What are the criteria for choosing a suitable liver transplant donor?

Liver Transplant Donor Selection Criteria

Donor selection for liver transplantation requires systematic evaluation of both donor and recipient risk factors, with the fundamental principle being to balance donor organ quality against recipient urgency while prioritizing outcomes of mortality, graft survival, and post-transplant complications.

Deceased Donor Selection Framework

Brain Death Donors (DBD) - Standard Criteria

DBD livers from donors of any age should be considered suitable for transplantation after balancing potential additional risk factors present in the donor, graft, and recipient 1.

Steatosis Assessment

• Mild steatosis (<30% macrovesicular): Safe for transplantation with conventional cold storage when no additional risk factors present 1, 2
• Moderate steatosis (30-60%): Requires careful risk-benefit assessment and should ideally be matched with recipients having Balance of Risk (BAR) score ≤9 1, 2
• Severe steatosis (>60%): Should not be used due to unacceptable risks of primary non-function and graft loss 1, 2
• Microvesicular steatosis does not preclude graft use and can be safely used up to BAR score ≤18 2
• Liver biopsy is indicated when donor BMI >25 kg/m² or any liver function abnormality exists 3

Age Considerations

• Donor age alone should not exclude judicious use of DBD livers 1
• Older donors (>70 years) are associated with increased biliary complications but similar graft and patient survival when carefully matched 1
• The synergistic effect of age with other risk factors (steatosis, prolonged ischemia) must be considered 1

Laboratory Parameters

• Elevated donor transaminases (even ALT >1,000 IU/L) have no impact on post-transplant outcomes and should not exclude donation 1
• Donor hypernatremia, even >155 mEq/L, is not associated with worse post-transplant outcomes in recent data 1

Donation After Circulatory Death (DCD) - Controlled

Both donor and recipient risk factors should be considered to optimize controlled DCD outcomes, while combining several risk factors should be avoided or else advanced perfusion preservation strategies should be applied 1.

Critical DCD Donor Factors

• Cold ischemia time <6 hours is essential to protect against adverse outcomes including ischemic-type biliary lesions (ITBL) 1
• Donor hepatectomy time (DHT) <60 minutes is crucial, as prolonged DHT is an independent risk factor for ITBL, graft loss, and death 1
• Donor age <60 years appears reasonable when other non-modifiable risk factors are present 1
• Donor BMI >25 or >30% steatosis requires careful selection and recipient matching, as moderate macrosteatosis increases rates of post-reperfusion cardiac arrest, AKI, and primary non-function 1

DCD Recipient Matching

• Match controlled DCD livers to recipients with MELD <25 1
• Avoid recipients requiring pre-transplant mechanical ventilation, as this is associated with higher graft failure risk 1
• Exercise caution when transplanting DCD livers into recipients with acute organ failures requiring intensive care support 1

Uncontrolled DCD Donors

Livers from uncontrolled DCD donors recovered with normothermic regional perfusion should be restricted to recipients in whom the risk of continued waiting outweighs the risk of adverse post-transplant outcome 1.

Living Donor Selection Criteria

Evaluation of live liver donor candidates should be performed according to an established protocol and include liver anatomical, parenchymal, and volumetric assessment; age- and sex-appropriate screening for clinically relevant as well as silent co-morbid conditions 1.

Mandatory Living Donor Requirements

• Age between 20-65 years 3
• Within 3 degrees of consanguinity (or emotionally related) 3
• Voluntary donation without coercion 3
• BMI <30 kg/m² 3
• ABO blood type identical or compatible 3
• Macroscopic steatosis ≤10% on biopsy (biopsy indicated if BMI >25 kg/m²) 3
• Live donor liver remnant must be at least 30% of pre-donation volume or mass 1

Volumetric Requirements

• Estimated graft volume of 40% to recipient standard liver volume ratio is the lower limit 3
• Left liver is first choice for donor safety, provided it satisfies the lower limit 3
• Right liver harvesting indicated only if estimated remnant liver volume is >30% of donor's total liver volume 3

Screening Requirements

• Comprehensive screening for procoagulant conditions, MASLD, cardiovascular disease, cancer, infectious diseases, and psychosocial risk factors 1
• Indocyanine green retention test and dynamic CT evaluation 3

Infectious Disease Considerations

Viral Hepatitis

• Anti-HBc positive donors: Should be preferentially directed to HBV-exposed recipients; prophylaxis with lamivudine initiated immediately if recipients lack anti-HBs 1
• Anti-HCV positive grafts: Generally safe in HCV-positive recipients; should be avoided in HCV-negative recipients 1
• HIV-positive donors: Can be used in HIV-positive recipients with undetectable viral load on definite anti-HIV therapy with informed consent 1

SARS-CoV-2

• Liver donation from SARS-CoV-2-positive donors should not be contraindicated 1
• SARS-CoV-2 monitoring and antivirals should be provided to recipients considering drug-drug interactions 1

Bacterial and Fungal Infections

• Donors with select bacterial infections can be safely used with appropriate therapy to both donor and recipient 1
• Highly resistant bacteria (vancomycin-resistant Enterococcus, carbapenemase-producing Klebsiella) require discussion with infectious disease specialist given high risk 1

Special Donor Circumstances

Donors with Cancer History

• Risk of cancer transmission vs. risk of death on waiting list must be weighted 1
• Individual value-based and shared-decision making required if waiting list mortality risk outweighs transmission risk with informed consent 1
• Utilization depends on tumor site and stage 1

Domino Transplantation

• Domino liver transplantation from donors with familial amyloidotic polyneuropathy can be considered in selected recipients 1
• Close monitoring for de novo TTR-neuropathy and cardiomyopathy required post-transplant 1

Advanced Preservation Strategies

Machine perfusion strategies should be used to increase the donor organ pool and organ utilization 1.

Normothermic Regional Perfusion (NRP)

• In situ abdominal NRP can be used to recondition and assess controlled DCD livers 1
• In situ abdominal NRP should be used for uncontrolled DCD livers, with additional ex situ dynamic machine perfusion considered 1
• Assessment criteria during NRP: stable pump flow, stable or declining lactate (sampled every 30 minutes), stable transaminases, and good macroscopic appearance 1
• Evaluation timing: up to 2 hours for controlled DCD, up to 4 hours for uncontrolled DCD 1

Ex Situ Machine Perfusion

• Perfusion preservation strategies should be considered to reduce adverse post-transplant outcomes, particularly biliary complications, when using extended criteria and DCD grafts 1
• Normothermic machine perfusion may allow assessment and potential "defatting" of moderately and severely steatotic grafts 2

Critical Pitfalls to Avoid

• Never combine multiple donor risk factors (elderly age + steatosis + prolonged ischemia) without advanced perfusion strategies 1
• Minimize donor hepatectomy time through experienced donor surgeon involvement 1
• Avoid using recipient MELD score as criterion for DBD liver acceptance/rejection in that particular recipient 1
• Do not use severe macrosteatosis (>60%) grafts regardless of recipient urgency 1, 2
• LDLT experience should be concentrated in high-volume centers with sufficient training to minimize risks 1