The increasing incidence of pediatric stone disease has coincided with significant advances in technology and equipment, resulting in drastic improvements in management. Miniaturization of both ureteroscopes and percutaneous nephrolithotomy (PCNL) equipment has facilitated access to the entirety of the urinary tract and has made ureteroscopy a first-line therapy option along with shock-wave lithotripsy for kidney and ureteral stones. Advances in PCNL have decreased patient morbidity while preserving stone clearance rates. In this review, the advances in operative approach for ureteroscopy and PCNL in children and its applicability to current surgical management of pediatric stone disease are discussed.
Key points
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The incidence of pediatric nephrolithiasis is increasing.
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Efforts must be made to minimize radiation exposure for both diagnostic and interventional procedures in the pediatric age group.
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Knowledge of the available instrumentation is critical for successful and safe stone removal.
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Miniaturization of equipment and improved optics have facilitated surgical access to all portions of the collecting system and decreased patient morbidity.
Introduction
The incidence of pediatric stone disease has increased drastically over the past 2 decades, particularly in the adolescent age group. This increase in pediatric stone disease has made pediatric urolithiasis an increasingly recognized problem across the world with significant health care cost. In turn, this has coincided with further refinement in the diagnosis, metabolic assessment, and management of the pediatric stone patient. Surgical therapy for pediatric stone disease has undergone significant refinement during that timeframe, decreasing the morbidity of surgical intervention with miniaturization of equipment and drastically improved optics, thereby strengthening the pediatric urologist’s armamentarium by significantly improving ureteroscopy (URS) and percutaneous nephrolithotomy (PCNL) for application to children.
Introduction
The incidence of pediatric stone disease has increased drastically over the past 2 decades, particularly in the adolescent age group. This increase in pediatric stone disease has made pediatric urolithiasis an increasingly recognized problem across the world with significant health care cost. In turn, this has coincided with further refinement in the diagnosis, metabolic assessment, and management of the pediatric stone patient. Surgical therapy for pediatric stone disease has undergone significant refinement during that timeframe, decreasing the morbidity of surgical intervention with miniaturization of equipment and drastically improved optics, thereby strengthening the pediatric urologist’s armamentarium by significantly improving ureteroscopy (URS) and percutaneous nephrolithotomy (PCNL) for application to children.
Epidemiology
The incidence of stone disease in the pediatric population has been increasing worldwide. Population and institutional studies have revealed a startling increase in stone disease over the past 2 decades, particularly for the adolescent age group (12–17 years of age). Review of the Pediatric Health Information System hospitals identified a 10-fold increase from 125 children in 1999 to 1389 in 2008. Identification of systemic risk factors resulting in this increase has identified hypertension, diabetes, salt intake, decreased water intake, and increased/decreased body weight, although the strength of these associations has varied by study. Metabolic derangements are common in children and could explain recurrence rates as high as 55% after surgical intervention. Hypocitraturia, hypercalciuria, and oliguria are the most common causes identified in pediatric 24-hour urine assessment. Most stones in children are calcium-containing with a much smaller proportion of uric acid compared with adults. Contrary to the adult population, girls are slightly more likely to develop stone disease than boys. Boys appear to be more susceptible to developing stones in the first 10 years of life, while this ratio shifts to girls in the second decade. Non-Hispanic whites are more likely to develop stones than Hispanic and black children.
