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Ann Liver Transplant 2024; 4(2): 37-38

Published online November 30, 2024 https://doi.org/10.52604/alt.24.0028

Copyright © The Korean Liver Transplantation Society.

Small-for-size grafts in living donor liver transplantation: Improving risk assessment for better outcomes

Hae Won Lee

Department of Surgery, Seoul National University Bungdang Hospital, Seoul National University College of Medicine, Seongnam, Korea

Correspondence to:Hae Won Lee
Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, 82 Gumi-ro 173beon-gil, Bundang-gu, Seongnam 13620, Korea
E-mail: lansh@hanmail.net
https://orcid.org/0000-0002-3312-9295

Received: November 6, 2024; Accepted: November 18, 2024

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

See original paper on 80

Living donor liver transplantation (LDLT) is one of the important and effective solutions for the shortage of deceased donor organs, providing life-saving treatment for many patients with end-stage liver disease or hepatic malignancies. However, using small-for-size grafts (SFSG), defined by a graft-to-recipient weight ratio (GRWR) of less than 0.8, remains challenging for transplant surgeons due to the increased risk of complications [1,2]. Traditionally, a GRWR of at least 0.8 has been considered the minimum safe threshold, but recent evidence suggests that smaller grafts can still be successful under specific conditions.

In this issue of the Annals of Liver Transplantation, a notable study investigates the risk factors associated with using SFSGs in LDLT based on the data collected from a single center in Korea. The authors analyze three key risk factors: recipient age of 60 years or older, a MELD (model for end-stage liver disease) score of 15 or higher, and male donor status [3]. The findings indicate that these factors collectively affect graft survival, providing a novel approach for assessing the risks associated with SFSGs. The results are significant and provide valuable insights into patient outcomes. Recipients without any identified risk factors had a graft survival rate of 100% at 5 years even using SFSGs. Those with one risk factor had a survival rate of 72.7%, while recipients with two or more risk factors had a survival rate of 54.5% (p=0.015). These results highlight the need for a careful approach to decision-making when using SFSGs in LDLT.

There are several essential points to consider from this study. First, the study indicates that recipient age remains an important consideration, as older recipients may still pose a higher risk for GRWR <0.8 transplants and careful selection is necessary to ensure optimal outcomes. Second, the risk factors showed consistent effects across different types of grafts. However, the small sample sizes in subgroup analyses suggest that these results should be interpreted cautiously. Third, the study was intended to validate the results of a previously conducted multicentric cohort study in Korea [4]. However, because the authors’ institution is also participating in the formation of Korean national cohort, some of the authors’ single-center data may overlap with data from the previous study, and therefore, it is difficult to assert that this study achieved complete external validation. Finally, it is not always a GRWR <0.8 which results in small-for-size syndrome (SFSS). It is more importantly a state of relative portal hyperperfusion resulting in a cascade of microcirculatory changes [5,6]. Therefore, other various factors apart from graft volume including the degree of recipient’s portal hypertension, graft condition and adequate vascular inflow/outflow can lead to a relative insufficiency of graft size. It is for this reason that portal flow modulation has recently emerged as one of the methods to prevent SFSS. This study did not consider hemodynamic factors due to the limitations of a retrospective study. Additional research including hemodynamic factors appears to be needed in the future.

Nonetheless, these findings hold substantial implications for clinical practice. In evaluating the suitability of LDLT with SFSGs, transplant teams must thoroughly assess the cumulative impact of the identified risk factors. The risk stratification model proposed by the authors is a valuable tool for guiding patient selection and facilitating evidence-based decision-making. The findings of this validation study are an important step in expanding the safe use of SFSGs in LDLT. Integrating these validated risk factors into standardized selection protocols with or without portal vein modulation could help centers worldwide achieve better outcomes with SFSGs with or without portal vein modulation. Most importantly, this evidence-based approach moves us closer to the goal: ensuring the best possible outcomes for recipients.

There was no funding related to this study.

