“V-Plasty” technique using dual synthetic vascular grafts to reconstruct
outflow channel in living donor liver transplantation
Long-Bin Jeng, MDa, b, c, , , Ashok Thorat, MDa, c, Ping-Chun Li, MDa, c, d, Ming-Li Li, MDc, d, Horng-Ren Yang, MDa, b, c, Chun-Chieh Yeh, MDa, b, c, Te-Hung Chen, MDa, b, e, Chia-Hao Hsu, MDa, b,e, Shih-Chao Hsu, MDa, b, e, Kin-Shing Poon, MDc, f
a Organ Transplantation Centre, China Medical University Hospital, Taichung, Taiwan
b Department of Surgery, China Medical University Hospital, Taichung, Taiwan
c College of Medicine, China Medical University, Taichung, Taiwan
d Department of Cardiovascular Surgery, China Medical University Hospital, Taichung, Taiwan
e China Medical University, Taichung, Taiwan
f Department of Anaesthesiology, China Medical University Hospital, Taichung, Taiwan
Background
The reconstruction of outflow is a crucial step in living donor liver transplantation. This study describes a suitable technique that uses synthetic vascular conduits in presence of multiple draining veins of right lobe of liver and the outcome of the recipients to evaluate safety of using multiple synthetic grafts.
Methods
From March 2011 to September 2014, 325 patients underwent right lobe living donor liver transplantation. Expanded polytetra-fluoroethylene (ePTFE) grafts were used in total 155 of the liver allografts. Among these, 16 liver grafts required dual ePTFE grafts to reconstruct the outflow due to presence of multiple hepatic veins.
The mean diameters for venous branches of segment 5 (V5) and 8 (V8) were 5 mm (range, 4–8 mm) and 7 mm (range, 5–9 mm). The mean diameter of inferior right hepatic veins was 8 mm (7–10 mm). All the recipients who received the right liver with dual ePTFE grafts showed satisfactory inflow and outflow immediately after reconstruction as measured by Doppler flowmetry. Postoperative ultrasonographic studies showed no disturbances in outflow. Protocol dynamic computed tomography performed in the second postoperative month showed 100% patency rates of the artificial grafts. At median follow-up of 24 months graft survival was achieved in 88%, whereas the patency rates of the ePTFE grafts were 100%.
Conclusion
The use of “V-Plasty” technique using dual artificial vascular grafts is a safe and feasible technique in the presence of various allograft venous anomalies & ensures a single venous channel for outflow reconstruction. Our study also suggests that ePTFE graft may be a useful interposition material without serious complications.
PROPER VENOUS OUTFLOW RECONSTRUCTION is an important consideration in
addition to graft size and portal inflow in LDLT, because severe allograft congestion can lead to postoperative hepatic dysfunction and septic complications.1 and 2 Anomalies in venous outflow are not uncommon in right lobe liver
grafts that increase the risk of outflow complications.3 In the absence of satisfactory
venous drainage, the portal inflow has damaging effects on the graft by delaying graft regenerative capacity and leading to hepatic dysfunction, known as small-for-size syndrome.4
As the result of deceased donor scarcity, LDLT is major source of liver allografts in Asia.5Excluding donors because of the presence of vascular anomalies may further
decrease the chance for a patient with end-stage liver disease (ESLD) to receive a liver transplantation. Large and multiple inferior right hepatic veins (IRHVs) drain substantial portions of the liver, and their presence increases the complexity of venous outflow reconstruction. Available options include the inclusion of these vessels by venoplasty into a single lumen or a second or even third veno-caval anastomosis. Second and/or third anastomosis is difficult in less-available anatomical space and the warm-ischemia time increases with every anastomosis, which may further cause postoperative morbidity. Back-table venoplasty via the use of venous grafts or synthetic conduits to form a single-outflow channel seems a feasible alternative in such situations.
