A Liver Graft Should Not Be Selected by the Side but Determined by Volume in Adult Living Donor Liver Transplantation

Living donor liver transplantation (LDLT) was first indicated for pediatric patients in whom left-sided (left lateral sector) grafts have usually been used.1 The first right liver graft, reported in 1994, was not planned before surgery but was changed from left to right during the operation because of the anatomy of the left lobe of the liver.2 The first successful adult case, reported in 1994, received a left liver graft.3 Before 1998, LDLT was performed exclusively using left liver grafts in adult patients. It was the Hong Kong group that first used the right liver graft electively for adult patients.4 The right liver used then was not the same as the now widely used right liver graft but contained the middle hepatic vein trunk in the graft and was called an extended right liver graft. Now, the widely used right liver graft does not contain the middle hepatic vein trunk, but only the tributaries, which thus sometimes needs reconstruction to maintain the outflow to the vena cava. It is called a modified right liver graft and was first devised by Gyu Lee5 in Korea. In Japan, the right liver graft has been used for adult cases since 1998, and in some centers, it has been routinely used. However, other centers did not exclude the use of the left liver graft; instead, they determined the type of graft based on the volumes. The criteria by which the kinds of graft have been determined have been the graft volume per standard liver volume ≥40% or per body weight ≥0.8. This threshold level has a tendency to be decreased (eg, standard liver volume ≥35% or per body weight ≥0.7) by some transplant centers. If the left liver satisfies these standards, the left liver will be used as the first choice, but if not, the right liver is considered. In 2003, the national data on the living donor were reported, disclosing the higher risk of complications was in the donor of a right liver.6 Influenced by the report, the use of the right liver for adult patients increased but was not universally established in Japan. According to the Registry of the Japanese Liver Transplantation Society, the number of patients who received left liver (±caudate lobe) was 2795, and that of right liver was 3534 up to the end of 2021, and the outcome of adult patients receiving the left liver was comparable with that receiving the right7 (Figure 1).FIGURE 1.: The graft survival of living donor liver transplantation stratified by kinds of grafts in Japan (made using data in Liver Transplantation in Japan).7In contrast, most transplant centers elsewhere in the world, maybe in consideration of the poor outcomes from using left liver grafts in the initial experiences, abandoned the left liver and used the right liver exclusively for adult patients. Halazun et al8 showed comparable graft survival between left and right in LDLT; however, left liver grafts represented only approximately 5% of adult LDLT performed in the United States. According to the Korean Organ Transplant Registry, the left liver grafts represented approximately 3% of adult LDLT.9 Laparoscopic or robotic donor hepatectomy, now widely introduced, has been stylized for the right, seeming to accelerate the tendency. It is only recently that laparoscopic left hepatectomy has been reported.10 In this issue of Transplantation, Jo et al9 analyzed the outcome of LDLT using the Korean Organ Transplantation Registry data. They showed that the use of the left liver graft was not a significant prognostic factor in multivariate Cox proportional hazards regression analysis. Donor age (40 y or older) and recipient body mass index remained significant prognostic factors. Comparing the clinical outcomes between LDLT using left liver grafts and right, matching graft to recipient body weight ratios, it was shown that the prognosis of the patients with left liver grafts was poorer. However, donors who donated the left liver were older than donors of the right liver. The authors concluded that the left liver graft is still worth considering for LDLT. I applaud Jo et al for their impactful research on the significance of LDLT using left liver grafts. This study should inspire transplant surgeons to modify their reluctance to use left liver grafts in LDLT. In Korea and Japan as well as across the world, the side of the donor graft should not be selected simply by the side but determined by the liver volumes.