Objectives: To investigate the effect of stone fragmentation on late stone recurrence by comparing the outcome of extracorporeal shockwave lithotripsy (ESWL) and non-fragmenting percutaneous nephrolithotomy (PCNL), and to investigate factors contributing to recurrent calculi.
Patients and methods: We evaluated stone recurrence in 647 patients who initially achieved a stone-free status after ESWL and compared the outcomes to 137 stone-free patients treated with PCNL without stone fragmentation. Patients were evaluated every 3 months during the first year and every 6 months thereafter to censorship or time of first new stone formation. Stone recurrence rates were calculated using the Kaplan-Meier method. The effects of demographics, stone characteristics, and intervention on the recurrence rate were studied using the log-rank test and the Cox-regression analysis.
Results: For ESWL the recurrence rates were 0.8%, 35.8% and 60.1% after 1, 5 and 10 years, which were comparable to the 1.5%, 35.5% and 74.9%, respectively found in the PCNL group (P = 0.57). Stone burden (>8 mm) and a previous history of stone disease were significantly associated with higher recurrence rates regardless of the method of stone intervention (P = 0.02 and P = 0.01, respectively). In the ESWL group, a stone length of >8 mm showed a higher recurrence rate (P = 0.007). In both the ESWL and PCNL groups, there was a significant shift from baseline stone location, with an increased tendency for most new stones to recur in the calyces as opposed to the pelvis.
Conclusions: In comparison with PCNL, ESWL does not increase long-term stone recurrence in patients who become stone-free. The stone burden appears to be the primary factor in predicting stone recurrence after ESWL.
Keywords: ESWL, extracorporeal shockwave lithotripsy; Extracorporeal shockwave lithotripsy; Fragmentation; HR, hazards ratio; KUB, plain abdominal radiograph of the kidneys, ureters and bladder; NCCT, non-contrast CT; OSS, open stone surgery; PCNL, percutaneous nephrolithotomy; Percutaneous nephrolithotomy; Stone recurrence; US, ultrasonography.