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Kidney Stones (cont.)

There is no consensus as to why kidney stones form.

Heredity: Some people are more susceptible to forming kidney stones, and heredity may play a role. The majority of kidney stones are made of calcium, and hypercalciuria (high levels of calcium in the urine) is a risk factor. The predisposition to high levels of calcium in the urine may be passed on from generation to generation. Some rare hereditary diseases also predispose some people to form kidney stones. Examples include people with renal tubular acidosis and people with problems metabolizing a variety of chemicals including cystine (an amino acid), oxalate, (a type of salt), and uric acid (as in gout).

Geographical location: There may be a geographic predisposition to form kidney stones. There are regional "stone belts," with people living in the southern United States, having an increased risk of stone formation. The hot climate and poor fluid intake may cause people to be relatively dehydrated, with their urine becoming more concentrated and allowing chemicals to come in closer contact to form the nidus, or beginning, of a stone.

Diet: Diet may or may not be an issue. If a person is susceptible to forming stones, then foods high in calcium may increase the risk; however, if a person isn't susceptible to forming stones, diet will not change that risk.

Medications: People taking diuretics (or "water pills") and those who consume excess calcium-containing antacids can increase the amount of calcium in their urine and potentially increase their risk of forming stones. Taking excess amounts of vitamins A and D are also associated with higher levels of calcium in the urine. Patients with HIV who take the medication indinavir (Crixivan) can form indinavir stones. Other commonly prescribed medications associated with stone formation include dilantin and antibiotics like ceftriaxone (Rocephin) and ciprofloxacin (Cipro).

Underlying illnesses: Some chronic illnesses are associated with kidney stone formation, including cystic fibrosis, renal tubular acidosis, and inflammatory bowel disease.