What Are Kidney Stones? Symptoms, Causes, Diagnosis, Treatment, and Prevention

Kidney stones are common — if you haven’t had a kidney stone, you likely know someone who has. Kidney stones affect 1 in 11 people in the United States. Overall, about 19 percent of men and 9 percent of women in the United States will develop a kidney stone by the time they are 70 years old. (1)

Kidney stones (also called nephrolithiasis or urolithiasis) are hard, rock-like deposits that form in the kidneys, two organs that filter waste and extra fluid from the body. (1) Kidney stones typically develop when there is too much waste and not enough fluid in the kidneys. (2)

Passing a stone — the process of the stone moving out of the kidney and into and through the ureter (the tube that carries urine to the bladder) — can be excruciating. (3) “Some women say the pain is worse than childbirth,” says Naim Maalouf, MD, an associate professor of internal medicine at UT Southwestern Medical Center in Dallas.

Your body’s waste can include minerals and other substances that combine to form stones, ranging in size from a grain of sand to the size of a pea, or even as large as a golf ball. (4,5)

Types of Kidney Stones

There are two main types of kidney stones: calcium stones and noncalcium stones, explains Ganesh Shidham, MD, an associate professor of nephrology at the Ohio State University Wexner Medical Center in Columbus. High levels of the mineral calcium in the urine account for about 70 to 80 percent of all kidney stones, according to an article published in July 2015 in the journal Clinical Nutrition Research and other research. (6) Calcium can bind with other substances in the urine, such as oxalate and phosphate, to form stones. (7)

Stones that do not contain calcium include:

• Uric acid stones These form when the urine contains too much acid. (3)
• Cystine stones These develop when the urine contains too much of the amino acid cystine. (3)
• Struvite stones These form from the waste products of bacteria associated with infection and are composed of magnesium ammonium phosphate. (8)

Kidney stones can form in one or both kidneys. While in the kidney, a stone may not cause any symptoms. Likewise, stones that are as small as a grain of sand may pass out of the body unnoticed. But if a larger stone travels down a ureter, it can create a blockage that causes pain and a variety of other symptoms. (7)

Fortunately, a number of effective treatment options are available, many of which are minimally invasive. Moreover, doctors can perform tests to determine what caused your kidney stone and develop a plan for lifestyle changes and medication to prevent future ones, says Dr. Maalouf.

Pain is a classic symptom of kidney stones, says Prakash N. Maniam, MD, a urologist at Oviedo Medical Center in Oviedo, Florida. The pain is usually sharp and felt along the sides of the torso. It may radiate around to the abdomen and into the groin area as the stone moves through the urinary tract system, he says.

As the stone moves along the tract, it can block the natural flow of urine, which causes the kidney to swell, Dr. Maniam explains. The swelling activates nerves, which sends signals that are interpreted by the brain as an intense visceral pain, he says.

More than half a million people go to the emergency room because of kidney stones every year. (9)

Learn More About Why Kidney Stones Cause Pain

In addition to pain, blood in the urine and a burning sensation during urination are other common symptoms of kidney stones, says Maalouf. “Sometimes with severe pain, patients develop nausea and vomiting,” he adds.

“If stone pain and fever develop, go directly to the ER,” advises Timothy F. Lesser, MD, a urologist at Torrance Memorial Medical Center in Torrance, California. Fever is a sign of infection. (7) Notably, a kidney stone with a urinary tract infection (UTI) may cause sepsis (an extreme immune response to infection that can cause organ failure) and must be treated immediately. (10)

Other symptoms of a kidney stone can include frequent urination, a strong need to urinate, what looks like gravel in the urine, urine that smells bad, and cloudy urine. (1)

Learn More About Kidney Stone Symptoms and When to Seek Treatment

Some people are more likely to develop kidney stones than others. For example, men are more likely to have kidney stones than women, as are people with a family history of kidney stones, those with a history of UTIs, and those who have had kidney stones once before. (4)

You’re also more likely to develop kidney stones if you take certain medications, including: diuretics, calcium-based antacids (medicines that ease stomach acid), topiramate (an anti-seizure medication), and indinavir (an HIV treatment). (4) Calcium and vitamin C supplements may also increase your risk of forming kidney stones. (3)

And while medical conditions such as diabetes, high blood pressure, and obesity can increase the risk of kidney stones, healthy people can also develop them, says Anil Agarwal, MD, professor of internal medicine and director of interventional nephrology at the Ohio State University Wexner Medical Center in Columbus.

