Kidney stones are common — and notoriously painful. About 11 percent of men and 6 percent of women in the United States experience kidney stones at least once in their life, and those numbers are rising, according to the National Institutes of Health.

The bad news is that, in most cases, you won’t know you have a kidney stone until it’s blocking the flow of urine, sometimes causing severe pain and bleeding. The good news is that there are steps you can take to reduce your risk of developing one, says Samit Soni, MD, a urologist with Memorial Hermann Medical Group. The most important of those steps is crucial as warmer weather approaches: drinking plenty of water.

“Dehydration is one of the largest factors we see when we evaluate patients,” says Dr. Soni. “For our recurrent kidney stone formers, chronic dehydration is a big factor. But you could spend a week working outside in Houston during the summer and not drink enough water and potentially develop a kidney stone, even if it wasn’t a chronic issue.”

Kidney stones form when high levels of certain minerals are concentrated in urine. Calcium, typically in combination with other minerals, such as oxalate, phosphate or carbonate, is the most common culprit.

Dr. Soni sees an uptick in kidney stones every summer and fall, likely because of dehydration in the hotter months, although it’s not always easy to pinpoint a kidney stone’s exact beginning. They can take weeks or months to form, and can remain in the kidney for months or even years without causing symptoms before finally dropping into the ureter and causing blockage and pain. 

“It’s very unpredictable. And that’s the problem for patients with kidney stones: You don’t know when it’s going to disrupt your life,” says Dr. Soni. “They form and they drop whenever they want to.”

That can mean severe side or flank pain and burning during urination, often accompanied by nausea and sometimes by blood in the urine. “Those are the classic symptoms of passing a kidney stone, but they don’t always occur the same way in everyone,” Dr. Soni says. “More subtle symptoms can include a urinary tract infection that doesn’t go away. It can be a little bit of burning with urination that’s not due to an infection and doesn’t have an explanation. It can be just nausea without pain. Sometimes it could be abnormal kidney labs that don’t have a clear explanation.”

If you do have sudden, severe pain in the lower back, abdomen or groin, Dr. Soni recommends going to an ER or an urgent care center with imaging services to check for a kidney stone. If it’s small enough to pass on its own, all that’s usually needed is pain management.

“If you’re having pain, it means the stone is causing obstruction somewhere in the urinary tract, usually in the ureter. How quickly it passes depends on the size of the stone. If it’s one millimeter it might pass fairly quickly with minimal pain and a little nausea. If it’s four millimeters it could be several days of agonizing pain,” he says.

For stones that are four millimeters or smaller, urologists will typically recommend simply watching them to make sure they’re not growing.

“Only rarely do we intervene in small kidney stones,” says Dr. Soni. “One exception is if you’re a pilot. Pilots aren’t allowed to fly if they have a kidney stone, because for obvious reasons, we don’t want a pilot to pass a kidney stone on a flight.”

Stones that are five millimeters or larger, however, might never pass on their own, and surgery may become necessary. Left untreated, kidney stones can have devastating complications. If they block the kidneys for more than a few weeks, they can cause irreversible damage and, ultimately, kidney failure. Urinary tract infections combined with a kidney stone, meanwhile, can lead to sepsis.

“Some of the most common emergencies for urologists involve kidney stones in the setting of infection,” Dr. Soni says. “A kidney stone that is passing is not a medical emergency in itself, but if the patient developed kidney failure or a UTI on top of that stone, then basically the urine is stuck behind that stone and has nowhere to escape: The only place to go is the bloodstream. People can rapidly go into what’s called urosepsis, and that can quickly become life-threatening. If you have a kidney stone and you develop a fever or other signs of infection, then that warrants emergency treatment.”

Some people are genetically predisposed to develop kidney stones, and if you have a strong family history or personal history of forming stones, Dr. Soni recommends regular imaging to find them before they cause problems. “A larger stone might warrant a preemptive strike at the stone before it strikes you — especially since you can do it on your own terms, as opposed to a middle-of-the-night trip to the ER,” he says. “If we can get them before they get into the ureter, we can also offer less invasive treatment options, including lithotripsy, which is noninvasive and uses shock waves to break a large stone into smaller pieces. Sometimes we’ll perform a ureteroscopy, where we pass a delicate flexible scope through the ureter and use a laser to break the stone into tiny pieces. For the largest of stones, we have to enter the kidney with a very small incision to break them up with a combination lithotripter, which is essentially a jackhammer and a vacuum in one device.”

More research is also being done on the risk factors for developing kidney stones. Apart from dehydration, one of the biggest risk factors is obesity.

“Obesity plays a strong role in increasing your risk for kidney stones,” Dr. Soni says. “The other risk factors that we can control are decreasing salt intake, because it creates calcium in the urine; decreasing your animal protein intake, including fish and eggs, because that increases uric acid production; and increasing fruits and vegetables, especially citrus fruits, since they’re higher in citrate, which can inhibit stones from forming.”

Metabolic testing can help people with chronic kidney stones discover which minerals are contributing to the problem so they can more precisely pinpoint those areas, rather than attempting to eliminate every possible contributing factor from their diet, Dr. Soni says.

While you have an active kidney stone, however, no single food or dietary supplement will make it go away, he stresses. “I would urge people to be cautious of any over-the-counter products that claim to eliminate stones that have already formed,” he says. “There are a lot of products online that claim to eliminate or dissolve stones. But calcium-based stones, which are the vast majority of kidney stones, cannot be dissolved. ‘Herbal’ remedies are not regulated by the FDA — and you could be risking damage to your kidneys by taking them.” 

For more information, visit www.memorialhermann.org/services/conditions/kidney-stones.