Propensity score-matched analysis comparing retrograde intrarenal surgery with percutaneous nephrolithotomy in anomalous kidneys.

BACKGROUND: Endourologic interventions for urolithiasis in patients with anomalous kidneys can be challenging, and comparisons between these interventions are not well studied. We aim to compare the safety, outcomes and complications of retrograde intrarenal surgery (RIRS) versus percutaneous nephrolithotomy (PCNL) in patients with urolithiasis in anomalous kidneys. METHODS: A propensity score-matched pair analysis (PSM) was performed on pooled patient data from 20 centers. 569 patients with anomalous kidneys (horseshoe kidney [HSK], ectopic kidney, malrotated kidney) and urolithiasis who received either PCNL or RIRS as the primary modality of intervention from 2010 to 2020 were analyzed. Patients were matched based on calculated propensity scores by a regression model using age, sex, comorbidities, stone size, and renal anomaly type as co-variates. Multivariate logistic regression of factors (mode of treatment [PCNL or RIRS], comorbidities, stone size) and their effects on outcomes of stone-free rate (SFR), need to abandon surgery due to intraoperative difficulty, postoperative hematuria and sepsis and were analyzed when applicable. RESULTS: After PSM, there were a total of 127 pairs in each group. Overall, PCNL conferred a higher SFR compared to RIRS (OR=3.69, 95% CI 1.91-7.46, P<0.001), particularly in HSK (OR=3.33, 95% CI 1.22-9.99, P=0.023), and ectopic kidneys (OR=18.10, 95% CI 3.62-147.63, P=0.002), with no significant difference in malrotated kidneys. There was no significant difference in postoperative sepsis observed. Surgery was abandoned more often in RIRS than PCNL (6.3% vs. 0%, P=0.014). Although PSM provides a robust analysis due to baseline differences in the unmatched cohorts, this study was limited by an inevitable degree of selection bias. CONCLUSIONS: While both modalities are safe and efficacious, PCNL yields better SFR than RIRS in patients with anomalous kidneys, with no difference in postoperative sepsis rates. Patients may benefit from personalized management best carried out in high volume endourology centers.

Higher recovery and better energy dissipation at faster strain rates in carbon nanotube bundles: an in-situ study.

We report mechanical behavior and strain rate dependence of recoverability and energy dissipation in vertically aligned carbon nanotube (VACNT) bundles subjected to quasi-static uniaxial compression. We observe three distinct regimes in their stress-strain curves for all explored strain rates from 4 × 10(-2) down to 4 × 10(-4)/sec: (1) a short initial elastic section followed by (2) a sloped plateau with characteristic wavy features corresponding to buckle formation and (3) densification characterized by rapid stress increase. Load-unload cycles reveal a stiffer response and virtually 100% recoverability at faster strain rates of 0.04/sec, while the response is more compliant at slower rates, characterized by permanent localized buckling and significantly reduced recoverability. We propose that it is the kinetics of attractive adhesive interactions between the individual carbon nanotubes within the VACNT matrix that governs morphology evolution and ensuing recoverability. In addition, we report a 6-fold increase in elastic modulus and gradual decrease in recoverability (down to 50%) when VACNT bundles are unloaded from postdensification stage as compared with predensification. Finally, we demonstrate energy dissipation capability, as revealed by hysteresis in load-unload cycles. These findings, together with high thermal and electrical conductivities, position VACNTs in the "unattained-as-of-to-date-space" in the material property landscape.