Renal pelvic pressures during extracorporeal shock-wave lithotripsy

Renal pelvic pressures were studied in 4 patients with indwelling nephrostomy tubes undergoing extracorporeal shock-wave lithotripsy (ESWL). The pressures were monitored by attaching the patients' nephrostomy tubes to an electrical pressure transducer. Three of these patients had ureteral stents placed to prevent outflow obstruction from disintegrated stone fragments. The mean pelvic pressure increased from 17.0 cm H₂O at the start to 52 cm H₂O at the conclusion of ESWL. Two hours post-ESWL, the pressures declined to a mean of 27.0 cm H₂O. The maximum pelvic urine volume as determined by aspirating the nephrostomy tubes at the conclusion of the procedure was 6 cc. The observed rise in pelvic pressure may be explained by a sustained contraction of the pelvic smooth musculature.