Partial liver transplants are not only possible but are performed thousands of times each year worldwide, and the outcomes have steadily improved to the point where they rival those of whole-organ transplants. The procedure takes advantage of the liver’s remarkable ability to regenerate: a surgeon removes a portion of a healthy liver, implants it in the recipient, and both the donated piece and the donor’s remaining liver grow back toward full size within weeks. There are two main routes to a partial graft, each with its own trade-offs for donors, recipients, and surgical teams.
Two Ways to Get a Partial Liver
The first and more common route is living donor liver transplantation (LDLT), where a healthy person voluntarily donates part of their liver to someone who needs it. The second is split liver transplantation (SLT), where a single deceased donor’s liver is divided and given to two recipients. Between 2002 and 2009 in the United States, about 2,272 partial liver transplants were performed, representing roughly 5% of all liver transplants; three-quarters of those were living donor procedures and the remainder were split grafts.1PubMed Central. Outcomes in partial liver transplantation: deceased donor split-liver vs. live donor liver transplantation
In living donation, the donor undergoes major abdominal surgery to have a lobe removed. In split transplantation, a surgical team divides a deceased donor’s liver, usually giving the smaller left lateral segment to a child and the larger right extended segment to an adult.2PubMed Central. Split liver transplantation A more technically demanding version splits the liver into two roughly equal halves for two adult recipients.3Liver Research. Expert consensus on split-liver transplantation Both approaches aim to solve the same problem: there are far more people waiting for a liver than there are whole organs available.
Why the Liver Can Be Split at All
The liver is the only solid organ that can regenerate to near-original size after a large portion is removed. After a partial transplant, the donated piece begins growing almost immediately. In animal models, a graft that starts at 30% of the recipient’s original liver volume can reach roughly full volume within a week.4PubMed. Increased immune responses to regenerating partial liver grafts in the rat In humans the timeline is somewhat longer, but the graft typically reaches functional adequacy within a few weeks and approaches its final size within a couple of months.
This regeneration depends on a cascade of molecular signals. Two of the most important early triggers are proteins called TNF-alpha and IL-6, which are released by non-liver cells in the graft and kick-start the process of liver-cell division. When the graft spends too long in cold preservation before being implanted, production of these signals drops sharply, which slows regeneration and worsens survival. In rat experiments, treating recipients with IL-6 rescued the regeneration process and improved survival from about 40% to 90% when the graft had been cold-stored for ten hours.5PubMed. Cold ischemia decreases liver regeneration after partial liver transplantation in the rat: A TNF-alpha/IL-6-dependent mechanism Researchers have also explored boosting regeneration by activating a protein called STAT3 in the graft before implantation, which reduced injury and sped up regrowth in small-graft models.6PubMed. Ex vivo adenoviral gene transfer of constitutively activated STAT3 reduces post-transplant liver injury and promotes regeneration in a 20% rat partial liver transplant model
Right Lobe Versus Left Lobe
In living donor procedures, the surgeon typically takes either the right lobe or the left lobe of the donor’s liver. The right lobe is larger, accounting for roughly 60% of total liver volume, while the left lobe makes up the remaining 40% or so. In one comparison, right-lobe grafts had a median weight of about 675 grams and supplied around 52% of the recipient’s standard liver volume, while left-lobe grafts weighed about 450 grams and supplied around 41%.7JAMA Surgery. Characteristics of Liver Grafts in Living-Donor Adult Liver Transplantation: Comparison Between Right- and Left-Lobe Grafts
These size differences create a trade-off. Right-lobe grafts give the recipient more liver tissue, which lowers the risk of a dangerous complication called small-for-size syndrome. A large meta-analysis of 67 studies found that recipients of right-lobe grafts had a significantly lower rate of small-for-size syndrome and lower early death rates compared with left-lobe recipients. But this comes at a cost to the donor: right-lobe donors were about 63% more likely to experience major complications than left-lobe donors.8PubMed. Right Lobe Versus Left Lobe Living Donor Liver Transplantation: A Systematic Review and Meta-analysis of Donor and Recipient Outcomes Long-term graft and patient survival were similar between the two approaches, so the decision often hinges on the size match between donor and recipient and the donor’s anatomy.