Imaging
The imaging modality of choice in the pediatric population for a suspected stone is either a noncontrast CT scan and/or a renal bladder ultrasound (US). Although US is less sensitive and specific when compared with CT for overall stone recognition, CT scan unfortunately exposes the child to ionizing radiation, thereby increasing their risk of developing cancer. Despite these concerns, CT scan utilization is on the rise in the pediatric population, most likely because its sensitivity and specificity for stone diagnosis approach 100%. Although the cancer risk of a single CT scan is low, the fact that stone recurrence is common and can lead to multiple scans over an extended period of time could result in a lifetime of incremental radiation exposure. Comparing the diagnostic effectiveness of combined US and kidneys, ureters, and bladder radiograph (KUB) to CT scan in children presenting with symptomatic stones, the US and KUB resulted in the correct diagnosis 90% of the time. US and KUB were able to diagnose a stone and, if suspicion prompted subsequent CT, a strong argument could be made for them as screening tools. Factors that increase US sensitivity for stone detection include dilation of the ureter and/or pelvis, direct visualization of stones, and the lack of a ureteral jet. In 2012, the American Urological Association released guidelines identifying US as first-line screening tool for urolithiasis with CT scan reserved for situations in which the diagnosis is unclear or if it is necessary for more precise surgical planning. That being said, US poorly identifies ureteral stones and can overestimate stone size, particularly when stones are less than or equal to 5 mm, which can negatively impact surgical planning.
Workup
The signs and symptoms of stone disease vary in the pediatric population based on age and underlying comorbidities. Older children can present similar to adults with renal colic, abdominal pain, nausea, and vomiting. In younger children, the diagnosis can be much less obvious and can present with hematuria, urinary tract infection (UTI), abdominal pain, nausea, and vomiting. A detailed history for all patients should include identification of any underlying medical conditions and medications, dietary habits including fluid intake, and family history of stone disease.
In general, all children with nephrolithiasis should undergo routine metabolic workup, even first-time stone-formers. This metabolic workup should include a complete metabolic blood panel and a 24-hour urine collection, which should include supersaturation profiles of calcium oxalate, calcium phosphate, and uric acid, which can be elevated even in the setting of normal 24-hour urine values, increasing the risk for stone development. Patients with renal anomalies (ureteropelvic junction [UPJ] obstruction, calyceal diverticulum, vesicoureteral reflux) and those that undergo surgical stone removal warrant further assessment because their risk of recurrence is significantly elevated. Lao and colleagues examined recurrence rates in patients undergoing surgical intervention for stone disease. They found a 5-year overall recurrence rate of 55%, which was significantly more likely to occur for renal stones (93%) than ureteral stones (26%), and those undergoing PCNL (100%) were more likely to recur than those that underwent URS (28%). Hypercalciuria and/or hypocitraturia have been identified in anywhere from 70% to 90% of pediatric patients with urolithiasis and present not only a risk for recurrence but also a target for dietary modification and medical intervention. Population studies seeking to identify systemic illnesses associated with stone development parallel those in adults have identified hypertension, obesity, and diabetes as systemic illnesses that may increase risks for developing stone disease. As insights into the medical aspect of stone disease continue to make gains, this assessment and targeted medical therapy will be able to be incorporated into surgical management to decrease recurrence rates.
Ureteroscopy
Treatment options for pediatric stone disease include shock wave lithotripsy (SWL), URS, PCNL, and open stone removal via an open or a minimally invasive approach. Guidelines published in 2007 identify URS as first-line treatment, along with SWL, in the management of ureteral and renal calculi in the pediatric patient. Before that time, URS was recommended as second-line therapy because of poor instrumentation. Indeed, URS along with SWL has now become the first-line therapy for renal and ureteral stones at many institutions.
Technique
The authors’ technique is as follows. All patients are administered perioperative intravenous antibiotics and general anesthesia. The patient is then placed in the dorsal lithotomy position. Cystoscopy is performed and intraoperative urine culture is always obtained. The ureteral orifice is cannulated with either a sensor or a guide-wire and an appropriately sized open-ended catheter is inserted to perform a retrograde pyelogram and to determine ureteral diameter and whether it will accommodate the ureteroscope. If it appears as though the ureter is too narrow, a double J stent is placed and a staged URS is performed. If the ureter is of sufficient caliber, a dual lumen catheter is placed and a second wire is inserted. A ureteral access sheath is then placed to facilitate scope passage and stone removal and to decrease ureteral trauma. The authors use the holmium:YAG laser for lithotripsy when appropriate. For intrarenal and proximal ureteral access, they use a 7.5-Fr ureteroscope and for distal stones a 7.5-Fr semirigid ureteroscope. When a ureteral stent is left in place, the authors try to leave a tether when appropriate to facilitate removal; otherwise, it is removed in 1 to 8 weeks endoscopically under general anesthesia. Follow-up consists of US 4 to 8 weeks after URS.
