Dr. Hubert Swana provides a comprehensive overview of pediatric kidney stones: what causes them, new advancements in surgical management, and common issues assosciated with pediatric kidney stones.
Hi, good afternoon, everybody, and thank you very much for letting me speak with you today. Um, I've really enjoyed my time here, uh, working with everyone in Saint Louis, and, uh, hopefully, myself and my pediatric urology colleagues can provide uh service and consultation for all your patients. So, what I'd like to speak about today is just, just to provide an update on, uh, kidney stone care uh for children. And what I'd like to review is the epidemiology of pediatric stone disease here in the United States. We'll also review new guidelines. The American Neurologic Association in 2018 and the European Association for Urology in 2022 created new guidelines specifically for children regarding the diagnosis and the management of stones, and then We'll move on to discuss new advancements in surgical management of pediatric stone disease. Um, most of them, we are actually able to offer our children at slit and also at our outpatient surgery centers as well. And then we'll focus on some specific issues including the recurrence stones prevention and how to manage an asymptomatic stone. So, anyone who's treated kids over the last 10 to 15 years uh has noticed that there's been an increase in kidney stones, and this has also garnered a lot of attention from the lay press. Uh here are just a couple of recent headlines. And To start our discussion, I'd like to go over some historical data. You know, historically, adults had about a 9 to 11% chance throughout their lifetime of developing a kidney stone, while children had about a 1% chance. Historically, this was a male disease and Caucasian middle-aged men were the typical patients that developed a stone. Historically, there was also more kidney stone disease in the south, in the southeast. Um, they referred to a kidney stone belt. And in general, the overall hospitalization rates for kidney stones in adults was about 62 per 100,000. For children, it was only 4.7 per 100,000. But over the past 25 years, there's been a lot of evidence to support this. Um, I'd like to review just a few of the, of the better studies, um, and we'll start by looking at some single institution and state studies and then some larger surveys of pediatric hospitals. So the first study is by Taysian in South Carolina, and South Carolina is interesting because they actually have very good record keeping. They capture all their emergency department visits, surgeries, and admissions in the state, and actually make these available to researchers. And so they looked at this 15 year period and they reviewed over 4.6 million patients and they found 152,000 unique patients that received either emergency care, inpatient care, or surgical care for kidney stones. And what they found was that there's a mean annual incidence that increased about 1% annually from 206 to 239 per 100,000 people over that 15-year period. But the other thing that they found was that the greatest increase was amongst teenagers between the ages of 15 and 19 years old, and every 5 years, on average, they, they increased about 26%. Uh, one of the co-authors on this study actually specifically looked at ER visits for children in South Carolina. And what they found was for girls, uh, the incidence nearly tripled, you know, up 7.7 per 100,000 all the way up to 21.9, and for boys, it, it nearly doubled. It went from 8 to 15. And then Dr. Karam, he looked at patients that went to 29 different emergency rooms, and these were spread out throughout the New York and New Jersey area, and they were a combination of urban ERs, rural ERs, and academic ERs, and they identified 1.3 million visits and over 1000 of them were for renal colic. Uh, the median age was 16 years, and, uh, interestingly, 61% of them were in girls. And if you look at the percentage of ER visits, um, it nearly doubled, and increased 86%. And uh this graph here just shows, you know, the very steep linear rise uh in the uh in the percentage of patients that went to the ER. Um, now, Roth and Company, they actually looked at inpatients. They used the PIS database. That was a pediatric hospital inpatient sample, and these were inpatients. Now these inpatients are, they're the more severe cases. These are patients that require inpatient admission or were admitted after uh pediatric stone surgeries for inpatient stays, and they found over nearly 8000 children. And what they found is in the FIS hospitals between '99 and 2008, it was a tenfold increase from 125 patients in 1999 to nearly 1400. And the mean number of stone cases per hospital per year, uh, nearly tripled as well from 13.9 to 32.6. And when they looked at the rates of pediatric stone patients as a percentage of overall total hospital patients. They