The Reflux Technique for Safe Delivery of Obsidio

Abstract

Obsidio, a polyethylene glycol-based hydrogel conformable embolic agent, is a 510(k) cleared device with shear-thinning technology, enabling precise and durable embolization. This case describes its use in an 88-year-old patient undergoing preoperative embolization for a metastatic deposit in the left acetabulum from renal cell carcinoma. While distal embolization was initially achieved with ethylene-vinyl alcohol copolymer, persistent proximal feeders required additional embolization. A reflux technique was employed, allowing controlled proximal cast formation while minimizing distal migration. Comprehensive tumor vascular occlusion was achieved, enabling surgery with minimal blood loss. This case demonstrates Obsidio's versatility and highlights the reflux technique's role in optimizing outcomes for complex embolization procedures.

 

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Keywords

Obsidio - embolization - cancer

Introduction

Obsidio (Boston Scientific, Massachusetts, United States) is a recently introduced liquid embolic agent designed for peripheral embolization. Composed of a polyethylene glycol (PEG)-based hydrogel, it transitions from a liquid to a solid state upon contact with ionic solutions such as blood.[1] This unique property allows the agent to create a durable cast that conforms to the vessel anatomy, offering precise and controlled embolization.

Unlike ethylene-vinyl alcohol copolymer (EVOH)-based liquid embolics or adhesive embolics like n-butyl cyanoacrylate (glue), Obsidio is nonadhesive and less prone to complications associated with polymerization.[2] [3] Additionally, its PEG-based structure reduces inflammatory responses. Obsidio offers several advantages that enhance its utility in embolization procedures. It comes premixed, eliminating the need for additional preparation. The polymerization rate is rapid, ensuring fast and predictable cast formation, which minimizes the risk of nontarget embolization. However, its initial liquid phase exposes to a risk of distal embolization, particularly in high-flow vessels or complex vascular anatomy. It should not be mixed or flushed with saline for this purpose.

To address this risk, we present a technique that leverages the reflux property of Obsidio to create a proximal cast, minimizing the chances of nontarget embolization.

 

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Case Presentation

An 88-year-old patient with metastatic renal cell carcinoma and a medical history of atrial fibrillation on apixaban, hypertension, hyperlipidemia, abdominal aortic aneurysm, and coronary artery disease status post-percutaneous coronary intervention with stent placement was referred for preoperative embolization of the left acetabulum ([Fig. 1A], arrow). The goal was to reduce tumor vascularity and minimize intraoperative bleeding.

Fig. 1 (A) Coronal CT view showing a lesion in the left acetabulum (B) Digital subtraction angiography (DSA) demonstrating a hypervascular acetabular lesion (C) Non-substracted DSA showing embolization of the feeder artery using Lava (D) Non-subtracted DSA showing additional arterial feeders (E) Non-subtracted DSA showing embolization of proximal branches branches with Obsidio (F) DSA showed complete embolization is achieved.

Under general anesthesia, the right femoral artery was accessed, and a 5F catheter sheath was placed. After crossover access, a 4F C2 catheter was advanced into the gluteal artery. Digital subtraction angiography showed hypervascular lesion ([Fig. 1B]). Distal embolization of the main arterial feeder vessel was successfully performed using a TruSelect microcatheter (2.0, Boston Scientific) and EVOH (Lava 34, Syrtex; [Fig. 1C], arrow).

However, persistent concerns regarding additional feeders from the proximal artery ([Fig. 1D], arrows) prompted the use of Obsidio for proximal embolization. Instead of pulling back the microcatheter, slow, controlled injection under real-time fluoroscopy was performed distally in the artery, with the catheter maintained firmly in this location. This reflux technique was employed to monitor cast formation as while it allowed the agent to flow backward. The initial cast already solidified was pushed proximally by the more liquid phase remaining more distal. It improved the monitoring of the agent delivery and helped prevent distal migration into unintended areas ([Fig. 1E], arrows) as Obsidio was less liquid and more viscous when reaching the ostium of these vessels located more proximally. The microcatheter was subsequently withdrawn, completing the procedure ([Fig. 1F]).

Comprehensive tumor vascular occlusion was achieved, and subsequent surgery (insertion of intramedullary rod with reconstruction, for femoral shaft fracture) proceeded with minimal blood loss (<150 mL).

 

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Discussion

This case illustrates the versatility of Obsidio in addressing complex embolization challenges. While EVOH-based embolics or glue are effective for distal control and tumor penetration, they may not suffice when proximal control is required as they could diffuse distally, leading to potential adverse events such as nontargeted embolization.[4] Obsidio's unique nonadhesive properties and ability to form a solid cast upon ionic interaction make it a valuable complement in such scenarios.

The reflux technique demonstrated here provides controlled proximal embolization by utilizing Obsidio's predictable cast formation. By injecting the agent distally and allowing it to reflux proximally, a solid cast is formed without significant distal migration ([Fig. 2]). Key aspects of success include slow, controlled injection to prevent uncontrolled distal migration, and real-time fluoroscopic monitoring to ensure precise cast formation and avoid nontarget embolization. Despite its advantages, careful patient selection and operator expertise are crucial. The risk of distal embolization during the liquid phase requires precise technique and vigilant monitoring.

Fig. 2 Illustration demonstrating the Obsidio reflux technique.

This case illustrates the importance of tailoring embolization strategies to clinical scenarios. While EVOH provides effective distal embolization, Obsidio, guided by the reflux technique, ensures proximal control, reducing intraoperative blood loss and optimizing outcomes. Future research should further explore Obsidio's role in complex embolization procedures, including head-to-head comparisons with other liquid embolics, to refine its applications and expand its clinical utility.

 

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Die Autoren geben an, dass kein Interessenkonflikt besteht.

Acknowledgments

The authors thank the technologists and nursing staff of MSK.

Disclosures/Conflict of Interest

F.H.C. is consultant for GE HealthCare.

• References

• 1 Pal K, Patel M, Chen SR. et al. A single-center experience with a shear-thinning conformable embolic. J Vasc Interv Radiol 2024; 35 (08) 1215-1220
• 2 Filippiadis D, Soulez G, Cornelis FH. Genicular artery embolization for symptomatic knee osteoarthritis: New perspectives on the temporary-permanent dilemma. Diagn Interv Imaging 2024; 105 (04) 125-126
• 3 Hu J, Albadawi H, Chong BW. et al. Advances in biomaterials and technologies for vascular embolization. Adv Mater 2019; 31 (33) e1901071
• 4 Haber Z. Transarterial embolization of bone metastases. Tech Vasc Interv Radiol 2023; 26 (01) 100883

Publikationsverlauf

Artikel online veröffentlicht:
03. Juli 2025