What Are Kidney Stones?

Kidney stones, or renal calculi, are solid masses made of crystals. Kidney stones originate in your kidneys, but can be found at any point in your urinary tract. The urinary tract includes the kidneys, ureters, bladder, and urethra.

Types of Kidney Stones

Not all kidney stones are made up of the same crystals. The different types of kidney stones include:

Calcium

Calcium stones are the most common. They can be made of calcium oxalate (most common), phosphate, or maleate. Vitamin C and spinach contain oxalate. Calcium-based kidney stones are most commonly seen in young men between the ages of 20 and 30.

Uric Acid

This type of kidney stone is more common in men than in women. They can occur in people with gout or those going through chemotherapy.

Struvite

This type of stone is found mostly in women with urinary tract infection. These stones can be quite large and cause urinary obstruction.

Cystine

Cystine stones are rare. They occur in both men and women who have the genetic disorder cystinuria.

Other

Medications like triamterene and acyclovir also can cause stones.

Risk Factors for Kidney Stones

The greatest risk factor for developing kidney stones is making less than one liter of urine per day. This why they are frequently seen in premature infants, who tend to have kidney problems. However, kidney stones are most likely to occur between the ages of 20 and 40.