Analysis of Clinical Characteristics, Radiological Predictors, Pathological Features, and Perioperative Outcomes Associated with Perinephric Fat Adhesion Degree

BACKGROUND: To assess the clinical characteristics, radiological predictors, and pathological features of perinephric fat adhesion degree (PFAD) graded based on fixed criteria and to determine the impact of adherent perinephric fat (APF) on retroperitoneal laparoscopic partial nephrectomy (RLPN) outcomes. METHODS: 84 patients undergoing RLPN were included and graded into 4 groups based on PFAD. Univariate and multivariate analyses were performed for clinical characteristics and radiological predictors of PFAD. Perioperative data were compared between APF groups and non-APF groups. Masson staining determined collagen fibers. Immunohistochemistry detected CD45 immune cells and CD34 vessels. RESULTS: 20, 28, 18, and 18 patients were graded as normal perinephric fat (NPF), mild adherent perinephric fat (MiPF), moderate adherent perinephric fat (MoPF), and severe adherent perinephric fat (SPF), respectively. Multivariate analysis revealed that gender (p < 0.001), age (p = 0.003), and hypertension (p = 0.006) were significant clinical risk factors of PFAD, while radiological predictors included perinephric stranding (p = 0.001), posterior perinephric fat thickness (p = 0.009), and perinephric fat density (p = 0.02). APF was associated with drain output (p = 0.012) and accompanied by immune cells gathering in renal cortex near thickened renal capsule with many vessels. CONCLUSIONS: Clinical characteristics and radiological predictors can evaluate PFAD and may assist to guide preoperative surgical option. Pathological features of APF reflect decapsulation and bleeding during kidney mobilization at RLPN.