Is a 1.2 mm left hepatic artery diameter adequate for pediatric liver transplantation with a related living donor?

Hepatic Artery Diameter in Pediatric Living Donor Liver Transplantation

A left hepatic artery diameter of 1.2 mm is inadequate for pediatric liver transplantation with a related living donor, as it carries a high risk of hepatic artery thrombosis that could compromise graft survival and patient outcomes.

Technical Considerations for Hepatic Artery Anastomosis in Pediatric LDLT

The hepatic artery anastomosis represents one of the most challenging aspects of pediatric living donor liver transplantation (LDLT), particularly when using left lateral segments (segments II-III). According to established guidelines and research:

• The European Association for the Study of the Liver (EASL) guidelines note that recipient procedures in LDLT are challenging due to the small size of anastomoses, with arteries typically measuring 3-4 mm in diameter 1
• Hepatic artery thrombosis is a significant complication in pediatric LDLT, with higher rates historically reported with smaller caliber arteries 2
• Successful pediatric LDLT programs have reported very low hepatic artery thrombosis rates (1%) when appropriate arterial diameter selection criteria are applied 3

Strategies for Small Caliber Arteries

When faced with a small hepatic artery diameter of 1.2 mm, several approaches should be considered:

1. Two-step strategy for arterial enlargement: A flow-induced enlargement technique can be employed where the smaller arterial branch is ligated during a first-step laparoscopic procedure, inducing approximately 30% enlargement of the remaining branch. The donor hepatectomy can then be performed about a week later when the artery has enlarged to a more suitable diameter 2

2. Microvascular techniques: Collaboration with microsurgeons for hepatic artery anastomosis has been shown to decrease arterial complications when dealing with small vessels 4

3. Alternative vascular grafts: When direct anastomosis is not feasible due to small vessel size, interposition grafts using the recipient's inferior mesenteric vein can be considered 5

Risk Assessment and Decision Making

The decision to proceed with a donor artery of 1.2 mm diameter should consider:

• The risk of hepatic artery thrombosis is significantly higher with vessels smaller than 2 mm
• Studies have shown that successful pediatric LDLT typically involves arterial diameters larger than 2 mm (2.38±0.4 mm) 6
• The consequences of hepatic artery thrombosis are severe, potentially leading to graft loss and patient mortality

Recommendations

Based on the available evidence:

1. Reject the donor with 1.2 mm left hepatic artery for direct transplantation without intervention
2. Consider implementing a two-step strategy to enlarge the arterial diameter before proceeding with donation 2
3. If proceeding is absolutely necessary due to urgent recipient need, ensure:
   • Involvement of an experienced microsurgeon
   • Availability of appropriate interposition grafts
   • Use of an operating microscope rather than surgical loupes

Caveat

While technical innovations have improved outcomes in pediatric LDLT, the primary consideration must be donor and recipient safety. The risk of hepatic artery thrombosis with a 1.2 mm vessel outweighs the potential benefits, especially when alternative approaches (including waiting for a more suitable living or deceased donor) may be available.