The author has no conflicts of interest to declare.

  1. Heaton N. Small-for-size liver syndrome after auxiliary and split liver transplantation: donor selection. Liver Transpl 2003;9:S26-S28.
    Pubmed CrossRef
  2. Gruttadauria S, Pagano D, Luca A, Gridelli B. Small-for-size syndrome in adult-to-adult living-related liver transplantation. World J Gastroenterol 2010;16:5011-5015.
    Pubmed KoreaMed CrossRef
  3. Yoo YJ, Kang M, Koh HH, Min EK, Lee JG, Kim MS, et al. Validation of risk factors for graft-to-recipient weight ratio less than 0.8 graft in living donor liver transplantation with single center data. Ann Liver Transplant 2024;4:80-85.
    CrossRef
  4. Kim DG, Hwang S, Kim JM, Choi Y, You YK, Choi D, et al; Korean Organ Transplantation Registry Study Group. Outcomes and risk factors for liver transplantation using graft-to-recipient weight ratio less than 0.8 graft from living donors: multicentric cohort study. Ann Surg 2024;279:1018-1024.
    CrossRef
  5. Rammohan A, Rela M, Kim DS, Soejima Y, Kasahara M, Ikegami T, et al; ERAS4OLT.org Working Group. Does modification of portal pressure and flow enhance recovery of the recipient after living donor liver transplantation? A systematic review of literature and expert panel recommendations. Clin Transplant 2022;36:e14657.
    Pubmed CrossRef
  6. Hakeem AR, Mathew JS, Aunés CV, Mazzola A, Alconchel F, Yoon YI, et al. Preventing small-for-size syndrome in living donor liver transplantation: guidelines from the ILTS-iLDLT-LTSI Consensus Conference. Transplantation 2023;107:2203-2215.
    Pubmed CrossRef

Article

Editorial

Ann Liver Transplant 2024; 4(2): 37-38

Published online November 30, 2024 https://doi.org/10.52604/alt.24.0028

Copyright © The Korean Liver Transplantation Society.

Small-for-size grafts in living donor liver transplantation: Improving risk assessment for better outcomes

Hae Won Lee

Department of Surgery, Seoul National University Bungdang Hospital, Seoul National University College of Medicine, Seongnam, Korea

Correspondence to:Hae Won Lee
Department of Surgery, Seoul National University Bundang Hospital, Seoul National University College of Medicine, 82 Gumi-ro 173beon-gil, Bundang-gu, Seongnam 13620, Korea
E-mail: lansh@hanmail.net
https://orcid.org/0000-0002-3312-9295

Received: November 6, 2024; Accepted: November 18, 2024

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Body

See original paper on 80

Living donor liver transplantation (LDLT) is one of the important and effective solutions for the shortage of deceased donor organs, providing life-saving treatment for many patients with end-stage liver disease or hepatic malignancies. However, using small-for-size grafts (SFSG), defined by a graft-to-recipient weight ratio (GRWR) of less than 0.8, remains challenging for transplant surgeons due to the increased risk of complications [1,2]. Traditionally, a GRWR of at least 0.8 has been considered the minimum safe threshold, but recent evidence suggests that smaller grafts can still be successful under specific conditions.

In this issue of the Annals of Liver Transplantation, a notable study investigates the risk factors associated with using SFSGs in LDLT based on the data collected from a single center in Korea. The authors analyze three key risk factors: recipient age of 60 years or older, a MELD (model for end-stage liver disease) score of 15 or higher, and male donor status [3]. The findings indicate that these factors collectively affect graft survival, providing a novel approach for assessing the risks associated with SFSGs. The results are significant and provide valuable insights into patient outcomes. Recipients without any identified risk factors had a graft survival rate of 100% at 5 years even using SFSGs. Those with one risk factor had a survival rate of 72.7%, while recipients with two or more risk factors had a survival rate of 54.5% (p=0.015). These results highlight the need for a careful approach to decision-making when using SFSGs in LDLT.

