What causes kidney stones?

What are kidney stones?

Kidney stones are hard lumps that form inside the kidneys when certain substances in urine become too concentrated. They can vary in size from tiny grains to stones that are large enough to cause serious pain.

Many people in the UK will experience a kidney stone at some point in their lives. Some stones pass out of the body without treatment, while others may need medical help.

What causes kidney stones to form?

Kidney stones usually develop when urine contains too much stone-forming material and not enough fluid. The most common substances involved are calcium, oxalate, uric acid and cystine.

When these substances build up, they can join together to form crystals. Over time, the crystals can grow into larger stones.

Dehydration and low fluid intake

Not drinking enough fluids is one of the biggest risk factors for kidney stones. If urine becomes too concentrated, it is easier for minerals to clump together.

This can be more likely during hot weather, after heavy exercise, or if someone does not drink regularly throughout the day. Pale urine is often a sign that you are well hydrated.

Diet and lifestyle factors

Diet can play a role in some cases. A high intake of salt, animal protein and foods rich in oxalate, such as spinach, may increase the risk for some people.

Being overweight and not getting enough physical activity may also make kidney stones more likely. A balanced diet and healthy lifestyle can help lower the chances of developing them.

Medical conditions and family history

Some people are more prone to kidney stones because of underlying health conditions. These can include gout, inflammatory bowel disease, recurrent urinary infections and some metabolic disorders.

Family history also matters. If a close relative has had kidney stones, your own risk may be higher.

How kidney stones can be linked to medications

Certain medicines can increase the risk of stones in some people. These may include some diuretics, antacids containing calcium, and certain treatments used for conditions such as HIV or epilepsy.

This does not mean these medicines should be stopped without advice. If you are concerned, speak to a GP or pharmacist before making any changes.

Can kidney stones be prevented?

Drinking enough water is one of the best ways to reduce your risk. Most people should aim to pass pale urine during the day, although individual needs can vary.

It may also help to cut down on salt, keep a healthy weight and follow any dietary advice given by your doctor. If you have had a stone before, you may be offered tests to find out why it happened.