Safety and Efficacy of “Dusting and Pop-Dusting” with High-Power Laser for Treatment of Large Pediatric Stones with Ureteroscopy and Lasertripsy: Prospective Outcomes from a University Teaching Hospital

Abstract

Introduction:

The wide use of high-power laser has changed the landscape of ureteroscopy and lasertripsy (URSL). We wanted to look at the role and outcomes of high-power holmium:yttrium–aluminum–garnet laser for URSL in pediatric stone disease.

Methods:

A prospective analysis of consecutive pediatric patients treated with “Dusting and Pop-dusting” using a high-power laser was done between January 2016 and March 2022. The project was registered with our audit committee. Data were analyzed for patient demographics, stone characteristics, operative details, procedural outcomes, and complications. Stone-free rate (SFR) was defined as fragments ≤2 mm on postoperative ultrasound imaging 2–3 months after the procedure.

Results:

A total of 35 patients underwent 43 procedures (1.2 procedure/patient) during the study period with a mean age of 9.4 years (range 1–16 years) and a male:female ratio of 13:22. The stone location was in the kidney in 32 (91.4%) patients of which 8 were in multiple renal locations. The mean stone size was 18 mm (range 10–39 mm), with the pre- and post-stent rates of 37% and 56%, respectively. An access sheath was used in 19 (44%) procedures. The overall SFR on ultrasound scan was 94% (n = 33) with no procedural complications noted in our series and a mean length of stay of 0.9 days.

Conclusion:

Pediatric URSL using a high-power laser achieves a high SFR even for large and multiple renal stones with no complications noted in our prospective series. Parents must, however, be counseled about the need for staged procedures, which might be needed for large stones.

Introduction

For the past two decades more pediatric stones are being managed using ureteroscopy and lasertripsy (URSL).^1,2 Although shockwave lithotripsy and percutaneous nephrolithotomy are still first line for small and large pediatric stones, respectively, URSL is still increasing in both these settings.³

The role of URSL in the pediatric population has expanded as a result of technological innovations, digital and smaller sized ureteroscopes, better training, and high-power laser lithotripsy.^4

–7 The use of holmium:yttrium–aluminum–garnet (Ho:YAG) laser and new thulium fiber laser (TFL) has led to a big surge in URSL across all patient groups.

There has also been a modification in laser lithotripsy technique from “stone retrieval, dusting, fragmentation” to “pop-dusting” now, which has increasingly been used for single-session URSL for large ureteral and renal stones.^8,9 With “Pop-dusting” technique, a two-stage treatment using a holmium laser is done. An initial low-power high-frequency long pulse contact dusting is done (0.3–0.5 J/40–50 Hz), followed by noncontact mode—“pop-dusting” (0.5–0.7 J/20–40 Hz).¹⁰

Previous studies have shown that dusting and pop-dusting might be the new cornerstone for treatment of large bilateral or multiple stones in the adult setting.¹¹ Although dusting is good for avoidance of repeat fragment retrieval, and may be adequate treatment for soft stones, pop-dusting is good for large or harder stones and enhances stone clearance.

We wanted to look at the role and outcomes of high-power Ho:YAG laser for URSL in pediatric stone disease using the “dusting and pop-dusting” technique.

Methods

A prospective analysis of consecutive pediatric patients treated with “Dusting and Pop-dusting” using a high-power laser was done between January 2016 and March 2022. The project was registered with our “Clinical Effectiveness and Audit department” (audit number 6901). The patients were all pediatric patients (≤16 years of age) and were treated for large stones (minimum size of 1 cm).

The high-power laser used in our study was either was a 100 W Ho:YAG system or a 60 W Ho:YAG Moses laser (Lumenis, Inc.), delivered through a 200–272 μm laser fiber (Lumenis, Inc.). The energy setting varied from 0.3 to 0.6 J with a frequency of 20–50 Hz giving a total power of 6–30 W. We started with dusting setting and switched to pop-dusting for completion of the procedure ([0.3–0.5 J; 40–50 Hz] to [0.5–0.6 J]; 20–40 Hz]). We restricted the total power to up to 15 W in the ureter and 25 W in the kidney.

Our ureteroscopy technique in pediatric patients was as described previously.¹² After discussion in a stone specialist multidisciplinary team (MDT) meeting and informed consent, patients underwent cystoscopy and placement of safety wire. All patients had semirigid ureteroscopy with a 4.5–6F (Richard Wolf) ureteroscope over a working wire, followed by flexible ureteroscopy using Storz Flex X2 ureteroscope. A ureteral access sheath (UAS) was used per surgeon discretion (9.5–11.5F, 35 cm, Cook Flexor sheath) for larger stones provided the ureter could accommodate it. All patients had ultrasound pre- and postprocedure for assessment of stones.

