Usability of Cryopreserved Aortic Allografts for Middle Hepatic Vein Reconstruction During Living-Donor Liver Transplantation

Pre-operative assessment of living liver donors' liver anatomy and volumes

Decades of experience supports LDLT as a favorable strategy to reduce waitlist mortality. The multiple regenerative pathways of hepatocytes and other hepatic cells justify the rationale behind it. Nonetheless, living liver donation is still underused and its broader implementation is challenging, mostly due to variability in practices leading to concerns related to donor safety. A non-systematic literature search was conducted for peer-reviewed original articles related to pre-operative evaluation of living liver donor candidates. Eligible studies were synthesized upon consensus for discussion in this up-to-date review. Review of the literature demonstrate that the importance of preoperative assessment of vascular, biliary and liver volume to ensure donor safety and adequate surgical planning for graft procurement is widely recognized. Moreover, data indicates that anatomic variants in vascular and biliary systems in healthy donors are common, present in up to 50% of the population. Therefore, comprehensive mapping and visualizations of each component is needed. Different imaging modalities are reported across practices and are discussed in detail. Lastly, assessment of liver volume must take into account several technical and donor factors that increase the chances of errors in volume estimation, which occurs in up to 10% of the cases. Experience suggests that maximizing donor safety and lessening their risks is a result of integrated experience between hepatobiliary and transplant surgery, along with multidisciplinary efforts in performing a comprehensive pre-operative donor assessment. Although technical advances have increased the accuracy of volume estimation, over- or under-estimation remains a challenge that needs further attention.

Feasibility of modified endarterectomized aortic allograft for middle hepatic vein reconstruction in living donor liver transplantation: A retrospective cohort study

BACKGROUND

Cryopreserved allografts and artificial vascular grafts were introduced to meet the increasing demand for adequate vascular substitutes for middle hepatic vein (MHV) reconstruction during living donor liver transplantation (LDLT). This study evaluated patency outcomes after engraftment of a modified endarterectomized aortic allograft (MEAA) without any additional patches.

METHODS

This retrospective double-arm study was conducted in single tertiary referral center between January 2015 and July 2018. Of 1,047 adult patients who underwent single-graft LDLT with a modified right lobe (MRL), 111 patients who received grafts with MHV reconstruction using MEAA were selected. The control group comprised 434 patients who underwent MHV reconstruction using iliac vein allografts. The main outcome measure was the short-term patency of the MEAA. The secondary outcome was the incidence of graft-associated complications.

RESULTS

Clinically significant MHV stenoses requiring stenting occurred in 3 patients (2.7%) in the MEAA group and in 17 patients (3.9%) in the iliac vein group (P = 0.778). Three-month and one-year patency rates on Doppler ultrasonography and computed tomography were 88.5% and 54.0%, respectively, in the MEAA group and 84.0% and 42.2%, respectively, in the iliac vein group, indicating the superior patency outcomes with MEAA (P = 0.017).

CONCLUSIONS

MHV reconstruction using MEAA during LDLT of a MRL graft is technically simple, achieves clinical outcomes comparable to iliac vein grafts, and is effective in expanding the allograft vessel pool for LDLT.

Venous outflow reconstruction using a polytetrafluoroethylene (PTFE) graft in right lobe living donor liver transplantation: A single center study

BACKGROUND

Venous outflow reconstruction is very important especially in right lobe living donor liver transplantation without middle hepatic vein. Various interposition (venous or synthetic) grafts have been recommended for reconstruction of anterior sector tributaries.

METHODS

We aimed to describe our surgical technique and analyze anterior sector venous reconstruction using expanded polytetrafluroethylene graft. Retrospective analysis of prospectively collected data for 760 primary right lobe living donor liver transplantations performed at our institute between December 2011 and June 2018. Reconstruction of anterior sector: expanded polytetrafluroethylene (group A, n = 705) and autologous vein (group B, n = 55).

RESULTS

Pretransplant characteristics were comparable among both groups. Group A has significantly lower cold ischemia time (68.7 ± .3.5 minutes vs 127.8 ± 7.2 minutes; P < .001) and anhepatic time (116.3 ± 5.5 minutes vs 190.81 ± 9.35 minutes; P < .001) compared with group B. There was no difference in recovery pattern of liver functions, morbidity, and mortality between the 2 groups. One- and 6-month patency rates of interposition grafts were 97.6% and 84.4% (group A) and 96.4% and 78.1% (group B), respectively.

CONCLUSION

In centers with limited access to homologous or autologous vascular grafts, use of expanded polytetrafluroethylene graft for anterior sector venous outflow reconstruction in right lobe living donor liver transplantation is a viable option with excellent patency and patient outcomes.

