treatment to remove your stone. Infections can be treated with antibiotics. Stones that are stuck can be removed in several ways:

Extracorporeal shock wave lithotripsy (ESWL)

This is the most common method of dealing with kidney stones. The kidney stone is located using X-ray imaging or ultrasound scanning. While you are lying down, a machine called a lithotriptor sends targeted shock waves to break up the kidney stone into crystals small enough to be passed in your urine. You may feel some pain as the stone breaks up, so the procedure is usually performed under local anaesthesia.

Ureteroscopic stone removal

If a stone is lodged in the ureter, a narrow, flexible instrument called a cystoscope can be passed up through the urethra and bladder. The stone is captured and removed, or broken up with a laser beam or shock waves generated by a device attached at the end of the cytoscope. This procedure is usually done under a general anaesthetic.

Percutaneous nephrolithotomy (PCNL)

Large stones can be surgically removed from the kidney. The surgeon makes a small cut in your back and uses a telescopic instrument called a nephroscope to pull the stone out or break it up with shock waves or a laser.

PCNL is performed under general anesthesia. This can temporarily affect your co-ordination and reasoning skills, so you should not drive, drink alcohol, operate machinery or sign legal documents for 48 hours afterwards. If you are in any doubt about driving, please contact your motor insurer so that you are aware of their recommendations, and always follow your doctor's advice.

Prevention

To help prevent any type of kidney stone you should drink more fluid. You should aim to drink at least three litres every 24 hours, or enough to make your urine clear rather than a yellow colour. Talk to your doctor for more advice on this.

It used to be thought that reducing the amount of calcium in your diet would lower the risk of developing calcium stones. However, research has shown that a diet containing normal or even increased amounts of calcium containing food (such as dairy products or green leafed vegetables) may be more helpful.

If you get calcium oxalate stones, cut down on foods that have high levels of oxalate - chocolate, tea, rhubarb, cooked spinach and asparagus.

If you get uric acid stones you should eat less meat, fish and poultry, and your doctor may prescribe medicine to help reduce the level of uric acid in your urine.

You should discuss dietary changes with your doctor as they are not appropriate for everyone.

If you get cystine stones, your doctor may prescribe medicines to reduce the chance of the stones forming.

If you develop struvite or "infection" stones your urine must be kept free of the bacteria that are causing the infection. This may mean taking long-term antibiotics.

Further information

Search for "kidney stones" on healthinsite.gov.au

Sources

The information on this factsheet is intended to be a guide only and is not intended to be nor should be relied on as a substitute for professional medical advice. It is also not intended to be for medical diagnosis or treatment. BUPA Australia makes no warranties or representations regarding the quality, accuracy or completeness of the information. BUPA Australia is not liable to readers of the information for any loss or damage suffered arising out of the use of or reliance on the information, except that which can be excluded by law.