No Injury Observed in Kidneys Treated with Burst Wave Lithotripsy in Therapeutically Anticoagulated Pigs

Introduction: Current American Urological Association guidelines recommend that patients with acute obstructive kidney stone requiring continuous anticoagulation/antiplatelet therapy should not be treated by shockwave lithotripsy or percutaneous nephrolithotomy because of the risk of catastrophic renal hemorrhage possible with those techniques. Currently, ureteroscopy is the only recommended surgical treatment. We evaluated if burst wave lithotripsy (BWL) could be used in these cases by treating pigs with BWL while undergoing anticoagulation therapy. Materials and Methods: Six pigs (31-37 kg) were given 200 units/kg porcine heparin, and then the right kidney of each animal was treated with a dose of BWL (18,000 ultrasound pulses at 10 Hz, 20 cycles/pulse, peak positive pressure of 12 MPa) known to fracture kidney stones. The contralateral kidney served as a control. Therapeutic anticoagulation was confirmed by evaluating activated partial thromboplastin time (aPTT). Microhematuria was checked by urine test strips. Kidneys were subsequently evaluated for hemorrhagic injury via MRI. Results: aPTT was significantly elevated (>100 seconds) throughout the entire treatment period (p = <0.001) indicating therapeutic anticoagulation. Gross hematuria was not observed in any of the pigs. After BWL, microhematuria averaged 145.8 red blood cells (RBC)/μL in the BWL-treated kidney and 48 RBC/μL in the control kidneys, and there was no statistically significant difference noted in microhematuria rates between the two groups (p = 0.16). Hemorrhagic injury measured only 0.10 ± 0.02% of the tissue in the BWL-treated kidneys and 0.12 ± 0.04% in the control side, with a paired difference of -0.03 ± 0.05%, showing no significant difference (p = 0.58). Conclusions: A typical clinical dose of BWL causes no hemorrhagic injury to the kidney even during therapeutic anticoagulation therapy. This result suggests that BWL should be safe to use in patients with stone undergoing anticoagulation/antiplatelet therapy.