Kidney stones are stone-like lumps that can develop in one or both of the kidneys.

The medical name for stones in the kidneys is nephrolithiasis. If the stones cause severe pain, this is known as renal colic.

Symptoms of kidney stones

Small stones may be passed out painlessly in the urine and may even go undetected. However, it is fairly common for a stone to block part of the urinary system, such as:

• the ureter – the tube connecting the kidney to the bladder
• the urethra – the tube urine passes through out of the body

If this happens, it can cause severe pain in the abdomen or groin and sometimes causes a urinary tract infection.

Read more about the symptoms of kidney stones.

What causes kidney stones?

The waste products in the blood can occasionally form crystals that collect inside the kidneys. Over time, the crystals may build up to form a hard stone-like lump.

This is more likely to happen if you don't drink enough fluids, are taking some types of medication, or have a medical condition that raises the levels of certain substances in your urine.

Read more about the causes of kidney stones.

After a kidney stone has formed, your body will try to pass it out of the body in urine. This means it will often travel through the urinary system (the kidneys, kidney tubes and bladder).

How common are kidney stones?

Kidney stones are quite common and usually affect people aged 30 to 60 years. They affect men more than women.

It is estimated that renal colic affects about 10-20% of men and 3-5% of women. 

Treating and preventing kidney stones 

Most kidney stones are small enough to be passed in your urine, and it may be possible to treat the symptoms at home with medication.

Larger stones may need to be broken up with X-rays or ultrasound in hospital, or you may need to have them surgically removed.

Read more about the treatment of kidney stones.

It is estimated that up to half of all people who have had kidney stones will experience them again within the following five years.

To avoid getting kidney stones, make sure you drink plenty of water each day so that you don't become dehydrated. It is very important to keep your urine diluted to prevent waste products forming into kidney stones.

Read more about preventing kidney stones.