16-26 Segment 1: Kids’ Kidney Stones

kidney stones in kids

 

Kidney stones in children and adolescents used to be unusual. Over the last 30 years, they’ve become much more common. Experts discuss why this may be occurring, why doctors still sometimes miss the diagnosis, and how kidney stones are treated in children.

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Guests:

  • Dr. Gregory Tasian, pediatric urologist and clinical epidemiologist, The Children’s Hospital of Philadelphia and Asst. Prof. of Urology and Epidemiology, University of Pennsylvania
  • Dr. David Goldfarb, Professor of Medicine and Physiology, New York University Medical School and Clinical Chief of Nephrology, New York Langone Medical Center.

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Pediatric Kidney Stones

Reed Pence: Parents of young children are undoubtedly familiar with the phrase, “Mommy, I have a tummy ache.” Usually, with a little TLC and maybe some ginger ale, the symptoms go away. But increasingly, parents are dealing with kids whose stomach pains persist. They eventually wind up in the ER with a diagnosis that, up until recently, was associated only with adults — kidney stones.

Gregory Tasian: Often I see families of children who have gone to the emergency department multiple, multiple times and then finally make it to our children’s hospital after receiving multiple imaging studies and someone finally thinks of stones or they obtain a CT scan or ultrasound for another reason, they find they have a stone. So it’s not in the forefront of a lot of physicians minds because stones were once rare and now are becoming much more common. So it hasn’t been something that physicians readily thought of.

Pence: That’s Dr. Gregory Tasian, a pediatric urologist and clinical epidemiologist at the Children’s Hospital of Philadelphia, and Assistant Professor of Urology and Epidemiology at the University of Pennsylvania.

Tasian: Pediatric kidney stones definitely used to be rare. When you’re looking at stone disease across the whole population in both children and adults, the prevalence, which is the proportion or the population that have had stones at some point in their life, has increased probably by about 70% over the last 30 years. So we know that it’s nearly doubled over a 30 year time period across the United States. What was unclear was in which populations is it increasing at the fastest rate and who are those particularly vulnerable populations — which is why we did the study that we did.

Pence: Tasian’s study of kidney stone patients in South Carolina showed the greatest increase in children between the age of 15 and 19 years old.

Tasian: Among that age group, it’s increasing by about 5% per year, at least in South Carolina. And comparing it to other diseases such as obesity, we don’t see nearly as fast of increases in obesity as we do in kidney stones. So the rate at which it’s increasing is dramatic.

David Goldfarb: There’s a rise in pretty much every age group and although, you know, this is a disease that’s more male than female, there’s evidence that it’s increasing both in men and woman. It’s increasing in children as well. And although this is a disease that’s much more common in whites than in blacks, it’s occurring more frequently both in whites and blacks, so pretty much the entire nation is affected and suffering from more kidney stones.

Pence: Dr. David Goldfarb is Professor of Medicine and Physiology at the New York University Medical School and Clinical Chief of Nephrology at New York Langone Medical Center. He says researchers have lots of ideas as to what may be causing this increase in kidney stones, but no one knows for sure.

Goldfarb: This has been attributed to changes in people’s diet. The increased prevalence of obesity and diabetes may be part of this. People eat more salt and protein than we did 100 year ago. Many people eat less dairy, there’s evidence that dairy is protective. And then you know, one of my personal hypotheses recently has been that there are more people living in cities, which tend to be hotter than rural areas. And that’s my hypothesis regarding urban heat islands. If it’s hotter, you’ll lose more fluid through your skin. And that means that a smaller proportion of the fluid that you drink is going to be in the urine.

Pence: Goldfarb says there’s also a genetic component.

Goldfarb: It clearly has the genetic basis although the genes are not really well understood. We did a twin study that showed that when one twin was affected by kidney stones, the other twin was likely to have the condition as well if they were identical or monozygotic twins.

Tasian: When you have a change in the prevalence of a disease or the incidence of a disease over such a short period of time, it’s clear that something is changing in the population. And kidney stones, when you look at what determines whether or not a child or an adult would get a kidney stone, it’s that interaction between genetics, you know, things such as sex, family history, some possible genetic predisposition to having a stone. Behaviors is a second cause. So what we eat, what we drink, how much of it. And then the third is the environment, the temperature outside, possible other determinants of stones in the environment. And when you look at the population, the only thing that really changes at such a dramatic rate over a short period of time, are behaviors. So what are children and adolescents doing now that they weren’t doing 20 or 30 years ago that could be contributing to that increase in kidney stones?

Pence: Maybe texting and playing video games? Not getting enough exercise, and consequently, not drinking enough fluids?

Goldfarb: There are data that suggests that people who are more active have fewer kidney stones. And exactly why that’s the case has not really been demonstrated but is one that’s certainly worth looking at.

Pence: How about obesity? Tasian says research thus far has not linked childhood obesity with pediatric kidney stones.

Tasian: Anecdotally, as a urologist and a kidney stone surgeon, it’s often not obese patients. And that really lines up with what we’ve seen in research. Among adults, obesity has been associated with a higher risk of kidney stones. Metabolic syndrome has been associated with a higher risk of kidney stones. The data are much fewer and sparse among children, but the few studies we have, there have not been as clear linkage between obesity and stones among children.

