The idea of using a living donor as a donor source for in situ liver transplantation originated in 19661 and 19692. It took more than two decades to develop from a concept to clinical practice. With the increasing maturity of liver transplantation technology since the 1980s, the rapidly growing donor demand has triggered the rapid development of living liver transplantation, especially in countries where cadaveric organs are scarce. The first attempt at living liver transplantation was performed in Brazil on December 8, 1988 by Raia3 et al. in a 4.5-year-old girl with congenital biliary atresia. The donor liver was taken from the left outer lobe of the donor, but the child unfortunately died during hemodialysis on the sixth postoperative day. They performed a second attempt at living liver transplantation on July 21, 1989. The recipient was a patient with Caroli’s disease with liver fibrosis. The donor recovered well after surgery, but the recipient had a delayed recovery of liver function and was still jaundiced at 24 days postoperatively. No further recovery was reported for this patient. During the same period, in July 1989, Strong4 and others in Australia performed the world’s first successful adult-to-child living liver transplantation using a donor liver taken from the left outer lobe of the donor. The donors, both Japanese, traveled to Brisbane, Australia, where they hoped to obtain a cadaveric donor liver to complete the liver transplant. In the same year Singer5 at the University of Chicago initiated a discussion on the research and ethics of living transplantation with the aim of establishing norms for obtaining consensus. Since then Broellsch6 and others have further refined the surgical technique, eventually making living liver transplantation a valuable technical operation for saving pediatric patients. The technique of adult-to-child living liver transplantation was rapidly adopted in Asia, where there is a significant shortage of cadaveric-derived donors. Nagasue7 et al. in Japan performed the first such procedure in 1989. The recipient survived for 285 days before dying of donor rejection and multiple organ failure. Subsequently, Ozawa8 et al. performed the first successful living liver transplantation in Japan in June 1990. After four cases of post-transplant hepatic artery thrombosis, they introduced microsurgical revascularization techniques as a routine for hepatic artery reconstruction, a revolutionary innovation that revolutionized the prognosis of living liver transplantation.9 In Hong Kong Yeung10 et al. performed the first such procedure in the region in 1993. Lee11 et al. performed their first procedure in Korea in 1994. In the same year in Taiwan, Chen Zhaolong12 et al. also performed the first living liver transplantation in the region.13 In 1997, Dou Kefeng13 performed the first living liver transplantation in mainland China in Xi’an. By 2002, a total of 509 adult-to-child living liver transplants had been performed at five major liver transplantation centers in Asia, with Kyoto University in Japan performing the largest number of cases.14 In all but one of these procedures, the donor was obtained from segments II and III, and sometimes extended to segment IV, of the donor’s left liver. In that adult-to-child liver transplantation, Yamaoka15 et al. decided on an ad hoc basis to excise the right half of the liver, excluding the middle hepatic vein, as the donor. The reason for changing the donor’s surgery from a left hemicolectomy to a right hemicolectomy was due to an anatomical variation in the left hepatic artery of the donor liver. In the following years, living liver transplantation gradually expanded to include transplantation of young children with a single segment of liver16 and even liver transplantation of newborns with a reduced volume single segment.17 Living liver transplantation in children also developed rapidly in Europe. The first living liver transplantation in Europe was performed by Broelsch et al in October 1991, followed by Boillot18 in Lyon in July 1992 Otte performed the second and third living liver transplantation in Belgium in July 1993. Because there are more patients with end-stage liver disease in adults than in children, this technique was tried in adults soon after the successful use of living liver transplantation in pediatric patients. The first attempt to use a left hemi-liver donor for adult patients was made by Haberal19 as early as 1991, but the results were disappointing. It was not until 1993 that Makuuchi20 and his team, a Shinjuku University scholar in Japan, successfully performed the first adult-to-adult living liver transplantation with a donor taken from the left hemi-liver. The recipient was a 53-year-old female patient with primary biliary cirrhosis, and the donor was her son. This left hemihepatic donor contained the middle hepatic vein and was 45% of the recipient’s standard liver volume. We performed the same procedure on July 12, 1994, in Hong Kong between a husband and wife.21,22 The recipient suffered a sudden onset of fulminant liver failure during pregnancy. The patient’s husband, as the donor, weighed 82 kg, while the patient weighed 57 kg (see Figure 1.1). The donor liver