Kidney stones are small, hard crystalline lumps that can form in the kidneys. They can then travel to other parts of the urinary system blocking the flow of urine, and can cause infection and kidney damage. They can also be very painful.

What causes kidney stones and who can have them?

It’s rare for a child to have a kidney stone. They are more usual in adults between the ages of 20-40.

There are several different reasons why kidney stones might develop in children. The most common cause is an infection of the urinary tract. In other cases, there are inherited problems that make the kidneys leak higher amounts of stone-forming substances, such as calcium, oxalate, uric acid or cysteine. Also some medical treatment such as chemotherapy can be involved.

In some patients, an underlying cause can’t be identified.

Doctors know that kidney stones are more likely to develop in people who don’t drink enough fluids. When the body is dehydrated, the kidneys concentrate the urine to ensure the body loses as little water as possible. This also increases the concentration of stone-forming substances and can lead to stone formation.

What are the signs and symptoms of a kidney stone?

Sometimes there are no clear symptoms. A stone that remains in the kidney and is small enough not to interfere with normal kidney function is called a ‘silent’ stone and many people never know they have one.

But if a stone interferes with normal flow of urine, or causes an infection, it can lead to symptoms including severe pain in the back or side, abdominal swelling, nausea and vomiting, fever and pain on passing urine and blood in the urine.

How is it normally diagnosed and treated?

A scan such as an X-ray or ultrasound scan can show the presence of most kidney stones. A CT scan typically shows the size and location of a stone very well.

Most stones are quite small and can pass out of the body in urine within a few days without the need for specific treatment. In some cases though the stone might be too big to be passed or may be causing damage or infection. There are several non-surgical treatment options including breaking the stone using a special machine that gives out shock waves and allows the stone to be passed normally in the urine. Sometimes though traditional surgery, making an incision (cut) in the kidney or ureter to remove the stone, may be the best option.

The best way to find out why a stone has developed is by having it analysed for its chemical composition. Therefore, if a stone is passed, it is very important to retrieve it, so your doctor can send it for analysis.

Can it be prevented?

Keeping well hydrated will help. Your doctor will advise you on how much water you should aim to drink. If investigations show that the kidneys are leaking too much stone-forming substances, a special diet or medication may be necessary.

For more help and information

• Children’s Kidney Trust
• Kidney Research
• The National Kidney Foundation

Last reviewed by Great Ormond Street Hospital: 10 January 2007

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