# Laparoscopic and robotic extravascular stenting of the left renal vein for anterior nutcracker syndrome in a single-center series

## TL;DR

This paper presents a standardized surgical approach for treating nutcracker syndrome using laparoscopic or robotic stenting, showing high success rates and defining key postoperative metrics for effectiveness.

## Contribution

The study introduces a reproducible framework combining intraoperative steps and postoperative hemodynamic targets for treating nutcracker syndrome.

## Key findings

- A postoperative aortomesenteric peak systolic velocity (AM PSV) of ≤72 cm/s was identified as a primary success threshold with high sensitivity and accuracy.
- An AM/hilum PSV ratio of ≈2.0 was proposed as a secondary replicability metric.
- The five-in-a-row checklist aligned with achieving the AM PSV target, enhancing procedural consistency.

## Abstract

Nutcracker syndrome (NCS) arises from extrinsic compression of the left renal vein (LRV) between the superior mesenteric artery and the abdominal aorta. Extravascular stenting (EVS) has emerged as a minimally invasive alternative to historical operations and endovascular stents. We report a single-center series spanning 2010 to 2025 and propose a standardized, reproducible framework that couples intraoperative process quality with objective postoperative hemodynamic targets.

We retrospectively analyzed 22 consecutive NCS patients treated with laparoscopic or robot-assisted EVS. We standardized five intraoperative steps (five-in-a-row: fibrotic-ring resection, proper length tailoring/placement, sufficient superior mesenteric artery mobilization, complete division of LRV tributaries, stable anterior fixation). Postoperative duplex ultrasound metrics included aortomesenteric (AM) LRV peak systolic velocity and the AM/hilum peak systolic velocity (PSV) ratio. Thresholds were determined by receiver operating characteristic-Youden index; performance was summarized at fixed cutoffs, with bootstrap for the ratio and exploratory OR/AND combinations.

Complete success was achieved in 18 of 22 patients (81.8%). Data-driven analysis identified a postoperative AM PSV of ≤72 cm/s as the primary attainment threshold, yielding a sensitivity of 1.00, specificity of 0.75, accuracy of 0.95, and area under the receiver operating characteristic curve (AUC) of ≈0.917. The AM/hilum ratio showed a Youden-optimal cutoff of ≈1.90 (clinically ≈2.0) with an AUC of ≈0.56, supporting its role as a sensitivity/replicability metric rather than a standalone gatekeeper. OR and AND combinations demonstrated expected trade-offs; a simple 0/1/2 composite score achieved an AUC of ≈0.78. The five-in-a-row checklist was concordant with attaining the AM-PSV target on Doppler ultrasound examination.

Laparoscopic or robot-assisted EVS is a safe, feasible, and effective option for NCS. We a propose postoperative AM PSV of ≤72 cm/s as a unified, reproducible primary quantitative end point, with an AM/hilum ratio of ≈2.0 as a secondary, replicability-oriented metric. Integrating these targets with a standardized five-in-a-row checklist establishes a process-outcome loop that enhances procedural reproducibility and supports sustained symptom relief over the available follow-up.