Stone-free rate (SFR) was defined as fragments ≤2 mm on postoperative ultrasound imaging 2–3 months after the procedure. Removal of fragments for analysis was done using the Ngage nitinol stone extractor (Cook Medical). A 4.7F ureteral stent (Cook Medical) or an overnight ureteral catheter was inserted at the end of the procedure in some cases, based on the clinical decision taken by the surgical team.

If required, stent removal was arranged after a period of 6–8 weeks under a general anesthetic. Perioperative antibiotics were given as per the urine culture results or the departmental protocol. Data were analyzed for patient demographics, stone characteristics, operative details, procedural outcomes, and complications. The complications were reported as per Clavien–Dindo classification system.

Results

A total of 35 patients underwent 43 procedures (1.2 procedure/patient) during the study period with a mean age of 9.4 years (range 1–16 years), with 13 boys and 22 girls in the study (Table 1). Eight patients needed a second completion URSL procedures. The stone location was in the kidney in 32 (91.4%) patients of which 8 had them in multiple renal locations.

Table 1.

Patient Demographics, Stone Characteristics, and Procedural Outcomes

Cumulative stone length	M:F	Number of patients (procedures)	Mean age (range)	Mean cumulative stone length (mm) (range)	Stone location	Pre-/post-op stent (%)	Access sheath use	Staged procedure	SFR	Mean LOS (days) (range)
10–15 mm	9:9	18 (21) (1.16 procedure/patient)	8.4 (1–16)	12.1 (10–15)	Renal—13 Ureter—3 Multiple renal—2	9 (42.8%)/11 (52.3%)	12 (57.1%)	4 patients	17 (94.4%)	0.68 (range 0–2)
16–20 mm	1:7	8 (10) (1.25 procedure/patient)	10.2 (2–16)	17.9 (16–20)	Renal—6 Multiple renal—2	2 (20%)/4 (40%)	6 (60%)	2 patients	7 (87.5%)	1.2 (0–3)
>20 mm	3:6	9 (12) (1.33 procedure/patient)	10.6 (6–15)	29.4 (23–39)	Renal—4 Ureter—1 Multiple renal—4	3 (25%)/4 (33.3%)	4 (33.3%)	2 patients (one needing 2 procedures)	9 (100%)	0.83 (0–2)
Total	13:22	43 (35) (1.2 procedure/patient)	9.4 years (1–16 years)	18.2 (10–39)	Kidney:Ureter (Multiple) 32:3 (8)	14 (32.5%)/24 (55.8%)	19 (44.1%)	8	33 (94.2%)	0.9 (0–3)

LOS = length of stay; SFR = stone-free rate.

The mean stone size was 18 mm (range 10–39 mm), with the pre- and post-stent rates of 32.5% and 55.8%, respectively, and a UAS used in 19 (44.1%) procedures. The overall SFR was 94.2% (n = 33), and a mean length of stay of 0.9 days (range 0–3 days), with no procedural (intra- or postoperative) complications noted in our series for a mean follow-up of 4 months (range 2–8 months).

We then subdivided the patients into three groups based on cumulative stone size of 10–15 mm (n = 18), 16–20 mm (n = 8), and >20 mm (n = 9). For a mean stone size of 12.1, 17.9, and 29.4 mm, the mean number of procedures/patient were 1.16, 1.25, and 1.33, with an SFR of 94.4%, 87.5%, and 100%, respectively. Staged procedures were required in 4 (22%), 2 (25%), and 2 (22%) patients in the three groups, respectively.

Discussion

Meaning of the study

The role of modern high-power lasers using the technique of dusting and pop-dusting is safe and effective in the pediatric patients. Although our study showed a high SFR of 94%, there were no procedural complications noted in this prospective study done for a 5-year period. Patients with larger stone size did need greater number of procedures to achieve a stone-free status. The mean hospital stay was <24 h and routine stenting was not done pre-ureteroscopy.