also saw a significant increase. It went from 18.4 per 100,000 to 57 per 100,000 as well. So their adjusted annual increase was 10.6% per year. And just to make sure that this doesn't, uh, due to the fact that these hospitals were busier, they actually compared it to appendicitis rates, and the appendicitis rates actually stayed the same. So, that was their internal control. um. Bush actually uh looked at the same uh hospitals and they found risk factors for hospitalizations for kidney stones. And what they found was in terms of odds ratio, Uh, girls that were white, uh, patients that were white, uh, patients that were older than 8, had a greater odds ratio of being admitted for kidney stone disease. Uh, patients were more likely to be admitted in the late summer, which makes sense. And interestingly, as, as opposed to historical data, rather than being admitted more in the South, uh, North Central region patients were, were more likely to be hospitalized for stone disease. Uh, kidney stone disease, uh, accounted for about 1 out of 685 admissions. And the highest percentage of hospitalizations were Florida, but then also two hospitals in the Midwest, Indiana and Minnesota. So, next, I'd like to focus on the risk factors for kidney stones. Uh, the two most common ones are dehydration and a high salt diet. Um, infections also, um, are involved in a significant number of patients with kidney stones. Also, patients that have underlying anatomic abnormalities, either obstruction at the ureter or pelvic junction or ureteral vascular junction, or your ureter seals. In these cases, stasis of urine allows for increased concentration and crystallization of stones. Uh, patients that are immobile also have an increased risk for kidney stones. And certain medications um also um lead to kidney stone formation and about 40% of children with kidney stones have an underlying metabolic issue. I'd like to focus next on obesity. Uh, the initial studies were equivocal, but now there's growing evidence that suggests that patients that are overweight or obese, uh, have an increased risk of kidney stone formation. Um, here in Missouri, um, We rank about 27th out of the 50 states. About 31% of children are considered either overweight or obese, and in Illinois, actually they rank a little bit worse. They're 42 with about almost 35% of patients being either overweight or obese. This is a study out of uh Los Angeles, and they looked at their stone patients and then they stratified them based on their pubertal status, you know, their age, and then also their sex, and then compared that to uh um age and sex match control population. And what they found was that post pubertal females with kidney stones had a higher mean BMI than the controls. They also saw that uh pre-pubertal males with uh kidney stones had higher BMI's in control. And pre-pubertal and pubertal males, um, stone patients, uh, they were more likely to be overweight or obese than their non-stone counterparts. When they looked at the stone analysis of these patients, um, overweight and obese children formed more calcium oxalate stones. And that also makes sense because we know that obese individuals have higher urinary oxalate excretion and concentration in their urine, and also insulin resistance can also lead to greater oxalate production um by the liver. So next, I'd like to focus on the diagnosis and management of uh kidney stones. And then this is just a picture of um a management algorithm, but really, the workup depends on the acuity of the presentation. You know, an acute situation is a lot different than an incidentally identified kidney stone. So, In terms of the history, most of the times, uh, patients or children with kidney stones will actually have a positive family medical history about 3/4 of the time. Uh, you also, uh, definitely should look out for congenital urinary anomalies, and you may get clues from previous urinary surgeries. Uh, obviously, in the acute phase, uh, you want to focus on radiologic assessment and urine analysis, and we'll talk about that in a little more detail later. But really, the main thing in the acute phase is to determine whether or not the patient needs to be transferred or if you need to call a urologist, um, and whether or not to start uh antibiotics. So, some additional things to focus on, obviously, immobilization, any history or predisposition to uh malabsorption, uh history of cystic fibrosis. Uh, patients that have recurrent skeletal fractures, uh, may have issues with hyperparathyroidism. And then other questions you might want to ask about are prematurity, whether or not they were treated with uh Lasix, um, and use of sup supplemental vitamin D or certain nutrition formulas are, are actually quite high in calcium and phosphorus. Um, also, the patient's medication history is really important. Um, anti-convulsants and diuretics, uh, can predispose, uh, patient