Public Health

What doctors wish patients knew about kidney stones

Sara Berg, MS , News Editor

AMA News Wire

What doctors wish patients knew about kidney stones

Jun 28, 2024

Sharp pain that radiates from your back can cause a moment of panic. But what may seem like an ordinary backache could be a telltale sign of a kidney stone, which is an agonizing condition affecting 1 million people in the U.S. each year. These tiny, crystalline deposits often form silently in the kidneys, waiting to make their painful debut. This sudden onset of symptoms can transform daily routines into urgent medical concerns, highlighting the importance of understanding and addressing kidney stones.

The AMA’s What Doctors Wish Patients Knew™ series gives physicians a platform to share what they want patients to understand about today’s health care headlines.

In this installment, Ryan L. Steinberg, MD, a urologist who specializes in the treatment of kidney stones at the University of Iowa Health Care, discussed what patients need to know about kidney stones. University of Iowa Health Care is a member of the AMA Health System Program, which provides enterprise solutions to equip leadership, physicians and care teams with resources to help drive the future of medicine.

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Kidney stones tend to be more common in the summer, said Dr. Steinberg. “In fact, we have a time of the year we call stone season, which is roughly June to October where we see things ramp up in terms of people coming into the ER with stone symptoms and new clinic referrals.”

“There’s this big stripe across the South from Arizona through the Carolinas where stones are more prevalent which we call the stone belt,” he said. “Moving north the incidence of stones decreases as the weather stays a bit cooler.”

The best way to describe kidney stones is they “are literally little, tiny rocks that form on the inside of your kidney,” Dr. Steinberg said, noting “there are some that are harder than others.”

“Some can be kind of crumbly like chalk. Some of them can be hard, almost like concrete,” he said. “And the question about how hard or soft they are is really based on what kind of mineral they are made out of.”

“Kidney stones typically will present with a backache or flank pain. So, that’s pain in the back, usually not low down such as right above the butt, instead located right underneath the ribs,” Dr. Steinberg said. “Some people will say that the pain wraps around their side and heads down towards their pelvis or towards their private parts.”

Meanwhile, other people “may just have pain by the bladder if the stone is really far down towards the bladder and is trying to pass,” he said. Aside from “pain, blood in the urine and burning or pain with urination are also common symptoms.

“Sometimes if the pain is so bad, people can just have nausea or vomiting and it can be hard for them to stay hydrated with a kidney stone,” he added.

“Kidney stones that are not actively trying to pass out of the kidney, down to the bladder in most cases don’t cause pain,” Dr. Steinberg said. “So, you can live with them for years and years without having trouble or problems.”

“But, if that little sucker decides it’s going to dislodge and try to pass, it could cause trouble down the line,” he said.

“The most recent estimate puts kidney stones now at about one in 10 people in their lifetime,” Dr. Steinberg said. “So, just over 11% will have a kidney stone.”

“It used to be that it was way more common in men to get kidney stones and over the last 30 to 40 years that gap has significantly closed,” he said.

This is due to a lot “of different reasons. The classic kidney stone formed in a ‘meat and potatoes’ kind of guy, who consumed a lot of animal protein,” Dr. Steinberg said. “Obesity also plays a role in this. the increasing level of obesity across all patients—regardless of gender—has contributed to the overall increase we are seeing.

“There are other elements that are slightly unique to women,” he added. For example, women have a “higher likelihood of having urinary tract infections, which can then lead them to forming an infectious type of stone called ‘struvite’ as well.”

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“People previously would usually show up for the first time in their 40s or 50s. Nowadays, we are seeing more and more people in their 20s and 30s forming their first stone,” Dr. Steinberg said. “Further, with the childhood obesity epidemic we are currently in, we’re also seeing many more stones in the pediatric population as well.”

“While we are definitely seeing more stones in younger populations, it’s less directly about age, and more about some of the risk factors for stone formation that may be present,” he said.

“Kidney stones typically are classified as calcium or noncalcium. So, about 80% to 85% of stones will fall into the calcium kind of bin,” Dr. Steinberg said. “The majority of those will be calcium oxalate stones. That’s the most common type that we see.”

“There’s also calcium phosphate stones, which are a little bit less common and can show up as a result of other disease processes or just purely on their own,” he said. “The other 15% to 20% is kind of a mixed bag. You have about 8% of people who will have uric acid stones, which is a totally different type of stone.

“Those stones are made of uric acid, which is a substance that we see in people who often have high meat intake,” Dr. Steinberg added. Then “you have about 8% of patients who have struvite or infectious kidney stones that are created from a really bad urinary tract infection and the bacteria can lead to crystallization.”

“And then there’s a smattering of 5% or less of all sorts of rare types of kidney stones. Cystine stones are one type of rare kidney stone which forms as a result of a rare genetic condition in how the body managed a certain amino acid (cysteine),” he said.

“There are some people who—based on specific conditions—may be predisposed to forming stones,” Dr. Steinberg said.

That includes people with diabetes, obesity and gastrointestinal issues such as Crohn’s disease and ulcerative colitis. It also includes people who have had weight-loss surgery, or had parts of their intestines or colon removed for cancer or for other reasons.

