Living donor liver transplantation (LDLT) is a technically complex procedure requiring various levels of technical expertise within the procedure itself. Historically, arterial complication rates were reported between 15 and 25% after hepatic artery reconstruction (HAR) hence, procedure itself being the crucial step of the operation, with a potentially significant cause of morbidity and mortality . Introduction of microsurgery dramatically decreased complication rates, current series reporting complication rates between 0 and 6% . Arterial anastomoses in LDLT are different than deceased donor transplantation in regards to vascular anatomy, diameter, hemodynamics, the orientation of the graft and recipient vascular structures. Here we describe the standard techniques of HAR and outcomes in LDLT in view of the current literature.
A successful HAR has three key factors, these are selection of the recipient artery, the quality and length of the graft artery, anastomosis technique of which the latter not necessarily has the utmost importance in every clinical scenario. A very short graft arterial stump or an intimal detachment in the recipient inflow artery could easily become the determinant of the technique and outcome of HAR in any given patient.
The donor artery by definition represent the highest tissue quality from healthy donor; however, limited by graft artery stump size and diameter both of which have varying level of importance in HAR. Further, in many experienced LDLT centers, it is not handled in the back-table unless the surgeon performing the back-table procedure is the same person performing the anastomosis to prevent unintended damage.
One of the most challenging scenarios would be a rather short hepatic artery stump, coming from an older donor with relatively poorer vessel quality and smaller arterial diameter. This scenario should be anticipated in preoperative planning and discussed by the donor and recipient surgical teams during the donor operation. Once the graft is procured, it could only be handled with precise anastomosis technique by an experienced vascular or microsurgeon. As rotation of the short stump graft artery will not be possible, the back-wall first technique will be necessary. If the surgeon is not familiar with the back-wall first technique, extension of the graft artery with an arterial graft at the back-table would probably be the safest approach . The authors prefer radial artery, a segmental part of recipient hepatic artery or gastroepiploic artery for conduit [4–5].
More than 40% of left lobe grafts and 5% of right lobe graft had multiple hepatic arteries and there is a dilemma on which one or both stumps should be reconstructed . In general, back bleeding from recessive arterial stump after reconstruction of dominant stump was most important clue to anastomosis or ligation of the former. This can also be tested during graft harvest on the donor side with cooperation with the donor team. There were some controversies on the incidence of biliary complications between single and multiple anastomosis . We prefer multiple anastomosis whenever it is feasible on the right lobe graft and selectively on the left lobe graft for the following reasons; identification of dominant stump may sometimes be difficult because almost half of dual arterial stumps have similar size making it difficult to appreciate the dominant one. Second, recessive stump usually located deeper site than dominant stump, especially in the right lobe graft. So previous dominant arterial reconstruction may make second anastomosis difficult or sometimes even impossible. Again, one key element for decision is during graft harvest with cutting the recessive one first to see the arterial backflow when the dominant artery was intact. Oftentimes, one will see there is good flow but it is not the exact pulsatile flow that comes from the dominant hepatic artery. There is obviously a pressure difference arising from intrahepatic resistance and circulation. On the right graft, when the recessive artery is responsible from the anterior section inflow and pressure drive for the venous outflow, one can speculate that might also have an impact on outflow reconstructions patency rate .
There are several important factors for inflow artery selection. The size and the quality of graft artery will determine the inflow artery. It is crucially important to have all three hepatic arteries (left, middle, right with secondary branches) undamaged during hepatoduodenal ligament dissection in the recipient. After confirming satisfactory flow, recipient-to-graft vessel orientation, diameter match and intimal quality are more important factors for selection. A final key step is choosing the anastomosis site on the inflow artery. Although fulminant liver failure or metabolic liver disease patients without cirrhosis have relatively spared hepatic arteries, there are various clinical factors with the cirrhotic recipient that may have an impact on the arterial quality. Hyperdynamic circulation of cirrhotic patient especially with portal vein thrombosis, hepatic arteries got stiffer with intimal thickness despite an increase in diameter. Transarterial embolization procedures have been reported to be associated with diseased and/or damaged hepatic arteries, which may cause arterial intimal thickening resulting with easy detachment . Atherosclerosis leads to media layer calcifications, which should be avoided with further cutting proximally until a healthy segment for anastomosis site is achieved.
