With miniaturization of instruments and refinement of surgical technique, the management of pediatric stone disease has undergone a dramatic evolution. While shock wave lithotripsy (SWL) is still commonly used to treat upper tract calculi, the use of ureteroscopy (URS) has dramatically increased and is now the procedure of choice for upper tract stone burdens less than 1.5 cm at centers with significant experience. Percutaneous nephrolithotomy (PCNL) has replaced open surgical techniques for the treatment of large stone burdens greater than 2 cm, with efficacy and complication rates similar to the adult population. Large institutional series demonstrate comparable stone-free and complication rates with SWL, URS, and PCNL, but concerns remain with these techniques regarding renal development and damage to the pediatric urinary tract. Randomized controlled trials comparing the efficacy of SWL and URS for upper tract stone burdens are needed to reach consensus regarding the most effective primary treatment modality in children.
Surgical management of urolithiasis in children has evolved dramatically over the past 2 decades. In the 1980s, the advent of shock wave lithotripsy (SWL) revolutionized pediatric stone management and is currently the procedure of choice in treating most upper tract calculi in industrialized nations. However, with miniaturization of equipment and refinement of technique, access to the entire pediatric urinary tract is now possible. In a growing number of centers, ureteroscopy (URS) is being performed in cases that previously would have been treated with SWL or percutaneous nephrolithotomy (PCNL). Recent data from large single-institution series demonstrate stone-free and complication rates for URS that are comparable with those for SWL, but prospective trials are necessary before consensus regarding the most effective primary treatment modality can be reached. This article provides a directed review of the literature, focusing on recent advances in the surgical management of pediatric stone disease.
Incidence of urolithiasis in children
The incidence and characteristics of nephrolithiasis in children reflect a wide geographic variation, but stones occur in children of all ages without clear gender predominance. Although uncommon in the western hemisphere, pediatric stone disease is considered endemic in developing nations including India, Turkey, Pakistan, and countries in the Far East. In these areas, ammonium acid urate and uric acid stones predominate, strongly implicating dietary factors. Despite this discrepancy between hemispheres, nephrolithiasis in children is increasing in occurrence globally, likely reflecting westernized lifestyle and dietary changes, including higher salt intake from processed foods, and decreased water consumption.
It is established that children with anatomic abnormalities, urinary tract infections, and metabolic disturbances are considered to be at high risk for stone development. In developing nations, recent reports suggest that a metabolic risk factor can be found on urine studies in 84% to 87% of children, most commonly hypercalciuria or hypocitrauria. However, evidence is accumulating that stones in a majority of westernized children are calcium based without any evidence of metabolic abnormality on 24-hour urine collection. In a retrospective study of 1440 Pakistani children, Rivzi and colleagues reported that while diet, dehydration, and poor nutrition remain the major causative factors of pediatric nephrolithiasis, there is an emerging predominance over the past decade of upper tract calculi more consistent with adult populations. Recent data support this trend: in a modern series of 150 children managed over an 8-year period, Kalorin and colleagues reported that 57% of stones detected in children younger than 10 years were located in the upper tract.
Diagnosis, metabolic evaluation, and surveillance
Renal calculi in neonates and younger children are often diagnosed with ultrasound. Although anatomic location and the associated presence of hydroureteronephrosis can be accurately assessed in a majority of children, up to 40% of calculi may be missed using ultrasound. Despite the increased sensitivity of computed tomography (CT) compared with ultrasound, concerns regarding radiation exposure limits its use in young children. Although speculative, risk as high as 1 fatal cancer for every 1000 CT scans performed in young children has been reported. Investigators recently have begun to reassess diagnostic thresholds in an effort to reduce radiation exposure without sacrificing diagnostic efficacy, particularly in children with complex stone histories requiring serial imaging studies.
In the authors’ practice, asymptomatic calculi incidentally diagnosed with ultrasound are followed with serial ultrasound or plain abdominal films to minimize radiation exposure. Noncontrast helical CT is the diagnostic test of choice in older children presenting acutely with flank pain, but is reserved for younger children for whom plain films or ultrasound are nondiagnostic. Following definitive therapy, children are ideally followed in a multidisciplinary stone clinic including urologic, renal, nutrition, and endocrine evaluation if necessary. Routine evaluation includes urine culture, 24-hour urine collection, and office-based ultrasound or abdominal films to detect recurrence. While there is abundant reference material in the adult literature, data regarding standard 24-hour urine reference values for stone risk factors in children is just beginning to emerge, and identifying normal 24-hour urine parameters for nonstone formers is currently is the subject of prospective evaluation in the authors’ practice. Follow-up is individualized and is based on age, anatomy, stone burden, and any underlying metabolic abnormality.