Pence: Experts may not know the cause for the increase in children’s kidney stones, but people who’ve had one know one thing—they can be extremely painful.

Tasian: Usually it’s a pain in the flank, so in the side more towards the back underneath your ribs. And in children, that pain is often in the belly. So it doesn’t localize, it doesn’t go to the particular side as often as it does in adults. So in adults it will typically be flank pain, nausea, vomiting, maybe some blood in the urine. In children, it’s largely the same, but I would say often times, the pain in the belly is more generalized and it’s not specifically localized in to one location.

Pence: Tasian says kidney stones are made of crystals that form in the urine due to super saturations of certain minerals.

Tasian: Stones can be anything from, you know, one or two millimeters, all the way up to stones that are multiple centimeters and fill the entire kidney. And the reason they hurt is because they block the flow of urine and when you block the flow of urine, the kidney expands because the urine has nowhere to go. And when the kidney expands, it causes the nerves to be excited and that leads to pain, nausea, all the things you associate with stones.

Goldfarb: The number that I usually use is that your finger is about 20 millimeters across in width. So seven millimeters is less than half the width of your finger. But I’ll tell you what a big stone is. A five-millimeter stone, one quarter of the width of your finger, is a stone that will pass about 50% of the time and 50% of the time you will wind up with a urologist’s assistance in passing that stone. So, 50/50 is a five millimeter stone, seven millimeter stone about 20% of those will pass, about 80% are going to require a urologist’s assistance.

Pence: Tasian says diagnosis of kidney stones in children is typically accomplished through ultrasound rather than a CT scan, which is commonly used for adults.

Tasian: And the reason for that is there’s no radiation with ultrasound and you’re able to detect stones with a lot of greater accuracy and sensitivity in children than you are in adults just simply because the body size is usually smaller. But across the United States, CT is still the most commonly utilized diagnostic imaging modality and there’s tremendous variation. So a child who is seen, for example, in Philadelphia may have an ultrasound. However that same child, if they lived in say South Dakota, they may have a CT scan. So there’s tremendous variation.

Pence: If it’s clear that a stone simply won’t pass, Tasian says it can be surgically removed.

Tasian: Thankfully over the last 20 years, we have been able to develop smaller and smaller instruments, which allow the minimally invasive approach to stones. So no incisions, often be able to access small stones and take care of small stones in the kidney as well as the ureter with a ureters scope which is a long, thin, flexible scope that you can visualize the stone and remove it, often using a laser. And that allows for effective and safe removal of stones.

Pence: There’s also another intervention for kidney stones called extracorporeal shockwave lithotripsy, or ESWL for short.

Tasian: You deliver shocks to the kidney and it breaks up the stone and then the patient passes it themselves. I have reservations about that among all patients but particularly children, because we found that shockwaves are associated with a higher risk of developing high blood pressure.

Goldfarb: Takes less than an hour, usually there’s something in the range of 1,000-2,000 shocks. You can think of it as like a big spark plug, a charge goes across that spark plug and generates something called a shock wave. It’s possible using those machines to focus that shockwave on the kidney stone and hit it and soft tissues will generally absorb less of that shockwave and something hard like a kidney stone. Still, you do want to cut down the shockwave intensity or number for thinner people and children would be in that group.

Pence: Unfortunately, doctors say that people who have a kidney stone once will likely develop another one, but nobody knows for sure just how long that will take.

Goldfarb: The study that I like to quote is sort of the extreme that showed that stones could form in less than 90 days. That’s a study where looking at U.S. army soldiers getting to Kuwait demonstrated that the average that a kidney stone presented to the emergency room was about 90 days after arriving in Kuwait. So I think that’s the extreme, because, you know, it’s very hot, it’s more than 100 degrees Fahrenheit, people are carrying equipment so they’re having vigorous exercise and the result would be that they would wind up with a kidney stone in a relatively short period of time. Assuming this happens to you as a relatively young person, it’s considered highly prevalent. So in over the course of let’s say, 20 years or so, about 80% of people who had their first stone would have at least a second one. But there are people who have a stone once a year.

Pence: Anyone who’s had just one kidney stone will tell you they wouldn’t want to go through it again and again.

Goldfarb: A lot of attention has to be given to thinking about why an individual is forming kidney stones. And then try to address their risk factors. Can you change your diet; increase your fluid intake and specifically we’re looking for people to have more than two liters of urine a day. So it’s not enough to say to people, drink a lot. I want to be very specific and quantitative about the fluid prescription that I offer. And then recognizing that for the people who have more than one stone, medications may be very appropriate.

Tasian: Among adults the risk of having another stone after a first one is about 50%, five to 10 years after having that first stone. In children, we have some preliminary data that we’re preparing right now that looks like the risk of a recurring stone is about 50% within three years of having that first stone, so may be similar, may be a little bit higher recurrence rate than adults. But certainly a high proportion of those children who have one stone will have at least another one within a relatively short period of time.

Pence: It’s yet another reason to tell your kids—go out and play!

You can learn more about our guests Dr. Gregory Tasian and Dr. David Goldfarb by visiting our web site at radiohealthjournal.net.

Our writer/producer this week is Polly Hansen.

I’m Reed Pence.

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