Figure 36.1 Ex situ split done on the back table once the liver has returned to the transplant centre. Ex situ split has the advantage of not prolonging the donor procedure at the expense of the other teams involved, and potentially prolonging the surgery on a donor who becomes unstable during the procurement.

2.  The arterial anatomy is carefully examined next. This is the most variable part of the split procedure. If the arterial supply to the segment II–III graft arises from the left gastric artery, the procedure is simplified a great deal, as long as no supplementary arterial branches from the proper hepatic artery can be identified. If the anatomy is normal, the junction of the left and right arteries is identified, and if possible, the arterial supply to segment IV is left with the right side. At this point, the surgical team must agree on where the hepatic artery is divided. The right artery may be divided just distal to the bifurcation, leaving the left artery in continuation with the coeliac axis. This permits the arterial supply in the infant to be reconstructed with a coeliac patch to the aorta and is a more reliable reconstruction and less prone to thrombosis, particularly when the recipient hepatic artery is very small or in cases of retransplantation. This compels the adult recipient transplant team to reconnect the donor right hepatic artery to the recipient artery, or alternately, an arterial iliac graft can be used to lengthen the donor artery and make the arterial anastomosis in the recipient less complicated. With few exceptions, this is the method that has been adopted at our centre when the primary offer has been made to the child.
  When the primary offer has been made to the adult patient, the adult team will usually not agree to separate the right arterial vessels from the coeliac axis, and thus the paediatric team must deal with the arterial supply, as it would in cases of live donors, using the left hepatic artery to revascularise the liver. This is not usually a problem.

3.  The main portal vein is usually left with the right graft, as the left portal vein is all that is necessary in most cases of the paediatric recipients. The left portal vein branches to segment IV are divided in the recessus of Rex, along with the few branches to the caudate lobe. This allows for more length on the left portal vein, and the left vein is divided just beyond the portal vein bifurcation.

4.  The bile duct is divided at the portal plate in the recessus of Rex. A 2 or 3 mm probe is inserted through the main bile duct and directed into the left duct to facilitate the identification of the best location to divide the duct. This is usually just below the portal vein and just deep to the capsule of the liver. The duct is divided sharply with a knife. In many cases, a small accessory duct to segment II may be identified just posterior to the main duct, and may require a second biliary anastomosis in the recipient.

5.  Once the main vascular and biliary structures have been divided, all that is left is to complete the parenchymal transection. The posterior-ventral surface of the liver is scored from the bile duct and portal vein area, along the ductus venosus, to the area just to the right of the left hepatic vein. There are small branches of the bile duct and portal vein to the caudate lobe that may require ligation (Figure 36.2). The anterior surface of the liver is scored just to the right of the falciform ligament that stays with the left graft, along the anterior-posterior surface of the liver, to join the line of transection already determined by the division of the bile duct.

The parenchyma may be divided in a number of ways, including the traditional division of the liver with a blunt instrument and ligation or suture ligation of all major vascular and biliary pedicles in the parenchyma. We use a LigaSure™ with a dolphin tip to traverse the parenchyma and have found that this is faster and better at sealing vessels and bile ducts than the traditional methods of tying.

Segment II–III grafts usually weigh between 250 and 300 g and can be used in children whose weight is between 7 and 25 kg, although much attention must be paid to the requirements of the individual patient and the size variability of the segment II III graft before a final determination can be made as to whether the recipient would need a whole left lobe or a monosegmental graft.

In cases where the left lobe must be split, the principles of splitting remain the same. Great attention must be paid to the anatomy of the hepatic artery and, in particular, the segment IV vessel that may come off the right hepatic artery. This may make splitting of livers for left and right lobe combinations more problematic.

The left lobe graft comes with the middle hepatic vein, and this may interfere with drainage of the right lobe if the anterior sectors drain via V5 and V8 into the middle vein.

The portal vein dissection is easier since this does not require tying off any left portal vein branches, and the bile duct may be transected more to the right, trying to ensure that the segment IV duct that drains obliquely into the left main duct remains with the left graft.

The parenchymal transection is longer since the liver is thicker in this area, and the tissue traverse starts in the gall-bladder fossa and continues posteriorly to the vena cava.

Figure 36.2 The caudate lobe vessels are separated from the left side of the liver, while a probe is in the bile duct as a guide to where the left hepatic duct should be divided.

Left lobe grafts are rarely required in infants unless the segment II–III graft is unusually small in an adult, or if the donor is another child. In the latter case, the right lobe may be too small to transplant into an adult, and a size reduction only is necessary.

Monosegmental grafts may be called for if the recipient is very small, and additional tissue must be removed (Figures 36.3 through 36.5). This is done quite uncommonly. Segment III is removed by following the plane of the segment III portal vein, and all of the dissection is done intraparenchymally.

36.3.2  Graft implantation (Figures 36.6 and 36.7)

The operation is similar to other methods of liver transplantation, and the hepatectomy will not be described in detail at this point. The only cautionary note should be in trying to preserve as much as possible the length of the recipient hepatic artery and portal vein. While split transplantation provides flexibility in the allocation of the coeliac axis and portal vein and extrahepatic duct, it is prudent to preserve as much of the recipient vessels as possible to allow for unexpected complications.

Figure 36.3 A segment II–III split graft is being further prepared for resecting segment III to use as a monosegmental graft in a very small baby. The graft measures 15 cm in width from the liver tip to the dividing line along the falciform ligament.

Figure 36.4 The segment II–III graft is subdivided.

After the reimplantation, flow in the vessels is carefully assessed using Doppler flow probes. The biliary anastomosis is done almost exclusively by using a hepaticojejunostomy since there is rarely more than a small duct opening on the surface of the liver. Duct-to-duct anastomoses are rarely possible.

In almost 25% of cases, there are more than two ducts present and two smaller anastomoses are necessary. Ducts from segment IV may be present at the portal plate, and these can be safely tied off if they are recognised.

36.4  RESULTS

36.4.1  Frequency of split liver transplantation

In the United States, 10%–15% of all paediatric transplants are split livers according to Scientific Registry of Transplant Recipients (SRTR) data. Worldwide, rates differ, but in general, it is universally thought that split liver transplantation is a modality that should be used more often than it is [6].

Although about 20% of adult livers meet UNOS split criteria, it is felt that only a small percentage of these livers are offered for split. If only 10% of splittable livers were utilised to transplant a child and an adult, the paediatric liver waiting list would be completely eliminated [7,8]. In the American adult experience, <1% of transplants are from livers that have been divided as compared with whole organ grafts.

Figure 36.5 The segment II graft is ready for implantation. One can see the artery with the aortic cuff in the lower left of the picture, and the outlines in blue on the surface of the liver of the hepatic vein (black arrow) and portal vein (white arrow). The width of the graft has been reduced to about 8 cm.

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