to kidney stones. Uh, the patient is on a ketogenic diet, they're at higher risk of uric acid stones and calcium stones. Also trying to determine sort of, uh, their overall sodium intake is important. And, uh, as we mentioned, if they have any urogenital anomalies or if they've had surgeries that predispose them to stasis, if their bladder neck has been closed or Uh, if they have issues with neurogenic bladder, um, and require catheterization, they are at increased risk of infection and subsequent stone formation. So, in terms of the urinalysis, in addition to looking for blood and um and also for leukocytes and uh bacteria, you can also look at the crystals, but you have to be careful with that because oftentimes you will see calcium crystals in stone formers and more often than you will in normal subjects. However, Even if you see them, there, there's no real diagnostic significance because it can or cannot occur in patients with or without stones. Uh, same thing with uric acid crystals, you know, you may be able to see them in a patient without a stone, especially if their urine is acidic. But the two times where it's diagnostic, if you do see cystine crystals or strevite crystals, um, that will provide you a diagnosis even in the absence of a stone analysis. So, um, in terms of the metabolic assessments, um, that should be postponed until after the acute events and after they're treated with antibiotics. Uh, as I mentioned, about 40% of children will have an identifiable metabolic predisposition, and the initial assessment should repeat the urine analysis to make sure there's no infection. And then check uh serum electrolytes, calcium phosphorus, magnesium, uric acid. In select cases, you may want to consider parathyroid hormones and vitamin D levels. And then uh we also check a 24 hour urine uh for volume, calcium, and other electrolytes. Uh, we always like to have the stone analysis, um, when stone analysis for children are surveyed, the majority of them are calcium oxalates, followed by calcium phosphate, and then uric acid, strevite, and cysteine stones are a minority. Uh, stone analysis is really the only way to determine drug stones, uh, and infections are an unlikely cause of non-strevite kidney stones. So in terms of how children present, the typical presentation for an adult is acute renal colic. There's localizing pain to the flank. It's usually severe, it comes in waves. And the waves of pain correlate with peristalsis and distension of the kidney, and that leads to severe pain, nausea and vomiting. Um, and then as the stone moves, the pain can actually move from the flank, radiating down to the abdomen as it moves down the ureter. And once it approaches the ureteral vesicle junction, pain can be referred either to the groin or testicle in boys or to the labia in girls as it tries to pass through the UBJ. Um, they also can present with urinary frequency, uh, into Syria as it's going through the urethra. But children present a little bit differently. Uh, they typically present with abdominal pain, but oftentimes it's hard to localize. Um, they just complain of abdominal pain. Uh, about 8 to 20% of them present initially with a urinary tract infection. Now, it's different. Infants, um, up to 75% of them actually present with a urinary tract infection first. And only about a third of them have gross hematuria. Um, and especially for children that are under the age of 12, only about 7% of them have uh localizing unilateral renal colic. So very different than adults. So, in the introduction, I mentioned the two societies that created newer guidelines for the management of children with kidney stones, and I'd like to specifically review the recommendations now for imaging and workup, initial management, and neurologic intervention. So in terms of diagnostic imaging, um, pretty much both agree that if imaging is going to be done, ultrasound should be the primary imaging modality. Uh, it's actually very good for finding stones in the kidney. It'll find about 90% of renal stones and about 50% of your renal stones, whereas a KUB will only detect about 30 or 60%, and that really depends on multiple factors. Patients' body habitats, presence of stool or gas in the uh in the colon as well. CT has always been the most sensitive and the most specific, but, uh, they've always come at a cost of much higher radiation doses. And so, I'd like to just talk about a typical case. You know, this is a 16 year old girl who develops a sudden onset of flank pain and nausea. She's afebrile, and this is her first episode of stone. Uh, the history and physical is otherwise unremarkable, and then, obviously, the first imaging study would be the ultrasound. And this actually shows the typical ultrasound findings that you can see. You know, you'll see the stone, uh, you'll actually see a twinkle artifact, and you'll also see an acoustic