Presented by: Chi Fai Ng MD
SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong

Introduction

To compare the efficacy and safety of standard or extended focal zone (FZ) size in shockwave lithotripsy (SWL) for patients with renal stones.

Materials

In this prospective study conducted between April 2018 to October 2022, patients with renal stones were randomized to receive SWL with either standard or extended FZ. Treatment was delivered using a Modulith SLX-F2 lithotripter with a maximum of 3000 shocks at 1.5 Hz. The primary outcome was treatment success at 12 weeks after a single SWL session, defined as the lack of a stone or stone fragment <4 mm on computed tomography. Secondary outcome included the incidence of perinephric hematoma, stone-free rate and changes in the urinary levels of acute renal injury markers. 

Results

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320 patients were recruited, and 276 patients were randomized into the 2 groups. The two groups had similar baseline parameters. was significantly better for standard FZ (74.3%) than extended FZ group (59.3%) (p = 0.009). Standard FZ also had significant better stone free rate (36.8% vs 23.0%, p = 0.013) and less pain after treatment. Both groups had similar perinephric haematoma formation rate, unplanned hospital admission rate and changes in urinary acute renal injury markers. 

Conclusion

The standard focal zone has better treatment efficacy and similar safety when compared with extended focal zone during SWL for renal stone. 

Funding

Hong Kong UGC Research Matching Grant 8601454

Co-Authors

Chi Hang Yee, MD
SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong

Jeremy Teoh, FRCS Ed (Urol)
SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong

Peter Chiu, PhD
SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong

Angel Kong, MPhil
SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong

Becky Lau, MSc
SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong

Vincy Ho, PhD
SH Ho Urology Centre, Department of Surgery, The Chinese University of Hong Kong

Ka Tak Wong, MBChB
Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong

Winnie Chu, MD
Department of Imaging and Interventional Radiology, Prince of Wales Hospital, The Chinese University of Hong Kong