Radical nephrectomy (RN) is established as the gold standard treatment for renal cell carcinoma (RCC). The technological advancements and the widespread adoption of robot-assisted surgery have led to an increased implementation of robot-assisted RN [1,2]. The occurrence of inferior vena cava (IVC) thrombus is observed in 4%-10% of RCC patients [3]. Post-RN with IVC thrombectomy, the 5-year survival rate for patients with nonmetastatic RCC ranges from 50%-65%, making RN the sole curative treatment option for this subset of patients [4]. While open surgery has traditionally been the approach of choice for RCC with IVC thrombus, the evolution of minimally invasive surgery technologies has facilitated a growing adoption of robot-assisted RN (RARN) with IVC thrombectomy in selected cases [5-8]. For individuals undergoing RN for RCC, robot-assisted surgeries confer benefits over the open surgical approach, including reduced hospital stay durations and diminished complication rates. RARN yields outcomes comparable to those of laparoscopic RN, albeit at increased expenses [9]. Crocerossa et al. [9] conducted a subgroup analysis of 2 studies [10,11] to evaluate the benefits and drawbacks of robotic versus open level I-II [12] IVC thrombectomy alongside RN. This subgroup analysis unveiled a significantly reduced transfusion rate for the robotic surgery cohort, alongside a pronounced advantage of the robot-assisted technique in reducing the length of hospital stays and the overall rate of complications, without impacting the rate of major complications [9]. Nevertheless, conducting RARN with IVC thrombectomy poses significant technical challenges and is linked with considerable risks of morbidity and mortality. Thus, meticulous patient selection and strategic surgical planning are paramount. This review aims to encapsulate the latest progress and provide a detailed account of the step-by-step surgical techniques involved in RARN with IVC thrombectomy.

The preoperative evaluation of the thrombus’s extent and characteristics is crucial for guiding decision-making and surgical strategy, including the selection of a surgical approach and determining the necessity for cardiopulmonary bypass. While venacavography was once regarded as the gold standard for imaging, it carries risks of vascular complications and contrast-induced renal insufficiency. Presently, computed tomography (CT) and magnetic resonance imaging (MRI) stand as the primary imaging modalities for preoperative assessment in RCC cases with IVC thrombosis. Multiplanar CT imaging has emerged as the go-to for the diagnosis and staging of RCC, boasting a sensitivity and specificity of 93% and 97%, respectively, in identifying tumor thrombus [13]. MRI surpasses CT in sensitivity regarding the evaluation of a thrombus’s extent and features, providing both direct and indirect signs of caval wall invasion, such as contact with the caval wall, unusual signals from the IVC wall, obstruction of the IVC lumen, and alterations in IVC diameter [14-16]. The timing of these imaging assessments is critical for surgical planning, as the evolution of the tumor thrombus might necessitate significant alterations to the surgical approach. Consequently, it is advised that both CT and MRI be performed within a 30-day window, and ideally no more than 14 days prior to the operation [17].

While numerous classifications have been suggested, lacking consensus on the optimal one for determining the surgical strategy, the classification by Neves and Zincke [12] subsequently modified by Blute et al. [18] is presently the most widely utilized. The levels of tumor thrombus are categorized as 0 (thrombus confined to the renal vein, identified either clinically or during pathological examination), I (thrombus extending ≤ 2 cm above the renal vein), II (thrombus extending >2 cm above the renal vein but remaining below the hepatic veins), III (thrombus at the level of or surpassing the hepatic veins but not reaching the diaphragm), and IV (thrombus extending above the diaphragm). The management of a level III thrombus in the IVC presents a significant challenge to surgeons due to its reduced accessibility. Ciancio et al. [19] developed an alternative classification to more precisely define level III thrombus by its anatomical position relative to the hepatic veins (categorized into IIIa: infrahepatic thrombus, IIIb: hepatic thrombus, IIIc: suprahepatic, infradiaphragmatic thrombus, and IIId: suprahepatic, supradiaphragmatic, infraatrial thrombus), introducing a method for the safe resection of these tumors via a transabdominal route without the need for cardiopulmonary bypass (Table 1). The determination of the surgical approach (e.g., open vs. robot-assisted, and the usage of cardiopulmonary bypass) primarily depends on the thrombus level. Other considerations include tumor size and location, as well as the surgeon’s expertise and preference. For patients with thrombi at a lower level, robot-assisted surgery may be executed by experienced surgeons at highvolume institutions.

