Is Portal Venous Pressure Modulation Still Indicated for All Recipients in Living Donor Liver Transplantation?

International multicenter study of ultralow graft-to-recipient weight ratio grafts in adult living donor liver transplantation

Decreasing the graft size in living donor liver transplantation (LDLT) increases the risk of early allograft dysfunction. Graft-to-recipient weight ratio (GRWR) of 0.8 is considered the threshold. There is evidence that smaller volume grafts may also provide equally good outcomes, the cut-off of which remains unknown. In this retrospective multicenter study, 92 adult LDLTs with a final GRWR ≤0.6 performed at 12 international liver transplant centers over a 3-year period were included. Perioperative data including preoperative status, portal flow hemodynamics (PFH) and portal flow modulation, development of small for size syndrome (SFSS), morbidity, and mortality was collated and analyzed. Thirty-two (36.7%) patients developed SFSS and this was associated with increased 30-day, 90-day, and 1-year mortality. The preoperative model for end-stage liver disease and inpatient status were independent predictors for SFSS (P < .05). Pre-liver transplant renal dysfunction was an independent predictor of survival (hazard ratio 3.1; 95% confidence intervals 1.1, 8.9, P = .035). PFH or portal flow modulation were not predictive of SFSS or survival. We report the largest ever multicenter study of LDLT outcomes using ultralow GRWR grafts and for the first time validate the International Liver Transplantation Society-International Living donor liver transplantation study group-Liver Transplantation Society of India consensus definition and grading of SFSS. Preoperative recipient condition rather than GRWR and PFH were independent predictors of SFSS. Algorithms to predict SFSS and LT outcomes should incorporate recipient factors along with GRWR.

Outcomes and Risk Factors for Liver Transplantation Using Graft-to-Recipient Weight Ratio Less Than 0.8 Graft From Living Donors: Multicentric Cohort Study

OBJECTIVE

To compare graft survival after living donor liver transplantation (LDLT) in patients receiving graft-to-recipient weight ratio (GRWR) <0.8 versus GRWR≥0.8 grafts and identify risk factors for graft loss using GRWR<0.8 grafts.

BACKGROUND

Favorable outcomes after LDLT using GRWR<0.8 grafts were recently reported; however, these results have not been validated using multicenter data.

METHODS

This multicentric cohort study included 3450 LDLT patients. Graft survival was compared between 1:3 propensity score-matched groups and evaluated using various Cox models in the entire population. Risk factors for graft loss with GRWR<0.8 versus GRWR≥0.8 grafts were explored within various subgroups using interaction analyses, and outcomes were stratified according to the number of risk factors.

RESULTS

In total, 368 patients (10.7%) received GRWR<0.8 grafts (GRWR<0.8 group), whereas 3082 (89.3%) received GRWR≥0.8 grafts (GRWR≥0.8 group). The 5-year graft survival rate was significantly lower with GRWR<0.8 grafts than with GRWR≥0.8 grafts (85.2% vs 90.1%, P =0.013). Adjusted hazard ratio for graft loss using GRWR<0.8 grafts in the entire population was 1.66 (95% CI: 1.17-2.35, P =0.004). Risk factors exhibiting significant interactions with GRWR<0.8 for graft survival were age ≥60 years, Model for End-stage Liver Disease score ≥15, and male donor. When ≥2 risk factors were present, GRWR<0.8 grafts showed a higher risk of graft loss compared with GRWR≥0.8 graft in LDLT (hazard ratio 2.98, 95% CI: 1.79-4.88, P <0.001).

CONCLUSIONS

GRWR<0.8 graft showed inferior graft survival than controls (85.2% vs 90.1%), especially when ≥2 risk factors for graft loss (among age 60 years or above, Model for End-stage Liver Disease score ≥15, or male donor) were present.

Post Living Donor Liver Transplantation Small-for-size Syndrome: Definitions, Timelines, Biochemical, and Clinical Factors for Diagnosis: Guidelines From the ILTS-iLDLT-LTSI Consensus Conference

BACKGROUND

When a partial liver graft is unable to meet the demands of the recipient, a clinical phenomenon, small-for-size syndrome (SFSS), may ensue. Clear definition, diagnosis, and management are needed to optimize transplant outcomes.

