New Stone Formation: A Comparison of Extracorporeal Shock Wave Lithotripsy and Percutaneous Nephrolithotomy

Abstract

There is theoretical concern that stone recurrence rates may be higher following extracorporeal shock wave lithotripsy (ESWL) compared to other techniques because of residual stone debris. We documented all new stone formations in 298 consecutive patients who initially achieved a stone-free status following ESWL for renal calculi less that 2 cm in largest dimension, and compared the findings to those of 62 patients treated with percutaneous nephrolithotomy without ultrasonic fragmentation. Stone-free status was assessed by a centrally reviewed plain abdominal film and renal tomograms at 3 months. A plain abdominal film was repeated at 12 and 24 months to detect recurrence. New stones formed in 22.2% of patients after ESWL and 4.2% after percutaneous nephrolithotomy at 1 year (p = 0.004), and in 34.8% versus 22.6%, respectively, at 2 years (p =0.190). Furthermore, more new stones recurred in the lower and mid calices compared to baseline location in the ESWL group (chi-square <0.0001), which was not observed in the percutaneous nephrolithotomy group. Our data support a trend toward higher stone recurrence rates in ESWL treated patients, which may be due to microscopic sand particles migrating to dependent calices and acting as a nidus for new stone formation.