POST TIME: 4 November, 2019 00:00 00 AM
What causes kidney stones?
Whatever your risk factors, it's a good idea to do what you can to reduce your chances of developing kidney stones. One of the best things you can do is drink plenty of water. "One of the best treatments to prevent kidney stones is adequate hydration," Borofsky says
U.S.News & World Report

What causes kidney stones?


Kidney stones are among the most painful medical conditions you can experience, experts and patients agree. Typically made of calcium, kidney stones are hard pellets formed by excess minerals and salts inside the kidney. If they travel out of the kidney and into the ureter, they can block the flow of urine, causing the kidney to swell. This creates surges of acute pain in the mid-back, abdomen and sides. For men, it can cause severe pain at their penis.

There's no one factor that causes kidney stones in most patients, says Dr. James Simon, a nephrologist in the Glickman Urological & Kidney Institute at Cleveland Clinic. "While there are some causes that can be pinpointed and treated in some patients, in the majority of people with kidney stones, we do not find a single cause," Simon says.

Kidneys are bean-shaped organs located on each side of your spine, right below the rib cage, according to the National Institute of Diabetes and Digestive and Kidney Diseases. Healthy, well-functioning kidneys filter about a half-cup of blood every minute, filtering wastes and excess water to make urine. Urine flows from the kidneys to the bladder through two thin tubes called ureters.

Types of kidney stones

There are several different kinds of kidney stones, and some are more common than others. Calcium stones and uric acid stones are among the most common types of kidney stones, Simon says. Other types of kidney stones include struvite stones, which are typically caused by a bacterial infection that raises the urine pH level to neutral or alkaline, and cystine stones, which are associated with a genetic condition, according to Harvard Health.

More men than women develop kidney stones, says Dr. Sean Nordt, an associate dean of academic affairs and endowed professor of pharmacy at the Chapman University School of Pharmacy in Irvine, California. He's also an adjunct associate professor of emergency medicine at UC Irvine in Orange, California and an emergency room physician at UC Irvine Medical Center. Overall, about 10% of men and 7% of women develop kidney stones, according to epidemiological studies.

Half of all people who form kidney stones will have another one in the next five to 10 years, and in some cases they can form more rapidly than that, says Dr. Michael Borofsky, an assistant professor in the department of Urology at the University of Minnesota Medical School in Minneapolis.

Because there's no single cause of kidney stones, there's no "silver bullet" strategy to prevent them. Physicians typically advise patients to focus on their diet and lifestyle to reduce the risk of kidney stones, Simon says. The goal of the adjustments is to make a person's urine less favorable for stone formation.

Kidney stones form when your urine contains more crystal-forming substances than your urine's fluid can dilute, says Dr. Cybele Ghossein, a nephrologist at Northwestern Memorial Hospital. She's also a professor of nephrology and hypertension at the Northwestern University Feinberg School of Medicine.

Not drinking enough fluids to dilute calcium and other substances in the urine is the most common risk factor for developing kidney stones, she says. But there are others.

Here are eight risk factors for kidney stones:

Inadequate fluid intake.

High sodium consumption.

Too much oxalate.

Animal protein consumption.

Obesity and diabetes.

Family history.

Certain medications.

Calcium supplements.

1. Inadequate fluid intake

Deficient water intake is a common risk factor for developing kidney stones, Simon says. "If the urine is too concentrated (like when it's dark yellow in color), the concentrations of calcium and other stone-causing elements increases," he says.

That bumps up the risk they will crystallize and form kidney stones. Once someone forms a kidney stone or stones for the first time, drinking enough water to urinate about 64 ounces of urine a day may decrease the risk of forming new stones. If someone drinks six to eight cups of fluids per day, they should produce 60 to 65 ounces of urine per day, says Dr. S. Adam Ramin, a urologist and medical director of Urology Cancer Specialists in Los Angeles. He also writes a blog on kidney stones.

The amount of fluids you should drink daily varies depending on age, level of activity and climate. Most people are fine if they consume four to eight glasses of fluids a day, Simon says. In addition to plain water, beverages like milk, juice and herbal teas and fruits like watermelon and vegetables like cucumbers are good sources of fluids.

2. High sodium consumption

 Diets high in salt -- which have a high sodium content -- increase the risk of forming many types of kidney stones, Simon says. Many people think of salt and sodium as the same thing, but they aren't. Salt is a mineral, comprised of sodium and chloride, according to the Heart Foundation. The sodium found in salt is bad for your health. The foundation advises consumers to read food labels to keep track of sodium content.