METHODS

A Consensus Scientific committee (106 members from 21 countries) performed an extensive literature review on specific aspects of SFSS, recommendations underwent blinded review by an independent panel, and discussion/voting on the recommendations occurred at the Consensus Conference.

RESULTS

The ideal graft-to-recipient weight ratio of ≥0.8% (or graft volume standard liver volume ratio of ≥40%) is recommended. It is also recommended to measure portal pressure or portal blood flow during living donor liver transplantation and maintain a postreperfusion portal pressure of <15 mm Hg and/or portal blood flow of <250 mL/min/100 g graft weight to optimize outcomes. The typical time point to diagnose SFSS is the postoperative day 7 to facilitate treatment and intervention. An objective 3-grade stratification of severity for protocolized management of SFSS is proposed.

CONCLUSIONS

The proposed grading system based on clinical and biochemical factors will help clinicians in the early identification of patients at risk of developing SFSS and institute timely therapeutic measures. The validity of this newly created grading system should be evaluated in future prospective studies.

Preventing Small-for-size Syndrome in Living Donor Liver Transplantation: Guidelines From the ILTS-iLDLT-LTSI Consensus Conference

Small-for-size syndrome (SFSS) is a well-recognized complication following liver transplantation (LT), with up to 20% developing this following living donor LT (LDLT). Preventing SFSS involves consideration of factors before the surgical procedure, including donor and recipient selection, and factors during the surgical procedure, including adequate outflow reconstruction, graft portal inflow modulation, and management of portosystemic shunts. International Liver Transplantation Society, International Living Donor Liver Transplantation Group, and Liver Transplant Society of India Consensus Conference was convened in January 2023 to develop recommendations for the prediction and management of SFSS in LDLT. The format of the conference was based on the Grading of Recommendations, Assessment, Development, and Evaluation system. International experts in this field were allocated to 4 working groups (diagnosis, prevention, anesthesia, and critical care considerations, and management of established SFSS). The working groups prepared evidence-based recommendations to answer-specific questions considering the currently available literature. The working group members, independent panel, and conference attendees served as jury to edit and confirm the final recommendations presented at the end of the conference by each working group separately. This report presents the final statements and evidence-based recommendations provided by working group 2 that can be implemented to prevent SFSS in LDLT patients.

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

BACKGROUND

Portal inflow modulation (PIM) aimed at reducing portal hyperperfusion is commonly used in living donor liver transplantation (LDLT) to reduce the risk of small-for-size syndrome (SFSS). Many different techniques, both pharmacological and surgical have been used for this purpose. There is, however, little consensus on the best method of PIM, its exact role in preventing SFSS and on early post-LDLT recovery.

OBJECTIVES

To identify whether modifications of portal pressures and flows enhance recovery after LDLT and to provide international expert panel recommendations.

DATA SOURCES

Ovid MEDLINE, Embase, Scopus, Google Scholar, and Cochrane Central.

METHODS

Systematic review following PRISMA guidelines and recommendations using the GRADE approach derived from an international expert panel.

PROSPERO ID

CRD42021260997.

RESULTS

Five hundred and ninety four articles were identified through databases' search. Of the 24 included for a final review by the working group (WG), there were five randomized control trials, four prospective studies and 15 retrospective series. Six outcome measures which were likely to influence early recovery after LDLT, especially in small-for-size grafts (SFSG) were shortlisted. These included acute kidney injury, SFSS, morbidity including sepsis, length of ICU and hospital stay, morbidity of the PIM technique and overall mortality. The WG noted that PIM in this subset of LDLT recipients had a beneficial effect on all the outcomes measures.

CONCLUSIONS

Considering all decision domains, the panel recommends pre- and intraoperative actual graft weight validation, portal pressure/flow measurements, and a comprehensive donor evaluation for the determination of potentially small-for-size/ small-for-flow grafts as mandatory. (Quality of Evidence: Moderate | Grade of Recommendation: Strong) Pharmacological PIM helps improve early renal function in LDLT recipients. (Quality of Evidence: High | Grade of Recommendation: Strong) In selected patients with SFSG, PIM helps reduce SFSS/EAD and sepsis. (Quality of Evidence: Moderate | Grade of Recommendation: Strong) PIM in the form of splenectomy has increased morbidity compared to splenic artery ligation (SAL). (Quality of Evidence: Low | Grade of Recommendation: Strong) In LDLT recipients with SFSG, PIM may help reduce morbidity/mortality. (Quality of Evidence: Low | Grade of Recommendation: Strong) In LDLT recipients with SFSG, modification of portal pressures and flows enhances recovery after LDLT. (Quality of Evidence: Moderate | Grade of Recommendation: Strong).