shadow. And then secondary findings, you'll see hydronephrosis in the obstructed ureter as well. Now, we are all very sensitive to the effects of radiation and especially in children because they're cumulative. And so, In terms of the radiation doses that are involved, um, here's just sort of a typical outline of, um, different types of radiation exposures. Natural background is about 3 millisieverts per year. Um, and so, uh, if you take an airline flight, it's about 0.04, so that's about 4 days of background radiation exposure. A chest X-ray is about 0.01, so it's about the same amount you would get exposed to just, you know, being out and about. Here on Earth, and a KUB is about 0.5 to 1.1 millisieverts, and that really depends, you know, larger patients get, you know, larger doses and historically, um, a standard CT KUB, looking for stones or non-contrast CT scan, it's about 4 to 5 millisieverts, so. There's been a lot of effort to try to reduce that, and then they actually now have ultra low dose CT scans where the mean sieverts is about 1, so maybe 1 to 2 KUBs as compared to a standard CT scan. And what they found is they actually performed quite well and similar to um a standard CT. Now, this paper was, was still a little aggressive, you know, they recommended that the ultra low dose CT scan should be considered as the first line modality, but um the current recommendations still recommend ultrasound and it makes sense. If you can avoid any radiation in a child, uh, that would, that would be preferable. And here's just an example of an ultra low dose CT and a standard CT, and you can actually see you do lose uh resolution, but for finding high density items such as a kidney stone, it's usually not an issue. But here is actually an uh micro or submillisievert CT scan. So now they can actually go down to 0.5 millisieverts, so about the same or less uh radiation than a, than a standard KUB. And then with image processing, you can actually see that you can actually get quite good resolution and still identify very small kidney stones. So, um, here's one study where they actually can lower the mean effective dose to 0.5 millisieverts. And for renal calculi, when compared to a standard KUV it's more sensitive, uh, it's almost as specific. And then for, uh, stones in the ureters, it's more sensitive and as specific. So, um, we're working with our um radiologist at Slit to do this. Uh, when you work at such low millisiever doses, there's a lot of post image processing that has to be done, and that takes a lot of time and computing power. Um, but, but obviously, anything that can be done to minimize radiation, um, is a priority. So moving on to the same case that we talked about. Um, she's afebrile. This is her first stone. She went to either the ER or your office and she was able to have her pain managed with ibuprofen, and the urinalysis was positive only for blood. So, this is a patient that should do well with uh medical management. And I'd like to discuss conservative or medical expulsive therapy, and according to the guidelines, you know, in pediatric patients with an uncomplicated ureter ureteral stone, less than 10 millimeters. Uh, clinicians should offer observation with or without medical explosive therapy using alpha blockers, and all the studies have been performed using a specific alpha blocker called tamsulosin or Flomax. Now, parents should be informed that this is off-label, um. But when you look at the trials of medical explosive therapy, even in the control arms or the non-treatment arms, 62% of patients that had a stone under 5 millimeters spontaneously passed it. And if it was larger than 35 larger than 5 millimeters, 35% passed these stones, and the two trials that they leaned on did show uh facilitation of stone passage. So parents often ask, you know, well, how long are we gonna wait? And uh it's prudent to uh limit the, the course of observation to a maximum of 6 weeks uh from the initial presentation to avoid uh renal injury. But that really depends on the symptommatology of the patient, you know, oftentimes if they are having symptoms off and on, families and patients usually won't wait that long and we usually, you know, uh, work with the families and if after a few weeks they're still having issues with intermittent renal colic. Um, we offer them, uh, some sort of therapy. And all this evidence is based on uh uh grade B level evidence. So, now, if the situation is different, you know, for example, if our patient had a high fever of 103 and her urinalysis suggested infection. And obviously we would be uh thinking differently. So, we'd be working on intervention, intravenous antibiotics, uh, likely transfer and uh likely uh urgent decompression. And in terms of the surgical indications, uh, especially if there's an infection, fever, uh, positivity, and hydronephrosis, we would like to start antibiotics and decompress