Prognostic variables for shockwave lithotripsy (SWL) treatment success: no impact of body mass index (BMI) using a third generation lithotripter.

OBJECTIVE

• To investigate the effect of different variables including body mass index (BMI) on therapy outcome in patients with upper urinary tract stones treated with a third generation lithotripter, as BMI has been reported to be an independent predictor for stone-free status after extracorporeal shockwave lithotripsy (SWL) performed with first or second generation lithotripters.

PATIENTS AND METHODS

• In all, 172 patients with kidney stones with a mean (range) size of 9.2 (3.0-32.0) mm were included in the study. • In all, 91 patients (52.9%) were treated with a ureteric stent in situ. • For SWL therapy a third generation, electromagnetic lithotripter (Siemens Lithoskop™) was used. Stone-free status was reached, when no more treatable stones were present (no stone or stone < 3 mm). • BMI, stone size and localization, age, gender, treatment parameters and ureteric stent in situ were evaluated for their prognostic relevance on therapy success.

RESULTS

• The mean (range) BMI of all patients was 27.8 (19.0-58.6) kg/m(2). • Patients were categorized into two groups: A) patients that were stone free after one treatment; B) patients with residual stones. The mean (sd) BMI was 27.4 (4.6) kg/m(2) and 28.4 (6.1) kg/m(2) for A and B, respectively. • Univariate and multivariate analysis for freedom of stones showed that only stone size (P < 0.01) and presence of a ureteric stent (P = 0.01) were independent prognostic variables. • BMI had no significant influence on therapy outcome (P = 0.51).

CONCLUSIONS

• Using a third generation lithotripter, BMI was not an independent predictor of stone-free rate after SWL therapy of kidney stones. • This effect might be attributed to a greater penetration depth of the shockwave energy. Stone size and a ureteric stent in situ were the only variables with prognostic significance.