Comparison of this study with others reported in the literature

Our study has reinforced the safety of high-power lasers in the pediatric patients. This has also been shown in a previous study by Chung et al., who recommend that high-power laser using pop-dusting can be used for large and hard stones.¹¹ Although TFL is the “new kid on the block,”¹³ a recent systematic review and meta-analysis has shown no difference in SFR between holmium laser with pulse modulation and TFL.¹⁴

In a recent large global study across 8 centers, 314 pediatric retrograde intrarenal surgery were analyzed retrospectively.¹⁵ For a 5-year period, for a mean stone size of 10.7 ± 4.6 mm and 49.4% patients being pre-stented, the SFR was 75.5% and the overall complication rate was 13.7%. They further subdivided the study based on age groups (<5 years, 5–10 years, and >10 years), and the overall complications were higher for patients <5 years of age. This is similar to a recent study by Sinha et al. who showed a good SFR for both early and late childhood, but complications and the need for second procedure were marginally higher in the early childhood group.¹⁶

In contrast to our study where pre-stenting was done in 32.5% and UAS was used in 44.1%, a recent Nordic study reported on 23 patients (47 procedures) where none of the patients were pre-stented and a UAS was not used in any case.¹⁷ Their initial and final SFR was 61% and 90% with an overall complication rate of 17.5%. Notably urinary tract infection was noted in 12.5%, in contrast to our study that had no complications. UAS has previously shown to reduce sepsis rates by reducing intrarenal pressure and improving drainage,¹⁸ and whether this would have made a difference in their study is difficult to know given the small numbers.

We used high-power holmium laser for our study. A randomized control trial using low-power holmium laser and TFL in adult setting showed a superior result using TFL.¹⁹ A more recent retrospective study on TFL using low-power holmium laser in the pediatric setting looking at a total of 125 procedures in 109 patients²⁰ showed an SFR and complication rates of 70% vs 59%; and 25% vs 22% with TFL vs holmium laser, respectively, with the authors concluding that TFL was associated with higher SFR without compromising operative time and safety.

Although this study was done for a mean stone size of 18 mm and an average of 1.2 procedures were needed for an SFR of 94%, on comparison of our current results with our previous article published in 2015 using a 20 W holmium laser, we performed 1.5 procedure per patient for a mean stone size of 9.6 mm and an SFR of 95%.²¹ This shows that high-power laser using dusting and pop-dusting technique can be used to treat larger stones in lesser number of procedures. We also restricted the total power below 15 W in the ureter and 25 W in the kidney to avoid any laser thermal damage.^22,23 Care must especially be taken in the ureter as ureteral stricture can occur with inappropriate use of laser.²⁴

Strengths and limitations of the study

The strength of the study is its prospective nature with consecutive patients included in the analysis. Although it reflects a single-center study, all patients were managed within an MDT setup by an experienced endourology team. We used a high-power holmium laser for all cases. Although our study did not use the TFL, with newer studies showing its advantage, this needs to be explored further in future studies. We did not perform a quality of life or cost analysis, which are aspects that need to be considered in future studies.

As our data were based on ultrasound assessment for stone size, stone volume measurement was not carried out either. Postoperative complications were assessed on their first follow-up and perhaps future studies should focus on long-term follow-up of these patients. Similarly, procedural and lasing times would also be useful to capture.

Areas of future research

Although our study did not use any endourology-related predictive tools for outcome measure, recent work has suggested the use of nomograms and grading tools, which can help in outcome prediction and decision-making.²⁵ The authors do add that these need to be tailored to individual patients based on the consent, expectations, and their specific clinical scenarios. Measurement of quality of life, radiation dose, and cost of treatment should also be carried out in future studies.^26,27

Conclusion

Pediatric URSL using a high-power laser achieves a high SFR even for large and multiple stones with no complications noted in our prospective series. With the evolution of lasers, dusting and pop-dusting will set a new benchmark for treating large, multiple, and complex stones even in the pediatric setting. Parents must, however, be counseled about staged procedures, which might be needed for larger or complex stones.

Footnotes

Authors' Contributions

Data contribution and writing by B.K.S. Data collection by V.M. Data contribution and editing by A.P., F.R., M.M.S., and S.G.

Ethical Approval and Consent

All parents were consented for the procedure and the study was registered as an audit (6901) with the “Clinical effectiveness and audit department.” The research protocols performed in this study complied with the ethical principles of the Declaration of Helsinki. Name of the ethical board: “Southampton Clinical effectiveness and audit department” approval no. 6901.

Availability of Data and Materials

Because of the possibility of compromising the privacy of research participants, the data supporting this study is not publicly available. However, they can be obtained from the corresponding author B.K.S. at bhaskarsomani@yahoo.com upon reasonable request.

Author Disclosure Statement

No competing financial interests exist.

Funding Information

No funding was received for this article.

Abbreviations Used

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