Does Mini-Percutaneous Nephrolithotomy Cause Increased Intrarenal Pressure During Percutaneous Nephrolithotomy and is This Mitigated by a Suctioning Sheath? A Randomized Control Trial

Introduction: Intrarenal pressure (IRP) generated during percutaneous nephrolithotomy (PCNL) may have the potential to cause renal damage and/or sepsis. It has been suggested that mini-PCNL (mPCNL) can further increase IRP but that a suctioning sheath may mitigate this elevation. We sought to measure IRP throughout the PCNL process, randomizing patients getting mPCNL to receiving two different mPCNL sheaths, one suctioning and the other nonsuctioning, and then comparing them with patients undergoing standard PCNL (sPCNL) using a 24F sheath. Patients and Methods: Twenty patients meeting the eligibility criteria for mPCNL were randomized into two groups: suctioning mPCNL (s-mPCNL) with a single-step dilator and continuous suction sheath (ClearPetra™, 18F, n = 10) and nonsuctioning mPCNL (ns-mPCNL) with a metallic dilator and sheath (Storz MIP-M™, 17.5F, n = 10). A group of 10 patients undergoing sPCNL using a balloon dilator with a Polytetrafluoroethylene (PTFE) sheath (NephroMax™, 24F, n = 10) were included as a control. IRP was measured with a 0.014″ COMET™ II Pressure guidewire retrogradely positioned in the renal pelvis. Gravity irrigation was utilized. Pressure data captured include baseline IRPs, retrograde pyelogram (RPG), needle entry, fascial dilation, tract dilation, sheath insertion, nephroscopy, and lithotripsy. The primary outcome was differences in mean and peak IRP during each stage. Categorical data were compared using chi-square or Fisher's exact tests. Continuous variables were analyzed using one-way analysis of variance. Results: Peak and mean IRPs (millimeters of mercury or mm Hg) were similar at baseline and during RPG, needle insertion, and fascial dilation in the two experimental groups and in the control group. During tract dilation and sheath placement, both the mPCNL sheaths generated much higher peak IRP compared with the 24F balloon dilation control group but similar to each other (dilation: 36.6 and 38.6 vs 6.9, p < 0.001; sheath placement: 36.6 and 35.3 vs 13.8, p = 0.039). During nephroscopy, ns-mPCNL generated greater peak IRP compared with s-mPCNL and the control group (41.8 vs 19.09 and 24.15; p = 0.019). The highest peak IRP for each group occurred during RPG and when a nephroscope was placed through a narrow infundibulum. Conclusions: Compared with balloon dilation, coaxial dilation with mPCNL sheaths generates significantly higher IRP. During nephroscopy, ns-mPCNL sheaths generate higher IRP compared with standard and suctioning sheaths. Highest IRPs are generated during RPG and when a nephroscope goes through a narrow infundibulum. These findings can inform improved sheath and nephroscope design. Further research assessing the effect of high IRP on postoperative pain, sepsis, and renal injury is needed.