The inclusion of a middle hepatic vein (MHV) in a right liver allograft in LDLT remains a topic of debate. Hepatic venous outflow of the median sector (corresponding to Couinaud segment V, VIII, and IV) is drained mainly into the MHV.6 We follow a flexible approach in inclusion of the MHV in the graft depending
on the donor size and drainage of segment 4b into the MHV.4 In the presence of small
remnant in donors (<30%), we harvest the right lobe without MHV. In such situations, MHV tributaries can be reconstructed with venous grafts that help to decrease the congestion in the anterior sector and effectively provide a functioning liver mass comparable to an extended right liver graft.7
Venoplasty can be accomplished using venous conduits such as cryopreserved venous allografts,8 autologous allogenic venous grafts,9 recipient umbilical vein,10 or synthetic
expanded polytetra-fluoroethylene graft (ePTFE) grafts.11 Use of synthetic vascular
grafts in LDLT remains limited. The ePTFE grafts are readily available and recent experiences in LDLT have confirmed the safety of their use with good patency rates.11 and 12
Thus, the venous outflow for the undrained segments can be reconstructed using vascular grafts with various technical modifications. Although, few centers use synthetic vascular grafts, the technique of using dual artificial grafts and its feasibility has not been described. Herein, we describe a “V-Plasty” technique, whereby MHV tributaries on the cut surface and IRHVs are reconstructed by the use of 2 ePTFE grafts to form a common outflow with the right hepatic vein (RHV).
Materials and methods
From March 2011 to September 2014, 325 patients received right lobe LDLT at the institute of China Medical University Hospital, Taiwan. A total of 112 (34%) patients received grafts without the MHV requiring reconstruction of venous drainage of the anterior sector using a ePTFE vascular graft. Another 112 (34%) allografts had one or more additional IRHVs. In 68 of these patients, a second anastomosis of the IRHV to the vena cava was performed whereas 44 patients required ePTFE vascular grafts to form a common draining channel that included a single large and/or multiple IRHVs due to the difficulty of second venous anastomosis to the inferior vena cava (IVC). Of these 44 patients, 16 received right liver grafts that were devoid of the MHV along with presence of multiple IRHVs requiring dual venous grafts to restore the venous drainage. These 16 patients were included in study cohort to analyze the impact and safety of using dual synthetic vascular grafts in a single liver allograft.
Selection of reconstruction method. Each of the patients in selected cohort (n = 16) received a right lobe liver allograft that was devoid of the MHV and had multiple IRHVs (2 or more). The “V-Plasty” technique using 2 ePTFE grafts to form a common outflow channel was used in these patients because of difficulty in performing a second and third IVC anastomosis as the result of multiple IRHVs (2 or more). At our institute, we include all MHV tributaries with a diameter of ≥4 mm for anastomosis with the ePTFE graft.
Clinical data of the study cohort such as age, sex, underlying diagnosis, coagulation profile, and postoperative liver functions, including aspartate aminotransferase, alanine aminotransferase, total bilirubin, and alkaline phosphatase, were analyzed. Operation-related data such as graft weight, graft-to-recipient weight ratio, warm ischemia time, and cold ischemia time were noted. The variations of bile duct, hepatic artery, portal vein, and hepatic venous drainage of the donor liver were studied by computed tomography (CT) and magnetic resonance imaging and confirmed by operating. The synthetic vascular graft used in each case was ePTFE (Gore-Tex Propaten Vascular Graft, Inc, Flagstaff, AZ).
Evaluation of hepatic inflow and outflow. Volumetric blood flow in the hepatic artery and portal vein was measured using a Doppler flow meter after completion of the vascular reconstruction and repeated at the end of operation before closing the abdomen. If any disturbances were detected, they were addressed immediately.
All the recipients were followed by ultrasonography on postoperative day 1, 3, and 7 and then weekly thereafter for first month to evaluate graft tissue perfusion, venous outflow, and graft regeneration. Any suggestions of flow disturbances by abdominal ultrasonography were further confirmed by a multiphase dynamic liver CT. Abdominal CT was done in the third postoperative month in all the recipients to assess the patency of vascular grafts. The patency rate of the ePTFE grafts was defined as the percentage of ePTFE grafts that functioned well after implantation on follow-up CT.
