The percentage of Americans who experience kidney stones has been on the rise since the 1970s, an increase primarily attributed to food choices. Now, about 1 in 10 people will get a kidney stone in their lifetime, but making dietary changes can reduce that risk.
Drinking plenty of water, limiting salt intake and losing weight, if overweight, are among the best ways to prevent kidney stones. Consuming enough calcium and limiting intake of animal protein also can help. Consuming high amounts of beets, chocolate, spinach, rhubarb, tea and most nuts is known to increase risk.
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The National Kidney Foundation says it also is important to avoid extra calcium supplements and high doses of vitamin C supplements. More specific dietary guidelines, however, depend on the type of stone one is trying to prevent from forming.
What are kidney stones made of?
Kidney stones form when substances in the urine combine and crystallize because there is not enough urine volume. These hard deposits are painful to pass and sometimes require medical intervention. They are often the source of recurrent urinary tract infections.
The prevalence of kidney stones in the U.S. increased from 3.8% in the late 1970s to 10% in mid-2010s, according to the National Kidney Foundation. About 11% of men and 9% of women now have kidney stones at least once during their lifetimes.
Recurring kidney stones are of particular concern because they increase the risk of chronic kidney disease. After a person has a kidney stone, the risk of having another within the next five to seven years increased by 50%.
The most common types of kidney stones are calcium oxalate, calcium phosphate and uric acid stones. Calcium oxalate stones occur when calcium and oxalate combine together in the urine. This typically occurs when a person has high amounts of oxalate and low amounts of calcium, and is not drinking enough fluids.
People who get calcium oxalate kidney stones are advised to eat a diet higher in calcium and lower in oxalates. Foods that are high in calcium include cow's milk, yogurt, cheese, broccoli, kale, dried beans, salmon and calcium-fortified juices and cereals. Foods that are high in oxalates – which should be reduced – include spinach, rhubarb, strawberries, tea, dried peans and beans, nuts, nut butters and wheat bran.
It is important to remember that calcium is not the main cause of calcium oxalate stones, according to the National Kidney Foundation. A diet low in calcium actually increases the risk of developing a kidney stone.
Uric acid kidney stones form when there is a buildup of purine, a byproduct of animal proteins in the urine. To prevent uric acid stones, people should consume less red meat, alcoholic beverages, sugar-sweetened beverages, meat-based gravies, sardines, anchovies and shellfish. Instead, their diets should mostly include vegetables, fruits, whole grains and low-fat dairy products.
Other less common chemicals that can form stones include cystine, struvite and xanthine. Cystine stones occur to people with Cystinuria, a hereditary disorder that causes the kidneys to excrete too much of a certain chemical. Struvite stones are formed in response to a urinary tract infection. They can grow quickly, with very few warning symptoms. Xanthine stones are the result of Xanthinuria, a rare hereditary disorder that causes excess xanthine to accumulate in the kidneys.
Certain medications can help prevent kidney stones. Potassium citrates prevent uric acid stones and thiazide diuretics, such as hydrochlorothiazide, reduce calcium in the urine.
A recent study suggests that thiazide diuretics actually don't work any better than a placebo at preventing painful kidney stones. But because of the study's small patient population and the way it was designed, many experts say more research is needed before patients should be advised to stop taking these pills.
Treating kidney stones
Kidney stones can be as small as a grain of sand or as large as a golf ball. Symptoms include pain in the back or side, blood in the urine, nausea or vomiting, feeling the need to urinate more often or not being able to urinate at all, having urine that smells bad or looks cloudy, and fevers or chills.
Drinking lots of water can help the body pass a stone. But sometimes a large kidney stone gets trapped in the ureter, the tube between the kidney and the bladder. When this happens, it can cause bleeding and block urine from leaving the body. In cases like this, surgery will likely be needed.
Smaller kidney stones often don't need treatment and can pass through the urinary tract system. When the stones are bigger and won't pass on their own, people may need medications to decrease pain and other symptoms and to relax their ureters. Surgery may be necessary to break down the stones and to retrieve them.
It is possible to have kidney stones for years and not know it. They usually cause symptoms when they leave the kidneys. For some people though, kidney stones can develop pretty quickly.
Kidney stones can be diagnosed through imaging tests such as X-rays, CT scans and ultrasounds, as well as blood and urine tests.
Kidney stones are most common in white men in their 30s and 40s, but they can happen to anyone at any age and sometimes run in families.
The most common risk factors include not drinking enough liquids, consuming a diet high in the minerals that form the stones, having a family history, having a blockage in the urinary tract or having a medical condition that increases the risk.
Medical conditions linked to an increased risk for kidney stones include having high calcium levels in the urine, high blood pressure, diabetes, obesity, osteoporosis, gout, cystic fibrosis, parathyroid disease and inflammatory bowel disease.
Weight loss surgery or other procedures on the stomach or intestines can increase a patient's risk, too. So can certain medications, such as the calcium-based antacids used to treat osteoporosis, certain antibiotics, and certain HIV and seizure drugs.