Higher sodium intake causes the kidneys to put out more calcium into the urine, increasing the calcium concentration. Limiting your sodium intake to 2,000 milligrams a day (or less) has been shown to reduce the risk of forming new kidney stones. Read food labels to keep track of your sodium intake.

3. Oxalate in the diet

Oxalates are natural compounds found in many foods, Ramin says. Foods with significant amounts of oxalate include broccoli, spinach, chocolate and nuts. Excess intake of these kinds of foods may lead to formation of calcium oxalate stones in urine. Under normal circumstances, oxalates bind to calcium from the foods we eat during digestion in the gastrointestinal tract and are excreted as stool.

However, oxalate that doesn't bind to calcium can go to the kidney, where it is excreted as urine, Borofsky says. When a person has too much oxalate in the diet, it can lead to an excess amount of oxalate in the urine. This in turn can lead to the formation of calcium oxalate crystals and eventually stones, Borofsky says.

Eating foods high in oxalate does not necessarily mean you'll get kidney stones, such offerings are merely a risk factor. The University of Chicago has an online publication with advice on portions of foods high in oxalate.

Physicians point out that having sufficient calcium in your diet prevents oxalates from entering the bloodstream and reaching the kidneys. "A diet rich in calcium helps reduce the amount of oxalate being absorbed by your body, so stones are less likely to form," according to the Cleveland Clinic.

It's not possible to quantify how much of any type of oxalate-rich food a person would have to eat to put themselves at risk of developing a kidney stone. It's important to keep in mind that 90% of the population never develops a kidney stone.

If you're concerned that consuming a particular food item may put you at risk of developing a kidney stone, consult a health care professional.

4. Animal protein consumption

 Animal proteins -- particularly red meat -- produce high amounts of acid in the kidney, which your kidneys need to handle, Simon says. This can cause an increase in calcium in the urine, which can lead to kidney stones. Animal protein consumption is also associated with acidic urine, which can contribute to the forming of uric acid kidney stones, he says. "Kidney stone patients may want to decrease the amount of red meat," Simon says. They should consider an eating regimen higher in fruits and vegetables, like the DASH diet.

5. Family history

Releasing large volumes of calcium in the urine runs in families, Ghossein says. The vast majority of kidney stones are formed by excessive amounts of calcium in the urine. Having a relative who has had kidney stones caused by excessive calcium in the urine is a risk factor, she says. The closer the familial relationship, the higher the risk.

6. Obesity and diabetes

Some research suggests that obesity and Type 2 diabetes can be risk factors for developing kidney stones, Nordt says. Having one or both of these conditions could change your urine composition, which could increase the risk of developing kidney stones. If you have either or both of these conditions, talk to your physician about kidney stone risks and what you can do to mitigate them.

7. Certain medications

Taking certain medications can cause the formation of kidney stones, Ghossein says. For example, indinavir, an anti-viral medication used to treat HIV, can lead to the formation of kidney stones. Other medications that can contribute to kidney stones include decongestants like ephedrine and anticonvulsants, such as topiramate, felbamate and zonisamide, according to UW Health, the academic medical center and health system for the University of Wisconsin.

Some diuretics used to treat high blood pressure and some antibiotics can also increase the risk of kidney stones, Nordt says. If you're taking any of these types of medications, talk to your physician or pharmacist about the risk of developing kidney stones.

8. Calcium supplements

If you're consuming a normal or even mildly high amount of calcium through your diet, chances are there's no need to worry about kidney stones. But boosting your intake of calcium with calcium supplements may increase the risk of developing kidney stones -- especially if you have two uncommon medical conditions, Ramin says.

One is hyperparathyroidism, the other is renal tubular acidosis. Hyperparathyroidism is a condition in which one or more of your parathyroid glands become overactive and secrete too much parathyroid hormone, according to the Cleveland Clinic.

 This is not a common condition; about 100,000 people in the U.S. develop hyperparathyroidism annually according to the clinic. Renal tubular acidosis is a disease that occurs when the kidneys fail to excrete acids into the urine, according to the National Institute of Diabetes and Digestive and Kidney Diseases. This causes a person's blood to become too acidic and can lead to kidney stones.

If you take calcium supplements and are worried about kidney stones, talk to your doctor or your pharmacist.

Whatever your risk factors, it's a good idea to do what you can to reduce your chances of developing kidney stones. One of the best things you can do is drink plenty of water. "One of the best treatments to prevent kidney stones is adequate hydration," Borofsky says.