Diagnosis, metabolic evaluation, and surveillance
Renal calculi in neonates and younger children are often diagnosed with ultrasound. Although anatomic location and the associated presence of hydroureteronephrosis can be accurately assessed in a majority of children, up to 40% of calculi may be missed using ultrasound. Despite the increased sensitivity of computed tomography (CT) compared with ultrasound, concerns regarding radiation exposure limits its use in young children. Although speculative, risk as high as 1 fatal cancer for every 1000 CT scans performed in young children has been reported. Investigators recently have begun to reassess diagnostic thresholds in an effort to reduce radiation exposure without sacrificing diagnostic efficacy, particularly in children with complex stone histories requiring serial imaging studies.
In the authors’ practice, asymptomatic calculi incidentally diagnosed with ultrasound are followed with serial ultrasound or plain abdominal films to minimize radiation exposure. Noncontrast helical CT is the diagnostic test of choice in older children presenting acutely with flank pain, but is reserved for younger children for whom plain films or ultrasound are nondiagnostic. Following definitive therapy, children are ideally followed in a multidisciplinary stone clinic including urologic, renal, nutrition, and endocrine evaluation if necessary. Routine evaluation includes urine culture, 24-hour urine collection, and office-based ultrasound or abdominal films to detect recurrence. While there is abundant reference material in the adult literature, data regarding standard 24-hour urine reference values for stone risk factors in children is just beginning to emerge, and identifying normal 24-hour urine parameters for nonstone formers is currently is the subject of prospective evaluation in the authors’ practice. Follow-up is individualized and is based on age, anatomy, stone burden, and any underlying metabolic abnormality.
Conservative management
Conservative management of pediatric nephrolithiasis closely mirrors that of adults. Even in very young children, renal calculi smaller than 3 mm are likely to spontaneously pass, and stones 4 mm or larger in the distal ureter are likely to require endourologic treatment. In the authors’ practice, if a child’s pain is controlled with oral analgesia, clear liquids are tolerated, and there is no evidence of urinary tract infection, parents are offered a closely monitored trial of spontaneous passage for 4 to 6 weeks prior to definitive therapy. Based on efficacy demonstrated in the adult population, tamsulosin may be offered on an individualized basis as adjunctive therapy to facilitate ureteral expulsion. A ureteral stent is placed acutely in children with evidence of an infected genitourinary system, refractory colic, or uncontrolled nausea and vomiting. Under these circumstances definitive therapy is delayed 7 to 14 days following stenting to allow for system decompression, ureteral orifice dilation, and resolution of edema before endourologic management is undertaken.
Pediatric considerations
Special considerations in the endourologic management of stone disease in children include preservation of renal development and function, prevention of radiation exposure, and minimizing the need for retreatment. Despite advances in endourologic equipment and technique, controversy remains regarding the contribution of SWL to future development of diabetes or hypertension, and whether ureteral orifice dilation during URS leads to ureteral stricture formation or development of vesicoureteral reflux. International consensus is lacking as to the most effective surgical management of pediatric stone disease because of the lack of prospective randomized trials comparing treatment modalities and disparity in the access to emerging technologies. Regardless of treatment modality, the presence of residual stone fragments is associated with adverse clinical outcome, and every attempt should be made to achieve a stone-free status. Surgeon experience is paramount to facilitate complete stone clearance and minimize retreatment rates. The decision regarding the most efficacious primary treatment modality must be individualized per child based on age, anatomy, location, and composition of stone burden.
Antibiotic use
Use of perioperative antibiotics in the management of pediatric urolithiasis closely mirrors that in adult patients. Per the 2008 American Urologic Association best practice statement on antibiotic prophylaxis, up to 24 hours of perioperative antibiotics are indicated in all patients undergoing upper tract instrumentation. Appropriate agents include fluoroquinolones, trimethoprim-sulfamethazole, first- and second-generation cephalosporins, and ampicillin in combination with an aminoglycoside. A urine culture is mandatory before all upper tract procedures to determine if the urine is sterile, and culture results are used to guide preoperative antibiotic therapy, particularly for percutaneous procedures, patients with high-grade obstruction, or patients with an indwelling stent. In the authors’ practice, children with a negative urine culture undergoing uncomplicated SWL and URS procedures receive perioperative cefazolin, and all children undergoing a percutaneous procedure or that have a preexisting ureteral stent/nephrostomy tube receive a fluoroquinolone or ampicillin/gentamicin. Use of postoperative antibiotics is controversial and is determined on a per child basis, especially with recent data demonstrating an increased risk of developing resistant bacterial strains with prolonged use of antibiotic prophylactic therapy.
