What are the causes of kidney stones?
The kidneys filter the blood and remove excess water and waste chemicals to produce urine. Urine travels from each kidney down the tube (the ureter) draining urine from the kidney into the bladder. This is called the urinary tract.
Many waste chemicals are dissolved in the urine. The chemicals sometimes form tiny crystals in the urine which clump together to form a small stone. Most kidney stones are small and pass out with the urine. Some stones become stuck in a kidney or in the ureter.
In most cases, there is no known reason why a stone is formed. Most stones are made of calcium. However, in most cases, the amount of calcium and other chemicals in the urine and blood is normal.
What makes stones more likely?
You are more likely to form a stone if your urine is concentrated. For example, if you exercise vigorously, if you live in a hot climate or if you work in a hot environment when you may lose more fluid as sweat and less as urine.
You are also more prone to develop kidney stones if you have:
- Repeated (recurrent) urine infections.
- Repeated (recurrent) kidney infections.
- An abnormal kidney - for example, with scars or cysts on it.
- A close relative who has had a kidney stone.
Underlying causes are uncommon
In a small number of cases, a medical condition causes the kidney stone. Various uncommon conditions can lead to high levels of chemicals in the body, such as calcium, oxalate, uric acid and cystine. If the level of these chemicals is high enough in the urine, they can form into stones.
Do some medicines make kidney stones more likely?
Taking certain medicines can make you more prone to making kidney stones. Examples include:
However, many people safely take these medicines without developing kidney stones. If you think that a medicine you are taking is the cause of your kidney stone, you should not stop taking the medicine but discuss it with your doctor.
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Further reading & references
- Guidelines on Urolithiasis; European Association of Urology (2015)
- CUA guideline on the evaluation and medical management of the kidney stone patient; Canadian Urological Association (November 2016)
- Guidelines for acute management of first presentation of renal/ureteric lithiasis (excluding pregnancy); British Association of Urological Surgeons (February 2012)
- Renal or ureteric colic - acute; NICE CKS, April 2015 (UK access only)
- Macneil F, Bariol S; Urinary stone disease - assessment and management. Aust Fam Physician. 2011 Oct 40(10):772-5.
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