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Does Patient Obesity Impact the Effectiveness of Extracorporeal Shockwave Lithotripsy?
Eugene Kramolowsky1, Nada L Wood1, Mark Monahan1, Ruth Butler1, Susan Taylor2
1Virginia Urology, Richmond, VA;2Washington and Lee University, Lexington, VA
Introduction:The incidence of upper tract urinary stones is higher in obese patients with body mass index (BMI) > 30. Does obesity impact stone free rate of SWL? We compared normal and overweight (BMI <30) patients with obese (BMI>30) patients to determine stone free rate.
Materials & Methods: 1975 consecutive SWL procedures done on a Lithotron lithotriptor by 20 urologists using a consistent protocol for>95% of patients were reviewed. KV and number of shocks delivered were consistent in groups. Age and sex distribution was comparable. To evaluate outcomes, the group was divided into 1095 SWL patients with BMI of <30 (normal and overweight) and 880 patients with BMI >30 (obese). Size and location of the stones were compared as was stone free status on plain film of the abdomen and pelvis at 4-6 weeks (94% of patients). Statistical differences between groups were determined by Students-t or Chi-square analysis.
Results: Overall stone-free rate for patients with BMI <30 was 66.7% and 57.2% for BMI>30 (p<0.005). Stone-free rate evaluated by stone location was 62.5% for renal; 72.1% for ureteral in non-obese and 53.1% for renal; 63.7% for ureteral in obese patients (p<0.005 renal; p<0.010 ureteral). Stone size analysis showed higher stone free rate in the non-obese patient, particularly for larger stones greater than 75 mm2 (52.8% and 39.2%)(p<0.005); <25 mm2 (83.5% and 77.3%)(p<0.010); 25-75 mm2 (65.6% and 63.2%) (n.s); for BMI <30 and BMI >30 respectively.
Conclusions: SWL remains the mainstay of treatments but appears to be less effective in obese patients (BMI>30).
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