A kidney stone is a hard deposit made of minerals and salts that forms inside the kidney. Some stones are as small as a grain of sand and pass without being noticed. Others grow larger and can block the flow of urine, which causes pain.
How stones form
Urine contains many dissolved minerals. When there is too little water or too much of certain minerals, they can stick together and slowly form crystals. Over time the crystals can grow into a stone.
Common factors that raise the risk
- Not drinking enough fluid, which makes urine concentrated.
- Diet, for example a diet very high in salt or in animal protein.
- Family history of kidney stones.
- Medical conditions that change how the body handles minerals.
- Some medicines and supplements.
- Being overweight and certain metabolic conditions.
- Repeated urinary infections, which can lead to some types of stones.
Symptoms to watch for
- Severe pain in the side or back that may spread toward the lower abdomen or groin
- Blood in the urine
- Burning or a frequent urge to pass urine
- Nausea or vomiting
Not every stone causes symptoms, and the type of stone matters. That is why the stone is often analysed, and why a doctor may suggest tests to understand what caused it.
When to get help
See a doctor if you have severe flank pain, blood in the urine, or recurrent stones. Seek urgent care if the pain comes with fever, or if you are unable to pass urine.
This article is for general educational purposes and is not a substitute for professional medical consultation, diagnosis or treatment. Treatment recommendations depend on each person’s clinical condition and medical evaluation.
