Dr. Chan on prevention, diagnosis, and treatment of kidney stones in pediatric patients

Katherine Chan, MD, MPH

In this interview, Katherine Chan, MD, MPH, provides an overview of the Pediatric Kidney Stone Clinic at the University of North Carolina and also discusses prevention, diagnosis, and treatment of kidney stones in pediatric patients. Chan is vice chair for research, director of the Pediatric Kidney Stone Clinic, director of Pediatric Urology Research, and an associate professor of urology at the University of North Carolina, Chapel Hill.

Please provide an overview of the Pediatric Kidney Stone Clinic at the University of North Carolina.

I'm the director of our pediatric stone program at the UNC Department of Urology. I work closely with our staff both in the department of urology as well as the department of medicine, and specifically the pediatric nephrologists who are housed within that department. We have 4 full-time pediatric urologists at UNC, including myself. We also have a team of pediatric nephrologists that's led by Dr. Keisha Gibson. We work closely in partnership with them to provide comprehensive stone care. By that, I mean we provide surgical treatments for kidney stones, and we also help patients manage their stones medically; for example, helping them perhaps with spontaneous passage of their stones. And then we partner with our pediatric nephrology colleagues, who do primarily the metabolic evaluation for children who have kidney stones, and that really focuses on identifying risk factors in terms of why they form the stones, and then they also focus on something called secondary prevention, which is figuring out how to prevent more stones from happening in the future. Supporting this, we also very importantly have 2 wonderful pediatric urology nurses. They help with a lot of the care coordination, which is very important because a lot of these patients require a significant amount of surveillance imaging as well as imaging during their acute stone episodes, and then ordering of lots of testing, such as blood tests and urine tests to help identify those metabolic causes of stone disease.

What are the most common symptoms of kidney stones in children, and how might they differ from the presentation in adults?

Pediatric patients do have a somewhat heterogeneous or variable presentation of their stone disease. A lot of that is dependent upon their age. There tends to be different presentations in younger vs older children. And when I say older children, I'm primarily referring to teenagers. Teenagers tend to present more like adults in that they have sort of classic symptoms of what we call renal colic, which is severe flank pain, nausea, and vomiting and perhaps even blood in the urine. Interestingly, younger children may have a little bit of a different presentation, and that is partially related to the different causes of stones in kids. For example, they may present with irritability, vomiting, perhaps even nonspecific abdominal pain, urinary tract infections, and even microscopic blood in the urine. In addition, there are some differences in terms of the presentation based on age, gender, race, and even area of the country.

What are the biggest risk factors for kidney stones developing in children, and are there any specific dietary or lifestyle changes you recommend for prevention?

Kidney stones in children are quite a bit different than in adults. In adults, we think of dietary factors being really important. And interestingly, stones are more common in adults than in children. In children, we're more concerned about metabolic or genetic abnormalities, meaning things that they inherited from their parents. And to that end, children also have a much higher risk of recurrent stone disease. Stones that recur in children happen about 40% to 50% of the time. That's why the American Urological Association guidelines recommend doing a complete metabolic evaluation in all children. But as far as the biggest risk factors in children, the most common cause overall is metabolic. Of those metabolic causes, hypercalciuria, or high calcium levels in the urine, is overall the most common metabolic abnormality in children with kidney stones. And that is found in about 50% to 97% of children with identifiable metabolic disease. This can be caused by a variety of different things such as disturbances in the kidney, the intestinal tract, and the bone. So it really is quite heterogeneous and really, the underlying etiology, and again, the prevalence and the incidence and all these risk factors really vary a lot in terms of gender, age, race, dietary habits, and even some socioeconomic factors. Interestingly, boys are more affected in the first decade of life, and their main risk factor tends to be obstructive processes in the urinary tract. Girls are more affected in the second decade of life, and their main risk factor is UTIs, particularly in post pubertal and sexually active girls. There are some racial differences too. Stones are more common in non Hispanic White children compared to Hispanic children, and they're least common in African American children. Interestingly, there's a higher incidence reported in children who live in Western countries and rural communities and also hot and dry climates such as North Carolina.