Posttransplantion anticoagulation therapy and antibiotics. Recipients did not receive any form of anticoagulation therapy except for antiplatelet agents after transplantation. Aspirin (100 mg) was given to all the recipients from the fifth postoperative day and continued for 2 years.
All the recipients received antibiotics for 5 days and thereafter as required. Our institute protocol is to administer ampicillin 1 g intravenously 4 times a day and the third generation cephalosporin cefotaxime 2 g intravenously 3 times a day. The antibiotics may change as per the culture sensitivity report if available. Loss of
follow-up, death, or obstruction of the vascular grafts was considered as the end point of the study.
Recipient characteristics. The study cohort consisted of 10 men and 6 women with a mean age of 51 years (range, 32–65; Table I); 7 recipients had hepatitis B virus– related ESLD, and 3 recipients had hepatitis C virus–related ESLD. Hepatocellular carcinoma was the indication of transplantation in remaining 6 recipients. Liver function assessed preoperatively showed 9 recipients were Child-Pugh class C, 6 were class B, and 1 was class A. The model for end-stage liver disease score ranged from 12 to 18. The follow-up period ranged from 6 to 36 months (median, 24 months). Operative technique.
Donor surgery.
A description of donor surgery is beyond the scope of this article and hence described in brief. Before harvesting the right lobe, the remnant left liver volume was considered. Prior to donor operation, segment 4a volume was calculated with magnetic resonance imaging. The total residual volume of the left lobe (Segment 2, 3, 4b) needed to be >30%. Segment 4a often becomes congested after ligating its venous tributaries, so the volume of segment 4a was not considered in remnant liver volume. The technical considerations of whether to include the MHV in the graft and when to reconstruct the smaller veins on the cut surface are shown in Fig 1 and Fig 2.Also, we used an occlusion test of the venous tributaries of segment 4A after isolating them during the parenchymal dissection to evaluate the severity of congestion in segment 4A. If congestion was severe, we diverted the parenchymal dissection plane towards the right side, leaving the MHV in the donor remnant liver.
We did not ligate the segmental venous branches until the parenchymal transection of liver was completed. Instead, we looped all the major tributaries to minimize the congestion of the graft liver. When liver allograft was to be harvested, we divided the venous branches of segment 5 and 8 if MHV was to be preserved (Fig 3, A and B). If MHV was included in the graft, then we transected the MHV such that the venous drainage of segment 4b remained intact. 4
Back-table venoplasty via the use of artificial vascular grafts. As liver allograft obtained for every recipient was devoid of the MHV and had multiple draining IRHVs, the outflow channel reconstruction during the back-table venoplasty became an important step to allow an adequate veno-caval anastomosis ensuring adequate drainage for the allograft. We adopted the technique of dual ePTFE grafts to reconstruct common outflow by anastomosing the various venous openings on the cut surface of allograft and multiple RHVs to the ePTFE grafts.
“V-Plasty” technique. We use the name “V” Plasty because after reconstruction of the MHV and the IRHV tributaries using these dual ePTFE grafts, the venoplasty appears V-shaped with 2 grafts forming each limb of “V” (Fig 4). On the back table, the donor surgeon examined the congested area carefully and its MHV branches as well as the IRHV orifices. Subsequently, the donor surgeon decided on the drainage type of the MHV branch. The artificial vascular grafts used were thin-walled ePTFE grafts with internal diameter of 8–10 mm. Segments 5 and 8 are the constant tributaries if the MHV is not included in the graft. Several other smaller tributaries, however, may be present on the cut surface between the major venous branches of segments 5 and 8. We included all the tributaries with a diameter of ≥4 mm so as to provide satisfactory venous drainage of the anterior sector.
One end of ePTFE vascular graft was anastomosed to the segment 5 venous opening (V5) with a 6-0 prolene suture in continuous fashion. In cases of double V5s, a venoplasty of the V5s to achieve a single orifice was performed. If the distance was not adequate to allow the venoplasty, the second V5 branch was anastomosed to the ePTFE in an end-to-side fashion.
