The Influence of Super-Mini Percutaneous Nephrolithotomy on Renal Pelvic Pressure In Vivo

Renal pelvic pressure (RPP) is expected to rise during percutaneous procedures. A very small tract size was expected to bring high RPP, and super-mini percutaneous nephrolithotomy (SMP) uses a 14F sheath, which is even smaller than that used in mini-percutaneous nephrolithotomy, so the RPP in SMP was more worrisome. Interestingly, the sheath had suction, which aimed to decrease the RPP, so we measured the RPP in an in vivo model to explore the relationship of implying negative pressure through the sheath with the RPP.Seventy-four consecutive patients were enrolled for RPP measurement during SMP between April 2016 and July 2017. Prospective RPP measurements were recorded using the MINDRAY-PM9000 monitor by connecting its baroceptor of the invasive blood pressure channel to a retrogradely inserted renal pelvic open-ended ureteric catheter. RPP data were collected each second by a computer program. All data were evaluated statistically with SPSS 13.0 software.During SMP with a 14F irrigation-suction sheath, the average RPP was 19.51 ± 5.83 mm Hg. The median accumulative time of RPP ≥30 mm Hg was 55 (3-345) seconds. Postoperative fever was recorded in four patients (5.4%). A receiver operating characteristic -curve analysis showed that when suction pressure was set to 0.03 Mpa (≈230 mm Hg), irrigation pressure between 200 and 250 mm Hg, and the irrigation flow to 320 mL/minute, the accumulative high RPP was more likely <50 seconds, and the sensitivity and specificity were 75.0% and 66.7%, respectively.The RPP in SMP remains <30 mm Hg. Controlling the pressures as well as the flow of irrigating saline is important for the safety and efficiency of percutaneous procedures.