Factors that may contribute to the formation of kidney stones include: (11)

• Not drinking enough water
• Not getting enough calcium
• A diet high in salt or sugar
• Eating large amounts oxalate-rich foods (such as nuts, spinach, chocolate, and certain teas)
• Drinking colas, which contain phosphate and have a high sugar content
• Consuming too much animal protein
• A lack of citrate, a substance that help prevent stones from forming
• Family history and genetics

Kidney stones are less common in Hispanics or African Americans. (12)

Learn More About the Different Types of Kidney Stones and What Causes Them

If you notice symptoms that suggest you have kidney stones, including sharp abdominal pain, it’s a good idea to contact your primary care provider, who will refer you to a specialist if needed. (4) Seek emergency care if you experience pain so severe that you can’t find a comfortable position to sit in, pain accompanied by nausea and vomiting, pain accompanied by fever and chills, blood in your urine, or trouble passing urine. (7) And even if you don't need medications to help pass a kidney stone or cope with the pain of passing it, it's a good idea to see your doctor for a urinalysis test to determine the cause of the stone and discover ways to prevent more stones.

If your doctor suspects you have a kidney stone, he or she will likely ask you about your personal and family medical history to determine if you’re genetically predisposed to kidney stones or if you have any medical conditions that could increase your risk, such as diabetes. Your doctor may also ask about your dietary habits, especially those that may increase your risk of stones. (3)

Then, you can expect to receive a physical exam and undergo some combination of imaging tests, urine tests, and blood tests to look for an underlying diagnosis and factors contributing to the stones. Some of these tests can help determine the cause of your stones. (7)

The most common imaging tests used for diagnosing kidney stones are a computerized tomography (CT) scan (which creates three-dimensional images of the body) or an ultrasound (which uses sound waves to create real-time images). (7,13,14) Imaging tests should examine the kidneys, the ureters, and the bladder for the stone, says Sean Hashmi, MD, a nephrologist at Kaiser Permanente in Woodland Hills, California.

Urine tests may include the following:

• Urine pH test A dip stick urinalysis can determine the pH of the urine, meaning how acidic or alkaline it is. (15) The results can help doctors figure out what type of stone you have, says Dr. Hashmi.
• Urinalysis with microscopy Urine may be analyzed under a microscope to look for crystals made of minerals that are associated with specific types of kidney stones, says Hashmi. This test can also help doctors find evidence of bleeding or infection, Maalouf says.
• 24-Hour urine collection This test requires patients to collect all their urine in a container over a 24-hour period. (16) From this urine sample, doctors can tell whether people are predisposed to stone formation, says Maalouf.

In addition to imaging tests and urine tests, your doctor may order blood tests, which may help identify underlying conditions contributing to stones, detect anemia, diagnose infection, and measure electrolytes (salts and minerals that may be altered because of a kidney stone), says Hashmi. Blood tests can also help doctors check kidney function. (7)

Finally, if you pass a stone, you should bring it to your doctor for a stone analysis, says Dr. Shidham. They vary in size and shape, and may be as small as a grain of sand, or as large as a pea. Generally, kidney stones look like yellow or brown pebbles, and may have smooth or jagged edges. (4) On the basis of the results, doctors may be able to determine the type of stone and then prescribe certain drugs or recommend specific lifestyle changes that help to prevent another one, he adds.

Learn More About Kidney Stone Diagnosis and What to Know Before Your Appointment

A kidney stone often goes unnoticed until it starts to pass into your ureters. (7) Once this happens, symptoms typically appear without warning. You’ll likely feel sharp, stabbing pain at the bottom of your ribcage, though the pain can shift into the genital area as well. (17)

The pain from kidney stones often comes in waves, and you may feel better for a few hours before the pain comes back. (17)

Depending on the size of the stone, it can take up to six weeks to pass (though many patients opt for interventions within that time frame). Small stones may take only a few days to a week to pass. Your doctor will likely prescribe medications to help you manage the pain during this time. (17)

You may not always need treatment for a kidney stone. A small stone can pass through the urinary tract without intervention. But larger stones can block the ureter and cause pain and other symptoms. (7)

Kidney stone pain can be severe at first and may require carefully administered narcotics for relief, says Ralph V. Clayman, MD, a professor in the department of urology at the University of California in Irvine. Subsequent pain can often be managed using nonsteroidal anti-inflammatory (NSAID) medication, he says.

Drinking a lot of water (enough to produce at least two liters of urine each day) can help to pass the stone. (7) In addition, doctors may prescribe tamsulosin, which is a medication that relaxes the muscles of the ureter, helping the stone pass, says Dr. Lesser.

If a stone is too big to pass or a patient has an intolerable amount of pain, doctors may intervene with procedures that either break up or remove the stones, says Lesser.