Small-For-Size Syndrome and Graft Inflow Modulation Techniques in Liver Transplantation

BACKGROUND

Partial liver transplantation has recently been proposed to alleviate organ shortages. However, transplantation of a small-for-size graft is associated with an increased risk of posttransplant hepatic dysfunction, commonly referred to as small-for-size syndrome (SFSS). This review describes the etiology, pathological features, clinical manifestations, and diagnostic criteria of SFSS. Moreover, we summarize strategies to improve graft function, focusing on graft inflow modulation techniques. Finally, unmet needs and future perspectives are discussed.

SUMMARY

In fact, posttransplant SFSS can be attributed to various factors such as preoperative status of the recipients, surgical techniques, donor age, and graft quality, except for graft size. With targeted improvement measures, satisfactory clinical outcomes can be achieved in recipients at increased risk of SFSS. Given the critical role of relative portal hyperperfusion in the pathogenesis of SFSS, various pharmacological and surgical treatments have been established to reduce or partially divert excessive portal inflow, and recipients will benefit from individualized therapeutic regimens after careful evaluation of benefits against potential risks. However, there remain unmet needs for further research into different aspects of SFSS to better understand the correlation between portal hemodynamics and patient outcomes.

KEY MESSAGES

Contemporary transplant surgeons should consider various donor and recipient factors and develop case-specific prevention and treatment strategies to improve graft and recipient survival rates.

Intraoperative High Fraction of Inspiratory Oxygen is Independently Associated with Worse Outcome After Living-Donor Liver Transplantation: A Retrospective Study

Background

Ischemia and reperfusion injury is an important factor that determines graft function after liver transplantation, and oxygen plays a crucial role in this process. However, the relationship between the intraoperative high fraction of inspiratory oxygen (FiO₂) and living-donor-liver-transplantation (LDLT) outcome remains unclear.

Patients and Methods

A total of 199 primary adult-to-adult LDLT cases in Kyoto University Hospital between January 2010 and December 2017 were enrolled in this study. The intraoperative FiO₂ was averaged using the total amount of intraoperative oxygen and air and defined as the calculated FiO₂ (cFiO₂). The cutoff value of cFiO₂ was set at 0.5.

Results

Between the cFiO₂ <0.5 (n = 156) and ≥0.5 group (n = 43), preoperative recipients’ background, donor factors, and intraoperative parameters were almost comparable. Postoperatively, the cFiO₂ ≥0.5 group showed a higher early allograft dysfunction (EAD) rate (P = 0.049) and worse overall graft survival (P = 0.036) than the cFiO₂ <0.5 group. Although the cFiO₂ ≥0.5 was not an independent risk factor for EAD in multivariable analysis (OR 2.038, 95%CI 0.992–4.186, P = 0.053), it was an independent risk factor for overall graft survival after LDLT (HR 1.897, 95%CI 1.007–3.432, P = 0.048).

Conclusion

The results of this study suggest that intraoperative high FiO₂ may be associated with worse graft survival after LDLT. Avoiding higher intraoperative FiO₂ may be beneficial for LDLT recipients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00268-022-06544-7.

HPi: A Novel Parameter to Predict Graft-related Outcome in Adult Living Donor Liver Transplant

BACKGROUND

Portal hyperperfusion is frequently associated with early allograft dysfunction (EAD). It is imperative to identify patients who would require portal inflow modulation. We aimed to identify factors associated with hyperperfusion-related graft injury and develop a predictive index for the same.

METHODS

Prospectively maintained database was queried to identify 135 adult living donor liver transplant recipients between September 2016 and July 2020. According to the calculated sample size, 96 patients were randomly selected for "test cohort". The remaining 39 patients made the "validation cohort." EAD was defined according to the A2ALL study. "Hyperperfusion index (HPi)," defined as posttransplant portal pressure gradient (ΔPpost)/graft-to-recipient splenic volume ratio (GRSVR), was devised on the basis of laws of flow dynamics and regression analysis.