Recent advances
Efforts to decrease radiation exposure in the pediatric population have led to the pursuit of alternative methods to fluoroscopy to facilitate URS. In adult patients, US guidance has successfully facilitated entire procedures, without compromise of operative times, stone-free rates, or complication rates. The authors recognize that although the radiation exposure for a single procedure is low, the recurrent nature of stone disease and the increased susceptibility of the pediatric patient to radiation make minimizing radiation exposure imperative. As such at the authors’ institution, they have begun to use US guidance in select routine URS and double J stent insertion procedures in place of fluoroscopy. Alternatively, others have found that intraoperative radiation utilization can be significantly reduced with user education, monitoring, and institution of a radiation safety checklist. Regardless of the method, efforts to minimize or abstain from radiation utilization are imperative in this age group.
Perhaps the biggest advancement facilitating URS in the pediatric patient is equipment miniaturization and advancements in optics. Previously, adult-sized equipment was used in a limited fashion in children. This shift has allowed for retrograde access to the entire collecting system via URS and made it a viable treatment option along with SWL ( Fig. 1 ). Semirigid ureteroscopes are now as small as 4.5-Fr and have been used successfully in the pediatric population. A self-dilating 4.5-Fr scope has a tapered tip with a 6.5-Fr body, particularly suited for distal or midureteral stones; this has allowed intubation of smaller-sized ureters without the need for dilation. Authors highlight the atraumatic nature of scope passage, which obviates postoperative stent insertion. Visualization was not impaired as stone free rates after 1 procedure were 97%. The 4.5-Fr Wolf ureteroscope (Wolf, USA) has a 6° lens with a 3.3-Fr working channel that accommodates a 150-μm laser fiber or a 3-Fr basket. An additional advantage of the 4.5-Fr scope was a drastically decreased need for ureteral dilation to remove the stones successfully. Further studies have since shown that in children less than 3 years old, the 4.5-Fr ureteroscope offers a distinct advantage in successful stone removal and complication rates when compared with the 7.5-Fr ureteroscope. One group found no difference in outcomes or complication rates in children undergoing rigid (8-Fr) or semirigid (6.9-Fr) URS.
Active dilation
Although advancements in instrument miniaturization have made URS feasible in small children, the ureter does not always accommodate even the smallest of equipment now available. In such cases, options include active or passive ureteral dilation of the ureter and ureteral orifice. Active dilation includes passage of coaxial dilators or dilation with a balloon dilator. Indications for active dilation include a ureter that was not prestented or when difficulty is encountered with scope insertion. The benefit of coaxial dilators versus balloon dilation is the tactile feedback that provides assessment of the ureteral lumen, the determining factor to proceed with ureteral dilation versus stent insertion for passive dilation. Long-term sequelae of active dilation in the pediatric population are unknown at this time and, because most follow-up consists of renal bladder US to look for hydronephrosis, strictures in the absence of significant dilation can be missed.
Passive dilation
Passive dilation, on the other hand, involves insertion of a double J stent, and after 1 to 2 weeks the patient’s ureter is sufficiently dilated to facilitate scope passage and stone removal. In theory, this approach is less traumatic to the ureter, although a direct comparison in the literature is lacking. One drawback to this approach is that the child is exposed to a second anesthetic to complete the stone removal, and possibly a third if a stent is left without a tether and endoscopic removal is required. Attempts to preoperatively identify patient characteristics, such as height, weight, and body mass index, and correlate them to the ability to perform URS without pre-stenting were inconclusive. The authors were able to use coaxial dilators to successfully perform URS in 13 of 30 (60%) patients, although the remainder required stent placement for passive dilation. The decision to prestent or to dilate is left to the surgeon’s discretion and is determined by the ease of catheter, scope, and access sheath passage. It is prudent not to hesitate to place a stent for passive dilation if resistance is encountered. At the authors’ institution, they place a stent for when a ureter does not readily accommodate scope passage and rarely pursue active dilation.
