Transsinusoidal portal vein embolization with ethylene vinyl alcohol copolymer (Onyx): a feasibility study in pigs

Endohepatology: The endoscopic armamentarium in the hand of the hepatologist

ABSTRACT

Recent advances in the field of hepatology include new and effective treatments for viral hepatitis. Further effort is now being directed to other disease entities, such as non-alcoholic fatty liver disease, with an increased need for assessment of liver function and histology. In fact, with the evolving nomenclature of fat-associated liver disease and the emergence of the term "metabolic-associated fatty liver disease" (MAFLD), new diagnostic challenges have emerged as patients with histologic absence of steatosis can still be classified under the umbrella of MAFLD. Currently, there is a growing number of endoscopic procedures that are pertinent to patients with liver disease. Indeed, interventional radiologists mostly perform interventional procedures such as percutaneous and intravascular procedures, whereas endoscopists focus on screening for and treatment of esophageal and gastric varices. EUS has proven to be of value in many areas within the realm of hepatology, including liver biopsy, assessment of liver fibrosis, measurement of portal pressure, managing variceal bleeding, and EUS-guided paracentesis. In this review article, we will address the endoscopic applications that are used to manage patients with chronic liver disease.

Non-Adhesive Liquid Embolic Agents in Extra-Cranial District: State of the Art and Review of the Literature

This review focuses on the use of “new” generation of non-adhesive liquid embolic agents (NALEA). In literature, non-adhesive liquid embolic agents have mainly been used in the cerebral district; however, multiple papers describing the use of NALEA in the extracranial district have been published recently and the aim of this review is to explore and analyze this field of application. There are a few NALEA liquids such as Onyx, Squid, and Phil currently available in the market, and they are used in the following applications: mainly arteriovenous malformations, endoleaks, visceral aneurysm or pseudoaneurysm, presurgical and hypervascular lesions embolization, and a niche of percutaneous approaches. These types of embolizing fluids can be used alone or in combination with other embolizing agents (such as coils or particles) so as to enhance its embolizing effect or improve its possible defects. The primary purpose of this paper is to evaluate the use of NALEAs, predominantly used alone, in elective embolization procedures. We did not attempt a meta-analysis due to the data heterogeneity, high number of case reports, and the lack of a consistent follow-up time period.

Portal vein embolization with ethylene-vinyl alcohol copolymer for contralateral lobe hypertrophy before liver resection: safety, feasibility and initial experience

Background

To report our preliminary experience with preoperative portal vein embolization (PVE) using liquid ethylene vinyl alcohol (EVOH) copolymer.

Methods

Retrospectively review of patients with primary or secondary liver malignancies scheduled for extensive hepatectomy after the induction of future liver remnant (FLR) hypertrophy by right or left PVE with EVOH as the only embolic agent between 2014 and 2018 at two academic centers. Cross-sectional imaging liver volumetry data obtained before and 3-6 weeks after PVE were used to assess the FLR volume (FLRV) increase, degree of FLR hypertrophy and the FLR kinetic growth rate (KGR).

Results

Twenty-six patients (17 males; mean age, 58.7±11 years; range, 32-79 years) were included. The technical and clinical success rate was 100%. PVE produced adequate FLR hypertrophy in all patients. Embolization occurred in all targeted portal branches and in no non-target vessels. The %FLRV increased by 52.9%±32.5% and the degree of FLR hypertrophy was 16.7%±6.8%. The KGR was 4.4%±2.0% per week. Four patients experience minor complications after PVE which resolved with symptomatic treatment. The resection rate was 84.5%. One patient died during surgery for reasons unrelated to PVE.

Conclusions

Preoperative PVE with EVOH copolymer is feasible, safe, and effective in inducing FLR hypertrophy.

Future liver remnant growth after various portal vein embolization regimens: a quantitative comparison

Purpose: To compare the efficacy of right portal vein embolization using ethylene vinyl alcohol (EVOH-PVE) compared to other embolic agents and surgical right portal vein ligation (PVL).Material and methods: Patients with right sided liver malignancies scheduled for extensive surgery and receiving induction of liver hypertrophy via right portal vein embolization/ligature between 2010-2016 were retrospectively evaluated. Treatments included were ethylene vinyl alcohol copolymer (Onyx®, EVOH-PVE), ethiodized oil (Lipiodol^®, Lipiodol/PVA-PVE), polyvinyl alcohol (PVA-PVE) or surgical ligature (PVL). Liver segments S2/3 were used to assess hypertrophy. Primary outcome was future liver remnant growth in ml/day.Results: Forty-one patients were included (EVOH-PVE n = 11; Lipiodol/PVA-PVE n = 10; PVA-PVE n = 8; PVL n = 12), the majority presenting with cholangiocarcinoma and colorectal metastases (n = 11; n = 27). Pre-interventional liver volumes were comparable (p = .095). Liver hypertrophy was successfully induced in all but one patient receiving Lipiodol/PVA-PVE. Liver segment S2/3 growth was largest for EVOH-PVE (5.38 ml/d) followed by PVA-PVE (2.5 ml/d), with significantly higher growth rates than PVL (1.24 ml/d; p < .001; p = .007). No significant difference was evident for Lipiodol/PVA-PVE (1.43 ml/d, p = .809).Conclusions: Portal vein embolization using EVOH demonstrates fastest S2/3 growth rates compared to other embolic agents and PVL, potentially due to its permanent portal vein embolization and induction of hepatic inflammation.