RESULTS

Overall, 40 patients (29.6%) had EAD, six 90-d mortalities (4.4%) were attributable to EAD. In the test cohort, EAD patients (n = 29, 30.2%) had lower GRSVR (1.00 versus 2.22, P < 0.001), higher ΔPpost (14.8 versus 11.9, P = 0.004), and HPi (20.89 versus 8.67, P < 0.001). Multivariate analysis revealed GRSVR, ΔPpost, and HPi as significant factors to predict EAD. Receiver operating characteristic determined cutoff of HPi ≥9.97 could predict EAD with sensitivity of 90% and specificity of 73% (F-score = 0.712). HPi ≥16.25 predicted 90-d mortality with sensitivity of 100% and specificity of 78.9%. Patients with higher HPi had delayed graft-related recovery. Non-EAD patients had a higher 1-y (96% versus 79%) and 2-y (88% versus 79%) survival. The cutoff of HPi was validated well in the validation cohort (F-score = 0.645) (Hosmer-Lemeshow test, P = 0.89).

CONCLUSIONS

While predicted GRSVR may help identify at-risk patients preoperatively, intraoperatively calculated HPi is more accurate in identifying patients who would require portal inflow modulation. Achieving an HPi below target cutoff significantly decreases the risk of EAD even in low-GRSVR patients.

Successful Simultaneous Subtotal Splenectomy During Left Lobe Auxiliary Liver Transplantation for Portal Inflow Modulation and Severe Hypersplenism Correction: A Case Report

Adult-to-adult living donor liver transplantation with small partial liver grafts often requires intraoperative portal inflow modulation to prevent portal hyperperfusion and subsequent small-for-size syndrome (SFSS). However, there are concerns about the specific morbidity of these modulation techniques. This study aims to lower post-perfusion portal venous pressure and correct severe hypersplenism in a patient with end-stage liver cirrhosis by simultaneous subtotal splenectomy during auxiliary partial orthotopic liver transplantation (APOLT). A 29-year-old man was diagnosed with cryptogenic cirrhosis and severe portal hypertension suffered recurrent acute variceal bleeding, severe thrombocytopenia, and massive ascites before admission to our hospital. After the recipient's left liver was resected, we performed APOLT using his 51-year-old father's left lobe graft with a graft-to-recipient weight ratio of 0.55%. Intraoperatively, simultaneous subtotal splenectomy was performed to lower graft post-perfusion portal vein pressure below 15 mmHg and correct severe hypersplenism-related pancytopenia. The recipient's postoperative hospital course was uneventful with no occurrence of SFSS and procedure-related complications. Platelet and leukocyte counts remained in the normal ranges postoperatively. The living donor was discharged 6 days after the operation and recovered well-with no complications. After a follow-up period of 35.3 months, both the recipient and donor live with good liver function and overall condition. This is the first case report of simultaneous subtotal splenectomy during APOLT using small-for-size living-donated left liver lobes, which is demonstrated to be a viable procedure for modulating portal inflow and correcting severe hypersplenism in selected adult patients with end-stage liver cirrhosis. APOLT using a small-for-size liver graft may be a safe and feasible treatment option for selected adult patients with end-stage liver cirrhosis.

Importance of reconstruction of middle hepatic vein tributaries of right-lobe grafts in living donor liver transplantation: demonstration of the reconstruction technique

PURPOSE

The aim of the present study on living donor liver transplantation (LDLT) using a right-lobe graft without the middle hepatic vein (MHV) was to investigate the clinical impact of MHV tributary reconstruction using our criteria and techniques.

METHODS

The medical records of 40 patients who underwent adult LDLT using a right-lobe graft without the MHV between April 2008 and December 2020 were retrospectively reviewed. In this cohort, the criterion for MHV tributary reconstruction was estimated drainage volume of each MHV tributary greater than 100 mL. The drainage vein of segment 8 (V8) was reconstructed as the common orifice of the right hepatic vein and V8 using a venous patch graft, and that of segment 5 was reconstructed using artificial vascular grafts. The outcomes were compared between the groups with and without MHV tributary reconstruction. Factors associated with postoperative massive ascites were also investigated.

