Medical Edge Newspaper Column

When Organs Form Stones

August 5, 2007
Dear Mayo Clinic:
Will calcium or Fosamax cause gallstones or kidney stones? Will drinking enough water flush the stones out? -- Homewood, Ill.

Answer:
Calcium supplements and the drug Fosamax (generic name: alendronate) are usually prescribed to prevent or treat osteoporosis, in which loss of calcium and other minerals from the bones render them porous, weak and brittle.

Given the mechanism behind this condition, it makes sense that consuming extra calcium -- through diet, pills or both -- can curb the progression of osteoporosis in patients who already have it and help prevent it among those who don't. Calcium has a tendency to form kidney stones, however, which increases as the daily intake rises. Therefore most doctors recommend limiting calcium consumption to 1,200 milligrams per day for the average person over age 50, and 1,500 mg for patients with osteoporosis. Although different individuals have different thresholds of calcium intake that initiate kidney-stone formation, these limits work well for most people.

Fosamax, a member of the chemical class of drugs called bisphosphonates, prevents osteoporosis through an altogether different mechanism. By inhibiting bone breakdown, bisphosphonates help preserve bone mass. And because they contain no calcium or other stone precursors, these drugs have no known connection to the formation of kidney stones.

Fosamax is not without side effects, however. Most common is gastrointestinal (GI) irritation -- heartburn or stomach upset, for example -- which occurs in patients to varying degrees. Taking Fosamax with meals is not an option, because the medication will bind tightly to calcium and phosphorus in the food, thereby preventing its absorption. Although GI irritation is sometimes severe enough for a patient to discontinue the drug, most people have little problem if they take it as directed.

Calcium has its side effects, as well. In addition to increasing the tendency to form kidney stones, it too might cause GI irritation. It can also result in constipation, though some forms -- calcium citrate and calcium phosphate -- are considered less likely to do so than the more common calcium carbonate.

Kidney stones begin forming when the concentration in urine of certain materials -- most often calcium, but also oxalate, phosphorus, and certain organic compounds -- becomes high enough to form small crystals. If such levels are sustained, crystals may grow or combine over time to form small hard masses, or stones. Most kidney stones eventually pass into the bladder without causing permanent damage, though their passage can be painful.

The best way to prevent kidney stones, or to reduce their size or possibly help them dissolve (often referred to as "flushing out"), is to drink lots of fluids -- usually at least 6 to 8 glasses a day, and in some cases as many as 12 glasses a day. Hearing this, people sometimes imagine lining up the glasses of water and quaffing them all in short order -- a daunting, even dangerous, prospect. What's most important here is increased fluid intake over the course of the day, and just about any fluid will do -- including coffee, tea, or soft drinks -- although about half of this intake should be water. Such intake dilutes the urine, preventing the high mineral concentrations that could otherwise lead to kidney stones.

There's no self-help preventive option like this for gallstones, which begin forming when the bile stored in the gallbladder becomes chemically unbalanced, causing it to form hardened particles consisting most often of cholesterol. Calcium and Fosamax have no effect on this process, and gallstones cannot be flushed out with increased fluid intake. Certain individuals simply make bile with a tendency to form gallstones, and there is nothing they can do to prevent them. It's best to be alert to gallstone symptoms, which typically occur intermittently, most often after large or fat-rich meals. These symptoms include indigestion, cramping pain in the upper-middle to upper-right abdomen, and, occasionally, nausea and vomiting.

Medications can sometimes dissolve gallstones, without requiring surgery. But for many people with gallstones that cause symptoms, removing the gallbladder is the preferred treatment. Elective gallbladder removal is among the most common surgeries performed in the United States.

-- Bart Clarke, M.D., Endocrinology, Mayo Clinic, Rochester, Minn.