[Slow delivery rate improves the outcome of extracorporeal shock wave lithotripsy]

To determine the efficiency of slow delivery rate of shockwaves (SW) on stone fragmentation and treatment outcomes in patients with renal and ureteral calculi.

Using the Siemens Lithostar Multiline, we treated 843 patients (229 renal and 614 ureteral stones) at a fast delivery rate (120 SW/min, between October 2003 and August 2006), 448 patients (139 renal and 309 ureteral stones) at a slow delivery rate (90 SW/min, between September 2006 and August 2008).

The stone free rates at 3 months after treatment of fast rate group and slow rate group were 60% and 53% (renal stones, P = 0.858), 82% and 91% (ureteral stones, P < 0.001), respectively. The average numbers of sessions required were 2.02 and 1.59 (renal stones, P = 0.018), 1.61 and 1.49 (ureter stones, P < 0.001), respectively. The mean total shots were 8,718 and 4,679 (renal stones, P < 0.001), 7,684 and 4,928 (ureteral stones, P < 0.001), respectively. The mean treatment times were 80 and 60 minutes (renal stones, P < 0.001), 72 and 62 minutes (ureteral stones, P < 0.001), respectively. The slow delivery group patients included more number of elders, stones located on lower renal calices and less frequency of pain at onset than the fast delivery group. Multiple logistic regression analysis revealed that slow delivery rate (90 SW/min) as well as age (younger), symptom (painful) at onset, stone location (middle and distal ureter) and size (small) was a independent (better) prognostic factors determining stone clearance after ESWL of upper urinary tract stones.

Slow rate shock wave delivery not only improved efficacy at ESWL treatments of upper urinary stones, but also decreased number of sessions, shock waves and treatment time required.