Every year, more than 3 million unlucky people head to the doctor to be diagnosed with a kidney stone when a pebblelike formation travels down the urinary tract. Since the beginning of civilization, humans have been plagued by this painful condition. In fact, scientists have discovered evidence of kidney stones in a 7,000-year-old Egyptian mummy.

Today, 10 percent of men and 5 percent of women will experience a kidney stone (also known as renal lithiasis) by the age of 70. Like the filter in an aquarium, the kidneys filter out waste from the blood. As a result, small, hard deposits of minerals and acid salts eventually accumulate on the surfaces of the kidneys. These substances typically dissolve in urine, but when the urine is concentrated—due to dehydration or some other reason—they may stick together to form a hard mass.

Ranging in size from a grain of sand to a golf ball, kidney stones don’t have any symptoms when they remain in the kidney. But when they travel through the urinary tract, severe pain and nausea occur. In the majority of cases, kidney stones will pass on their own after a few days or even weeks. But about 15 percent of cases require treatment, such as extracorporeal shock wave lithotripsy, in which shock waves are used to break the stone into smaller pieces. Doctors can also remove the stone in a minimally invasive procedure or insert a small stent to keep the passage open.

Experts aren’t exactly sure what causes kidney stones to form, but they know that a family history of the disease increases a person’s chances of suffering from it. Gout, high levels of uric acid or calcium, oxalosis (an excess of a substance called oxalate in the body), high blood pressure, and obesity also raise the odds. Dehydration and a diet that’s high in protein and sodium are risk factors as well.

ADDITIONAL FACTS

  1. Global warming has another unexpected side effect: Scientists say that the increasing temperatures will result in a jump in the number of people with kidney stones. That’s because the heat will lead to dehydration, a risk factor for the condition.
  2. Some people are susceptible to kidney stones that are made up mainly of calcium that binds to a chemical called oxalate. In these instances, doctors may recommend cutting back on foods high in oxalate, which include spinach, chocolate, and black tea.