uh the system as quickly as possible. Also, if a patient has intractable pain or vomiting, and they can't tolerate uh oral pain medicines or can't eat or drink, or if they fail conservative management, um, that's an indication for surgery. And we're very careful with patients that have renal insufficiency or a solitary kidney. So what I'd like to review next are. Contemporary techniques for kidney stone management and surgeries, um, just as a note, we as urologists define success in terms of stone-free rates. Uh, we'll also discuss complications and some surgical advances and new surgical uh techniques that we can use, uh, and are using uh at Slitch. So, these are sort of the traditional modalities, the shock wave lithotripsy, ureteroscopy, uh, percutaneous nephrolithotomy, and open surgery or minimally invasive surgeries, uh, I mentioned, although for pretty much historic reasons because they are very rarely performed. So in terms of his uh shock wave lithotripsy, historically, the success rates have been anywhere from 68 to 84% uh with one treatment. Oftentimes, they required several treatments, um, and traditionally, the shockwaves were actually focused using fluoroscopic guidance. Now, uh, at Slits and, uh, contemporary pediatric children's hospitals, the shock waves are actually guided with ultrasound, so we're able to avoid Additional radiation for our patients and the lithotrips are actually quite good. Um, they can get up to 88% stone free after one procedure. Uh, the complication rate is actually quite low. Um, there can be some nausea or vomiting. Uh, patients oftentimes have a little bit of blood in the urine. Steinstrasse or obstruction of the ureter from the stone fragments is rare, and then, uh, even more rare are hematomas of the, of the kidney, liver, or spleen. There are some theoretical concerns with shock wave lithotripsy to a pediatric kidney. Um, there are some animal models that do show that there's renal vessel vasoconstriction and some renal tubular injury. However, long-term studies for patients that have undergone shock wave lithotripsy as children haven't really been performed or reported yet, and there are some patients that developed subcapsular hematomas, and there's concern about Development of paged kidneys, but also not uh very uh often reported, so actually quite rare. OK. The next modality we'll discuss is ureteroscopy. Um, there, small telescopes are passed into the ureter, uh, with, uh, or before or, uh, actually after placement of a stent or just at the same time. Uh, and they're actually quite successful, about 88 to 94% of the time. For a distal ureral stone, uh, it can be cleared, and for stones that are in the kidney, uh, up to 82% can be cleared with one ureteroscopy. So, in general, the guidelines say for smaller intrarenal calculi, both shock wave lithotripsy and ureteroscopy are reasonable, but they also mention that additional procedures may be required. Now, The technologies that are used as adjuncts, laser lithotripsy and also ureteral access sheets are improving, such to the point where kidney stones that were actually quite large, for example, this patient, you can actually see that there's actually a large, almost 3 centimeter kidney stone. Historically, that patient would, would actually undergo a percutaneous approach, but now with uh stronger lasers and um Newer access sheets that actually simultaneously provide suction. We're actually able to remove these actually quite uh nicely. And this is just a uh a picture which actually shows this stone which is actually has been pulverized and just removed, and we did not have to go through her back. Um, The overall complication rates are also quite low, about 5%. Um, some patients do develop pyelonephritis afterwards. Um, the risks of ureteral perforation are very low, especially now with the ureteral access sheaths. Uh, vesicoureteral reflux that occurs is usually transient, and it's usually secondary to the dilation of the ureter that's required to pass the scopes. And delayed regional strictures are also becoming less common, especially with these uh radial dilating sheets that we use. Um, next, we'll talk about percutaneous nephrolithotomy, and this is reserved for, you know, the larger staghorn calculus as you can see here. It basically fills the entire collecting system and uh shock wave lithotripsy or ureteroscopy just, you know, it would just take too long or too many treatments. A small tract is made through the back into the kidney, and small scopes are passed and different types of energies are used to destroy the stone. And the stone-free rates are actually quite good, about 85% after one procedure. Uh, because you're actually going through the kidney, the complication rates are higher, uh, anywhere from 11 to 20%. Uh, these stones, stagger and calculi, are oftentimes associated with, uh, with struvite stones or infection