Artificial vascular graft migration into hollow viscus organs in patients who underwent right lobe living donor liver transplantation

BACKGROUND

To share our experience with hollow viscus migration of artificial vascular grafts (AVG) used for venous reconstruction of the right anterior sector in living donor liver transplantations (LDLT).

METHODS

Clinical, radiological, and endoscopic data of 13 right lobe LDLT patients (range: 26-67 years) with a diagnosis of postoperative AVG migration into adjacent hollow viscus were analyzed.

RESULTS

Biliary complications were detected in 12 patients. A median of four times endoscopic retrograde cholangiopancreatography (ERCP) procedures were performed in 11 patients prior to AVG migration diagnosis. A median of 2.5 times various percutaneous radiological interventional procedures were performed in eight patients prior to AVG migration diagnosis. The site of migration was the duodenum in eight patients, gastric antrum in four, and Roux limb in the remaining one patient. The migrated AVS were made of polytetrafluoroethylene (PTFE) in 10 patients and polyethylene terephthalate (Dacron) in three. The migrated AVGs were endoscopically removed in seven patients and surgically removed in six. Only one patient died due to sepsis unrelated to AVG migration.

CONCLUSION

AVG migration into the adjacent hollow viscus following right lobe LDLT is a rare and serious complication. Repetitive ERCP, interventional radiological procedures, infection related to biliary leakage, and thrombosis of AVGs are among the possible risk factors.

Refined surgical techniques to improve the patency of cryopreserved iliac artery homografts for middle hepatic vein reconstruction during living donor liver transplantation

Purpose

A cryopreserved iliac artery homograft (IAH) has not been considered suitable for middle hepatic vein (MHV) reconstruction during living donor liver transplantation (LDLT), primarily due to the low patency from its small diameter. We revised our surgical techniques for MHV reconstruction using an IAH to improve its patency.

Methods

This study analyzed the causes of early conduit occlusion and developed revised techniques to address this that had clinical application.

Results

The potential risk factors for early conduit occlusion were the small IAH size, small graft in the segment V vein (V5) and segment VIII vein (V8) opening, and small recipient MHV-left hepatic vein stump. These factors were reflected to our revised surgical methods which included endarterectomy of the atherosclerotic plaque, unification of the internal and external iliac artery branches for large V5, and branch-patch arterioplasty for large V8. IAH endarterectomy, branch unification technique, and branch-patch arterioplasty were applied to 8, 5, and 5 patients, respectively and resulted in 1-month occlusion rates of 37.5%, 20.0%, and 40.0%, respectively. The overall patency rates of the IAH-MHV conduits in our 18 patients were 66.7% at 1 month, 38.9% at 3 months, and 33.3% at 1 year.

Conclusion

Our refined MHV reconstruction using an IAH improved short-term MHV conduit patency, but did not effectively prevent early conduit occlusion, particularly with a small- or medium-sized IAH. Individualized reconstruction designs during LDLT operation are needed when an IAH is used for a modified right liver graft.

Hepatic vein in living donor liver transplantation

Right lobe living donor liver transplantation (LDLT) is a major development in adult LDLT that has significantly increased the donor pool by providing larger graft size and by decreasing risk of small-for-size graft syndrome. However, right lobe anatomy is complex, not only from the inflow but also from the outflow perspective. Outflow reconstruction is one of the key requirements of a successful LDLT and venous drainage of the liver graft is just as important as hepatic inflow for the integrity of graft function. Outflow complications may cause acute graft failure which is not always easy to diagnose. The right lobe graft consists of two sections and three hepatic venous routes for drainage that require reconstruction. In order to obtain a congestion free graft, several types of vascular conduits and postoperative interventions are needed to assure an adequate venous allograft drainage. This review described the anatomy, functional basis and the evolution of outflow reconstruction in right lobe LDLT.