Age itself is not a limiting factor for performing successful URS. Mokhless and colleagues published their experience with 21 children with ages ranging from 8 months to 6 years. None of the patients required ureteral dilation, and they were able to navigate the ureter with either a 6.9-Fr rigid miniscope or a 9.5-Fr rigid ureteroscope. They were unable to access the ureter in 1 patient and were able to completely remove the stone burden in 18 of 21 of their cohort. Only 3 of 21 patients required stenting after URS, suggesting that with the appropriate equipment URS remains an option for all age groups.
Ureteral access sheath
Ureteral access sheaths facilitate URS by reducing the trauma of repeat scope insertion across the UVJ and distal ureter for stone removal, decreasing intrarenal pressures, and facilitating visualization. These benefits of the ureteral access sheath for adult URS have been proven to carry over in the pediatric population, and in general, they are well tolerated by the smaller-sized ureter, albeit at times only after dilation. Caution must be taken, however, because passage of a ureteral access sheath has been shown to transiently compromise ureteral blood flow, although these changes were not persistent 72 hours after insertion. Complications related to ureteral access sheath center around ureteral perforation and occurred in 6 of 40 cases in a report by Wang et al. Despite a 10% rate of ureteral perforation, the rates of postoperative hydronephrosis did not differ in the sheath group versus the nonsheath group, although definitive excretory studies to rule out ureteral strictures were not performed. In adult patients, ureteral access sheath has resulted in ureteral injury rates as high as 46%, although prestenting the ureter significantly decreased these rates.
Postoperative stenting
Postoperative stenting is another practice that is left to the surgeon’s discretion. Trials in adult patients have revealed that uncomplicated URS can be safely performed without postoperative stent placement. No such randomized trials have been performed in pediatric patients to date but reports in which stents were not left indicate that it was done so without any complications. The decision to leave a stent is based on the duration of the procedure, the degree of ureteral trauma, and the amount of ureteral edema. Stent options include an open-ended catheter that is removed before hospital discharge, an internal double J stent with an externalized tether that can be removed by the family in 3 to 7 days, or an internalized double J stent that is removed under general anesthesia in 1 to 8 weeks.
Options for lithotripsy include ultrasonic, electrohydraulic, laser, and pneumatic lithotripters via URS. The holmium:YAG laser has been directly compared with the pneumatic lithotripter and has resulted in shorter operative times, improved stone-free rates, decreased complications, and decreased stone migration. Many reports have found that the pneumatic device is prone to pushing stones into the proximal ureter, which prolongs operative times, a major disadvantage to its use. The holmium:YAG laser is the preferred option for lithotripsy at the authors’ institution. All efforts should be made to remove all residual stone fragments regardless of size because in children they are prone to becoming symptomatic with hematuria and/or pain, have a high likelihood of size progression, and have a low likelihood of spontaneous passage.
Complication rates in pediatric URS can be grouped into infection, bleeding, and trauma. Review of the published literature reveals complication rates ranging from 0% to 15% ( Table 1 ). Infection is encountered most commonly in the form of transient fever, UTI, urosepsis, and/or pyelonephritis. Transient hematuria is the second most commonly encountered entity and rarely requires secondary intervention. Trauma to the small and delicate pediatric anatomy is an obvious concern. Reported rates of ureteral stricture range from 0-2%, although the true incidence of ureteral stricture formation is likely underestimated by the fact that follow up typically consists of renal bladder ultrasound. The true incidence of ureteral stricture formation is unknown because follow-up typically consists of renal bladder US, factors that can underestimate assessment of ureteral stricture formation. Ureteral perforation treated with double J stent insertion is a more common occurrence than ureteral stricture development requiring surgical repair.
