Matched pair analysis of wide versus narrow focus during shockwave lithotripsy for urolithiasis

Purpose: To compare stone clearance and complications between a 'wide' (9 × 50 mm) and 'narrow' shockwave focus (6 × 28 mm) when undertaking shockwave lithotripsy (SWL) in patients with renal or ureteric stones.

Methods: Data from patients undergoing SWL using the dual focus Storz Modulith SLX-F2 lithotripter at a single centre were prospectively collected between February 2018 and September 2020. Patients were matched by stone size, location, and number of treatments. Stone clearance, re-presentation within 31 days, symptoms, complications, and need for post SWL-interventions were compared using McNemar's test.

Results: Patients receiving wide focus SWL (WF-SWL, n = 152) were matched with patients receiving narrow focus SWL (NF-SWL, n = 152). Median stone size was 6 mm; energy delivered to WF-SWL and NF-SWL groups was comparable. Complete stone clearance was achieved in 55% of WF-SWL patients (n = 84) and 41% (n = 63) of NF-SWL patients (p = 0.04). Treatment was considered successful in 74% (n = 113) of WF-SWL cases and 66% (n = 100) of NF-SWL (p = 0.20). No difference in rates of readmission, post-procedural pain, haematuria, urinary tract infections, analgesia or antibiotic requirements were identified.

Conclusion: This service evaluation demonstrates no differences in rates of overall treatment success nor complications on comparing WF-SWL and NF-SWL.