These procedures include:

• Shock wave lithotripsy This procedure is the least invasive one for treating kidney stones, says S. Adam Ramin, MD, urologic surgeon and medical director of Urology Cancer Specialists in Los Angeles. For shock wave lithotripsy, doctors use a machine that generates a targeted high-energy shock wave to the kidney stone under imaging guidance. Urologists target the stone so that it breaks into pieces that patients pass on their own in their urine. (18)
• Ureteroscopy In this minimally invasive procedure, the urologist inserts a small, lighted tube called a ureteroscope with a camera at the tip up the urethra — the tube that empties urine from the bladder and outside of the body. (19) Once the scope is threaded into the ureter, says Dr. Ramin, a tiny wire basket is passed into the ureter to pull out the stone. For larger stones or stones stuck in the ureter, the surgeon may pass a small laser device through the scope to break the stone down so the fragments can pass on their own. (20)
• Percutaneous nephrolithotomy or nephrolithotripsy Both these minimally invasive procedures require urologists to make a small incision in the patient's back to create a pathway to the kidney, through which they insert a nephroscope, or a tube with a camera on the tip. This scope allows doctors to pass surgical tools to the kidney. If doctors use these tools to remove the kidney stone, the procedure is called a nephrolithotomy. If they use these tools to break up the stone first the procedure is called a nephrolithotripsy. (21)
• Robotic-assisted laparoscopic nephrolithotomy If the stone is large, a robotic-assisted laparoscopic nephrolithotomy may be an option for removing it, says Ramin. For this procedure, surgeons make small incisions in the abdomen through which to insert a scope and tiny surgical tools to access and open up the kidney to retrieve the stone. The surgeon controls these surgical tools from a computer console in the operating room. Robotic surgery results in less scarring and bleeding than an open procedure, which requires a larger incision, says Ramin.

Kidney stones call for conventional medical care, so don’t try to treat kidney stones with alternative therapies. (22)

Learn More About How Doctors Treat Kidney Stones

Prevention of Kidney Stones

Whether you’ve passed a kidney stone on your own, have undergone a procedure to remove or break one up, or you’ve never had one before, there are things you can do that help prevent new stones from forming. In fact, if you pass a kidney stone without addressing the root cause, chances are more will develop over time. (23) A variety of lifestyle changes and medicines can help prevent this from happening.

Your doctor can determine which approach is right for you (be it lifestyle changes, medication, or a combination) based on the type of stone you may have had in the past and the rest of your medical history, says Maalouf.

Lifestyle changes that can decrease the risk of developing a stone include:

• Drink more water. Drinking plenty of water helps ensure that your urine is less concentrated with stone-causing minerals, says Hashmi. It’s one of the best ways to prevent kidney stones, especially if you’re sweating a lot. (24) Aim to drink at least 64 ounces (roughly eight cups) of water per day to produce about two liters of urine per day. (7,25)
• Limit salt and sugar intake. A diet high in sodium and sugar can cause kidney stones by increasing the amount of calcium in your urine, says Hashmi.
• Get enough calcium. While a high urine calcium level contributes to kidney stones, you can still eat calcium-rich foods. In fact, calcium deters substances in the digestive tract that help kidney stones form, ultimately helping to prevent them. (25)
• Limit protein. Cut back on animal proteins, such as beef and chicken, says Hashmi. Too much protein (particularly animal protein) may lead to kidney stones (uric acid stones in particular). (25)
• Eat a healthy diet full of fruits and vegetables. Eat plenty of produce and other nutrient-rich foods to ensure you get enough potassium, magnesium, and citrate, which are all nutrients that may help prevent kidney stones. (3)
• Cut down on cola. The sugar in this fizzy drink may increase your risk of stones by causing you to excrete more calcium, oxalate, and uric acid, according to a study published in the Clinical Journal of the American Society of Nephrology. (26)
• Limit oxalate-rich foods. If you’ve had calcium oxalate stones, you may want to limit your consumption of foods high in oxalate, which include beans, berries, nuts, soy, sweet potato, wheat bran, and dark green vegetables such as spinach, says Hashmi.

Drugs used to prevent kidney stones include: (3)

• Potassium citrate, which lowers the acidity of the urine
• Thiazide diuretics, which lower calcium levels in the urine
• Allopurinol, which lowers uric acid in the urine
• Acetohydroxamic acid (AHA) for struvite kidney stones
• Cystine-binding thiol drugs for cystine stones

In addition to obesity, high blood pressure, and diabetes, underlying health problems, such as hyperparathyroidism (an overactive parathyroid gland) and inflammatory bowel disease (like Crohn’s disease) can also raise your risk of developing kidney stones. (7) Managing these conditions can help prevent future stones.

