Mini-Percutaneous Nephrolithotomy Less Injurious to the Kidney?

Background and Objectives: Percutaneous nephrolithotomy (PCNL) technique trends have shifted toward smaller caliber access sheaths, leading to a varied array of miniPCNL (mPCNL) systems. Urinary biomarkers have been validated as noninvasive direct markers of renal cellular injury. Our objective was to assess changes in biomarkers levels in the perioperative setting, comparing mPCNL suction (s-mPCNL), non-suction (ns-mPCNL), and standard PCNL (sPCNL) systems. Patients and Methods: PCNL systems used were as follows: s-mPCNL single-step dilator (ClearPetra™, 18F), ns-mPCNL metallic dilator and sheath (Storz MIP-M, 17.5F), and sPCNL with balloon dilation (Nephromax, 24F). Urine samples were collected at three time points: preoperatively (V1), 1 hour postoperatively (V2), and 10 days postoperatively (V3). Samples were analyzed using enzyme-linked immunofluorescent assay for key biomarkers-kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), and β2-microglobulin (β2M)-normalized to urine creatinine. The primary outcome was changes in urinary biomarkers. Results: Twenty patients were randomized into two groups: s-mPCNL and ns-mPCNL, and 10 patients were assigned to the sPCNL cohort. The mean differences and percent change in biomarker levels at different time intervals were calculated as follows: early injury (V1-V2), recovery (V2-V3), and long-term injury (V1-V3). There was a statistically significant rise in NGAL levels for both ns-mPCNL and s-mPCNL in the early injury interval (2.377; p = 0.004, 2.606; p < 0.001, respectively), and a subsequent fall in levels during the recovery interval for sPCNL, ns-mPCNL, and s-mPCNL (-4.720; p = 0.026, -2.427; p = 0.014, -3.141; p = 0.018, respectively). There was no statistically significant difference in all three biomarkers for all forms of PCNL in the long-term injury interval. Conclusion: There is a sharp rise in urinary biomarkers in the immediate postoperative setting, likely because of early tubular injury, more notable in ns-mPCNL systems that utilize metal sheaths. However, this is a transient effect that normalizes days later irrespective of the sheath size used during the PCNL.