On the surgical side, right-lobe living donor transplantation is considered more technically challenging, particularly because it often involves reconstructing multiple bile ducts and complex vein connections.9American Journal of Transplantation. Technical refinement of adult living donor liver transplantation: 15-year experience from Asan Medical Center Innovations like microscope-assisted artery reconstruction, intraoperative ultrasound, and the use of preserved vein grafts for drainage have helped centers improve their results over time.10Yonsei Medical Journal. Revolution and Refinement of Surgical Techniques for Living Donor Partial Liver Transplantation
How Donors Are Screened
A healthy person who volunteers to donate part of their liver goes through an extensive evaluation. The process screens for medical fitness, liver size, fat content, vascular anatomy, and psychological readiness. In a recent analysis of donor evaluation algorithms, the most common reasons for declining a potential donor were unfavorable liver volume measurements (about 40% of refusals) and metabolic factors like obesity or fatty liver disease (about 21%). A contrast-enhanced CT scan alone caught roughly two-thirds of unsuitable donors, and when combined with blood tests, ultrasound, and a physical exam, the workup identified about 87% of all donors who would ultimately be turned down.11PubMed. Optimization of surgical evaluation algorithms for living donor liver transplantation
The key safety threshold is how much liver the donor keeps. The general rule is that the remnant should be at least 35% of total liver volume. Below that threshold, the remaining liver takes longer to recover, and the risk of complications rises.12PubMed Central. Donor safety and remnant liver volume in living donor liver transplantation That said, some centers have safely pushed below 30% in carefully selected donors who are younger than 50, have minimal liver fat, and whose anatomy allows preservation of the middle hepatic vein.13PubMed. Selection and outcomes of living donors with a remnant volume less than 30% after right hepatectomy These exceptions are not routine, and they only happen at high-volume centers with significant experience.
The Risks Donors Face
Donating part of your liver is major surgery, and while most donors recover fully, the procedure is not without risk. In a prospective study of 393 donors, about 38% experienced at least one complication. Most of those were minor, but roughly a quarter had complications classified as potentially life-threatening, and about 2% had complications deemed life-threatening. Three donors in that cohort died, putting the mortality rate at about 0.8%.14PubMed Central. Donor Morbidity After Living Donation for Liver Transplantation The most common issues were infections (12%), bile leaks persisting beyond the first week (9%), incisional hernias (6%), and fluid collections around the lungs needing drainage (5%). About 13% of donors required at least one hospital readmission.
More broadly, the surgical mortality risk is estimated at about 0.1% for donating the left lateral segment and about 0.5% for donating the right lobe, reflecting the greater extent of surgery involved in right-lobe donation.15PubMed Central. Donor safety in live-related liver transplantation These numbers are small in percentage terms but large in ethical weight, since donors are healthy people undergoing surgery entirely for someone else’s benefit.
Psychological Impact on Donors
The physical risks get most of the attention, but the psychological toll deserves mention, too. In a multicenter prospective study tracking living liver donors over time, most fared well emotionally. The exception was donors whose recipients died. Among those donors, about a third reported feeling guilty at some point after the recipient’s death, and roughly one in five felt some degree of personal responsibility.16PubMed Central. Psychological Outcomes of Living Liver Donors from a Multi-Center, Prospective Study: Results from the Adult to Adult Living Donor Liver Transplantation Cohort Study (A2ALL) These findings underscore the need for ongoing psychosocial support, especially when outcomes are poor.
When the Graft Is Too Small
One of the unique risks of partial liver transplantation, whether from a living donor or a split organ, is small-for-size syndrome. This happens when the implanted piece of liver is not large enough to meet the recipient’s metabolic demands. The graft becomes overwhelmed by excessive blood flow through the portal vein, which damages tiny blood vessels inside the liver and leads to congestion, poor bile production, and rising bilirubin levels.
The main risk factor is a graft-to-recipient body weight ratio below about 0.8%, meaning the graft weighs less than 0.8% of the recipient’s body weight. Other contributing factors include fat accumulation in the graft above 30%, poor venous drainage, and prolonged time spent in cold storage before implantation.17PubMed Central. Small for size syndrome following living donor and split liver transplantation The recipient’s own condition matters, too: people with the most advanced liver disease are at greater risk because their bodies place higher functional demands on the new graft.18PubMed. Small-for-size syndrome after partial liver transplantation: definition, mechanisms of disease and clinical implications Surgeons try to prevent the problem by carefully matching graft size to recipient size and, in some cases, by modulating portal blood flow during or after the operation.
