Abstract
BACKGROUND: Nutcracker syndrome (NCS) diagnosis remains challenging due to the lack of non-invasive, reliable methods. Current techniques, including Doppler ultrasound and computed tomography angiography (CTA), lack hemodynamic data, with invasive measurement of the left renal vein-inferior vena cava (LRV-IVC) pressure gradient (true pressure gradient, TPG) being the gold standard. This study aimed to validate a novel non-invasive approach using finite element analysis (FEA) to simulate the LRV-IVC pressure gradient (SPG) to assist in diagnosing and monitoring NCS. METHODS: This retrospective study included 46 patients (35 NCS, 11 controls) who underwent CTA and invasive TPG measurement. Patient-specific 3D left renal vein (LRV) models were reconstructed from CTA data using MIMICS and 3-matic software. Hemodynamic simulations were performed via ANSYS (an engineering simulation software) to calculate SPG. Diagnostic performance of SPG and imaging parameters (e.g., beak sign, LRV diameter ratio) was evaluated using receiver operating characteristic (ROC) analysis. RESULTS: SPG showed no significant difference from TPG (5.6±3.9 vs. 5.5±1.9 mmHg, P>0.05) in NCS patients. Postoperative SPG and TPG decreased comparably (P<0.05). SPG achieved an area under the curve (AUC) of 0.808 [95% confidence interval (CI): 0.69-0.92] with 81.8% sensitivity and 80.0% specificity at a cutoff of 3.3 mmHg, outperforming traditional imaging markers. The aortomesenteric angle, LRV diameter ratio, and beak sign also demonstrated diagnostic utility. CONCLUSIONS: FEA-derived SPG correlates closely with invasive TPG, offering a reliable, non-invasive alternative for NCS diagnosis and postoperative monitoring. This approach enhances objectivity, reduces reliance on operator-dependent techniques, and may facilitate early intervention. Further refinement of FEA models and multicenter validation are warranted.