Beyond traditional nephrometry: a 3D quantitative framework for predicting pentafecta and evaluating mediation effects in nephron-sparing surgery.

PURPOSE: To establish a three-dimensional (3D) quantitative framework for predicting pentafecta achievement and to explore the underlying compensatory associations in nephron-sparing surgery (NSS).

METHODS

We retrospectively analyzed 375 patients undergoing NSS. Preoperative 3D morphometric metrics-specifically contact surface area (CSA) and retained blood-perfused renal volume (RBRV)-were extracted. Pentafecta was strictly defined by optimal perioperative success and 1-year functional preservation (eGFR loss < 10% without chronic kidney disease upstaging). Multivariable logistic regression, quadrant-based phenotypic analysis, and serial mediation modeling were performed to compare predictive performance and explore potential sequential clinical pathways.

RESULTS

Pentafecta was achieved in 203 patients (54.1%). The 3D quantitative framework, incorporating CSA, RBRV, and their interaction with baseline eGFR, significantly outperformed traditional nephrometry in discrimination (apparent AUC: 0.752, optimism-corrected AUC: 0.729 vs. 0.697; DeLong test, P = 0.004) and clinical net benefit. Quadrant-based analysis revealed a compensatory "Resilience" phenotype, suggesting that preserving substantial RBRV may effectively buffer the detrimental impact of high surgical complexity. Serial mediation analysis revealed a pattern consistent with statistical sequential mediation: the negative association between anatomical complexity (CSA) and pentafecta achievement was not direct (OR = 0.990, P = 0.683), but rather mediated through a potential sequential pathway involving prolonged warm ischemia time and subsequent postoperative day 1 acute kidney injury (AKI) (indirect effect, P = 0.033).

CONCLUSION

The 3D quantitative framework demonstrates superior predictive performance compared to traditional nephrometry in predicting pentafecta. Maximizing functional volume retention and preemptively mitigating the risk of ischemia-associated AKI appear paramount for individualized surgical planning and optimal long-term recovery.