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Overview of kidney stones

Kidney (renal) stones are a common and painful medical problem. They happen when there are too many crystals in your urine, which stick together and form hard stones.

These stones can be as small as a grain of rice or as large as an apple. They can happen anywhere in your urinary system, such as your kidneys, one of the tubes that drain urine from your kidneys (called your ureters) or your bladder.

Causes of kidney stones

urinary system showing kidneys, ureters, bladder, and urethraThere are several reasons why you might get kidney stones.

Kidneys stones are usually caused by a combination of factors.

Some kidney stones happen because you have high levels of chemicals such as calcium, uric acid or oxalate in your blood. These lead to different types of kidney stones such as:

Calcium stones

Calcium stones are the commonest type. They happen if you have a lot of calcium in your blood. You're more likely to get calcium stones if you don't drink enough fluid and you eat a lot of salt. See Eating to prevent kidney stones for information about eating to reduce your risk of getting kidney stones.

Uric acid stones

These stones are more common in men than in women. They happen because your urine is too acidic and there's a lot of uric acid in your blood. You're more likely to get uric acid stones if you don't drink enough fluid and you eat a lot of fish and red meat, especially offal meats such as liver, kidney and brains.

Struvite stones

These are slightly more common in women who get repeated urine infections. They're made up of magnesium, ammonium and phosphate.

Symptoms of kidney stones

Some people have no symptoms or mild symptoms such as aching in their lower back and urine infections. Sometimes the stones are found by chance when having an X-ray or scan for another reason.

If the stone moves from your kidney towards your bladder, you can get severe pain. You can also feel like you need to pass urine more often.

Sometimes people can pass kidney stones in their urine and have no or few symptoms. But kidney stones can get stuck and cause a blockage. This is called renal colic and can be very painful.

The symptoms of renal colic include:

If you have any of these symptoms, see your GP or after-hours healthcare provider as soon as possible for tests and pain relief. If you're very unwell, you may need to go to hospital.

Diagnosing kidney stones

If your doctor thinks you might have kidney stones, they will ask you about your symptoms and do a physical examination. They may then ask you to have some tests. These include:

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On the next page: Treating kidney stones

Written by HealthInfo clinical advisers. Endorsed by clinical director, Nephrology Department, Canterbury DHB. Last reviewed November 2019.


Page reference: 694506

Review key: HIKIS-19017