The influence of ureteral stent on renal pelvic pressure in vivo

The objective of this study was to explore the influence of ureteral stent on renal pelvic pressure by urodynamic study. 41 patients (with unilateral renal and/or ureteral calculi) after minimally invasive percutaneous nephrolithotomy (MPCNL) were placed a 4.7-Fr ureteral stent and 16-Fr nephrostomy tube. Renal pelvic pressure of these patients was measured by urodynamic study at the 5–7 days after MPCNL. Renal pelvic pressure (RPP), intraabdominal pressure (IAP), and vesical pressure (VP) during the filling and voiding phases were detected by urodynamic study with intravesical perfusion. At the baseline, intraabdominal pressure (IAP₀) was 27.52 ± 7.03 cmH₂O, renal pelvic pressure (RPP₀) was 33.07 ± 7.04 cmH₂O; at the maximum cystometric bladder capacity (MCBC) during the filling phase, vesical pressure (VP_vol) was 41.61 ± 10.34 cmH₂O, renal pelvic pressure (RPP_vol) was 39.44 ± 7.33 cmH₂O; at the maximum vesical pressure during the voiding phase, vesical pressure (VP_max) was 74.95 ± 12.79 cmH₂O, renal pelvic pressure (RPP_max) was 65.68 ± 17.03 cmH₂O. (1) There was a strong relationship between RPP₀ and IAP₀ (P = 0.0001); (2) There was statistical significance among RPP₀, RPP_vol and RPP_max (P = 0.0001); (3) RPP was higher than 40 cmH₂O during the voiding phase, and it was obviously relevant to the VP (P = 0.0001) but not to the MCBC (P = 0.2696). RPP increased mildly during the filling phase and dramatically during the voiding phase after stenting. RPP increased higher than the level required for a backflow (40 cmH₂O) during the voiding phase. So it was encouraged to remove the stent at earlier stage or decrease using the ureteral stent if possible.