The effect of piezoelectric shockwave lithotripsy with 2‐ and 8‐mm focus sizes on stone disintegration and renal injury

Objectives To compare the efficacy and safety of shockwave lithotripsy (SWL) using a narrow focus or wide focus for renal stones. Patients and Methods A double‐blind randomised trial included adult patients with a solitary radio‐opaque renal pelvic stone of 1–2 cm. Patients were randomised into two groups: narrow‐focus (2 mm) SWL and wide‐focus (8 mm) SWL. The stone‐free rate (SFR) and presence of complications such as haematuria, fever, pain, and peri‐renal haematoma were evaluated. Pre‐ and postoperative urinary markers (neutrophil gelatinase‐associated lipocalin [NGAL] and kidney injury molecule 1 [KIM‐1]) concentrations were compared to assess renal injury. Results A total of 135 patients were recruited for this study. The SFR after the first SWL session was 79.2% and 69.1% in narrow‐ and wide‐focus groups, respectively. There was a comparable rise in the median 2‐h NGAL concentration in both groups ( P = 0.62). However, the rise in the median (interquartile range [IQR]) 2‐h KIM‐1 concentration was significantly higher in the narrow‐focus group at 4.9 (4.6, 5.8) ng/mL compared with the wide‐focus group at 4.4 (3.2, 5.7) ng/mL ( P = 0.02). Nevertheless, the 3‐day NGAL and KIM‐1 urinary marker concentrations were significantly improved ( P = 0.263 and P = 0.963, respectively). The overall SFR after three sessions was 86.6% and 86.8% in the narrow‐ and wide‐focus groups, respectively ( P = 0.77). Both groups were comparable for complications, apart from the median pain score and the percentage of high‐grade haematuria, which were significantly higher in the narrow‐focus group ( P < 0.001 and P = 0.03, respectively). Conclusion Narrow‐ and wide‐focus SWL were associated with comparable outcomes and re‐treatment rates. However, narrow‐focus SWL was associated with significantly higher morbidity in terms of pain and haematuria.