Living-donor liver transplantation with inferior vena cava replacement in an infant recipient with advanced hepatoblastoma

Replacement of the inferior vena cava (IVC) after concurrent resection of hepatoblastoma-containing liver and retrohepatic IVC is regarded as a feasible option for pediatric living-donor liver transplantation (LDLT). This technique makes the extent of resection of LDLT comparable to that of deceased-donor liver transplantation (DDLT). We present one case of pediatric LDLT with IVC homograft replacement for advanced hepatoblastoma. The patient was a 10-kg 18-month-old girl suffering from large multiple hepatoblastomas, which were partially regressed by neoadjuvant chemotherapy. Because the tumors had invaded the retrohepatic IVC, there was a high risk of residual tumor cells at the IVC if it was preserved. Thus, we decided to replace the IVC during the LDLT operation. After a cold-stored fresh iliac vein homograft was prepared, we performed LDLT using her mother's left lateral section liver graft. A 4-cm-long common iliac vein homograft was attached to the liver graft at the back table. The left lateral-section graft with IVC attachment was implanted using the standard procedures like those of DDLT. We also did portal vein graft interposition. The patient recovered uneventfully and has been undergoing scheduled adjuvant chemotherapy to date. This is our second case of IVC homograft replacement for pediatric LDLT. In pediatric recipients, various vein homografts, such as iliac vein, IVC, and other large veins, can be used depending on the body size of the recipient and availability of vein homografts.

Homologous and heterologous assessment of a novel biomaterial for venous patch

OBJECTIVE

This study evaluated swine and bovine pulmonary visceral pleura (PVP) as a vascular patch. Venous patches are frequently used in surgery for repair or reconstruction of veins. Autologous patches are often limited by the number and dimension of donor tissue and can result in donor complications. Bovine pericardium is the most common heterologous patch used by vascular surgeons. Researchers, however, are continually seeking to improve heterologous and synthetic patches for improved outcome.

METHODS

The PVP was peeled from swine and bovine lungs and cross-linked with glutaraldehyde. After sterilization and rinsing, the PVP patches were implanted in the jugular vein (10 × 35 mm) of pigs and dogs. Patency was evaluated by ultrasound, and animals were euthanized at 2 and 4 months. Neoendothelium and neomedia were evaluated by histologic analysis.

RESULTS

The jugular vein patched by PVP in pigs and dogs remained patent at 2 and 4 months with no adhesions, inflammation, or aneurysm in the patches. The biomarkers of endothelial cells-factor VIII, platelet/endothelial cell adhesion molecule 1, and endothelial nitric oxide synthase-were detected in the neoendothelial cells. The expression of vascular smooth muscle cell (VSMC) α-actin was robust in the neomedia at 2 and 4 months. Neomedia composed of VSMCs developed to nearly double the thickness of adjacent jugular vein. The circumferential orientation of VSMCs in neomedia further increased in the 4-month group.

CONCLUSIONS

The cross-linked swine and bovine PVP patch has a nonthrombogenic surface that maintains patency. The PVP patch may overcome the pitfall of compliance mismatch of synthetic patches. The proliferation of vascular cells assembled in the neoendothelium and neomedia in the patches may support long-term patency.

Analysis of Risk Factors Affecting the Development of Infection in Artificial Vascular Grafts Used for Reconstruction of Middle Hepatic Vein Tributaries in Living Donor Liver Transplantation

BACKGROUND

To analyze the risk factors affecting the development of infection in artificial vascular grafts (AVGs) used for reconstruction of middle hepatic vein (MHV) tributaries in living donor liver transplantation (LDLT).

METHODS

Between January 2009 and January 2018, 1253 right lobe LDLTs were performed at our Transplant Institute, and MHV tributaries of the 640 right lobe liver grafts were reconstructed with AVG. Reconstructed MHV tributaries were removed due to AVG infection in 25 of these patients (case group; n = 25). To determine risk factors for AVG infection, right lobe LDLT patients without AVG infections were selected as control group (n = 615). Both groups were compared about demographic parameter, transcystic catheter usage, bile leakage, type of biliary anastomosis (duct-to-duct, telescopic duct-to-duct), number of graft biliary duct (=1 versus >1), number of biliary anastomosis (=1 versus >1), AVG thrombosis, AVG types (Dacron versus polytetrafluoroethylene). Univariate analyses were used for comparison of different variables, and variables with P ≤ 0.20 were taken into logistic regression model.

RESULTS

Univariate analysis shows that statistically significant differences were found between groups regarding bile leakage (P < 0.001), graft thrombosis (P = 0.002), transcystic catheter (P = 0.049), and AVG types (P = 0.013). Variables with P ≤ 0.20 were taken into logistic regression model. Multivariate analysis shows that bile leakage (odds ratio, 13.3) and AVG thrombosis (odds ratio, 9.8) were determined as independent and strong risk factors for development of AVG infection.

CONCLUSIONS

This study revealed that bile leakage and graft thrombosis are independent and strong risk factors for infections of AVGs used for anterior sector drainage reconstruction.