Thereafter, the ePTFE graft was curved gently so as to allow the inclusion of the other venous branches on the cut surface. The other venous branches were anastomosed to ePTFE graft with 6-0 prolene by an end-to-side technique. Segment 8 venous orifice (V8), if far away from the RHV and venoplasty not possible, also was anastomosed by an end-to-side fashion and the posterior edge of the other end of ePTFE graft was anastomosed to the anterior rounded wall of the RHV to form a common outflow channel (Fig 4, A and B).
If the segment 8 orifice was near the RHV, then we used the Cavitron ultrasonic surgical aspirator (DENTSPLY Corporate, York, PA) to dissect the intervening parenchyma, and segment 8 and the RHV were joined directly by venoplasty of posterior walls using 6-0 prolene. In this case, the ePTFE graft end was joined to the anterior wall of the segment 8 vein (Fig 4, C and D). The gap between the parenchyma and the ePTFE graft was later bridged with tissue glue. We also applied tissue glue around all the venous openings included in the graft so as to stop the bleeding after graft reperfusion, because achieving hemostasis is very difficult on the posterior aspect of the ePTFE graft if bleeding occurs after reperfusion.
Once the venous drainage of the anterior sector of the allograft was restored, the multiple IRHVs were included in ePTFE graft of adequate size (6 mm diameter). The caudal most IRHV was anastomosed the end of ePTFE graft with 6-0 prolene in an end-to-end fashion with continuous running sutures. The posterior margin of the other end of ePTFE graft was finally anastomosed to the inferior margin of earlier
reconstructed RHV to form a single outflow channel. The remaining IRHVs were anastomosed to the ePTFE graft by an end-to-side suture technique (Fig 5).
The single outflow thus established was then anastomosed to recipient IVC by 5-0 prolene suture in continuous fashion. A raising-flap technique for outflow reconstruction4was used in 2 patients. The portal vein anastomosis was done using
standard technique.
Results
Right lobe grafts. A total of 16 right liver allografts that were harvested from donors had type IVb hepatic venous anatomy as per Nakamura's classification.13 The MHV
was not included because of concerns about donor safety as the approximate liver remnant volume was <30%. Portal vein anatomy was type I in 14 grafts and type II in 2 allografts whereas the bile duct was type A in 12 grafts and type B in 4 grafts. The mean diameters of V5 and V8 were 5 mm (range, 4–8) and 7 mm (range, 5–9). The mean IHRV diameter was 8 mm (range, 7–10) (Table I). Dual ePTFE grafts were used to ensure proper venous drainage in all of these 16 grafts using the back-table venoplasty as described earlier. Graft-to-recipient weight ratio was 1.36 ± 0.49 (range, 0.8–2.3). The cold ischemia time ranged from 54 to 89 minutes (mean, 73) and the warm ischemia time ranged from 15 to 36 minutes (mean, 25).
Donor outcome. No living donor showed any abnormality of hepatic blood flow on routine follow-up ultrasonographic studies performed at 1 week and 3 months after donor hepatectomy. No major donor complications requiring reoperation or endoscopic/radiologic intervention occurred in any of the 16 living donors with type IVb hepatic vein anatomy.
Recipient outcome.
All 16 recipients who received a right liver allograft with
dual ePTFE grafts showed satisfactory inflow and outflow immediately after
reconstruction as measured by Doppler flow meter. The grafts showed no
signs of congestion after reperfusion, and all the segments of the liver
allografts had acceptable venous drainage. Four of the recipients required
double duct-to-duct biliary anastomoses because of type B biliary anatomy
in the grafts. Postoperative ultrasonographic studies showed no disturbances
in the outflow, and our protocol dynamic CT performed in the third
postoperative month showed 100% patency rates of the ePTFE grafts (Fig
6). The Doppler study at a median follow up of 24 months showed adequate
inflow and outflow without any evidence of thrombosis and graft
dysfunction. Graft failure requiring retransplantation did not occur in any of
the patients. The postoperative graft liver functions are shown in Table II.