volume was 42% of the recipient’s standard liver volume. In both cases, the left hemi-liver was successfully taken as a donor because the donor’s weight was greater than that of the recipient. However, despite the early success with left hemi-livers as donors, there has not been a significant increase in the number of adult-to-adult living liver transplants. The main reason for this is the limitation of donor size. Most patients with chronic liver disease in Asia are male, and their wives, who are willing to serve as donors, are often too small to serve as donors. In order to provide larger donor livers for adult patients, Professor Fan of the Queen Mary Hospital in Hong Kong began to design living liver transplantation using the right hemi-liver in 1996.23,24 The first operation was performed on May 9, 1996, on a patient with fulminant Wilson’s disease who weighed up to 90 kg, whereas the donor’s brother weighed only 74 kg. They removed the right half of the liver containing the middle hepatic vein as a donor, which weighed 910 g, representing 39% of the patient’s standard liver volume. Both donors and recipients recovered well and are alive and well today. The use of the donor liver containing the middle hepatic vein allowed the donor to no longer be excluded because of similar or smaller weight than the recipient (see Figures 1.2 and 1.3). Since the use of the right hemi-liver as a donor, the indications for living liver transplantation have expanded, especially for those patients who are at high risk.25-28 Living liver transplantation with a right hemi-liver donor is now used by many transplantation centers. Research related to living liver transplantation has also flourished (see Figure 1.4). Living liver transplantation is currently used in patients of Christian faith.29 The first right hemihepatic living liver transplant in Europe was performed in 1998 by a team led by Broelsch30 in Essen, Germany. Wachs31 reported the first right hemi-liver living liver transplant in the United States in 1998. Subsequently, Marcos32 and others, as well as several other centers around the world, have adopted the right hemi-liver as the primary donor model for adult living liver transplantation. However, due to concerns about postoperative liver failure in the donor, almost all of the right hemiportal living liver transplants performed at these centers did not include the middle hepatic vein in the donor. The debate on whether right hemi-liver donors need to include the middle hepatic vein remains inconclusive to date, but more centers are now taking a more flexible approach. A right hepatic donor that includes the middle hepatic vein is used if the graft is relatively small, the right hepatic vein is relatively thin, the pre-estimated blood return to segments V and VIII is high, and the recipient is in very poor preoperative condition or has severe portal hypertension.33-37 Donor safety has been a major concern since the beginning of living liver transplantation. To reduce the risk to the donor, Makuuchi38’s team chose to use a right liver excluding the middle hepatic vein as the donor, which is between the size of the left liver donor and the right liver donor (including the middle hepatic vein). This procedure is technically demanding and may only be performed in some centers with relatively mature technology. Until now, living liver transplantation using the right liver (excluding the middle hepatic vein) as the donor has not been used as a routine procedure. (See Figure 5.) The prevalence of fatty liver is high among the local population in Korea. Therefore, Lee39,40 et al. devised a dual-donor liver surgery protocol with primarily the left liver as the donor to reduce donor risk. These donors included situations such as donor-recipient volume mismatch or heavier steatosis in the donor liver (see Figure 6). This demand on donor resources and the complexity of the surgical technique is much higher than for other forms of donor. Although the development of this technique has expanded the indications for living liver transplantation, the risks to the donor are still worthy of discussion. In 2002 Cherqui41 et al. performed a laparoscopic donor liver resection technique. Initially this technique was restricted to the resection of segment II and III donor livers, but by 2006 it had been extended to the resection of right liver donors by Koffron42 and Kurosaki43 et al. The greatest advantage of laparoscopic donor liver resection is the reduction of postoperative donor wound pain and shorter hospitalization days, but donor safety and graft quality are still under observation. For the safety of the donor and the benefit of the recipient, laparoscopic donor liver resection requires much stricter anatomy of the donor’s hilar region than open surgery. The technique of living liver transplantation has continued to develop and improve in recent years. There is no doubt that living liver transplantation has saved many lives and many of the technical aspects and ethical issues debated in the early years have been resolved, but not completely. It is good to know that if we publish our results honestly and discuss them openly, we will be able to reach a consensus in the near future.