Biliary Complications
The bile ducts are the Achilles heel of partial liver transplantation. Because a partial graft is cut along a surgical plane rather than removed intact, the bile duct connections are smaller, more numerous, and trickier to reconstruct than in a whole-organ transplant. In a large multicenter study of over 3,600 adult living donor liver transplant recipients, bile leaks occurred in about 11% and biliary strictures (narrowing of the duct) in about 21%.19American Journal of Transplantation. Biliary Complications in Adult Living Donor Liver Transplantation: A Multicenter Study of 3633 Patients Having multiple bile duct connections to sew together, heavy blood loss during surgery, and a history of major abdominal surgery all raised the risk.
Improvements in understanding the blood supply to the bile ducts and the tissue layer surrounding them have led to new techniques for preparing the ducts before sewing them together, and these refinements have brought complication rates down substantially at experienced centers. Most biliary problems can now be managed without reoperation, using procedures like stenting through the skin or through an endoscope, though multiple duct connections and certain types of strictures remain stubborn challenges.20PubMed. Biliary complications after living donor liver transplantation
Partial Grafts for Children
Children, especially infants, are in many ways the ideal candidates for partial liver transplants. Small children need small grafts, and a whole adult liver is far too large for them. Partial grafts, whether from a living parent or from a split deceased-donor organ, can be size-matched much more precisely. For children with biliary atresia, the most common reason for pediatric liver transplant, the data strongly favor partial grafts in the smallest patients. In recipients weighing 7 kilograms or less, living donor grafts and deceased-donor partial grafts both outperformed whole-organ transplants, with better graft survival rates at one, five, and ten years, lower rates of blood-vessel clotting, and less need for retransplantation.21PubMed. Effects of recipient size and allograft type on pediatric liver transplantation for biliary atresia
Across a larger cohort of 882 pediatric biliary atresia patients divided by graft type, patient survival at median follow-up of about three years was roughly 95% for both whole-liver and living donor recipients, while split liver recipients had a somewhat lower survival rate of about 89%.22PubMed. Impact of allograft types on outcomes after pediatric liver transplantation due to biliary atresia The slightly worse results for split grafts likely reflect both the additional injury from cold storage and the technical challenges of splitting. In the broader population of infant transplants, the gap between partial and whole grafts has closed over time. A study tracking outcomes across three eras found that by 2006-2010, partial and whole deceased-donor grafts had comparable outcomes in infants, a significant improvement over earlier periods when partial grafts carried clearly higher risk.23PubMed Central. Deceased donor liver transplantation in infants and small children: are partial grafts riskier than whole organs?
Auxiliary Transplantation and Keeping Your Own Liver
There is a lesser-known variant of partial liver transplantation where the recipient keeps part of their own liver and a partial graft is placed alongside it. This is called auxiliary partial orthotopic liver transplantation (APOLT), and it is used primarily for acute liver failure rather than chronic disease. The idea is that if the patient’s own liver can recover, the transplanted piece serves as a temporary bridge. Once the native liver regenerates, immunosuppression can potentially be withdrawn and the graft allowed to shrink away on its own.
APOLT works best in younger patients, particularly children, with sudden-onset liver failure from causes like hepatitis A, hepatitis B, or acetaminophen overdose, where the native liver has a good chance of bouncing back.24PubMed. Auxiliary partial orthotopic liver transplantation in the treatment of acute liver failure It is increasingly accepted as a valid option in pediatric acute liver failure.25PubMed. Current status of auxiliary partial orthotopic liver transplantation for acute liver failure The major appeal is the possibility of a life free from lifelong immunosuppressive drugs, though not every patient achieves that outcome.
How Geography Shapes Practice
Where you live dramatically affects how likely you are to receive a partial liver graft. In East Asia, particularly Japan, South Korea, and Hong Kong, cultural and legal barriers to declaring brain death meant that deceased donor organs were scarce for decades. This drove the rapid development and widespread adoption of living donor liver transplantation through the 1990s and 2000s.26PubMed Central. Living donor liver transplantation: Eastern experiences Asian centers accumulated enormous experience, and many of the surgical innovations in the field, from vein reconstruction to graft-size optimization, were pioneered there.
