How far can we lower graft-to-recipient weight ratio for living donor liver transplantation under modulation of portal venous pressure?

Background. Smaller size grafts for living donor liver transplantation (LDLT) can enhance donor safety and expand donor availability. We previously reported that modulation of portal venous pressure (PVP) was key for successful LDLT with small grafts, and that it actively lowered graft-to-recipient weight ratio (GRWR) for adult-to-adult LDLT. This retrospective study investigated the outcome of LDLT using small grafts with PVP modulation. Method. This study analyzed 221 adult LDLT patients between March 2008 and December 2013 and divided them into 3 groups based on GRWR: large (L), GRWR >= 0.8% (n = 154), medium (M), >= 0.7% GRWR < 0.8% (n = 38); and small (S) GRWR < 0.7% (n = 29). Donor and recipient factors, PVP, pressure gradient between PVP and central venous pressure (CVP), occurrence of small for size syndrome (SFSS), ascites, and posttransplant laboratory data were compared across the 3 groups. Patient and graft survival were compared using Kaplan Meier methods. Results. There was no difference in patient or graft survival between the 3 groups. Amount of posttransplant ascites and posttransplant International Normalized Ratio were similar, but the S and M groups had more prolonged cholestasis. SFSS was identified in 17 %, 13 %, and 13 % in the S, M, and L groups, respectively (P = NS). Patients with a final PVP of <= 15 mmHg had better survival than patients with a final PVP of > 15 mmHg (P < .001). Multivariate analysis showed that donor age >40 years old, final PVP of > 15 mmHg, and pressure gradient of PVP-CVP > 5 mmHg were risk factors for inferior patient survival. Conclusion. We achieved satisfactory outcomes in LDLT with GRWR as low as 0.6% using PVP modulation. Thus, we currently set a lower limit of GRWR at 0.6% while protecting donor safety and expanding donor availability.