Stray radiofrequency current as a cause of urethral strictures after transurethral resection of the prostate

Purpose: This study was designed to define the pattern and significance of stray currents induced by two electrosurgical generators (ESGs) in relation to urethral strictures forming after transurethral resection of the prosta te (TURP). Materials and Methods: A 24F resectoscope irrigated with glycine was activa ted at various power outputs in different modes, with intact loops and loop s with faulty insulation, simulating TURF. The Valleylab and ERBE ESGs were compared for inducing capacitance. An ESG analyzer simulated tissue impeda nce and recorded the stray currents induced along the resectoscope sheath. A fresh pig liver was used for assessment of tissue damage caused by the cu rrents. Results: In the cutting mode, the ERBE ESG produced a mean stray current of 70 mA with an intact loop and 144 mA with a loop having faulty insulation. The Valleylab ESG produced 150 mA and 161 mA, respectively. In the coagula tion mode, the ERBE ESG produced an average leakage current of 35 mA and, w ith a loop with faulty insulation, 40 mA. The Valleylab ESG produced 148 mA and 151 mA, respectively. Conclusions: Electrical injury may represent a significant cause of urethra l stricture after transurethral electrosurgery. The critical power density of 7.5 W/cm(2) (which is likely to cause a urethral burn) may be reached, e specially with the use of loops with faulty insulation or nonconductive lub ricating gel. The ERBE ESG produced significantly less capacitance, decreas ing the risk of urethral electrical burn. Conductive gel prevents dangerous current concentration.