Shock wave lithotripsy
The emergence of SWL revolutionized the minimally invasive treatment of urolithiasis during the early 1980s. Initially reported in children in 1986, large series have reported complication, safety, and stone-free rates comparable with those of adults ( Table 1 ). When used as a primary treatment option for upper tract calculi, SWL efficacy ranges from 68% to 84% and has become the preferred treatment modality for uncomplicated renal and proximal calculi of 15 mm or less. In a contemporary series of 216 children (mean age 6.6 years) with a mean stone size of 14.9 mm undergoing SWL with the Dornier HM3 lithotriptor, Landau and colleagues reported a 3-month stone-free rate of 80%, demonstrating that efficacious stone-free rates can be achieved in appropriate candidates. Complications rates are minimal, and range in severity from hematuria and ecchymosis to obstruction with sepsis. Although well tolerated in children, current stone-free rates with SWL are difficult to interpret from the existing body of data due to discrepancies between studies with regard to type of lithotriptor, number of shocks administered, and retreatment rates. Recent data suggest that stone-free rates in children with a history of urologic condition or urinary tract reconstruction are low (12.5%) and, with alternative surgical techniques available, may be better served with URS or PCNL. Despite encouraging results, SWL has not been approved by the Food and Drug Administration for use in children, although it is a widely accepted treatment modality.
| Report | Lithotripter | Children/Renal Units | Mean Age (y) | Stone Location (%) | Mean Size (mm) | Retreatment Rate (%) | Stone Free (%) | Complications (%) |
|---|---|---|---|---|---|---|---|---|
| Myers et al | Siemans Lithostar | 446 | 13.7 R 14.1 U | 53.4 R 46.6 U | 12.3 R 7.3 U | 10.7 R 3.5 U | 67.9 R 91.1 U | Sepsis 0.2 |
| Muslumanoglu et al | Siemans Lithostar | 344 | 8.7 | 57.1 R 42.9 U | n/a | 53.9 | 73.3 | Overall 9.6 Steinstrausse 7.8 UTI 1.2 Colic 2.9 |
| Rizvi et al | EDAP LT02 Technomed | 262 | n/a | 67.6 R 32.4 U | n/a | 29.5 | 84.2 R 54.1 U | Colic 10.1 Fever 8.5 Steinstrausse 1.1 Hematuria 11.3 |
| Aksoy et al | Dornier MPL 9000 | 129/134 | 8.7 | 84.4 R 15.6 U | 15.7 | n/a | 85% | Overall 14.7 Steinstrausse 5.4 UTI 7.8 Hematoma 0.8 |
| Raza et al | Piezolith 2300; Dornier Compact Delta | 122/140 | 7.7 | n/a | 17.9 | n/a | 69 | Fever 2.9 Colic 7.2 Steinstrausse 2.4 |
| Demirkesen et al | Siemans Lithostar | 126/151 | 8 (median) | 66.9 R 33.1 LP | 10 R 6 LP | 40 | 71.5 | Overall 7.2 fever 0.8 Steinstrausse 6.4 |
| Nelson et al | Dornier Compact Delta | 111 | 10.5 | 87.4 R 12.6 U | 8 | 22 | 58.6 | Overall 7 Obstruction 2 UTI 2 Hematoma 2 |
| Landau et al | Dornier HM3 | 216 | 6.6 | 72.7 R 27.3 U | 14.9 R 9.5 U | 19.7 R 22 U | 80 R 78 U | Overall 2.8 Fever 0.5 Obstruction 0.5 UTI 0.5 Pain 0.9 |
SWL Technique in Children
General anesthesia is administered in a majority of smaller children to avoid both patient and stone motion, and the need for repeated repositioning. With modern lithotriptors, intravenous sedation has been successfully employed in select older children. Bowel preparation is seldom utilized to avoid dehydration and electrolyte imbalance postoperatively. The number of shocks delivered and the kilovoltage used vary per lithotripter, but the current consensus is that low power settings (17–22 kV) be used to prevent stone migration during the procedure, with 3000 shock waves per session (<2000 in very young children). A recent report assessed and compared the number and intensity of shock waves required for stone fragmentation in 44 children (mean age 5.9 years) and 562 adults (mean age 40.9 years). With an equivalent number of sessions (1.1 vs 1.1), the mean number of shockwaves (950 vs 1262, P <.001) and the kV required (11.8 vs 12.4, P <.001) were significantly reduced in the pediatric cohort. Although still a controversial matter and dependent on stone burden and anatomy, the authors do not routinely stent children prior to SWL. However, ureteral catheters are occasionally employed to aid in the localization of radiolucent calculi.