The posttransplant serum transaminases, total bilirubin levels, and
prothrombin times evolved appropriately and returned to an acceptable
range for all study subjects within 1 month of transplantation.
At a median follow-up of 24 months, graft survival was 93%. The patency rate achieved at the greatest follow-up period was 100% and no vascular intervention required in any of the recipients.
Two of the recipients (12%) showed biliary anastomotic stenosis in third postoperative month requiring endoscopic interventions. One patient died 10 months postoperatively of extrahepatic recurrence of HCC and pulmonary sepsis.
Discussion
Donors with anomalous hepatic vasculature often are deemed unsuitable because of the chances of complications in both the donor and the recipient. Because of scarce, deceased donation, however, LDLT is the only available means for an effective source of donor organs in Asia.14 Rejecting the donors because of the presence of
vascular anomalies, therefore, is not ideal. Also, associated congestion in the anterior section in a right liver without a MHV may lead to graft dysfunction that may be accentuated in the presence of one or more draining IRHVs. This technical challenge can be solved effectively by back-table venoplasty of the liver allograft to include all the hepatic veins so as to form a common draining channel. If only a single IRHV is present, we prefer a direct IVC anastomosis whenever feasible. In a right liver graft with multiple IRHVs, however, separate veno-caval anastomosis for every IRHV is almost impossible. In our studies, we noted that every single anastomosis to IVC increases the warm ischemia time by a minimum of 12 minutes. Hence, the use of vascular conduit remains only option in this regard.
Although synthetic vascular grafts have been in use in many centers as conduits for restoring the venous drainage of the graft,15 our “V-Plasty” technique with ePTFE
grafts has never been described previously. Our experience in 16 patients not only shows the safety of using multiple ePTFE grafts in LDLT but also presents a novel technique of forming a common outflow channel to establish an effective venous drainage that prevents possible hepatic venous congestion.
A modified right liver graft without the MHV is used in donors with smaller remnant liver volume (<30%).16 In this situation, venous tributaries of the MHV that are
present on the cut surface of the liver allograft are drained with interposition ePTFE grafts on the recipient side; this approach offers an ideal solution to the problem in
terms of both donor and recipient safety. The additional hepatic veins, such as an accessory RHV along with an IRHV, contribute major outflow of a right liver graft if the diameter is more than 5 mm.
To avoid an undue complexity of outflow reconstruction, all RHVs should be reconstructed on a back-table with vascular conduits. This procedure would require additional grafts, which can be either cryopreserved veins or autologous veins, such as a greater saphenous vein, left portal vein, or a paraumbilical vein,17, 18, 19 and 20 and this
operative procedure often is complex and time-consuming. Moreover, cryopreserved grafts often are unavailable or may not be suitable in the desired field. The “V-Plasty” technique using dual ePTFE grafts is a feasible, safe, and an effective alternative to all other complex procedures and provides adequate vascular outflow channel in the grafts with various hepatic venous variations.
There are several advantages of using ePTFE vascular grafts. First, ePTFE grafts are cost-effective and readily available. Second, differing lengths and diameters can be used in most situations. Third, studies including ours have confirmed the safety and long term patency rates of ePTFE grafts equivalent to cryopreserved vascular conduits.21
The theoretic increased chance of infection and thrombosis are the concerns that have precluded many transplant surgeons from using ePTFE conduits. It has been claimed that cryopreserved grafts improve infection resistance and patency compared with ePTFE grafts because a large percentage of luminal endothelial cells that remain viable at implantation are repopulated with recipient fibroblasts, which make them less thrombogenic.22 Because LDLT is a clean contaminated procedure, concern for
graft infection still exists. Although Shell et al23 claimed the safety of ePTFE grafts in
a contaminated field because they are inert, non-thrombogenic, and impervious in comparison with other synthetic grafts, the application of ePTFE in contaminated area still remains highly controversial. Other studies using prosthetic material elsewhere, such as during repair of an inguinal hernia, have found contrary findings, and recommended against use of synthetic grafts in possible contaminated filed. In our experience of 16 cases, no grafts thrombosed and patency rates of 100% were present at the median follow up of 24 months. Also, none of the recipients showed any signs of sepsis.