Learn More About What You Can Do to Prevent Kidney Stones

Some serious risks are associated with kidney stones. Left untreated, a kidney stone can block the ureters or make them narrower, increasing your risk of developing a kidney infection known as pyelonephritis (a type of UTI). (23) A kidney infection requires immediate medical attention. Otherwise, the infection can cause permanent kidney damage or spread to your bloodstream, leading to a potentially fatal infection (sepsis). (27)

While rare, kidney stones may damage your kidney if they cause infection or blockage. (3) Damage to the kidney can lead to a gradual loss of function over time, a condition known as chronic kidney disease. (28)

Kidney stones are becoming more and more common. (4,12) In the late 1970s, roughly 3.8 percent of the U.S. population were affected by kidney stones. By the late 2000s, this number jumped to 8.8 percent. (9) Now 1 in 10 people are expected to have a kidney stone at some point in their lives. (9)

Research based on data collected from 2007 to 2014 that was published in November 2018 in the Journal of Clinical Urology found that men older than 60 had the highest prevalence of kidney stones (17.8 percent) among all age groups during this time period, followed by men between ages 40 and 59 (12.6 percent). While the prevalence of kidney stones among men older than 60 remained stable during this time period, prevalence of kidney stones in women ages 20 to 39 nearly doubled between 2007 and 2013 (3.9 to 7.5 percent). When the researchers analyzed the data by race, though, they found that kidney stone incidence among non-Hispanic white women did not increase at all, but non-Hispanic Black women and Hispanic women saw a significant increase, suggesting that those minority populations accounted for the increase in kidney stone incidence among women. More research is needed to figure out why, but the study authors suggest higher rates of obesity among non-Hispanic Black women and Hispanic women compared with non-Hispanic white women may be part of the explanation. (29)

Favorite Orgs for Essential Kidney Stones Info

American Kidney Fund

This nonprofit helps people with kidney disease by providing prevention activities, health-education resources, and financial assistance programs for low-income Americans. You’ll find detailed information on kidney stone causes and risk factors, as well as how to prevent stones and other kidney problems.

Mayo Clinic

Learn about all aspects of kidney stones, from what causes them and symptoms you’ll experience to how a stone is treated. You can also connect with Mayo Clinic doctors and clinicians for kidney stone treatment.

National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)

This arm of the National Institutes of Health focuses specifically on health issues related to diabetes, kidney, and digestive diseases. The site’s contents are thoroughly reviewed by NIDDK experts, and it breaks down the latest research and information in a way that’s easy for visitors to understand. In addition to finding information on kidney stones and how to manage them, you can find related clinical trials.

National Kidney Foundation (NKF)

The NKF is one of the leading organizations dedicated to fighting kidney diseases of all types. It works on all aspects of kidney health. When it comes to kidney stones, you’ll find information about what causes them, what you can do to prevent them from occurring, and answers to several other common questions about kidney stones.

The University of Chicago Kidney Stone Program

The site was founded by Fredric Coe, MD, a prevention nephrologist at the University of Chicago who has spent years researching kidney stone prevention. Visit the site’s Kidney Stone Guide Book for articles that cover a variety of topics, including a practical guide to what to bring to your doctor appointments and how diet affects kidney stone development.

Urinary Stone Disease Research Network (USDRN)

The USDRN is an organization funded by the NIH and NIDDK and is made up of researchers who focus on determining who tends to develop kidney stones, what people can do to keep them from forming, and how to treat them most effectively. The “Kidney Stones 101” part of the website is a good place to start to learn more.

Favorite Source for Diet Advice

Cleveland Clinic

Confused about what you should and should not eat when trying to prevent a stone from forming? If you experience calcium oxalate kidney stones, visit this webpage from the Cleveland Clinic. It outlines six diet recommendations to help you minimize your risk.

Favorite Kidney Stone Blogs

CareBlog

CareBlog is the blog of the Urology Care Foundation, an organization dedicated to supporting urologic research and providing urologic health information to the public. The blog features information on kidney stones, as well as information on general urologic health (like healthy recipes that support urologic function and bladder health tips).

Kidney Stoners

Want to hear about kidney stones from people who’ve gone through the experience? Let this website, which was founded by Mike M. Nguyen, MD, MPH, an associate professor of urology at the Keck School of Medicine at the University of Southern California in Los Angeles, be your guide. You can read through essential information from experts, as well as patient accounts and contributor articles that answer questions you may be wondering about, such as: “Do vegetarians get kidney stones?” and “Does drinking a lot of water help a stone pass faster?”

With additional reporting by Lauren Bedosky.