| Author | No. Patients/No. Procedures | Pt. Age, y (mean) | Scope Type | Stone Location (%) | Stone Size, mm (mean) | Stone Free Rate/Adjunct | Staged/Preop Stent | Ureteral orifice Dilation | Postoperative Stent: No. (%) | Adjunct Procedures | Complications |
|---|---|---|---|---|---|---|---|---|---|---|---|
| al Busaidy et al, 1997 | 43/50 8.5/9.5/11.5 R | 0.5–12 (6.2) | 8.5 F/9.5/11.5 F R | 100 U | 4–22 12.6 | 84/94 | None | 12 coaxial 5 balloon | Not provided | Open 3 | Fever (12), hematuria (10), stent colic (ureteral perforation with stricture, 1 pt) |
| Bassiri et al, 2002 | 66 | 2–15 (9) | 8, 8.5, 9, 11.5 F | 100 U | 5–15 (8) | 88 | None | 25 balloon | 100 (ureteral cath) | 8; SWL 4, URS 1, open 3 | renal colic (1.5), gross hematuria (17), pyelonephritis (4.5) |
| Schuster et al, 2002 | 25/27 | 0.25–14 (9) | 11-Fr R 6.9-Fr F 8-Fr R | 7 R 93 U | 2–12 (6) | 92/100 | 4 (15) | 15 balloon | 19 (70) | 2 URS | Pyelonephritis (1 pt), stent migration (1 pt) |
| Satar et al, 2004 | 33/35 | 0.8–15 (7.4) | 6.9-10-Fr R | 100 U | 3–10 (5.3) | 94 | Not reported | 11 balloon | 12 (34) | 1 SWL | Stone migration (1 pt), failed stone removal (1 pt) |
| Hubert & Palmer, 2005 | 26/28 | 7.3–14.1 (10.3) | 4.5-8-Fr F, SR | Not reported | Not reported | 100 | 28 (100) | None | None reported | None reported | None reported |
| Raza et al, 2005 | 35/52 | 0.9–15 (5.9) | 6.8 Fr, SR | 100 U | 3–20 | 72–100 | 6 (12) | 2 coaxial | 7 Ureteral cath 4 JJ stent | 10 URS | Ureteral perforation (3.8), ureteral stricture (1.9), urinary retention (1.9), transient fever (10) |
| Minevich et al, 2005 | 58/65 | 1–12 (7.5) | 6.9 F SR, 7-Fr F | 10 P 90 U | Not provided | 98 | None | 20 coaxial 3 balloon | 55 (85) | 1 SWL | Ureteral stricture (1 pt) |
| Singh et al, 2006 | 18 | 4–13 (9.3) | 7.4-Fr F | 17 R 83 U | 2–14 | 100 | 18 (100) | 18 sheath | 18 (100) | None reported | None reported |
| Nerli et al, 2011 | 80/88 | 6-12 (9.5) | np,F | 70 U 30 R | 7–16 (10) | 90./97.5 | 25 (31) | Metal tip dilators | Not reported | 8; URS 6, SWL 2 | Intraop bleeding (7.5), Postoperative bleeding (10), fever (5) |
| Mokhless et al, 2012 | 21 | 0.7–6 (4.7) | 7 Fr, 9.5 F | 100 U | 0.4–13 (6) | 90.7 | None | None | 3 (14) | 2 URS | Ureteral perforation (5), stone migration (5), pyelonephritis (5) |
| Smaldone et al, 2007 | 100/115 | Mean 13.2 | 6.9 F, F 7.5 F, SR | 94 U 6 R | Mean 8.3 | 91 | 54 | 70 coaxial 24 sheath | (76) | 7 URS | Ureteral perforation (5), ureteral stricture (1) |
| Kim et al, 2008 | 167/170[54] | 0.25–18 (5.1) | 8-Fr F | 60 P 40 U | 3–24 (6.12) | 100 (≤10 mm) 97 (>10 mm) | 95 (57) | None | 100 | 3 URS | None reported |