Stone Size, Location, Composition, and Patient Age
Whereas early series focused primarily on the feasibility, safety, and efficacy of SWL in children, recent efforts have centered on identifying demographic, anatomic, and stone-related prognostic factors for treatment success. SWL is currently considered the primary treatment for upper tract calculi 15 mm or smaller in children, but evidence supporting this stone size cut-off is lacking, Ather and Noor analyzed the correlation between stone size and clearance in 105 children younger than 14 years. These investigators reported an overall stone-free rate of 95% after a mean of 1.7 treatments, with 5% of patients requiring additional procedures as adjuncts to SWL. With a maximum of 30 mm, mean stone size in the treatment success group was 14 mm compared with 16 mm in the treatment failure group. In contrast, Elsobky and colleagues reported a 91% stone-free rate versus 75% stone-free rate for mean stone diameter less than and greater than 10 mm, respectively. Recently, Shouman and colleagues reported a series of 24 children with a mean stone size of 31 mm undergoing SWL with the Dornier DoLi S device. In 53 sessions requiring a mean number of 3489 shock waves per session, stone-free and complication rates were 83.3% and 25%, respectively. While it is possible to treat very large stone burdens with SWL, concerns include the necessity of more shock treatments, more frequent retreatment sessions, and increased risk of postoperative obstruction. Further study delineating a clear size cut-off for uncomplicated upper tract stone burden is required to effectively counsel parents regarding the most effective first-line therapy for renal calculi between 1 and 1.5 cm.
Renal anatomy and stone location has been subject of recent interest. The subject of frequent debate in the adult population, the most effective management of lower pole calculi in children has yet to be determined. Stone-free rates from initial small retrospective SWL series range from 56% to 61% with retreatment rates as high as 40%. SWL failure and retreatment rates were associated with increased mean stone burden, increased infundibular length, and infundibulopelvic angle greater than 45°. Staghorn calculi are uncommon in children and represent a management challenge. Although monotherapy success rates are low in adults, acceptable stone-free rates in children have been achieved with SWL. In 23 children stratified by age with a mean stone burden of 1.6 cm, Lottmann and colleagues reported an overall stone-free rate of 82.6% with only one case of symptomatic obstruction. A ureteral stent was placed in 22% of children, and these investigators reported an 88% stone-free rate in children younger than 2 years compared with 71% in children aged 6 to 11 years. In 42 children with a mean stone burden of 3.2 cm stratified by ureteral stent placement, Al-Busaidy and colleagues reported an overall stone-free rate of 79%. Although stent placement did not affect stone-free rates, the investigators found that stent placement significantly reduced the major complication rate. The superior success rates with SWL monotherapy in children compared with adults have been attributed to softer stone composition, smaller relative stone volume, increased ureteral compliance to accommodate stone fragments, and smaller body volume to facilitate shock transmission. SWL safety and efficacy have been demonstrated even in very young children. McLorie and colleagues treated 34 children younger than 3.5 years (mean age 23 months) and reported an 86% overall stone-free rate (66% after one treatment) without major complications. Treatment of proximal ureteral stones has achieved similar success rates to renal stones in most pediatric series, although ureteral stenting is more commonly employed to aid in stone localization and clearance. Treatment of mid to distal ureteral calculi have historically been avoided in children because of difficulties with localization over the sacroiliac joint and concern regarding possible injury to developing reproductive systems.
SWL success by stone composition is similar between the adult and pediatric populations. Cystine stones are uniquely challenging due to their durability and high recurrence rates. While SWL monotherapy has demonstrated variable results in adults, there are few reports on the pediatric population. In a small recent series, Slavkovic and colleagues reported a 50% stone-free rate in 6 children with cystine stone burden ranging from 0.2 to 2.5 cm. Although stone-free rates were low, fragmentation was achieved in 100% of patients, and the stone dissolution was achieved with medical therapy in the remaining children following SWL. Investigators have proposed that cystine stones formed within 2 years of therapy may be more easily fragmented with SWL, and that stone number, and not diameter, may be more predictive of success.
