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Types of Liver Transplants

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Liver transplantation refers to the surgical replacement of a diseased liver with a donor-grafted organ. This is most commonly orthotopic (complete removal and replacement), but occasionally heterotopic, where the native organ is left in situ. The transplant may be whole liver, a reduced-size liver, or a liver segment, the latter as means of overcoming donor organ scarcity, particularly for pediatric recipients (Figure 29–1). Reduced-size liver grafts, such as a left-lateral segment or hemireduction graft, can be derived from either cadaver or living donors, or from split-liver transplantation, where two grafts are created from a single donor organ for two recipients, usually an adult and an infant.1

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FIGURE 29–1
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Surgical techniques for liver transplantation in children. Orthotopic whole-organ replacement, and reduced-size techniques. Donors are matched for size and blood type.

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MELD and PELD

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The United Network for Organ Sharing in the United States has devised the Model for End-stage Liver Disease (MELD) and Pediatric End-stage Liver Disease (PELD), which are numerical scales that are currently used for liver allocation.2 Similar systems exist in other countries. These scores are based on a patient’s risk of dying while waiting for a liver transplant, derived from objective and verifiable medical outcomes data. The MELD score, used for patients aged 12 years and older, is based on bilirubin, international normalized ratio (INR), and creatinine. The PELD score is based on bilirubin, INR, albumin, growth failure, and age, factors which better predict mortality in children. These scores do not alone determine the likelihood of getting a transplant. Other factors include matched (blood group and size) organ availability, the occurrence of higher priority exceptions (e.g., those with fulminant hepatic failure), and the distribution of MELD/PELD scores for other patients in a local area or region, and consideration for living donation. The PELD/MELD system also has designated exception scores assigned to specific liver conditions that have preserved liver synthetic function and thus corresponding low allocation scores, such as those children with metabolic liver diseases (e.g., urea cycle disorders) and hepatoblastoma. In addition, a program can request a higher exception score if the calculated score does not truly represent the patient’s condition. This is done by submitting an exception score request to their UNOS regional review board for consideration.

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Epidemiology

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The annualized incidence of liver transplantation in the United States is 10–12 per million total population, that is, 50–60 cases per million children/year (1/16,000 children), or about 600 children, one-third of these being infants. Approximately 55% of these transplants are for end-stage chronic liver disease, the majority of these due to biliary atresia (BA); about 25% are for metabolic liver diseases, 10% for acute liver failure, and 5% for liver tumors (Figure 29–2).3,...

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