RESULTS

Twenty patients underwent MHV tributary reconstruction. There were no significant differences in the amount of postoperative ascites, Clavien-Dindo classification ≥ III postoperative complications, and 90-day in-hospital mortality between the groups (P = 0.678, P = 1.000, and P = 0.244, respectively). On multivariate analyses, a low-estimated functional graft-to-recipient weight ratio, which was calculated using estimated graft volume minus the territory of MHV tributaries that was not reconstructed, was identified as an independent predictor of postoperative massive ascites (odds ratio, 40.479; 95% confidence interval, 3.823-428.622).

CONCLUSION

The present study suggests that selective MHV tributary reconstruction might be useful for achieving successful graft function.

Fluid dynamics analyses of the intrahepatic portal vein tributaries using 7-T MRI

BACKGROUND

Assessing portal vein (PV) hemodynamics is an essential part of liver disease management/liver surgery, yet the optimal methods of assessing intrahepatic PV flow have not yet been established. This study investigated the usefulness of 7-Tesla MRI with hemodynamic analysis for detecting small flow changes within narrow intrahepatic PV branches.

METHODS

Flow data in the main PV was obtained by two methods, two-dimensional cine phase contrast-MRI (2D cine PC-MRI) and three-dimensional non-cine phase contrast-MRI (3D PC-MRI). Hemodynamic parameters, such as flow volume rate, flow velocity, and wall shear stress in intrahepatic PV branches were calculated before and after a meal challenge using 3D PC-MRI and hemodynamic analysis.

RESULTS

The hemodynamic parameters obtained using 3D PC-MRI and 2D cine PC-MRI were similar. All intrahepatic PV branches were clearly depicted in eight planes, and significant changes in flow volume rate were seen in three planes. Average and maximum velocities, cross-sectional area, and wall shear stress were similar between before and after a meal challenge in all planes.

CONCLUSION

7-Tesla 3D PC-MRI combined with hemodynamic analysis is a promising tool for assessing intrahepatic PV flow and enables future studies in small animals to investigate PV hemodynamics associated with liver disease/postoperative liver recovery.

Can Living Donor Liver Transplantation in the United States Reach Its Potential?

Living donor liver transplantation (LDLT) is a vital tool to address the growing organ shortage in the United States caused by increasing numbers of patients diagnosed with end-stage liver disease. LDLT still only makes up a very small proportion of all liver transplantations performed each year, but there are many innovations taking place in the field that may increase its acceptance among both transplant programs and patients. These innovations include ways to improve access to LDLT, such as through nondirected donation, paired exchange, transplant chains, transplant of ABO-incompatible donors, and transplants in patients with high Model for End-Stage Liver Disease scores. Surgical innovations, such as laparoscopic donor hepatectomy, robotic hepatectomy, and portal flow modulation, are also increasingly being implemented. Policy changes, including decreasing the financial burden associated with LDLT, may make it a more feasible option for a wider range of patients. Lastly, center-level behavior, such as ensuring surgical expertise and providing culturally competent education, will help toward LDLT expansion. Although it is challenging to know which of these innovations will take hold, we are already seeing LDLT numbers improve within the past 2 years.

Clinical Significance of Spontaneous Portosystemic Shunts in Living Donor Liver Transplantation

Spontaneous portosystemic shunts (SPSS) are commonly observed in patients undergoing living donor liver transplantation (LDLT); however, their impact on the outcome after transplantation is unclear. We aimed to assess the type, size, and the effects of SPSS on outcomes after LDLT. A total of 339 LDLT recipients in a single institution were included. The type and diameter of the SPSS (splenorenal shunt [SRS], oesogastric shunt, and umbilical shunt) were retrospectively analyzed. A large shunt was defined as having a diameter ≤7 mm. No portal flow modulation was attempted over time. Portal complications were defined as stenosis, thrombosis, or hepatofugal flow requiring any treatment after transplantation. There were 202 (59.0%) patients who exhibited at least 1 large SPSS. Neither the size nor type of SPSS was associated with mortality, morbidity, or liver function recovery. However, the incidence of portal complications was significantly higher in patients with a large SRS (8.6% versus 2.9%; P = 0.04). Multivariate analysis of portal complications revealed 2 independent predictors: pre-LT portal vein thrombosis (PVT) and SRS size. The observed risk among recipients with pre-LT PVT was 8.3% when the SRS was ≤7 mm, but increased to 38.5% when the SRS was >15 mm. The present study suggests that large SPSS do not negatively affect the outcomes after LDLT. However, a large SRS is associated with a higher risk of portal complications, particularly in recipients with pre-LT PVT, for whom intraoperative intervention for SRS should be considered. Otherwise, a conservative approach to SPSS during LDLT seems reasonable.