The anatomical anastomosis may be the first choice for the HAR to the extent possible . In reported series, more than 90% of anastomosis are anatomical ones, referring anastomoses of branches of recipient hepatic artery to graft hepatic artery . A major issue when selecting the inflow site is size discrepancy between graft and recipient artery . In experimental models, the size discrepancy was reported to result with lower patency rates . The size discrepancy between graft and recipient artery can be seen in both internal diameter as well as intimal thickening. To address the former, the authors prefer not to go for more than 1 : 2 proportion, which would mean any of the inflow or outflow arteries do not have an internal caliber of more than two times of the counterpart. In order to have better size match, high hilar dissection is important to obtain a healthy segment of secondary branches of the right hepatic artery. This is not much of an issue on the left lobe and left lateral grafts. During HAR, size discrepancy of the anastomosis vessel ends should be shared by both the anterior and posterior walls. With the stay sutures in position, the discrepancy in vessel circumference can be gradually compensated for with individual stitches during suturing.
For a convenient HAR, the surgeon needs to tackle several obstacles that are inherent to the procedure itself. The anastomosis is located in a deep, moving field. Close cooperation between surgical and anesthesiology teams are necessary to control the depth of the respirations limiting the tidal volumes which will limit the superior–inferior movement of the surgical field. This is especially important while placing critical sutures; that are sutures at the angles or for hemostasis with where high magnification under surgical microscope is used. Depending on the recipient size, deep abdominal cavity may require longer instruments (18–21 cm). In order to decrease anteroposterior (A-P) distance, we prefer to rotate the table to the surgeons’ side 45–60° (right), place several gauzes under and behind the graft to elevate it and use self-retaining retractor to the medial graft side to fix it.
Approximator clamp, an atraumatic double-armed clamp moving on a side bar is a vital instrument for HAR and greatly facilitates the procedure providing orientation and tension-free anastomosis. The authors use an appropriately sized Acland Clamp (S&T Gmbh, Switzerland) for this purpose.
The anastomosis preparation is started with graft artery evaluation, arterial ends should be trimmed to have a smooth anastomotic interface, flushed with heparinized saline (10 U/ml) and gently dilated under magnification. Any clots are removed as well as adventitial tissues around the arterial orifice that could interfere with the anastomosis. The approximator clamp is placed about 1 cm from the arterial ends in both sides. We prefer to place a 2 cm x 2 cm rectangular mat cut from sterile glow for background contrast. Before starting the anastomosis, it is extremely important that the position is convenient for the surgeon, anastomosis site is tension free and stable as much as possible.
We prefer 7.0 prolene suture for arteries with internal diameters at least 3.5 mm, 8.0 for 2.0–3.5 mm, 9.0 for 1.5–2.5 mm and 10.0 for 1.0–1.5 mm diameter arteries, respectively (Fig. 1).
There are very different approaches to perform a HAR, the surgeon should be familiar with different variants and be ready to employ them in different clinical scenarios. Here we describe basic techniques, with evolving experience clinical microsurgeon will find it easy to make variations or employ a combination of techniques at a given clinical scenario.
After placement of the approximator clamp, stay sutures at 0’ and 180’ are placed and cut with a long suture stump for retraction. Then, the first suture will be in the middle of two stay sutures and not tied for easy visual inspection of the posterior layer. The second and third sutures will be between each stay suture and the middle suture. After evaluating the orientation of the sutures, free back-wall and confirming correct suture placement, the second, third and the middle sutures are tied at least three times. A surgical knot (double tie) is helpful in sutures with tension and size mismatch. The approximator is rotated and above steps repeated for the posterior layer, which is now anterior position with rotation. (Fig. 1a–c).
There are several variants reported in the literature, which authors may also employ time to time. A practical one, is continuous suture interrupted tie technique, which provides a faster anastomosis .
Continuous technique has several advantages; it is faster and provides easy adaptation to size mismatch. This technique also starts with stay suture placement at 0’ and 180’. The tied edge suture continuous with repeated sutures on both arteries. It should be applied cautiously in the diseased recipient artery with intimal thickening and detachment unless inside-to-outside bites are taken from the inflow artery (Fig. 2a and b).
An application of 1% lidocaine hydrochloride on the adventitial side of the vessel was performed to dilate the vessels to improve the volume of blood flow. Bleeding from needle holes usually stopped with the application of a small piece of oxidized regenerated cellulose (Surgicel 1902GB, Ethicon Inc). In case, conservative measures were not sufficient for bleeding control, we prefer to control the bleeding with a meticulously placed interrupted suture to prevent postoperative hemorrhage. The surgeon should not hesitate to apply a bulldog clamp to control inflow in order to achieve correct suture placement. Doppler ultrasonography was performed immediately to demonstrate patency of the anastomosis. We prefer routine Prostaglandine E1 for all LDLT procedures and low molecular weight heparin whenever international normalized ratio is 2 or less.