Additionally, “an overactive parathyroid gland or other thyroid disorders, other autoimmune disorders or people with a history of cancer who have gotten chemotherapy are all known risk factors of kidney stones,” he said. “And in fact, the simplest risk factor that we know of is family history. People who have had a family member with a stone are at a higher likelihood of having a stone themselves than somebody who hasn’t.”

But “that doesn’t necessarily mean that all of these people have an underlying genetic disorder. We think that genetics play a role in maybe 10% to 15% of all stone diseases,” Dr. Steinberg said, noting “there’s still a lot to be done in that area, but quite a bit of it on a family history side is really based on learned behaviors as it is your parents who teach you how to eat, how much to eat, and what foods to pick.”

A small stone is in the 3–5-millimeter range and “if they’re trying to pass, they will come out on their own with increased hydration,” Dr. Steinberg said. “So, making lots of urine to help propel the stone out and potentially some medication can help with that.”

“While it may not feel very good coming out, passing the stones on their own can avoid surgery,” he said, noting though that “the passage may take up to six weeks. If it doesn’t pass by six weeks, it’s unlikely to come out on its own so we’re going in to get them out.”

“There are three ways that we do the vast majority—99%—of all stone removals,” Dr. Steinberg said. “One of them is shockwave lithotripsy. … We propel high-intensity sound waves through people’s backs to try to shake or literally break stones into dust.

“In that case, people will still have to pass those dust particles or pieces, but that’s the least invasive and a very effective way of taking care of kidney stones,” he added. “The most common procedure we do now is called ureteroscopy. That’s a procedure where we take a small telescope which is placed up the urethra (pee tube) into the bladder all the way up into the ureter tube or potentially into the kidney. If you think about the way urine comes down from the kidney (down the ureter tube into the bladder and then out the body through the urethra),  we put the camera scope up backwards as to how urine normally flows.”

“And depending on the size and location of the stone, we may use a laser to break the stone,” Dr. Steinberg said. “Sometimes we will use the laser to break the stone into dust or grit where it must pass on its own out of the body. Other times, we may use the laser to crack the stones into small pieces and use a little grasper to actively remove those stones.”

“Last, probably about 15% of people will need a more invasive surgery called a percutaneous nephrolithotomy,” he said. “We make a small incision in the back about the width of your finger, and use that to pass a telescope in through people’s backs to be able to go and either grab stones and pull them out or grind up a stone and suction out the small pieces with a special device.”

“Studies have suggested that up to 50% of people will have another stone 5 to 10 years after having their first one,” Dr. Steinberg said. “That means 50% or more of people may not have another stone within five to 10 years, which is great.”

“Obviously, the people who we need to focus most closely on are those who have even more frequent stone issues, such as every one to two years—the really aggressive stone former,” he added. “In general, we prevent stones from reoccurring by being careful with the salt, animal protein and calcium in our diet and drinking lots of fluids.”

A urine test can help identify areas to focus on and is strongly recommended to guide prevention counseling, Dr. Steinberg said.

“It’s always tricky to pin it down to one food, but a few beverages that we know of that are high in things that cause stones are soda pops, especially dark colas,” Dr. Steinberg said. “That’s often a discussion that we have in clinic with patients. It is not necessarily about being punitive and telling them never to have another sip of your Mr. Pibb or Diet Dr. Pepper ever again.”

“Rather, it’s about moderation. If they’re coming in drinking a six-pack of that every day, we have to cut that back,” he added. “There’s something to be said for moderation and not necessarily taking away the things that people enjoy.. Those types of ‘treats’ should be the exception, not the rule in terms of how we should be eating or drinking.”

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The easiest thing to do is “drink lots of water,” said Dr. Steinberg. That means “in the average person, drinking 80 to 100 ounces of fluids a day with the goal being that you get your urine output to be about 2.5 liters per day, so just a little bit more than a two-liter bottle of pop worth of urine coming out.”

This “can help to reduce the risk of stone formation,” he said, noting it is also important to have a low animal protein and low sodium diet “to reduce the amount of uric acid and sodium that’s in the urine.”

“Lots of people think they have a calcium stone, so they better cut their calcium intake down,” Dr. Steinberg said. “There’s a surprising number of people who think they’re overdoing it but are actually doing just fine with their calcium intake.”

“Having a normal amount of calcium, which is very important for your nerves, muscles and bones, is really important,” he emphasized, noting the right amount of calcium depends on age and gender, “but typically we’re talking about 1,000 to 1,200 milligrams per day.”

But remember, “there are varying degrees of calcium in different types of leafy vegetables, dairy, meat and other foods,” Dr. Steinberg said.  

“Tylenol and ibuprofen are really great at dealing with pain and they actually are effective at reducing inflammation, which can sometimes help stones to pass,” Dr. Steinberg said. “Patients who do have really terrible pain may need stronger pain medication or anti-nausea medicine.”

“We do everything we can through medication, fluids and whatever we need to do to get that stone out as soon as possible,” he said. “When you’re passing a stone, it’s a pretty miserable time, but we’re here to help.”