The combination of a male donor's high muscle mass and quality is an independent protective factor for graft loss after living donor liver transplantation

We evaluated the hypothesis that grafts from donors with high muscle mass and quality may have a better outcome after living-donor-liver-transplantation (LDLT) than those from usual donors. A total of 376 primary adult-to-adult LDLT cases were enrolled in this study. Donor skeletal muscle mass index (SMI) and intramuscular adipose tissue content (IMAC) were used as markers of muscle mass and quality. In male donor cases (n = 198), those with higher SMI and lower IMAC than age-adjusted values were defined as the "high muscularity donors" (n = 38) and the others were defined as the "control" (n = 160). The high muscularity donor showed better 1-year (97% vs 82%, P = .020) and overall graft survival rate (88% vs 67%, P = .024) than the control group after LDLT. Contrastingly, the influence of the muscularity was not observed in female donor cases. Multivariable analysis including donor age confirmed that a high muscularity donor was an independent protective factor for overall graft survival after LDLT (hazard ratio, 0.337; 95% CI: 0.101-0.838; P = .017). Our study first confirmed that high muscle mass and quality of a male donor is a protective factor of allograft loss after LDLT, independently from donor age.

Pretransplantation splenomegaly frequently persists after liver transplantation and can manifest as hypersplenism and graft fibrosis - a retrospective study

The risk factors and clinical impact of post-transplantation splenomegaly (SM) are poorly understood. We investigated the predictors and impacts of post-transplantation SM in 415 LT patients at Kyoto University Hospital from April 2006 to December 2015. First, the predictors and clinical consequences of SM three years post-transplantation were analyzed among spleen-preserved recipients. Second, the clinical data of surviving recipients three years post-transplantation were compared between splenectomized and spleen-preserved recipients. There was no difference in indication for liver transplantation between these two groups. Third, survival outcomes were compared between splenectomized and spleen-preserved recipients. SM was determined as a SV/body surface area (BSA) higher than 152 ml/m² . In the first analysis, preoperative SM occurred in 79.9% recipients and SM persisted three years post-transplantation in 72.6% recipients among them. Preoperative SV/BSA was the only independent predictor of three year post-transplantation SM, which was associated with lower platelet (PLT), white blood cell (WBC) counts and significant graft fibrosis (21.4% vs. 2.8%). In the second analysis, spleen-preservation was related to lower PLT, WBC counts and a higher proportion of significant graft fibrosis (26.7% vs. 7.1%) three years post-transplantation. In the third analysis, spleen-preserved recipients showed worse survival than splenectomized recipients. In conclusion, preoperative SM frequently persists more than three years post-transplantation and is associated with subclinical hypersplenism, graft fibrosis, graft loss, and even death.

Impact on biliary complications of donor abdominal aortic calcification among living donor liver transplantation: a retrospective study

Abdominal aortic calcification (AAC) was reported as a poor prognostic factor among liver transplantation. However, donor AAC is not enough discussed. We analyzed the impact of the donor AAC level on graft function on outcomes following living donor liver transplantation (LDLT). A total of 133 consecutive patients who had undergone LDLT were divided into two groups (non-AAC group and AAC group) according to their donor AAC level by plain computed tomography. The rate of postoperative biliary complications (BC) was significantly higher in AAC group (N = 17) than in non-AAC group (N = 116; HR, 2.77; 95% CI, 1.32-5.83; P = 0.0008). The Cox proportional hazards regression model revealed that donor AAC (HR, 4.15; 95% CI, 1.93-8.97; P = 0.0003) and right lobe graft (HR, 2.81; 95% CI, 1.41-5.61; P = 0.003) increased the risk of BC. Conversely, splenectomy (HR, 0.39; 95% CI, 0.16-0.92; P = 0.03) decreased the risk of BC after LDLT independently. The long-term survival was also significantly worse in AAC group than in non-AAC group (HR, 2.25; 95% CI, 1.04-4.89; P = 0.04). Donor AAC was an independent prognostic factor for BC among patients undergoing LDLT. Although further investigations are needed to verify our results, the levels of donor AAC could be a useful tool to identify the risks of BC and predict better outcomes following LDLT.