Transcatheter embolization with Squid, combined with other embolic agents or alone, in different abdominal diseases: a single-center experience in 30 patients

Background

Squid, as Onyx, is an ethylene-vinyl alcohol copolymer (EVOH)-based liquid embolic agent developed for neuroradiologic interventions with poor application in abdominal district. Our aim was to evaluate safety, complications, and efficacy of transcatheter embolization using the two available formulations Squid-18 and 12, in 30 patients affected by different abdominal diseases.

Results

Transcatheter embolization with Squid, combined with other embolic agents, as poly vinyl alcohol (PVA) particles, coils and amplatzer plugs, or alone (type 2 endoleak), was performed in 30 patients, as follows: 10 portal vein embolizations (PVEs), 6 arteriovenous malformations (AVMs), 5 visceral artery aneurysms (VAAs), 4 type 2 endoleaks, 3 preoperative embolizations, 1 acute arterial bleeding, 1 female varicocele. Squid was always administered using dimethyl sulfoxide (DMSO) compatible microcatheters. Technical success, 30-day clinical success and complications were assessed.

Technical success was 90%. 3 patients (2 AVMs, 1 VAA) required re-intervention successfully performed in all cases. Major complications, cases of microcatheter entrapment and DMSO-related poor pain control were not recorded. 30-day clinical success was 93.3%: in 2 patients submitted to PVE a sufficient future liver remnant (FLR) hypertrophy was not achieved.

Conclusion

Squid was successfully used with low complication rate in many abdominal diseases showing a valid embolic action either combined with other embolic agents or alone in type 2 endoleak. The availability of different formulations (Squid-18 and Squid-12) variable for viscosity makes Squid preferable to Onyx as EVOH-based liquid embolic agent, even though comparable studies in different abdominal districts with a larger cohort of patients will be necessary.

Ethylene vinyl alcohol copolymer for occlusion of specific portal branches during preoperative portal vein embolisation with n-butyl-cyanoacrylate

OBJECTIVES

To evaluate the safety and efficacy of ethylene vinyl alcohol copolymer (EVOH) injection for selective occlusion of portal branches considered at risk for non-target embolisation during preoperative portal vein embolisation (PVE).

METHODS

Twenty-nine patients (mean age, 57 ± 17 years) submitted to PVE with n-butyl-cyanoacrylate (NBCA) and additional EVOH for selected portal branches were retrospectively analysed. Indications for the use of EVOH and the selected portal branches were evaluated. Degree of hypertrophy of the future liver remnant (FLR) and kinetic growth were assessed by CT volumetry performed before and 3-6 weeks after PVE. Clinical outcome and histopathological analysis of portal veins occluded with EVOH were reviewed.

RESULTS

EVOH was indicated intraoperatively for embolisation of selected portal branches that the operator reported at risk to provoke non-target embolisation with NBCA. Indications for the use of EVOH were embolisation of segment IV (n = 21), embolisation of segmental portal branches with early bifurcation (n = 7) and PVE in a 1-year-old girl with cystic hamartomas. All targeted portal branches were successfully embolised. There were no cases with non-target embolisation by EVOH. The degree of hypertrophy of the FLR was 14.3 ± 8.1% and the kinetic growth rate was 2.7 ± 1.8% per week.

CONCLUSION

EVOH is safe and effective for embolisation of selected portal vein branches considered at risk for non-target embolisation.

KEY POINTS

• EVOH is another effective liquid embolic agent for preoperative PVE. • EVOH is relatively simple to handle with a minimal risk of non-target embolisation. • During PVE, some portal branches considered complicated to occlude with NBCA may be efficiently embolised with EVOH.

Portal Vein Embolization Before Extended Hepatectomy in a Toddler With Mesenchymal Hamartoma

Portal vein embolization is widely used to induce hypertrophy of the future liver remnant before extended hepatectomy, decreasing the risk of postoperative liver failure. However, this percutaneous procedure has not been previously reported in a young child. The present report describes the case of a 14-month-old patient with a large multifocal mesenchymal hamartoma of the entire right liver, successfully resected after induction of future liver remnant hypertrophy by portal vein embolization.

