Adherent Perinephric Fat and Positive Surgical Margin in Laparoscopic Partial Nephrectomy: A Technique-Conditional...

Background/Objectives: Adherent perinephric fat (APN) is common in laparoscopic partial nephrectomy (LPN). It is absent from the lists of recognised positive surgical margin (PSM) predictors. We tested whether APN is associated with PSM risk and whether the effect varies by resection technique. Methods: We analysed 401 International Society of Urological Pathology (ISUP)-gradable renal cell carcinomas (31 PSM events; chromophobe RCC was excluded from the primary cohort because the WHO/ISUP grade is not assignable) carried out at three centres by eight surgeons from 2013 to 2024. Nested logistic models added APN, then an APN × enucleation interaction, to a guideline-based covariate set (tumour size, ISUP grade ≥ 3, cT1b stage, centre fixed effects, surgeon-documented enucleation). Firth penalisation and a 2000-replicate bootstrap were used to limit small-sample bias; they cannot add information beyond the 31 observed events. Results: APN was an independent PSM predictor (adjusted odds ratio [OR] 2.68, 95% confidence interval [CI] 1.21 to 5.95, p = 0.02). The effect was technique-conditional: APN × enucleation interaction OR 7.83 (95% CI 1.08 to 56.92, p = 0.04), consistent in direction across estimators but imprecise in magnitude. PSM occurred in 29.4% of APN-positive enucleation cases (odds ratio 10.21, 95% CI 2.07 to 50.30; Fisher exact p = 0.003), against 5.0% in enucleoresection and 10.8% in resection. Conclusions: In this cohort the APN-to-PSM association was technique-conditional. The penalty concentrates in enucleation; the rim-retaining strata gave estimates compatible with both no association and clinically important harm (OR 0.99 and 1.96, both intervals wide). Because the interaction rests on few margin events and the technique was not randomised, this finding is hypothesis-generating: when APN is encountered intraoperatively, retaining a parenchymal rim (enucleoresection or resection) rather than enucleation may be considered, pending prospective validation.