Small-for-size graft, small-for-size syndrome and inflow modulation in living donor liver transplantation

The extended application of living donor liver transplantation (LDLT) has revealed the problem of graft size mismatching called "small-for-size syndrome (SFSS)." The initial trials to resolve this problem involved increasing the procured graft size, from left to right, and even extending to include a right lobe graft. Clinical cases of living right lobe donations have been reported since then, drawing attention to the risks of increasing the liver volume procured from a living donor. However, not only other modes of increasing graft volume (GV) such as auxiliary or dual liver transplantation, but also control of the increased portal pressure caused by a small-for-size graft (SFSG), such as a porto-systemic shunt or splenectomy and optimal outflow reconstruction, have been trialed with some positive results. To establish an effective strategy for transplanting SFSG and preventing SFSS, it is essential to have precise knowledge and tactics to evaluate graft quality and GV, when performing these LDLTs with portal pressure control and good venous outflow. Thus, we reviewed the updated literature on the pathogenesis of and strategies for using SFSG.

Liver transplantation in patients with portal vein thrombosis: A strategic road map throughout management

BACKGROUND

Liver transplantation in the setting of portal vein thrombosis is an intricate issue that occasionally necessitates extraordinary procedures for portal flow restoration. However, to date, there is no consensus on a persistent management strategy, particularly with extensive forms. This work aims to introduce our experience-based surgical management algorithm for portal vein thrombosis during liver transplantation and to clarify some of the debatable circumstances associated with this problematic issue.

METHODS

Between 2006 and 2019, 494 adults underwent liver transplantation at our institute. Ninety patients had preoperative portal vein thrombosis, and 79 patients underwent living donor liver transplantation. Our algorithm trichotomized the management plan into 3 pathways based on portal vein thrombosis grade. The surgical procedures implemented included thrombectomy, interposition vein grafts, jump grafts from the superior mesenteric vein, jump grafts from a collateral and renoportal anastomosis in 56, 13, 11, 4, and 2 patients, respectively. Four patients with mural thrombi did not require any special intervention.

RESULTS

Thirteen patients experienced posttransplant portal vein complications. They all proved to have a patent portal vein by the end of follow-up regardless of the management modality. No significant survival difference was observed between cohorts with versus without portal vein thrombosis. The early graft loss rate was significantly higher with advanced grades (P = .048) as well as technically demanding procedures (P = .032).

CONCLUSION

A stepwise broad-minded strategy should always be adopted when approaching advanced portal vein thrombosis during liver transplantation. An industrious preoperative evaluation should always be carried out to locate the ideal reliable source for portal flow restoration.

Recent evolution of living donor liver transplantation at Kyoto University: How to achieve a one-year overall survival rate of 99%?

Previously, living donor liver transplantation was considered as a "high-risk, high-return" medical treatment due to the relatively high short-term mortality. It is our task to change "high-risk, high-return" into a "low-risk, high-return" situation. In this review article, the recent evolutions in living donor liver transplantation for both donors and recipients at Kyoto University such as portal vein pressure modulation, hybrid donor operation, and perioperative management considering sarcopenia, focusing on improvement of short-term outcomes are described. Under a paradigm of "marketing and innovation", various innovations and efforts have been made over the last decade aiming at improving the short-term outcomes of both donors and recipients. By doing so, excellent short-term results after living donor liver transplantation have been achieved, along with a potentially epoch-making discoveries.

Living donor liver transplantation in small-for-size setting

Small-for-Size Syndrome (SFSS) is one of the most feared complication of adult split liver and living donor liver transplantation. SFSS stems from a disproportionate/excessive portal vein flow relative to the volume of the implanted liver graft, and is currently one of the major practical limits to partial liver grafts' transplantation. In the last few decades many graft inflow modulation (GIM) techniques have been proposed to curtail the portal vein flow, allowing for successful transplantation of small partial liver grafts. Graft inflow modulation techniques span from Splenic Artery Ligation (SAL), to Splenectomy, Porto-Systemic Shunts and the lately proposed Splenic Devascularization. A patient tailored approach balancing the risk of SFSS with GIM specific morbidity, is more important than identifying the ideal GIM technique. Here we summarize the most recently published data to provide general indications in the challenging preoperative choice of a GIM techniques.

