Introduction: Infants who require liver transplantation represent a treatment challenge because chronic liver disease at this early age affects the child’s growth and development in a critical phase. Malnutrition and failure to thrive are frequent findings and can be a reflection of failure to refer to transplantation in a timely fashion. The present study aims to compare demographics, peri-operative data, and long-term outcomes according to recipient weight at the time of living donor liver transplantation (LDLT).
Methods: Retrospective cohort study from from January 1995 to December 2020. Studied groups included primary LDLT in patients with BW ≤ 7 kg and BW>7kg. 
Results: There were 1078 primary pediatric LDLT (756 BW>7kg, 322 BW ≤ 7 kg). In regards to demographic's comparison, the results show that the vast majority (87%) of patients  ≤ 7 kg had BA, presented malnutrition with significantly lower height/age and weight/age z-scores, and the median PELD score of 19 indicated advanced liver disease. Also, the majority of these infants (65.6%) presented ascites at the time of LDLT. Except for the rate of pre-transplant surgery (Kasai portoenterostomy), all the studied pre-transplant variables were significantly different between groups.  Children ≤7kg required more PRBC transfusion at LDLT (30.9ml/kg versus 15.5ml/kg, P<0.001). Portal vein complications were statistically different between the two groups, with higher frequencies in the BW ≤ 7 kg cohort. HAT (BW>7kg - 2.1% versus  BW≤ 7 kg - 2.8%, P=0.51) and retransplantation (BW>7kg - 3.4% versus  BW≤ 7 kg - 2.5%, P=0.47)  rates were not different between groups. Patients with BW ≤ 7kg required longer intensive care unit (ICU) and hospital stays. Patient and graft survival were not statistically different between groups. A cox regression analysis was performed in order to adjust for considered risk factors, including PELD/MELD scores, presence of ascites before the LDLT, z-scores, diagnosis (BA vs other) and age at LDLT. Related to the pre-transplant clinical status, only the PELD score remained as a significant factor impacting post-transplant survival.
Conclusion: Malnutrition and advanced liver disease were more frequent in BW ≤ 7 kg. Despite longer ICU and hospital stays and higher rates of PV complications, patient and graft long-term survival were similar, and long term survival was similar. Because the number infants with low body weight referred for transplantation is increasing over time, the challenge for the future is to achieve early referral to a transplant center, in better health and nutritional status for timely transplantation.