Graft-to-Recipient weight ratio, graft inflow modulation, and small-for-size syndrome: A multicenter prospective study from the LDLT registry

Introduction: Graft-to-recipient weight ratio (GRWR) is widely used to guide graft selection in living donor liver transplantation (LDLT), however its role as an independent predictor of postoperative outcomes and small-for-size syndrome (SFSS) remains debated. Graft inflow modulation (GIM) has been increasingly adopted to allow the safe use of smaller grafts. This study evaluated the impact of GRWR and GIM on short-term outcomes using data from a prospective international registry. Methods: An analysis of prospectively collected data from the International Living Donor Liver Transplant Registry (LDLTregistry.org) was conducted, including 1,944 consecutive LDLT performed at 55 centers (Sep 2023-Feb 2025). Recipients were stratified by GRWR (<0.60%, 0.60%-0.80%, >0.80%). Primary outcomes included major postoperative complications (Clavien-Dindo ≥3a), SFSS and 90-day mortality. Results: Lower GRWR was associated with higher rates of major complications, SFSS, and GIM use. Overall SFSS incidence, classified according to the ILTS-iLDLT-LTSI Consensus Conference Guidelines, was 36.9%, Grade B in 17.0%, and Grade C in 4.0%. SFSS of any grade increased progressively with lower GRWR: 33.4% in GRWR >0.80%, 43.7% in GRWR 0.60%-0.80%, and 63.1% in GRWR <0.60% ( p <0.001). Grade A SFSS was similar across groups ( p =0.12), whereas clinically significant SFSS (Grade B and C) was highest in the GRWR<0.6% (47.6%, p <0.001). 90-day mortality remained low (<5%) across all groups. Nearly half of small grafts were unexpectedly small, without worse short-term outcomes. On multivariable analysis, GRWR was not associated with major complications. Conclusions: GRWR influences short-term outcomes after LDLT but does not fully explain SFSS risk, which appears multifactorial. These findings support a shift away from graft size as the sole determinant of risk, toward a physiology-based, lobe-specific, and standardized intraoperative approach in LDLT.