Extracorporeal Shock Wave Lithotripsy: Long-Term Effectiveness
Overview
The study aimed to conduct a comprehensive audit spanning seven years with a three-year follow-up at a high-volume stone center that specializes in extracorporeal shock wave lithotripsy (ESWL). The primary objectives were to assess the efficacy of ESWL in stone clearance in comparison to existing knowledge and to understand the factors influencing this performance.
Methods involved retrieving data from patients who underwent ESWL treatment for renal or proximal ureteric stones at a single center from January 2012 to January 2019, ensuring a minimum three-year follow-up. A retrospective analysis cross-referenced parameters such as stone size, location, treatment, and the need for subsequent procedures. Ethical approval was obtained through Metro North HHS HREC, Queensland, Australia.
Results revealed that out of 1930 patients meeting inclusion criteria, 57% underwent left-sided ESWL, while 43% underwent the procedure on the right side. Stone size and location significantly influenced treatment outcomes. Small stones (<1 cm) exhibited an 81.9% clearance rate, medium stones (1–2 cm) had a rate of 60.6%, and stones (>2 cm) showed a clearance rate of 31.3%. Small stones located in an upper calyx demonstrated the highest clearance rate at 87.5%. Taking into account two procedures, 89% of stones were successfully treated.
ESWL emerged as a valid option for treating small and medium-sized renal calculi based on the study’s findings. The stone clearance rates observed at the center exceeded those reported elsewhere, affirming the efficacy of ESWL. Key factors contributing to success included X-ray imaging on the procedure day, substantial consultant involvement, and frequent intra-operative imaging. The study advocates for further research to elucidate factors influencing stone clearance rates, fostering more standardized outcomes. Additionally, the findings suggest a potential need for increased investment in ESWL provisions, particularly in Australian states like Queensland, to support its ongoing use amid the evolution of endourological techniques.
Introduction
The escalating global incidence of renal stone disease has led to a surge in overall stone interventions, posing a growing economic burden. Extracorporeal shock wave lithotripsy (ESWL), historically a primary treatment for small- to medium-sized renal stones, faces a decline in popularity. Australian Medicare Data analysis indicates a 56% reduction in ESWL provision per 100,000 population from 2000 to 2020, while alternative procedures like pyeloscopy and laser services have surged. Despite this shift, ESWL remains cost-effective at $730 per procedure compared to $1127 for pyeloscopy.
Advancements in endoscopic technology, featuring narrower and more flexible ureteroscopes with enhanced image resolution, have expanded intrarenal accessibility. These innovations, coupled with the ability to accommodate sophisticated lasers and stone extraction tools, contribute to the rise of endoscopic treatments. The increased availability of ureteroscopic equipment simplifies the learning and execution of these procedures, explaining the preference for ureteroscopy among early-career Urologists.
Despite the growing inclination toward endoscopic treatments, literature reveals comparable stone clearance rates between ESWL and ureteroscopy for small- and medium-sized stones in the proximal ureter and kidney. In this context, the study aims to conduct a comprehensive audit spanning seven years at a high-volume stone center, focusing on ESWL efficacy in stone clearance. The goal is to assess its performance compared to existing knowledge and gain insights into the factors influencing this performance.
Methods
This retrospective study, spanning seven years from 2012 to 2019 at a singular center, focuses on patients who underwent Extracorporeal Shock Wave Lithotripsy (ESWL). Ethical approval was obtained through Metro North HHS HREC, Queensland, Australia, and the analysis includes a follow-up until 2022 to ensure a minimum of three years of post-treatment evaluation.
Eligibility criteria encompassed patients over 17 years old with renal or proximal ureteric stones verified through noncontrast CT KUB and visible on XR or Ultrasound. Exclusions were made for individuals with recent ipsilateral stone procedures, anatomical factors affecting treatment, or contraindications to ESWL. Stone factors such as size, location, and number, along with patient demographics and medical history, were meticulously recorded.
Data management involved extracting information from patient operation notes into a secure Excel file. Stone size was categorized as small (<1 cm), medium (1–2 cm), or large (>2 cm), while stone location included upper calyx (UC), middle calyx (MC), lower calyx (LC), renal pelvis, and proximal ureter. Complication data was sourced from Emergency Medicine records.
