Risk Factors Survey for Extracorporeal Shockwave Lithotripsy-Induced Renal Hematoma

Background and Purpose: Shockwave lithotripsy (SWL) is a widely used treatment for patients with renal and ureteral stones because of its noninvasive approach. Although minor complications occur in most patients, a relative severe complication, perirenal or subcapsular hematoma, may also occur. We evaluate the possible risk factors for perirenal hematoma after SWL. Patients and Methods: Between 2001 and 2011, a total of 10,887 SWL treatments were performed for urolithiasis. All SWL procedures were performed using a Siemens Lithostar multiline lithotripter at a frequency of 2/sec under intermittent fluoroscopic guidance. All these patients underwent outpatient treatment without general anesthesia, but pethidine was administered for pain control. Treatment episodes were retrospectively reviewed for medical history, patient age, sex, body mass index (BMI), mean arterial pressure at induction, location of stone, total number of shockwaves, and peak shockwave intensity. We also compared the hematoma group with the control group (no hematoma formation after SWL with matched age and sex) for various factors. Results: After 10,887 treatment episodes on a total of 6177 patients during this period, subcapsular or perirenal hematoma developed in 20 patients for a total incident rate of 0.32%. Eighteen patients had the symptom of flank pain, and 2 patients received a diagnosis accidentally without symptoms. Four patients received a blood transfusion because of low hemoglobulin concentration. All of them received conservative and supportive treatment without surgical exploration. Ten (50%) patients had a history of hypertension. Renal hematoma developed in 11 patients at the second or third SWL treatment. Hypertension, higher BMI, and larger stone size are predisposing risk factors (P = 0.022, 0.026 and 0.026, respectively) for renal hematoma. Conclusions: Renal hematoma is a rare (incidence rate, 0.32%) but possibly lethal complication. The most common symptoms of renal hematoma are severe flank pain and hematuria. A history of hypertension and higher BMI are important predisposing factors to perirenal hematoma.