The 2 primary constituents linked to IVC thrombosis include the tumor thrombus, harboring tumor cells, and the bland thrombus, comprised solely of blood coagulum without tumor cells. Patients with RCC are subjected to a heightened risk of pulmonary embolism, attributed to the malignancy-associated hypercoagulability alongside venous thrombosis. The administration of anticoagulants prior to surgery is capable of mitigating the risk of pulmonary embolism and diminishing the thrombus size; thus, contemplating anticoagulant administration is advised. Lowmolecular -weight heparin emerges as the preferred choice, with its last dosage recommended 24 hours before the operation while warfarin serves as an alternative, ceasing at least 5 days before and bridged until the operation.

To date, no randomized, controlled studies have been performed to assess the utility of renal artery embolization prior to RN. Preoperative angioembolization can be considered since tumor thrombi have an independent blood supply arising from the renal artery and/or aorta in one third of cases. Angiographic infarction of the blood supply to the tumor thrombus can help shrink a large thrombus to a more manageable size, potentially avoiding the need for bypass or extensive mobilization of the liver [20]. Although we seldom use angioembolization, it can be considered in patients with (1) left RCC with thrombus when IVC thrombectomy is performed first and then left nephrectomy, (2) bulky retroperitoneal lymph nodes, or (3) extensive collateral circulations that get access to renal artery is difficult. The optimal timing for embolization is unknown. Despite angioembolization generally being executed the day preceding surgery, the potential for iatrogenic pulmonary embolization, flank discomfort, and tumor lysis syndrome warrants consideration [20]. Hence, opting for embolization immediately before surgery might prove advantageous.

The deployment of IVC filters may be contemplated to avert thrombus migration during surgical intervention; however, it is crucial to acknowledge the potential for inducing contralateral renal and hepatic vein thrombosis, embolism, and interference with IVC thrombectomy [20]. Should the implantation of an IVC filter be contemplated, positioning it within 48 hours before surgery is advised to minimize the possibility of thrombus infiltration into the filter [21].

For level II-IV thrombus, the employment of transesophageal echocardiography (TEE) is advocated to assess the thrombus extent, monitor for intraoperative thrombus dislocation, detect residual tumor, and evaluate cardiac function during IVC clamping [22-25].

Foremost in the preoperative preparations for RARN with IVC thrombectomy is ensuring the availability of a vascular surgeon on standby, prepared for any exigencies and conversion to open surgery.

RARN when dealing with high-level thrombectomy poses challenges, including prolonged operative times due to the need for dissecting the suprarenal IVC and an elevated mortality risk. For a level II thrombus situated above the porta hepatis, mobilization of the liver’s right lobe is necessary to ensure comprehensive IVC control; likewise, for a level III thrombus, both liver lobes must be mobilized.

Kundavaram et al. [27] introduced a pioneering approach in their report on 4 cases of RCC with level II-III IVC thrombus, achieving proximal intra- or retrohepatic IVC control exclusively through an intracaval Fogarty balloon catheter. Impressively, in one instance, a residual or secondary skip thrombus was excluded via robot-assisted flexible cystoscopy within the IVC lumen.

In a novel endoluminal strategy, Alahmari et al. [28] employed a Reliant® stent graft balloon catheter, maneuvered endovascularly through the right internal jugular vein under fluoroscopic guidance and positioned above the tumorous thrombus. Utilizing a balloon to occlude the suprarenal IVC emerges as a groundbreaking technique that can significantly diminish both the duration of surgery and the risk of complications in thrombectomies located beneath the portal vein. This is because it obviates the necessity for dissecting the suprarenal IVC in level II or III thrombectomies. Following cavotomy, the extraction of the thrombus can be facilitated by gently retracting the balloon. However, this method warrants further optimization regarding balloon size and placement. Precise positioning directly above the thrombus requires accurate measurement of the thrombus length via MRI, appropriate balloon insertion depth, and verification of thrombus and balloon placement with TEE. Nevertheless, postclamp visibility of the balloon within the infrarenal IVC and renal vein becomes compromised. Even substituting air or dye for water does not enhance visibility on TEE. Consequently, despite the bleeding risks, clamping the infrarenal IVC and renal vein subsequent to balloon positioning might provide a more reliable method for confirming balloon location. Balloon sizing should reflect the measured IVC diameter above the thrombus, with water injection guidelines from the product manual closely followed. Opting for a conservative water volume initially is advisable, with the option to safely add more water if the balloon’s presence is confirmed through cavotomy, thereby minimizing the risk of back bleeding and IVC damage. Cephalic IVC nonclamping method that significantly reduces operative time and complication rates in patients with level II-III IVC thrombus compared to conventional techniques [29]. By elevating pneumoperitoneum pressure from 12 to 20 mmHg, this method aids in achieving effective cephalic IVC control, thus expediently shortening surgery duration and mitigating complications associated with suprarenal IVC dissection. However, potential risks such as carbon dioxide embolization, hypercapnia, and challenging intraoperative bleeding from the cephalic IVC raise critical considerations.

