Current Evidence Base

Surgical options for pediatric nephrolithiasis include ureteroscopy (URS), shock wave lithotripsy (SWL), and percutaneous nephrolithotomy (PCNL). There are 8 recommendations for pediatric patients in the 2016 AUA/Endourological Society guidelines for the surgical management of urinary stone disease; 50% consider the size and location of stones, but none considers the age, sex, or complexity of the child, all of which may also affect the feasibility, success, and morbidity of a particular procedure.^1,2 None considers patient-prioritized or patient-reported outcomes.³ With the existing evidence base, it is not a surprise that there is variation in the preferred choice of surgical intervention for children with urinary stones by size and location. Here, we summarize the rationale for 2 real cases of pediatric stone disease and the role of size and location of stone in determining the approaches.

Case 1: 9-Year-old Boy With Autism With 1.5-cm Renal Pelvis Stone (1,400 Hounsfield Units)

The AUA guidelines recommend SWL or URS as first-line therapy for renal calculi <20 mm in children, although the strength of this evidence is weak (evidence grade C).

Option 1: URS

Considerations for this case, beyond the typical considerations of stone size and location, include prepubertal patient age, developmental delay, and scoliosis. The case for URS is centered around 3 tenets: (1) laser technology has made tremendous advances; (2) no incisions means less bleeding; and (3) patient safety comes first. An overview of comparative studies favors URS over PCNL for this scenario. A 2019 meta-analysis targeting upper urinary stones between 12 and 20 mm in size in pediatric patients found similar stone clearance after the initial and final procedures for URS and PCNL, while outcomes such as transfusion and hospital stay favored URS.⁴ Since the newest laser technologies (ie, high-power holmium with Moses and the thulium fiber laser) were introduced recently, this meta-analysis likely reflected older, low-power holmium technology. With the newer laser technologies, laser lithotripsy has been consistently faster and more efficient compared to the low-power holmium laser.^5-9 Another advantage of URS over PCNL is that there is no incision, meaning less bleeding. The transfusion rate following PCNL is ∼7%.⁴ Lastly, this patient’s autism and scoliosis may mask the ability to communicate patient experiences like pain and increase the risk of surgical complications,¹⁰ respectively.

Option 2: PCNL

The case for PCNL is supported by stone clearance, monotherapeutic success, avoidance of a stent, and safety of miniaturized access tracts (ie, mini-PCNL). A meta-analysis comparing stone clearance across several surgical modalities for intermediate (1-2 cm) renal calculi in children suggests that PCNL, when stratified by access-tract size, is equally effective, if not more so, compared to URS, while SWL is inferior.¹¹ PCNL access can be obtained under the same anesthetic, providing opportunities for monotherapeutic success. In contrast, pediatric URS poses challenges in ureteral access, especially among prepubertal children, with up to 72% of children requiring multiple anesthetics, mostly driven by stent placement and removal.¹² In addition to the procedural burden of stents, the prospective STENTS (Study to Enhance Understanding of Stent-associated Symptoms) demonstrated that even after 1 week of stent dwell time following URS, pain interference and urinary bother failed to return to baseline and only did so following stent removal.¹³ Meanwhile, miniaturization for PCNL has improved safety, with mini-PCNL (sheath size of 15F-20F) associated with <1% Clavien-Dindo grade III complications and a 3.3% transfusion rate.¹⁴ Notably, concepts of monotherapy, avoidance of ureteral stents, and quality of life in recovery have been highlighted in recent patient and caregiver listening sessions for the PKIDS (Pediatric Kidney Stone) Care Improvement Network clinical trial planning,¹⁵ making PCNL an attractive patient-centered option.

Case 2: 3-Year-old Healthy Girl With 4-mm Distal Ureteral Stone and 5-mm Ipsilateral Interpolar Stone Visible on Plain Film

The AUA guidelines recommend SWL or URS as first-line therapy for pediatric patients with a total renal stone burden <20 mm, and SWL or URS for pediatric patients with ureteral stones.^1,2

Option 1: URS

There are several reasons why URS is the superior approach in this 3-year-old female with a renal and distal ureteral stone. First, stone clearance is higher for URS compared to SWL, particularly for distal ureteral stones. In addition, there is a lower risk of re-treatment in this child with URS. Finally, there is the opportunity to obtain a stone specimen for analysis, which is not the case for SWL. A systematic review of surgical treatments for children with renal and proximal ureteral stones found that single-session stone clearance, defined as no residual fragments, was 2.3 times higher for URS compared to SWL.¹⁶ There was no difference in overall clearance, which may reflect re-treatment for SWL. However, URS had a lower efficiency quotient, which reflects prestenting for passive dilation, and stent placement for stone treatment and stent removal. There was no difference in complication between URS and SWL. Stone clearance for proximal ureteral stones was significantly higher than that of mid and distal ureteral stones following SWL, which is important because this patient had a distal ureteral stone.

Option 2: SWL

The case for SWL is based on 2 factors: small stone size and favorable stone location. Stone treatment with SWL can be accomplished safely without a stent in a single procedure. Much emphasis has been placed on meta-analyses favoring URS over SWL for renal and ureteral stones in children. However, the authors of one of these studies caution in drawing clinical inferences due to the very low–quality evidence for most comparisons.¹⁷ Numerous retrospective studies demonstrate a stone-free rate of 84%-90% after SWL for renal stones <10 mm in children,^18,19 which is comparable to URS. In treating ureteral stones <10 mm with SWL, Landau et al reported 100% stone clearance after a single session.²⁰ Jee et al demonstrated that in patients <7 years of age, stone clearance was 92% after an average of 1.2 sessions.²¹ The high rate of stent use in pediatric patients undergoing URS is a factor that must be taken into consideration as it translates into multiple anesthetics. Stent usage is associated with significant discomfort and has been associated with a higher rate of postoperative emergency department visits and opioid prescriptions compared to SWL.²² SWL is safe, with only rare serious safety events such as renal hematoma and Steinstrasse.¹⁶ Studies have confirmed no scarring by renal scintigraphy in long-term follow-up after SWL.²³

Conclusions

A multitude of appropriate treatment options—each balancing safety, efficacy, and patient experience—exist across the spectrum of pediatric kidney stone disease. While data are lacking to be able to provide personalized recommendations based upon stone and patient characteristics, emerging knowledge from the PKIDS trial, prospectively evaluating surgical outcomes for SWL, URS, and PCNL across 30 centers and 1,290 patients, will provide a substantial amount of information for patients, families, and surgeons.¹⁵