What causes kidney stones?
Doctors do not always know what causes a stone to form. While certain foods may promote stone formation in people who are susceptible, foodstuffs only contribute a small amount to the likelihood of forming stones.
More than 70% of people with a rare hereditary disease called renal tubular acidosis develop kidney stones. Cystinuria and hyperoxaluria are two other rare, inherited metabolic disorders that often cause kidney stones. In cystinuria, too much of the amino acid cystine, which does not dissolve in urine, is voided. This can lead to the formation of stones made of cystine. In patients with hyperoxaluria, the body produces too much of the salt oxalate.
When there is more oxalate than can be dissolved in the urine, the crystals settle out and form stones. A high concentration of calcium in the urine causes crystals of calcium oxalate or calcium phosphate to form in the kidneys or urinary tract. Other causes of kidney stones are hyperuricosuria (a disorder of uric acid metabolism), excess intake of vitamin D and blockage of the urinary tract. A high concentration of calcium may also lead to the patient developing gout.
Calcium oxalate stones may also form in people who have a chronic inflammation of the bowel or who have had an intestinal bypass operation, or ostomy surgery.