Kidney stones can develop in one or both kidneys and most often affect people aged 30 to 60.
They're quite common, with around three in 20 men and up to two in 20 women developing them at some stage of their lives.
The medical term for kidney stones is nephrolithiasis, and if they cause severe pain it's known as renal colic.
Symptoms of kidney stones
Small kidney stones may go undetected and be passed out painlessly in the urine. But it's fairly common for a stone to block part of the urinary system, such as the:
- ureter – the tube connecting the kidney to the bladder
- urethra – the tube urine passes through on its way out of the body
A blockage can cause severe pain in the abdomen or groin and sometimes causes a urinary tract infection (UTI) ↗.
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, if you're taking some types of medication, or if you 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 when you go to the toilet (in the urine). This means it will often travel through the urinary system (the kidneys, kidney tubes and bladder).
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 using ultrasound or laser energy. Occasionally, keyhole surgery may be needed to remove very large kidney stones directly.
Read more about treating kidney stones ↗.
It's 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 every day so you don't become dehydrated ↗. It's very important to keep your urine diluted (clear) to prevent waste products forming into kidney stones.
Read more about preventing kidney stones ↗.
The kidneys are two bean-shaped organs that are roughly 10cm (four inches) in length. They're located towards the back of the abdomen on either side of the spine.
The kidneys remove waste products from the blood. The clean blood is then transferred back into the body and the waste products are passed out of the body in your urine when you go to the toilet.