Doppler ultrasound follow-up of middle hepatic vein tributaries-interposition vessel graft in recipients of living donor liver transplantation using modified right lobe grafts

OBJECTIVE

To investigate the value of Doppler ultrasound (US) in recipients of living donor liver transplantation (LDLT) using modified right-lobe grafts (mRLGs) with obstruction of the middle hepatic vein tributaries (MHVTs)-interposition vessel graft (IVG).

METHODS

This study included 240 consecutive LDLT recipients in whom 564 MHVTs (>5 mm) were reconstructed using IVG. Regular follow-up Doppler US was performed to assess the patency of the MHVTs-IVG and, if there was an obstruction, to evaluate for the establishment of collateral drainage. MHVTs with obstruction were subdivided into those with and without intrahepatic veno-venous collaterals on Doppler US and were correlated with CT scans.

RESULTS

MHVTs-IVG obstruction was identified in 137 patients with 227 MHVTs on follow-up Doppler US (6.2  ±  4.7 months). 90 patients with 149 MHVTs in whom the time interval between Doppler US and contrast-enhanced dynamic CT scans was <1 week were classified into either collateral (68 patients with 121 MHVTs) or non-collateral (22 patients with 28 MHVTs) groups. The presence of intrahepatic veno-venous collaterals on Doppler US were significantly related to no remarkable hepatic venous congestion on CT by both per-patient and per-vein analyses (66 of 68 patients (97.1%) and 118 of 121 MHVTs (97.5%), p < 0.001 and p < 0.001, respectively).

CONCLUSION

On Doppler US follow-up of LDLT recipients using mRLGs, identification of intrahepatic veno-venous collaterals associated with obstruction of MHVTs-IVG suggests no remarkable hepatic venous congestion. Advances in knowledge: When an obstruction of a MHVTs-IVG is encountered on Doppler US follow-up of LDLT recipients using mRLGs, no further evaluation with CT is warranted if intrahepatic veno-venous collaterals are observed on Doppler US, as this finding suggests no remarkable hepatic congestion.

The choice of cryopreservation method affects immune compatibility of human cardiovascular matrices

Conventional frozen cryopreservation (CFC) is currently the gold standard for cardiovascular allograft preservation. However, inflammation and structural deterioration limit transplant durability. Ice-free cryopreservation (IFC) already demonstrated matrix structure preservation combined with attenuated immune responses. In this study, we aim to explore the mechanisms of this diminished immunogenicity in vitro. First, we characterized factors released by human aortic tissue after CFC and IFC. Secondly, we analyzed co-cultures with human peripheral blood mononuclear cells, purified monocytes, T cells and monocyte-derived macrophages to examine functional immune effects triggered by the tissue or released cues. IFC tissue exhibited significantly lower metabolic activity and release of pro-inflammatory cytokines than CFC tissue, but surprisingly, more active transforming growth factor β. Due to reduced cytokine release by IFC tissue, less monocyte and T cell migration was detected in a chemotaxis system. Moreover, only cues from CFC tissue but not from IFC tissue amplified αCD3 triggered T cell proliferation. In a specifically designed macrophage-tissue assay, we could show that macrophages did not upregulate M1 polarization markers (CD80 or HLA-DR) on either tissue type. In conclusion, IFC selectively modulates tissue characteristics and thereby attenuates immune cell attraction and activation. Therefore, IFC treatment creates improved opportunities for cardiovascular graft preservation.

Standardized surgical techniques for adult living donor liver transplantation using a modified right lobe graft: a video presentation from bench to reperfusion

After having experienced more than 2,000 cases of adult living donor liver transplantation (LDLT), we established the concepts of right liver graft standardization. Right liver graft standardization intends to provide hemodynamics-based and regeneration-compliant reconstruction of vascular inflow and outflow. Right liver graft standardization consists of the following components: Right hepatic vein reconstruction includes a combination of caudal-side deep incision and patch venoplasty of the graft right hepatic vein to remove the acute angle between the graft right hepatic vein and the inferior vena cava; middle hepatic vein reconstruction includes interposition of a uniform-shaped conduit with large-sized homologous or prosthetic grafts; if the inferior right hepatic vein is present, its reconstruction includes funneling and unification venoplasty for multiple short hepatic veins; if donor portal vein anomaly is present, its reconstruction includes conjoined unification venoplasty for two or more portal vein orifices. This video clip that shows the surgical technique from bench to reperfusion was a case presentation of adult LDLT using a modified right liver graft from the patient's son. Our intention behind proposing the concept of right liver graft standardization is that it can be universally applicable and may guarantee nearly the same outcomes regardless of the surgeon's experience. We believe that this reconstruction model would be primarily applied to a majority of adult LDLT cases.