In Western countries, particularly the United States and much of Europe, the availability of deceased donor organs meant less pressure to develop living donor programs, and split liver transplantation served as the primary strategy for expanding the organ pool. That split liver approach, when dividing for one child and one adult, now produces results comparable to whole-organ transplantation.2PubMed Central. Split liver transplantation The full right/left split for two adults remains more technically demanding, and centers performing it must have high annual transplant volumes and dedicated hepatobiliary surgery expertise. Strict donor criteria apply: donors generally need to be under 50, have minimal liver fat, and have short intensive-care stays.27PubMed Central. Technical Refinements and Results in Full-Right Full-Left Splitting of the Deceased Donor Liver
The Ethics of Asking a Healthy Person to Donate
Living donor liver transplantation sits in ethically unusual territory. In kidney donation, the donor can survive perfectly well with one kidney and the recipient can fall back on dialysis if a transplant is not available. In liver donation, the surgery is bigger, the risk is higher, and there is no equivalent of dialysis for end-stage liver disease. This raises a pointed question: should a living donor be allowed to donate a liver lobe to someone who has been turned down for a deceased donor transplant, perhaps because their prognosis is too poor?
One influential ethical analysis argues yes, with caveats. Because a living donor graft does not take an organ away from the common pool of transplant organs, and because there is no alternative life-sustaining treatment for liver failure, the threshold for accepting a recipient should be “slightly less benefit” than what is typically required for deceased donor listing.28PubMed Central. Should living donor liver transplantation be an option when deceased donation is not? In practice this means that some patients turned away from the deceased-donor waiting list may still be offered a living donor transplant, provided the donor is fully informed and the expected benefit is not negligible.
Machine Perfusion and Where the Field Is Heading
One of the most exciting recent developments is the use of machine perfusion to keep partial livers alive and functioning outside the body for extended periods. Traditionally, removed livers are stored on ice, which limits preservation time and can impair the regeneration process. Machine perfusion systems pump oxygenated fluid (or even blood) through the organ, keeping it metabolically active. Researchers have now demonstrated that split livers can be maintained on these machines for days, opening up possibilities that go well beyond simple preservation.29PubMed Central. Long-term machine perfusion of human split livers: a new model for regenerative and translational research
Partial grafts present unique engineering challenges for perfusion systems. They lack the intact vena cava that whole livers have, they often have more than one bile duct branch that needs to be hooked up, and they generate more debris in the circulating fluid than whole organs do. Specialized adaptations, including additional filters and a second gas exchanger, have been developed to handle these issues.30Journal of Hepatology. Machine perfusion and bioengineering of the liver In the near future, extended perfusion could allow surgeons to “treat” a partial graft before implanting it, for instance by reducing fat content, delivering gene therapies, or stimulating regeneration while the organ is still on the machine. The technology also has immediate practical value: a technique called hypothermic oxygenated perfusion has already been compared to standard cold storage in pediatric split grafts and shows promise for reducing the ischemia-related damage that has historically made split grafts slightly riskier.31PubMed Central. HOPE Mitigates Ischemia-Reperfusion Injury in Ex-Situ Split Grafts: A Comparative Study With Living Donation in Pediatric Liver Transplantation
Immune Responses in Regenerating Grafts
One underappreciated wrinkle of partial liver transplantation is that a regenerating graft appears to provoke a stronger immune response than a whole organ. In animal experiments, recipients of partial grafts showed more aggressive immune-cell infiltration of the graft, faster maturation of immune cells in the thymus, and a stronger specific immune reaction against the donor tissue compared to recipients of whole livers.4PubMed. Increased immune responses to regenerating partial liver grafts in the rat The exact reason is not entirely clear, but the rapid cell division during regeneration likely exposes more donor proteins to the recipient’s immune system, acting as a louder alarm signal. In practice, this means immunosuppression management after a partial liver transplant may require closer attention than after a whole-organ transplant, particularly in the early weeks when regeneration is most active.
Elastography, a non-invasive imaging technique that measures liver stiffness, has become a useful tool for monitoring grafts after transplantation. Increases in stiffness over time can signal developing fibrosis or rejection in the graft, allowing clinicians to intervene earlier without necessarily performing a biopsy.32SpringerLink (Abdominal Radiology). Elastography in the evaluation of liver allograft Combined with Doppler ultrasound to check blood flow through the reconstructed vessels, these tools give transplant teams a fairly detailed picture of how a partial graft is settling in.