What Are Kidney Stones?

Diagram of Kidney with Kidney Stones

Kidney stones (also called nephrolithiasis, urolithiasis, or calculi) are small, hard mineral deposits that form inside your kidney and may affect any part of your urinary tract system.

If the kidney stone moves in location or causes blockage of the urinary system, it can cause acute, severe pain. Most kidney stones can be treated without surgery and they pass from the body, but if you experience persistent pain, urinary blockage or infection, it may be necessary to remove the urinary obstruction. In some cases, the stone is too big to pass from the body; these stones may also need to be surgically removed.

There are many different types of kidney stones, but the most common are:

  • Calcium stones (calcium oxalate, apatite, calcium phosphate, brushite) are the most common type and make up more than three-quarters of all kidney stones. These stones can form because of poor fluid intake, diet abnormalities, abnormalities in the kidneys filtration or pH regulatory mechanisms, bowel disorders, hyperparathyroidism, and genetic abnormalities.
  • Uric acid stones are the second most common type of stones. These stones are not visible on regular x-rays and can only be detected with a computed tomography (CT) scan or, in cases of large stones, with an ultrasound. These stones are associated with diet abnormalities and diabetes mellitus.
  • Struvite stones are made from bacteria and are associated with recurrent urinary tract infections.
  • Cystine stones form secondary to a rare genetic disorder called cystinuria, which causes the excretion of large amounts of amino acids in the urine and results in stone formation.
  • Drug-induced stones can form as a result of various different medications.

Who is affected by kidney stones?

Kidney stones affect nearly 10% of all people, and symptoms can range from none to highly painful, requiring a trip to the emergency department. The National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) estimates that about one million people in the United States are treated for kidney stones each year. Consider these NIDDK statistics:

  • White people are more prone to kidney stones than Black people.
  • Although stones occur more frequently in men, the number of women who develop kidney stones has been increasing.
  • Kidney stones most often strike people between age 20 and 40 but can affect people of any age.
  • Once someone develops more than one kidney stone, they are more likely to develop additional stones.
  • Patients with a kidney stone who have a family history of stone disease are at higher risk of developing more stones in the future.

Kidney Stones

Related Resources

  • Cystoscopy: A cystoscopy is done using a telescope-like instrument called a cystoscope.

  • Intravenous Pyelogram (IVP): An IVP is an X-ray test that uses a contrast agent to show the urinary system.