Kidney Stones Causes, Symptoms and Treatment

What Are the Kidneys?

Part of the urinary system, your two kidneys are fist-sized, bean-shaped organs, located just below the rib cage, one on each side of the spine.

They have a number of important functions, mainly filtering the blood to remove waste and excess water, resulting in the formation of urine, which is stored in the bladder and emptied from the body through the urethra.

The kidneys also:

  • Balance the body’s levels of electrolytes, including sodium, potassium, and phosphate, to maintain the body’s balance of acids and bases
  • Produce hormones involved in regulating blood pressure, producing red blood cells, and maintaining bone strength
  • Prevent the buildup of waste and fluid in the body

Development of Kidney Stones

Kidney stones develop when the concentration of normal kidney substances (especially calcium, oxalate, and phosphorus) increases substantially.

This process — sometimes known as nephrolithiasis — can be due to various factors, including low fluid intake, diet, or medications such as diuretics and calcium-based antacids.

A number of issues can increase a person’s risk of developing kidney stones, including:

  • A family history of kidney stones
  • Medical conditions that affect the levels of urinary substances
  • Urinary tract blockage
  • Digestive problems
  • Recurrent urinary tract infections

Types of Kidney Stones

There are four main types of kidney stones: calcium, uric acid, struvite, and cystine stones.

Calcium stones, of which there are two forms — calcium oxalate and calcium phosphate — are the most common type of kidney stone.

In most cases, calcium oxalate stones form from high levels of calcium and oxalate in urine.

But if there are high levels of urine calcium and the urine is alkaline (has a high pH), calcium phosphate stones may form instead.

Uric acid stones develop from overly acidic (low pH) urine.

This can result from a diet high in purines, substances that are broken down to form uric acid and are found in high concentrations in animal protein.

Struvite stones, sometimes called infection stones, are made of magnesium, ammonium, and phosphate, and typically form in alkaline urine.

They develop from upper urinary tract infections, including kidney infections, when bacteria produce urease, an enzyme that helps convert urea (a compound in urine) into ammonia and other products.

Cystine stones result from a genetic disorder that causes cystine, an amino acid, to leak into the urine from the kidneys.


  • The Kidneys and How They Work; National Kidney and Urologic Diseases Information Clearinghouse (NKUDIC).
  • What I Need to Know About Kidney Stones; NKUDIC.
  • Kidney Stones in Adults; NKUDIC.
  • Scales et al. (2012). “Prevalence of kidney stones in the United States.” European Urology.
  • Kidney stones; MedlinePlus/NIH.