Clinical implications of clinically insignificant store fragments after extracorporeal shock wave lithotripsy

We determined the natural history and clinical significance of small, asymptomatic, noninfection related stone fragments after extracorporeal shock wave lithotripsy (ESWL).

We prospectively followed 160 patients with 4 mm. or less asymptomatic calcium oxalate/phosphate stone fragments after ESWL for 1.6 to 88.8 months (mean 23) to stone-free status, censorship or intervention. Kaplan-Meier estimates of probability to anatomical stone-free, decreased or stable status were determined as well as the probability of symptomatic episodes or required urological intervention.

Stone-free status or a decreased, stable or increased amount of residual stone occurred in 38 (23.8%), 26 (16.3%), 67 (41.9%) and 29 (18.1%) of the 160 patients, respectively. At 5 years after ESWL the probability of a stone-free, stone-free or decreased status, or stone-free, decreased or stable status was 0.36, 0.53, and 0.80, respectively. A total of 91 patients (56.9%) remained asymptomatic while 69 (43.1%) had a symptomatic episode or required intervention 1.6 to 85.4 months (mean 26) after ESWL (probability estimated at 0.71 at 5 years).

While patients with small noninfection related stone fragments after ESWL may be followed expectantly, a significantly number will require intervention or have symptomatic episodes within 2 years. The term clinically insignificant applied to any residual stone after ESWL is likely a misnomer.