Published data directly comparing the operative and oncologic outcomes of robot-assisted and open nephrectomy with IVC thrombectomy is scarce.

Gu et al. [10] conducted a retrospective, matched comparison involving 68 patients who underwent levels I-II IVC thrombectomy, dividing them into 31 robotic and 37 open IVC thrombectomies. The study revealed that the robotic cohort benefitted from a significantly reduced median operative time (150 minutes vs. 230 minutes, p<0.001), with the exception of left tumors which necessitated a conversion from a left to a right decubitus position for anatomical reasons. Contrarily, findings from Rose et al. [11] and Vuong et al. [30] indicated that the robotic group experienced a longer operative time compared to the open group (284 minutes vs. 242 minutes, p=0.03; 350.5 minutes vs. 208 minutes, p<0.01, respectively). A multi-institutional analysis leveraging the National Cancer Database dataset found no significant differences in operative times between the open and robotic groups (226 minutes vs. 260 minutes, p=0.922) [31]. Thus, the limited number of studies prevents drawing definitive conclusions regarding surgical time.

Gu et al. [10] also reported superior outcomes for the robotic group in terms of median estimated blood loss (250 mL vs. 1,000 mL, p<0.001), the rate of blood transfusion (6.5% vs. 54.8%, p<0.001), and the median transfusion requirement (420 mL vs. 790 mL, p=0.012) in comparison to the open group. Rose et al. [11] corroborated these findings, noting fewer blood transfusions in the robotic group (21% vs 82%, p<0.01) compared to the open group. The robotic platform facilitates meticulous hemostasis through enhanced visualization, enabling the surgeon to accurately identify and cauterize bleeding vessels. Additionally, the creation of pneumoperitoneum helps to reduce venous bleeding during the dissection of dilated perinephric vessels. These advantages are believed to contribute to reduced blood loss in robotic surgery over open surgery. The total postoperative complication rate was lower in the robotic group than in the open group (9.7% vs 29.0%, p=0.070). Two of the 3 complications (6.4%) in the robotic group were minor, while 1 patient (3.2%) experienced respiratory failure requiring mechanical ventilation [10]. The robotic group had 26% fewer complications compared to the open group (17% vs 43%, p<0.01) and there were no Clavien-Dindo classification grade IIIb or worse complications and no mortalities occurred in the robotic group [11].

Studies involving robotic IVC thrombectomy are noted for their variability and typically have brief follow-up intervals, spanning from 3 to 27 months) [32]. Chopra et al. [8] documented a median follow-up duration of 16 months (range, 12-39 months) for patients who underwent robotic caval thrombectomies, with all patients being alive at the last follow-up. Among these, 42% had undergone adjuvant therapy, and 45.8% experienced the emergence of metastatic disease. Although no direct, prospective comparisons have been made between open and robotic IVC thrombectomy, and questions regarding the long-term oncological superiority of robotic over open procedures remain unaddressed, existing oncologic data thus far are limited. Gu et al. [10] noted that the median follow-up durations for robotic and open surgery cohorts were 27.0 and 44.8 months, respectively (p<0.001), finding no significant disparities in progression-free survival (p=0.708) or overall survival (p=0.181) between the 2 groups; the surgical approach did not correlate with either progression-free or overall survival outcomes. Similarly, Rose et al. [11] found no significant statistical differences in either overall survival or recurrencefree survival during short-term follow-up. In the comparison of open versus robotic groups, the mean estimated overall survival was 48.7 months versus 50.6 months (p=0.16), while the mean estimated recurrence-free survival was 36.5 months versus 33.2 months (p=0.68).

RARN with IVC thrombectomy is intricate and demanding, carrying significant risks of morbidity and mortality. The decision to opt for an open versus robotic approach must hinge on meticulous patient selection, comprehensive preoperative planning, and the surgeon’s depth of experience.