What Causes Kidney Stones?
It isn't exactly clear what causes kidney stones to form in some people and not others. Usually it requires concentrated urine that allows minerals like calcium to come in close contact with each other. Changes in the acid-base balance (pH) of the urine, how concentrated it is, and the concentration of minerals and chemicals within the urine are all factors that can begin the formation of a stone.
Crystals can form the beginning of the stone and eventually grow large enough to cause problems. Concentrated urine often occurs during an episode of dehydration, setting the stage for the beginning of stone formation. The consequences of that stone, when it is large enough to cause an obstruction, may occur weeks, months, or years later.
Who Is at Risk for Kidney Stones?
More than 80% of patients with kidney stones are men.
There is a genetic component as well, and stone formers run in families, especially when it comes to difficulties metabolizing chemicals like cysteine, oxalate, and uric acid.
Geographically, there are "stone belts" in the United States and geography may play a part forming stones. There are both northern and southern belts. In the south, the hot climate may cause relative dehydration, especially in patients who do not drink enough fluids.
Excess vitamin D may be associated with increased risk of calcium kidney stones, but high calcium diets may or may not be a risk factor. In patients who are susceptible to forming stones, increased calcium in the diet may increase the frequency and number of stones formed.
Underlying medical conditions can be associated with stone formation including renal tubular acidosis, medullary sponge kidney, inflammatory bowel disease, cystic fibrosis, and hyperparathyroidism (a hormonal condition causing high levels of calcium in the bloodstream).
Can Medication Cause Kidney Stones?
Certain medications have been implicated in kidney stone formation. Patients taking diuretics or water pills increase calcium concentration in their urine. Patients who take calcium containing antacids and calcium supplements also increase their urinary calcium. Other medications associated with increased risk of stone formation include phenytoin (Dilantin), ceftriaxone (Rocephin), and ciprofloxacin (Cipro).
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Tintinalli, J. E., et al. Tintinalli's Emergency Medicine: A Comprehensive Study Guide. 7th ed. McGraw-Hill Professional, 2010.