There are several essential points to consider from this study. First, the study indicates that recipient age remains an important consideration, as older recipients may still pose a higher risk for GRWR <0.8 transplants and careful selection is necessary to ensure optimal outcomes. Second, the risk factors showed consistent effects across different types of grafts. However, the small sample sizes in subgroup analyses suggest that these results should be interpreted cautiously. Third, the study was intended to validate the results of a previously conducted multicentric cohort study in Korea [4]. However, because the authors’ institution is also participating in the formation of Korean national cohort, some of the authors’ single-center data may overlap with data from the previous study, and therefore, it is difficult to assert that this study achieved complete external validation. Finally, it is not always a GRWR <0.8 which results in small-for-size syndrome (SFSS). It is more importantly a state of relative portal hyperperfusion resulting in a cascade of microcirculatory changes [5,6]. Therefore, other various factors apart from graft volume including the degree of recipient’s portal hypertension, graft condition and adequate vascular inflow/outflow can lead to a relative insufficiency of graft size. It is for this reason that portal flow modulation has recently emerged as one of the methods to prevent SFSS. This study did not consider hemodynamic factors due to the limitations of a retrospective study. Additional research including hemodynamic factors appears to be needed in the future.

Nonetheless, these findings hold substantial implications for clinical practice. In evaluating the suitability of LDLT with SFSGs, transplant teams must thoroughly assess the cumulative impact of the identified risk factors. The risk stratification model proposed by the authors is a valuable tool for guiding patient selection and facilitating evidence-based decision-making. The findings of this validation study are an important step in expanding the safe use of SFSGs in LDLT. Integrating these validated risk factors into standardized selection protocols with or without portal vein modulation could help centers worldwide achieve better outcomes with SFSGs with or without portal vein modulation. Most importantly, this evidence-based approach moves us closer to the goal: ensuring the best possible outcomes for recipients.

FUNDING

There was no funding related to this study.

CONFLICT OF INTEREST

The author has no conflicts of interest to declare.

References

  1. Heaton N. Small-for-size liver syndrome after auxiliary and split liver transplantation: donor selection. Liver Transpl 2003;9:S26-S28.
    Pubmed CrossRef
  2. Gruttadauria S, Pagano D, Luca A, Gridelli B. Small-for-size syndrome in adult-to-adult living-related liver transplantation. World J Gastroenterol 2010;16:5011-5015.
    Pubmed KoreaMed CrossRef
  3. Yoo YJ, Kang M, Koh HH, Min EK, Lee JG, Kim MS, et al. Validation of risk factors for graft-to-recipient weight ratio less than 0.8 graft in living donor liver transplantation with single center data. Ann Liver Transplant 2024;4:80-85.
    CrossRef
  4. Kim DG, Hwang S, Kim JM, Choi Y, You YK, Choi D, et al; Korean Organ Transplantation Registry Study Group. Outcomes and risk factors for liver transplantation using graft-to-recipient weight ratio less than 0.8 graft from living donors: multicentric cohort study. Ann Surg 2024;279:1018-1024.
    CrossRef
  5. Rammohan A, Rela M, Kim DS, Soejima Y, Kasahara M, Ikegami T, et al; ERAS4OLT.org Working Group. Does modification of portal pressure and flow enhance recovery of the recipient after living donor liver transplantation? A systematic review of literature and expert panel recommendations. Clin Transplant 2022;36:e14657.
    Pubmed CrossRef
  6. Hakeem AR, Mathew JS, Aunés CV, Mazzola A, Alconchel F, Yoon YI, et al. Preventing small-for-size syndrome in living donor liver transplantation: guidelines from the ILTS-iLDLT-LTSI Consensus Conference. Transplantation 2023;107:2203-2215.
    Pubmed CrossRef
The Korean Liver Transplantation Society

Vol.4 No.2
November 2024

pISSN 2765-5121
eISSN 2765-6098

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