stones. So despite pre-treatment with antibiotics, uh, sometimes these patients can develop uro sepsis, um, because you're going through the kidney, which is very vascular. There's a slightly higher risk of bleeding uh with the need for transfusion. Uh, urine leak and need for a stent is about 4 to 6% afterwards. Uh, things like adjacent organ injury are quite rare, um, although it's slightly higher if you're trying an anterior approach rather than a posterior approach just because you have to work around the colon. Now, historically, access and work has been done using fluoroscopic guidance, but now we're working just using ultrasound guidance as well, so we're working with radiation-free uh modalities and then also the sheaths have been getting smaller and smaller as the scopes have gotten smaller. So historically, a fairly large sheath was required to pass these scopes. Um, historically, there would be 24 French, but now we can work with either 20 or 16 French uh sheets as well, uh, also, uh, minimizing morbidity. And again, I mentioned that surgeries are quite rare. You know, open surgery is uh really for the historical textbooks. Laparoscopic and robotic surgery. Potentially has a role, but only if the patient also has um a congenital obstruction, for example, if they have a ureteropelvic junction, obstruction that needs to be repaired at the same time. Sometimes we remove the stone and then uh do the pyloplasty at the same time. So, uh, lastly, I'd like to focus on just some specific issues to children with kidney stones. We'll uh look at recurrence, uh, talk a little bit about prevention and, and how to handle the asymptomatic stone. So Lau and colleagues looked at the recurrence rate 5 years for children that actually required upper tract surgery for a kidney stone, and it was actually quite high. Uh, over half of these patients after 5 years required a, had another stone, uh, event. Uh, 65%, uh, happened if they had abnormal anatomy, so, um, and then. Again, also with increased if they had underlying metabolic issues as well, either hypercalcilia or hypocitrauria. And so, uh, in terms of what is the guidance for a patient with an asymptomatic stone, let's say they're getting an ultrasound for something else and, uh, incidentally, you find a, a kidney stone in the lower pole of the kidney, but they've never really complained of flank pain. Um, the guidelines suggest that active surveillance with regular ultrasounds every 3 to 6 months is reasonable. And this is a study that supports that. Um, they actually followed 284 patients with asymptomatic stones that were in the lower pole of the kidney and less than 10 millimeters, and they basically just followed them with ultrasounds and Uh, 110 of them, uh, with a mean follow-up of, uh, almost 4 years, um, basically did fine. Um, and then there was a subset of patients that did require shock wave lithotripsy, uh, and then some actually did progress and needed ureteroscopy or a PCNL, the percutaneous nephrolithotomy. But what they found was that the stones that were larger than 7 millimeters and if there was a renal anomaly. Or stones that were composed of cysteine or struvite, they were more likely to require an intervention. Whereas, uh, and they did conclude that lower pole kidney stones, less than 10 millimeters could be managed with, with observation. Um, parents often ask, you know, how can we prevent a stone and hydration is important, so we recommend that they drink about half their body weight in ounces. uh. And that's body weight in pounds. So an 80 pound child recommend drinking about 40 ounces of water daily. Um, they can actually also use lemonade or real lemon juice, uh, as a good source of citrate, which is a pretty strong stone inhibitor. Um, they would just mix about 1/2 a cup of lemon juice with 8 cups of water. And then just to limit meat, salt, and foods high oxalates, um. Now, uh, we're also encourage them to uh to try to maintain a healthy weight, uh, and then lower the salt in the diets, uh, but we do not recommend limiting calcium. So in summary, Uh, the incidence of pediatric kidney stones is increasing. Um, We are working very closely with our radiologic colleagues to uh minimize or in most cases avoid the use of radiation either for diagnosis or now even treatment. And surgical techniques are evolving. They're less invasive, more effective, and as I mentioned, minimize radiation. So with that, I, I do want to thank you. This is our team, Doctor Copeland and Doctor Trax. We've been here a long time. Uh, Tina and Renee are nurse practitioners, and this is our staff that kind of keeps us all organized and whenever we need any assistance from our adult colleagues or when we transition our patients, we are fortunate to be part of a very large division with uh a lot of expertise from our adult colleagues. So thank you very much for, for your time.
Related Presenters