| Tanaka et al, 2008 | 50/52 | 1.2–13.6 (7.9) | 7.5-Fr F | 100 R | 1–16 (8) | 50/9258 | 17 (33) | 18 active 25 sheath | 51 (98) | 18; URS 14, PCNL/SWL 4 | None reported |
| Dave et al, 2008 | 19/28 | 2–16 (6.9) | 7.5-Fr SR | 100 R | Mean 17 | Pelvis 75 Polar 100 Staghorn 14 | N/A | 8 sheath | N/A | PCNL 1, URS 3, open 2 | Ureteral perforation (1 pt), urinoma (1 pt) |
| Herndon et al, 2006 | 29/34 | 2.5–17.5 (11) | 4.5-Fr SR 6.5-Fr SR | 100 U | Not reported | 96 | 4 (12) | None | 6 (17.6) | 1 URS | Ureteral perforation (2 pt) |
| Uygun et al, 2012 | 100 | 0.9–16 (6) | 7.5-Fr F 6.4-Fr SR 4.5-Fr SR | 52 U 48 R | 4–30 (12.8) | 81.3 kidney 100 ureter | 44 (44) | 44 balloon | 61 (61) | 9 SWL | Ureteral perforation (2 pts) |
| Dogan et al, 2011 | 642/670 | 0.3–17 (7.4) | 4-10-Fr SR | 100 U | Mean 8.9 | 90 | 207 (30.9) | 93 balloon 113 irrigation pump | 61.7 JJ 74.8 Ureteral catheter 25.2 | Stone migration (1.1), hematuria (1 pt), mucosal laceration (1 pt), ureteral perforation (5 pts), conversion to open (3 pts), pain (2 pts), febrile UTI (20 pts), urinary retention (1 pt), urethral stone (1 pt), UVJ obstruction (4 pts) | |
| Yucel et al, 2011 | 48/54 | 0.8–18 (7.6) | 7.5-Fr SR | 100 U | 4–20 (6.6) | 84.3 | 2 (4) | 4 balloon | 31 (61) | 4; 3 SWL, 1 URS | Ureteral perforation (1 pt), stone migration (6) |
| Tiryaki et al, 2013 | 32/54 | 0.6–17 (5.9) | 4.5-Fr R 7.5-Fr R 7.5-Fr F | 100 U | 4–18 (8.8) | 57/93 | 8 (19.5) | 3 sheath | 29 (71) | 15; URS | Extravasation (7.3), ureterovesical junction injury (1 pt), nausea/vomiting (1 pt) |
| Erkurt et al, 2014 | 65 | 0.5–7 (4.3) | 7.5-Fr F | 100 R | 7–30 (26) | 83/92 | 17 (7.7) | 40 sheath | N/A | 6; URS | Hematuria (9), UTI (15), ureteral injury (3) |
| Kocaoglu & Ozkan, 2014 | 36 | 1–13 (5.3) | 4.5-Fr SR | 100 U 14 P 14 M 72 D | 4–18 (8.4) | 97.4/100 | None | None | 34 | 1 SWL | Mild hematuria (8), febrile UTI (1 pt), stone migration (1 pt) |
A urine culture is recommended for all patients undergoing upper tract manipulation with URS. Antibiotic prophylaxis is recommended before upper tract manipulation. Postoperative antibiotic therapy is controversial. A common theme in pediatric urology is daily antibiotic prophylaxis, but controversy exists regarding the efficacy of this practice as one set of authors found equal UTI risk whether prophylaxis was administered. In the authors’ institution, if intraoperative urine culture is negative, then antibiotic prophylaxis is discontinued regardless of stent status unless the patient initially presented with an obstructed, infected stone.
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