Ethylene vinyl alcohol copolymer (Onyx®) in peripheral interventional radiology: indications, advantages and limitations

Onyx(®) is a remarkable liquid embolizing agent that may allow a well-trained operator to undertake challenging embolization procedures. In multiple interventional radiology indications, the physico-chemical properties of Onyx(®) allow safe embolization. The purpose of this article is to review the advantages and disadvantages of Onyx(®) and identify its main indications.

A review of animal models for portal vein embolization

BACKGROUND

Portal vein embolization (PVE) is a preoperative intervention to increase the future remnant liver (FRL) through regeneration of the non-embolized liver lobes. This review assesses all the relevant animal models of PVE available, to guide researchers who intend to study PVE.

MATERIALS AND METHODS

We performed a systematic literature search in Medline and Pubmed, from 1993-June 2013, using search headings "PVE" and "portal vein ligation". Articles were included when meeting the selection criteria: experimental animal study on PVE or portal vein ligation and experiments described in 5 animals or more.

RESULTS

Sixty-one articles were selected, describing six different animal models. Most articles reported experiments with rats, rabbits, and pigs. In rats, the increase in wet-weight ratio of the non-occluded liver or total liver weight is greatest in the first 7 d with values ranging from 75%-80.5% on day 7. The volume increase of FRL in the rabbit model is greatest in the first 7 d with values ranging from 33.6%-80% on day 7. In pigs, the largest gain in volume of the FRL was seen in the first 2 wk.

CONCLUSIONS

The choice of the model depends on the specific aim of the study. Evaluating the increase in liver volume and liver function after PVE, larger animals as the pig, rabbit, or the dog is useful because of the possibility to apply computed tomography volumetry. To evaluate mechanisms of regeneration after PVE, the rat model is useful, because of the variety of antibodies commercially available.

Partial liver volume radioembolization induces hypertrophy in the spared hemiliver and no major signs of portal hypertension

BACKGROUND

Post-treatment contralateral hemiliver hypertrophy has created an interest in lobar liver radioembolization (RE) as a pre-surgery tool.

METHODS

Liver and spleen volumes and function were studied in 83 patients submitted to partial liver volume RE at 4-8 weeks (T1), 10-26 weeks (T2), and >26 weeks (T3) after RE.

RESULTS

More than half of the patients had cirrhosis with hepatocellular carcinoma. The main finding was a progressive increase in the volume of the spared hemiliver (mean absolute increase at T3: 230 ml). The percentage of patients in whom the baseline ratio of spared volume to total liver volume was <40% dropped from 56.6% at baseline to 29.4% at T2 (P < 0.001). A significant and progressive increase in spleen volume but not in portal vein diameter was also observed. A small percentage of patients developed hypersplenism, mostly those without cirrhosis (16.0% at T2). Six patients (five with portal vein thrombosis, cirrhosis or both) developed signs of portal hypertension by T2.

CONCLUSIONS

The present results warrant further studies to better elucidate the mechanism underlying this phenomenon of spared hemiliver hypertrophy and to investigate its role as an alternative to portal vein embolization in the management of patients with potentially resectable liver tumours.

[Liquid embolic agents--Onyx as problem solver]

CLINICAL/METHODICAL ISSUE

Liquid embolic agents are used for permanent occlusion of capillaries but optimal administration properties are lacking.

STANDARD RADIOLOGICAL METHODS

The lack of visualization by fluoroscopy and the risk of serious complications are disadvantages of conventional embolic agents, such as ethanol and Histoacryl.

METHODICAL INNOVATIONS

Onyx is a liquid embolic agent consisting of ethylene vinyl alcohol copolymer dissolved in various concentrations of dimethyl sulfoxide (DMSO) and suspended micronized tantalum powder to provide contrast for fluoroscopy.

PERFORMANCE

The physicochemical characteristics of Onyx allow controlled application, forming a defined cast and permanent occlusion. Disadvantages are the high costs. Furthermore, the solvent DMSO requires special catheter material and causes pain during Onyx application.

ACHIEVEMENTS

Onyx has been primarily used for interventional neuroradiological treatment but peripheral applications are becoming increasingly more common.

PRACTICAL RECOMMENDATIONS

Currently, Onyx is mainly used for embolotherapy of endoleaks after endovascular aortic aneurysm repair, for treatment of acute arterial bleeding and for treatment of arteriovenous malformations.

Update on portal vein embolization: evidence-based outcomes, controversies, and novel strategies

Portal vein embolization (PVE) is an established therapy used to redirect portal blood flow away from the tumor-bearing liver to the anticipated future liver remnant (FLR) and usually results in FLR hypertrophy. PVE is indicated when the FLR is considered too small before surgery to support essential function after surgery. When appropriately applied, PVE reduces postoperative morbidity and increases the number of patients eligible for curative hepatic resection. PVE also has been combined with other therapies to improve patient outcomes. This article assesses more recent outcomes data regarding PVE, reviews the existing controversies, and reports on novel strategies currently being investigated.