Do different types of kidney stones have different causes?

Although insolubility/supersaturation is the root cause of all kidney stones, the specific cause depends on the composition of the stones.

Calcium stones, which are the most common, form when calcium combines with oxalate or phosphate to form stones. The tendency for this to occur depends on factors that affect the composition and concentration of these substances in the urine.

Cystine kidney stones can occur in people who have cystinuria, a genetic condition that increases the amount of the amino acid cysteine in the urine.^[1]

Uric acid kidney stones usually occur under conditions that affect uric acid levels in the urine, such as hyperuricemia (high uric acid levels in the blood) or chemotherapy.^[2][3] Uric acid stones may also form if the urine becomes highly acidic, with a common cause being chronic diarrhea.

Struvite, which is a salt composed of magnesium ammonium phosphate, can also form kidney stones, which are frequently associated with urinary tract infections.^[4]

Certain medications with poor solubility or medications that are metabolized into low-solubility metabolites may also form supersaturated solutions in the urine, leading to stone formation. An example of medications linked to kidney stones is the protease inhibitors indinavir and atazanavir, which are prone to crystallization and stone formation.^[5][6]

Kidney stones can also be caused by foods or supplements with low-solubility contaminants, such as melamine. Melamine may be present in nutritional supplements in particular, where it has been used as an additive to fraudulently increase the measured protein content.^[7][8] In China, melamine present in infant formula caused a crisis in 2008, resulting in the development of kidney stones in a few hundred thousand infants, many of whom required hospitalization, resulting in 6 fatalities.^[9]