Hepatic flow optimization in full right split liver transplantation

Portal flow modulation in living donor liver transplantation: review with a focus on splenectomy

Small-for-size graft (SFSG) syndrome after living donor liver transplantation (LDLT) is the dysfunction of a small graft, characterized by coagulopathy, cholestasis, ascites, and encephalopathy. It is a serious complication of LDLT and usually triggered by excessive portal flow transmitted to the allograft in the postperfusion setting, resulting in sinusoidal congestion and hemorrhage. Portal overflow injures the liver directly through nutrient excess, endothelial activation, and sinusoidal shear stress, and indirectly through arterial vasoconstriction. These conditions may be attenuated with portal flow modulation. Attempts have been made to control excessive portal flow to the SFSG, including simultaneous splenectomy, splenic artery ligation, hemi-portocaval shunt, and pharmacological manipulation, with positive outcomes. Currently, a donor liver is considered a SFSG when the graft-to-recipient weight ratio is less than 0.8 or the ratio of the graft volume to the standard liver volume is less than 40%. A strategy for transplanting SFSG safely into recipients and avoiding extensive surgery in the living donor could effectively address the donor shortage. We review the literature and assess our current knowledge of and strategies for portal flow modulation in LDLT.

Split-liver full-left full-right: proposal for an operative protocol

INTRODUCTION

Worldwide, organ shortage is a major limiting factor to transplantations. One possible way to face graft scarcity is splitting full livers into hemilivers; this procedure would allow transplantation in 2 adult recipients with the use of a single organ from a deceased donor.

OBJECTIVE

The goal of this study was to describe an adult-to-adult split liver operative protocol and share it between centers interested in exploring this procedure.

MATERIALS AND METHODS

A literature review was first conducted to elaborate on the present protocol; second, selection criteria for suitable deceased donors were identified. The technical aspects of performing the procurement were also analyzed; finally, the recipient selection criteria and the transplantation criteria were determined.

RESULTS

The donor characteristics should be consistent with the following: age≤55 years; weight≥70 kg; body mass index<28 kg/m2; intensive care unit stay<7 days; sodium level<160 mEq/L if the intensive care unit stay is >2 days; maximum transaminase value 3 times normal; hemodynamic stability; negative for hepatitis B surface antigen, hepatitis C virus, and human immunodeficiency virus; macrosteatosis<20%; macroscopic adequacy; and absence of anatomic anomalies requiring complex reconstruction. The procurement hospital should provide the preoperative computed tomography scan, liver dissector, and the intraoperative ultrasound. Indication for in situ or ex situ splitting depends on the hepatic vein outflow anatomy. Graft-to-recipient weight ratio should be ≥1%, and the graft-to-recipient spleen size ratio should be ≥0.6. United Network for Organ Sharing status 1 and 2A recipients are excluded, as are patients with transjugular intrahepatic portosystemic shunts. Hemiliver transplants are performed as in living-donor liver transplantation, and portal hyperflow is corrected by splenic artery ligation, splenectomy, and portal infusion of vasoactive drugs.

CONCLUSIONS

The present protocol was proposed to test the validity of the full-left full-right split liver procedure. A retrospective analysis found that 130 transplantations were suitable for this procedure according to the present protocol in the period January 1, 2008, through December 31, 2011 (65 donors). We believe that these numbers could be greatly increased once this procedure is proven feasible and safe within the proposed criteria.

A prospective policy development to increase split-liver transplantation for 2 adult recipients: results of a 12-year multicenter collaborative study

OBJECTIVE

To analyze in a multicenter study the potential benefit of a new prospective policy development to increase split-liver procedures for 2 adult recipients.

BACKGROUND

Split-liver transplantation is an important means of overcoming organ shortages. Division of the donor liver for 1 adult and 1 pediatric recipient has reduced the mortality of children waiting for liver transplantation but the benefits or disadvantages to survival when the liver is divided for 2 adults (adult-to-adult split-liver transplant, AASLT) compared with recipients of a whole graft have not been fully investigated.

METHODS

We developed a computerized algorithm in selected donors for 2 adult recipients and applied it prospectively over a 12-year period among 7 collaborative centers. Patient and graft outcomes of this cohort receiving AASLT either as full right grafts or full left grafts were analyzed and retrospectively compared with a matched cohort of adults who received a conventional whole-liver transplant (WLT). Univariate and multivariate analysis was done for selected clinical variables in the AASLT group to assess the impact on the patient outcome.

RESULTS

Sixty-four patients who received the AASLT had a high postoperative complication rate (64.1% grade III and IV) and a lower 5-year survival rate than recipients of a WLT (63.3% and 83.1%)

CONCLUSIONS

AASLT should be considered a surgical option for selected smaller-sized adults only in experimental clinical studies in experienced centers.

"Small-for-flow" syndrome: shifting the "size" paradigm

The "small-for-size" syndrome and "post-hepatectomy liver failure" refers to the development of liver failure (hyperbilirubinemia, coagulopathy, encephalopathy and refractory ascites) resulting from the reduction of liver mass beyond a certain threshold. This complication is associated with a high mortality and is a major concern in liver transplantation involving reduced liver grafts from deceased and living donors as well as in hepatic surgeries involving extended resections of liver mass. The limiting threshold for liver resection or transplantation is currently predicted based on the mass of the remnant liver (or donor graft) in relation to the body weight of the patient, with a ratio above 0.8 being considered safe. This approach, however, has proved inaccurate, because some patients develop the "small-for-size" syndrome despite complying with the "safe" threshold while other patients who surpass the threshold do not develop it. We hypothesize that the development of the "small-for-size" syndrome is not exclusively determined by the ratio of the mass of the liver remnant (or graft) to the body weight, but it is instead strictly determined by the hemodynamic parameters of the hepatic circulation. This hypothesis is based in recent clinical and experimental reports showing that relative portal hyperperfusion is a critical factor in the development of the "small-for-size" syndrome and that maneuvers that manipulate the hepatic vascular inflow are able to prevent the development of the syndrome despite liver-to-body weight ratios well below the "limiting" threshold. Measurements of hepatic blood flow and pressure, however, are not routinely performed in hepatic surgeries. Focusing on the "flow" rather than in the "size" may improve our understanding of the pathophysiology of the "small-for-size" syndrome and "post-hepatectomy liver failure" and it would have important implications for the clinical management of patients at risk. First, hepatic hemodynamic parameters would have to be measured in hepatic surgeries. Second, these parameters (in addition to liver mass) would be the principal basis for deciding the "safe" threshold of viable liver parenchyma. Third, the hepatic hemodynamic parameters are amenable to manipulation and, consequently, the "safe" threshold may also be manipulated. Shifting the paradigm from "small-for-size" to "small-for-flow" syndrome would thus represent a major step for optimizing the use of donor livers, for expanding the indications of hepatic surgery, and for increasing the safety of these procedures.

Meeting report of the International Liver Transplantation Society's 18th annual international congress: Hilton San Francisco Hotel, San Francisco, CA, May 16-19, 2012

From May 16-19, 2012, the International Liver Transplantation Society held its annual congress in San Francisco, CA. More than 1300 registrants attended the meeting, which included a premeeting conference entitled Balancing Risk in Liver Transplantation, focused topic sessions, and a variety of oral and poster presentations. This report is not all-inclusive and focuses on specific research abstracts on key topics in liver transplantation. As always, the new data herein are presented in the context of the published literature to further enhance knowledge in the field.