Inclusion of the MHV in the liver allograft or to reconstruct the anterior sector venous drainage remains a long-debated topic in the use of a right lobe LDLT. The MHV is an important source of venous drainage of right liver, and in 43% cases, the MHV is of equal size of the RHV and in 14% of cases is the dominant venous drainage.24 Apart from major venous branches from segments 5 and 8, many smaller
MHV in a liver allograft is our usual policy; however, we preserve the segment 4b venous drainage of the donor. If the estimated donor functional remnant is <30%, we avoid including the MHV in allograft. In such a situation, back-table venoplasty of the venous orifices on the cut surface of liver allograft is of paramount importance to avoid congestion of the anterior sector after reperfusion. Although venous collaterals between the RHV and the MHV exist, a flow signal in the venous drainage of segment V/VIII of a right liver graft without the MHV is obvious only on postoperative day 6 after implantation, and functional intrahepatic venous anastomoses may not form uniformly in every graft.25
The immediate effect after reperfusion may be venous congestion that leads to graft dysfunction in the immediate postoperative period. The severity is even more accentuated if there are undrained IRHVs. The appropriate technique to deal with this complex situation can ensure proper venous drainage of the graft liver, avoiding post transplant hepatic dysfunction. Dual ePTFE grafts can safely be used to form a common outflow channel that makes reconstruction of outflow in recipient much easier; avoiding second IVC anastomosis which may not be always feasible in such a restricted retrohepatic field and any delay will increase the warm ischemia that contributes to postoperative liver dysfunction.
Arguments against inclusion of smaller veins on the cut surface of the liver allograft are that the smaller channels thus established by back table anastomosis will eventually be obstructed with regeneration of the liver. However, the long-term patency of the interpositional conduits for anterior section drainage is not an important issue because its dysfunction causes no clinical impact during long-term follow-up. The intrahepatic venous collateral can be expected to develop by day 7 after transplantation,26 and hence, even if the smaller caliber anastomosis are
obstructed after few weeks, hepatic dysfunction does not occur.
In the absence of major thrombosis, the successful reconstruction of all venous tributaries appears to ensure regeneration of the anterior sector of a right liver allograft. In our study population, despite of the various venous anomalies, the mean warm ischemia time was 25 ± 8 minutes. The need of second IVC anastomosis was avoided, which often is difficult in the limited space of retrohepatic vena cava, especially when IVC caliber is small. We commonly use single ePTFE vascular graft whenever anterior sector veins need reconstruction. Certain situations arise where dual ePTFE conduits are needed to establish adequate outflow for the liver allograft. Use of the “V-Plasty” technique thus overcomes such complexity. This study also highlights the liberal and flexible use of artificial vascular grafts without any undue complications in centers where cryopreserved venous grafts are not available.
No special anticoagulation therapy was used in the 16 recipients who underwent “V” plasty with ePTFE grafts. We administered only aspirin 100 mg once daily as antiplatelet agent for the first 2 years after the transplantation starting from fifth postoperative day. The mean international normalized ratio at seventh posttransplant day was 1.1 ± 0.1. No evidence of thrombosis or outflow disturbance was noted in postoperative period and up to 2 years postoperatively. Under proper antibiotic prophylaxis in the postoperative period, infectious complications due to ePTFE grafts are rare.
In conclusion, venous anomalies of the graft liver can be addressed by using this novel technique of outflow reconstruction. The “V-plasty” technique using dual ePTFE grafts in the presence of 2 or more draining IRHVs for outflow reconstruction is a safe and feasible option that decreases the warm ischemia time and ensures a large single IVC anastomosis. No complex anticoagulation therapy is required postoperatively, and use of a simple antiplatelet agent is sufficient.
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