Advantages of the supine transgluteal approach for distal ureteral stone extracorporeal shock wave lithotripsy: Outcomes based on CT characteristics

BACKGROUND: Extracorporeal shock wave lithotripsy (ESWL) for distal ureteral stones can be performed in prone or supine position. The aim of this study was to investigate the advantages brought by the supine transgluteal ESWL approach for distal ureteral stones treatment using real-time ultrasound (US), and to show how computerized tomography (CT) scan parameters may be related to the outcomes. METHODS: Seventy consecutive supine transgluteal ESWL of distal ureteral stones were performed. All patients had a pre-treatment CT scan. The following parameter were evaluated: Stone size, Hounsfield Units, skin-to-stone distance, sciaticum majus foramen width, stone to ureteral ostium distance, fragmentation and expulsion perception during the treatment, and the stone-free status. Stone focusing was obtained US, which allows a real-time visualization of stone location and fragmentation. Follow-up included a kidney ureter bladder (KUB) film and US examination at 2-3 weeks after treatment (median time: 18 days). Stone-free condition was defined as the complete absence of stone fragments. A linear regression analysis was used to assess the possible variables mostly related to stone-free status. P<0.05 was considered as significant. RESULTS: Median number of SWL sessions for patient was 1 (IQR: 1-1), mean 1.2±0.5. The re-treatment rate for stonefree patients was 18.3%. Stone-free rate was 85.7%. A clear and real time US stone fragmentation was perceived by the surgeon during the treatment in 42/70 (60%) of patients and correlated to the definitive stone-free status (P=0.04). Stone to ureteral ostium distance was the only variable affecting the stone-free condition (P=0.01). CONCLUSIONS: Supine transgluteal SWL of distal ureteral stones provide satisfactory outcomes in terms of stone-free rate. The distance of the stone to the ureteral ostium, measured by CT, appeared to be the only significant variable connected to SWL success.