BACKWALL FIRST TECHNIQUE
Backwall first technique is used when there is short graft artery stump preventing rotation . Further, this technique can also be used when both the arteries are fragile or diseased that the rotation might result with further damage. This technique could be performed with a running or an interrupted fashion. After the stay sutures, the interrupted technique starts with donor side outside inside and recipient side inside out and tied until the second stay suture is reached. The anterior wall is performed in a routine fashion described above. The continuous technique may require more expertise and manipulation of the graft artery and may require more technical expertise (Fig. 3).
LOUPES VS. MICROSCOPE
The usage of surgical microscope is being criticized by its large hardware causing maneuvering issues in the operating room, requiring expertise with a long learning curve to use the device and representing difficulties for teaching . Microvascular reconstruction of hepatic artery is a complex procedure and for a surgeon from general or transplantation surgery background, it is a challenging task to acquire skills for basic microsurgery and then transitioning to clinical microsurgery. In a recent study, five neurosurgeons with 5-year surgical experience but without any experience in bypass surgery performed microscopic anastomosis on progressively smaller caliber silastic tubes [17▪]. In the cognitive phase of learning, that is, the beginning of learning, the trainees had a lot of information bits to learn, there was a high degree of change in performance with plateauing, which could be discouraging, however, with guidance and motivation from the instructors, their performance increased to a consistency level that represents a sign of passing beyond the cognitive stage of learning, and formation of a motor pattern. The overall direction of the learning curve was ascending, indicating the general progress in performance. Their results showed that for the task of microvascular anastomosis, 10 initial practice trials are required to pass through the cognitive stage and beginning of consistency phase. This results could also be applied to transplant surgeons trained to perform HAR as was the case in authors’ experience also from the mentor–trainee perspective. The process is an achievable goal with adequate training and constant supervision during the learning curve and surely, with continuous practice. From an administrative perspective, training a team member for microsurgery could be seen as an investment worth considering. Fundamentally, it is solving a major logistics issue of transplant teams, that is being dependent on an either a microsurgeon or a cardiovascular surgeon to perform the arterial anastomosis anytime there is an LDLT case, or worse when an arterial complication arises.
On the other hand, there is a growing body of literature suggesting equivalent results using surgical loupes instead of microscope (Table 1). Li et al.[18▪▪] recently reported a large experience of 766 recipients with a short beginning era with microscope (25 recipients) followed by 741 recipient HAR performed by surgical loupes by cardiovascular surgeons with a hepatic artery thrombosis rate of 1.2% and with a significantly faster anastomosis times. An important criticism was a possible purse string effect possibly resulting with biliary ischemia and anastomotic strictures [19▪,20]. This is infact a major concern when tying continuous suture lines using loupes an untoward and potentially underestimated technical fault that is very rare tying under microscope because of the completely diverse nature of handling suture material in different settings. Yagi et al. also reported replacing microvascular anastomosis to a continuous suture using 3.5× magnification with loupes with comparable outcomes . The authors explain their good results with delayed tying with fully expanded anastomosis line. In order to prevent a purse string effect, tying under high power magnification with the operation microscope offers two advantages over using loops. These are better visibility and limited force application to the microsurgical suture.
On the basis of our experience, the benefits of HAR with operating microscope in LDLT setting is not limited to performing the anastomosis itself, but also enable the surgeon to evaluate the donor and recipient vessels and eliminate the potential risk factors associated with HAT, such as damaged intimal edges separation of the intima and medial layer resulting with flaps, soft thrombi within the lumen of the arterial stumps and incorrect placement of hemostatic sutures.
In many institutions, consulting microsurgeons perform the HAR in LDLT. We believe transplant surgeons adequately trained and supervised using the standardized microsurgical techniques should be able to obtain excellent results. As with all demanding procedures, there is a learning curve. Close mentorship is essential in successful arterial reconstruction of living or deceased donor partial grafts, regardless of the device whether surgical microscope or loupe is used.
We would like to thank Celal Bayar for his assistance with graphics of the study.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
REFERENCES AND RECOMMENDED READING
Papers of particular interest, published within the annual period of review, have been highlighted as:
- ▪ of special interest
- ▪▪ of outstanding interest
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This is a well designed study, on training for and learning curve for microvascular anastomosis. An inspiring article for all who have interest in starting clinical microvascular surgery.
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Here, an in-depth description of hepatic arterial reconstruction techniques using a surgical loop is reviewed. This article gives detailed descriptions of each surgical step as wells as complications and their current management in living donor liver transplantation with accompanying illustrations.
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Excellent critical review of the article by Li PC, with insightful questions and comments.
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