A Possible Defense Against Kidney Stones

For approximately 1 million Americans every year, kidney stones easily outrank childbirth, migraine headaches and other kinds of hurt for the booby prize of “most pain I’ve ever had.”

Now those victims have some good news-new research by scientists at the Washington University School of Medicine in St. Louis has yielded information to explain why some people are more likely to develop kidney stones than others. That’s critical to developing tests for kidney stone risk and effective treatments.

The research was conducted on mice and the results published in The EMBO Journal, (the European Molecular Biology Organization). Human kidney function is similar to mouse kidney function.

Most kidney stones form when minerals in urine, such as calcium, crystallize and stick together. Risk increases with a diet lacking sufficient water and/or too much salt, which binds to calcium; the risk of developing stones also increases with age.

But the identification of a genetic component has been linked to an increased risk of as much as 65 percent.

Normally, kidneys process essential minerals from blood for transport back to the cells that perform the basic functions of life. Typically, the gene of note, claudin-14, is not active in the kidney, and when it is, appears to be the source of the problem. The new research shows that it can be neutralized by specific molecules, thereby enabling the kidney’s filtering system to work as it’s designed.

When people eat a diet high in calcium or salt and don’t drink enough water, claudin-14 prevents the calcium from re-entering the bloodstream. The excess calcium is expressed in urine, which leads to the formation of stones in the kidneys or bladder. When a stone gets stuck in the bladder, ureter or urethra, it can block the flow of urine and cause intense, seeing-stars pain.

Drugs that mimic the activity of the molecules that “turn off” claudin-14 could significantly reduce the likelihood that people with this genetic makeup would form stones. And a test could be developed to measure levels of claudin-14 in urine. If they are elevated, dietary modifications would be the first line of defense against developing stones.

Until treatment catches up with science, you should ensure sufficient hydration to help prevent the formation of kidney stones. The amount required depends on an individual’s activity level and the climate. The National Institutes of Health say that different kinds of kidney stones require different dietary modification. In general:

• If you’ve had a kidney stone, drink enough water and other fluids to produce at least 2 quarts of urine a day (eating fruit with a high water content, such as melon, can boost your fluid intake).
• If you work or exercise in hot weather, drink more to replace fluids lost through sweat.
• Avoid grapefruit and cranberry juices and dark colas, which have been found to increase the risk of stone formation.
• Ask your doctor about eating protein. Meat (especially organ meat such as liver), eggs and fish contain substances that break down into uric acid in the urine. Nonanimal protein (nuts, beans, etc.) can increase the excretion of calcium. Both encourage stone formation in some people.