How are kidney stones diagnosed in children? Are there any special considerations when performing tests or procedures on young patients?

Kidney stones can be diagnosed basically in 2 different ways. One is what we call an incidental finding on an x ray or an ultrasound. This is somebody who just happens to get an ultrasound or maybe a CT scan, and the radiologist identifies a kidney stone. And these children typically don't have any symptoms. They may have some underlying issue that caused the stone, and this is the first time they have become aware of it. Of the other category of people, and particularly children who are diagnosed with kidney stones, are those who actually do present with symptoms, the ones that we discussed previously, such as flank pain, nausea, vomiting, gross hematuria, things like that. As far as the special considerations, I'm so glad you asked. Children are not little adults, as we like to say. And one of the biggest considerations we have in imaging pediatric patients is radiation exposure. And so there's been a lot of attention paid to this in recent years, due to something called the ALARA principle, and that's as low as reasonably achievable in terms of the radiation dose. The mainstay of radiological imaging in the initial acute stone period is really ultrasound. And that's very different from adult patients, where everybody pretty much just gets a CT scan to diagnose them. With the ultrasound, what we do is really look for hydronephrosis or swelling of the kidney. And that, in combination with symptoms like flank pain, vomiting, etc, is almost diagnostic of a kidney stone. Interestingly, we oftentimes won't actually see the stone on ultrasound once it's passed into the ureter. We'll just see the upstream effects, where the actual kidney is swollen because of the blockage. We will sometimes, however, get a CT scan in children as well, and there are, interestingly, some low-dose noncontrast protocols for CTs in children that are specifically created for imaging children who may have kidney stones, and that may happen when perhaps the patient is symptomatic and there's just no stone seen by ultrasound examination or perhaps not much hydronephrosis.

What treatment options are available for kidney stones in children, and how is the decision made between conservative management and surgical intervention?

The treatment options for children are variable. The first consideration is really whether or not the child is symptomatic and also how symptomatic are they. For people who have these asymptomatic small stones up in the kidney that really aren't causing any blockage, that's a different consideration than somebody who ends up in the emergency room in severe pain. The child who's asymptomatic, they may actually elect observation for their stones. That's certainly 1 possibility. The other possibility is electing a treatment for that stone. Essentially, there are 2 main treatments for these small kidney stones that aren't causing a problem. For example, there's something called extracorporeal shock wave lithotripsy, which is an external type of sound wave that's applied to the kidney to break up the kidney stones. The other one, of course, is ureteroscopy, where we pass a telescope up into the ureter and up into the kidney to treat the stone. So it's pretty much the shock wave lithotripsy or ureteroscopy, which are the treatment options if the family elects to treat it at all. The second category that I mentioned is, again, those patients who are acutely symptomatic [and who] may have severe pain from their stone. Assuming that they don't have any type of serious issue like an infection in the urine, they may be offered several options. One of those is basically a spontaneous passage. And that's maybe assisted with some medications to help them pass the stone more efficiently. And that would be something where we usually give them a trial of passage for about 2 to 3 weeks, potentially with some re-imaging to see whether or not that's been successful. The other option is, again, if somebody is in severe pain, is just to go ahead and place a stent, which is like a drainage tube for the ureter, and then move on to treating the stone ultimately, and again, we can look at possibly ureteroscopy, or even shock wave lithotripsy in that kind of scenario. The final treatment option, which is pretty uncommon in kids, and again, this is a difference between pediatric stone disease and adult stone disease, is percutaneous nephrolithotomy. Kids tend to form pretty small stones. As I like to say, "They are little people with small stones that cause big problems." And so, generally speaking, we don't see as many large kidney stones in children that really require a percutaneous approach. So generally speaking, that's pretty uncommon. In those types of scenarios we typically engage with our adult endourology colleagues and we'll send them to my adult colleagues for treatment.