Limitations and Concerns
In children there is currently no consensus regarding the maximum size of residual stone fragments (RF) that are considered clinically significant, and as a result there is no clear definition as to what constitutes “stone-free” status. While children have been shown to have a greater capacity to clear fragments than adults, the presence of RFs has been correlated with adverse clinical outcome. Afshar and colleagues followed 26 renal units with RFs of 5 mm or smaller, and reported that while 31% were asymptomatic with no fragment growth, 69% had adverse clinical outcomes including RF growth or clinical symptoms. Patients with RF had a significant increase in adverse clinical outcome compared with stone-free subjects, and the presence of metabolic disorders was associated with RF growth. For these reasons, metabolic evaluations are now routinely being performed in children with a history of calculi, and every attempt should be made to achieve stone-free status. It is currently unclear whether placement of a ureteral stent prior to SWL facilitates fragment passage and improves stone-free outcomes. Although pre-stenting rates are not consistent across series, current relative indications include cases of solitary kidneys, staghorn calculi, large ureteral calculi, obstruction, and abnormal anatomy, not being based on total stone burden.
Although SWL is well tolerated in children with few complications, stone-free rates following single-session monotherapy remain as low as 44%. As a result, children are subjected to multiple treatments requiring general anesthestia. The need for multiple treatment sessions is concerning because the effects of shock waves on renal tissue are unclear. A growing body of evidence in adults indicates that shock waves result in renal vessel vasoconstriction, and that renal tubular injury and subcapsular hematoma from cavitation and shear forces are dependent on the kilovoltage applied. In a large series of 340 adult patients with a mean follow-up of 19 years post SWL, Krambeck and colleagues reported an increased risk of hypertension and diabetes mellitus related to bilateral treatment, number of administered shocks, and treatment intensity. Although these results are concerning, differences between pediatric and adult populations and limitations inherent to a questionnaire-based retrospective study make application of these data in children difficult. Retrospective studies with limited follow-up in children have reported that SWL and PCNL do not cause renal morphologic or functional alteration measured by glomerular filtration rate and serial dimercaptosuccinic acid functional studies, but long-term data to date are unavailable. To eliminate confounding variables and fully address the risks of chronic renal damage from SWL, long-term prospective data in children are clearly required.
Percutaneous nephrolithotomy
The safety and efficacy of PCNL for large stone burdens have been well established in adults. Initially urologists were reluctant to perform PCNL in children due to concerns regarding the use of large instruments in pediatric kidneys, parenchymal damage and the associated effects on renal function, radiation exposure with fluoroscopy, and the risks of major complications including sepsis and bleeding. However, with increasing experience ( Table 2 ), PCNL is currently being used as monotherapy and in combination with SWL (sandwich therapy) in children achieving stone-free rates ranging from 68% to 100%. Although there is no current international consensus, relative indications for PCNL as primary therapy in children include large upper tract stone burden (>1.5 cm), lower pole calculi greater than 1 cm, concurrent anatomic abnormality impairing urinary drainage and stone clearance, or known cystine or struvite composition.
| Study | No. of Children/Renal Units | Mean Age (y) | Stone Size (mm) | Transfusion (%) | Stone Free (%) | Sandwich Therapy (%) | Complications (%) |
|---|---|---|---|---|---|---|---|
| Badawy et al | 60 | 6 | n/a | 3.3 | 90 | 1.7 | Fever 8.3 Colon injury 1.7 Urine leak 3.3 Open conversion 5 |
| Zeren et al | 55/62 | 7.9 | 16.8 | 23.9 | 86.9 | 1.6 | Fever 29.8 Open conversion 1.6 |
| Rizvi et al | 62 | n/a | 47 | 25.3 | 67.7 | 27.4 | Open conversion 4.8 Fever 46.8 Urine leak 6.4 Hydrothorax 1.6 |
| Desai et al | 56 | 9.1 | 18.4 | 14.3 | 89.8 | 5.4 | Urine leak 5.4 |
| Salah et al | 135/138 | 8.9 | 22.5 | 0.7 | 98.6 | 0 | Urine leak 8 |
| Holman et al | 138 | 8.9 | 22.5 | 0.4 | 98.5 | 0 | Fever 1.1 Urine leak 8 |
| Samad et al | 169/188 | 8.2 | 27.2 | 4 | 59.3 | 34.5 | Fever 42.8 Hyponatremia 0.1 Obstruction 0.1 |
| Shokeir et al | 75/82 | 6.6 | 14.4 | 1.2 | 95.1 | 4.8 | Urine leak 1.2 |
Related posts:
Hypospadias: Etiology and Current Research
Cryptorchidism: Pathogenesis, Diagnosis, Treatment and Prognosis
Urologic Care of the Neurogenic Bladder in Children
Lower Urinary Tract Dysfunction in Childhood
Treatment Strategy for the Adolescent Varicocele
Laparoscopic and Robotic Approach to Genitourinary Anomalies in Children
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