The primary outcome measure was treatment success, defined as the absence of further ipsilateral stone procedures within three years. This criterion accommodated the variability in fragment detection between CT and X-ray. The center’s protocol for re-intervention focused on residual fragments ≥4 mm or those causing symptoms. Additionally, cystoscopic ureteric stent insertion for stones ≥15 mm was routine, and subsequent stent removal was not classified as a second stone procedure in cases where further ESWL was unnecessary. The study provides a comprehensive examination of ESWL efficacy, considering patient-specific factors and long-term outcomes.
Statistical Methods
Data synthesis involved the amalgamation of gathered information utilizing both categorical and continuous variables. Statistical analyses, including the Chi-squared test, binary regression, and odds ratio (OR), were employed to derive meaningful inferences from the available dataset. These analytical methods facilitated a comprehensive examination of the relationships and associations present within the collected data, contributing to a nuanced understanding of the variables under consideration.
Results
A total of 1930 patients, meeting the inclusion criteria, underwent extracorporeal shock wave lithotripsy (ESWL) over a 7-year period. Among them, 57% (n=1100) underwent left-sided ESWL, while 43% (n=830) underwent the procedure on the right side. The stone clearance rate, regardless of size or location, was 68.1% (n=1306), with 31.9% (n=611) requiring further ipsilateral stone procedures within 3 years. Stone size significantly influenced clearance rates, with small stones (<1 cm) exhibiting the highest clearance rate of 81.9%, compared to larger stones (>2 cm) with a 31% clearance rate. Stones between 1 and 2 cm in size had a successful treatment rate of 60.6%.
The location of the stone also played a role, with stones in lower calyces showing a higher overall clearance rate (70.7%, n=507). Small stones in an upper calyx demonstrated the highest success rate at 87.5% (n=120). When allowing for two procedures within 3 years, 89% of stones were successfully treated.
The logistic regression model indicated that small stones were three times more likely to be treated successfully (OR=3.02, 95% CI [2.36, 3.92]). Complications occurred in 9% of cases (n=85), with higher rates observed in patients with large stones (18%, n=25). Common complications included conservatively managed steinstrasse (3%, n=38) and haematuria (2%, n=23) for small- and medium-sized stones. Large stones presented more complications such as haematuria (13%, n=18) and stent-related symptoms (14%, n=19), including urinary frequency, dysuria, and pain. Retroperitoneal hematoma occurred in one patient in the series.
Conclusion
This study presents data from the largest stone center in Queensland, Australia, offering valuable insights into the efficacy of extracorporeal shock wave lithotripsy (ESWL) for small and medium renal stones. Despite a global shift towards endoscopic treatments, the study reinforces the relevance of ESWL as a viable option, with clearance rates of 84.4% for small and 63.5% for medium-sized stones.
The study attributes the center’s success to centralized services, extensive experience, and advanced imaging techniques, such as X-ray imaging on the day of booking and frequent intra-operative fluoroscopy. Dual imaging with intraoperative ultrasound and fluoroscopy enhances stone localization. The study also highlights the importance of heavy consultant urologist involvement and the unique practice of performing ESWL under general anesthesia.
Notably, the reported clearance rates exceed those in other regions, likely due to the centralization of services and enhanced stone localization practices. The overall complication rate of 9% aligns with existing literature, with complications more common in cases involving large stones, a practice less typical for the center, which favors percutaneous nephrolithotomy and pyeloscopy for such cases.
The study identifies state-based discrepancies in Australia regarding treatment trends, with ESWL practices influenced by population density and equipment availability. Further investment in ESWL equipment is recommended to address logistical challenges and support the resurgence of ESWL practice.
Despite the study’s limitations, such as being a single-center study and potential data inaccuracies, it provides valuable insights into the current trends and challenges in renal stone treatments. The research emphasizes the need for standardized approaches in Australia and suggests that the lessons learned during the COVID-19 pandemic may influence future management strategies, favoring outpatient ESWL to reduce hospital admissions and alleviate bed pressures.
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