Post-transplant inflow modulation for early allograft dysfunction after living donor liver transplantation

Background

To treat small-for-size syndrome (SFSS) after living donor liver transplantation (LDLT), many procedures were described for portal flow modulation before, during, or after transplantation. The selection of the procedure as well as the best timing remains controversial.

Case presentation

A 43-year-old female with end-stage liver disease underwent LDLT with extended left with caudate lobe graft from her donor who was her 41-year-old brother (graft volume/standard liver volume (GV/SLV), 35.7%; graft to recipient weight ratio (GRWR), 0.67%). During the surgery, splenectomy could not be performed owing to severe peri-splenic adhesions to avoid the ruined bleedings. The splenic artery ligation was not also completely done because it was dorsal to the pancreas and difficult to be approached. Finally, adequate portal vein (PV) inflow was confirmed after portal venous thrombectomy. As having post-transplant optional procedures that are accessible for PV flow modulation, any other procedures for PV modulation during LDLT were not done until the postoperative assessment of the graft function and PV flow for possible postoperative modulation of the portal flow accordingly. Postoperative PV flow kept as high as 30 cm/s. By the end of the 1st week, there was a progressive deterioration of the total bilirubin profile (peak as 19.4 mg/dL) and ascitic fluid amount exceeded 1000 mL/day. Therefore, splenic artery embolization was done effectively and safely on the 10th postoperative day (POD) to reverse early allograft dysfunction as PV flow significantly decreased to keep within 20 cm/s and serum total bilirubin levels gradually declined with decreased amounts of ascites below 500 mL on POD 11 and thereafter. The patient was discharged on POD 28 with good condition.

Conclusions

SFSS can be prevented or reversed by the portal inflow modulation, even by post-transplant procedure. This case emphasizes that keeping accessible angiographic treatment options for PV modulation, such as splenic artery embolization, after LDLT is quite feasible.

Current status of liver transplantation in Asia

In spite of early adoption of the brain death legislation, and all efforts at promoting deceased donation, various social, economic and cultural factors have acted as road blocks to the furthering of deceased donor liver transplantation (DDLT) in most Asian societies. On the other hand, Asian liver transplant centers have been the pioneers, innovators, and technical advancement catalysts for the world to follow, especially with regards to living donor liver transplantation (LDLT). With some high volume centers performing more than 200 LDLTs a year with good outcomes in the donor and recipient, techniques to expand the living donor pool have also been adopted like ABO-incompatible, paired exchange and dual lobe living donor liver transplants. Although large multicenter, and registry data as regards safety and outcomes of minimally invasive donor hepatectomy are awaited, expert centers have pioneered, and now regularly perform purely laparoscopic and robotic living donor hepatectomies, especially in Korea.

A systematic review of small for size syndrome after major hepatectomy and liver transplantation

BACKGROUND

Major hepatectomy (MH) and particular types of liver transplantation (LT) (reduced size graft, living-donor and split-liver transplantation) lead to a reduction in liver mass. As the portal venous return remains the same it results in a reciprocal and proportionate rise in portal venous pressure potentially resulting in small for size syndrome (SFSS). The aim of this study was to review the incidence, diagnosis and management of SFSS amongst recipients of LT and MH.

METHODS

A systematic review was performed in accordance with the 2010 Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guidelines. The following terms were used to search PubMed, Embase and Cochrane Library in July 2019: ("major hepatectomy" or "liver resection" or "liver transplantation") AND ("small for size syndrome" or "post hepatectomy liver failure"). The primary outcome was a diagnosis of SFSS.

RESULTS

Twenty-four articles met the inclusion criteria and could be included in this review. In total 2728 patients were included of whom 316 (12%) patients met criteria for SFSS or post hepatectomy liver failure (PHLF). Of these, 31 (10%) fulfilled criteria for PHLF following MH. 8 of these patients developed intractable ascites alongside elevated portal venous pressure following MH indicative of SFSS.

CONCLUSION

SFSS is under-recognised following major hepatectomy and should be considered as an underlying cause of PHLF. Surgical and pharmacological therapies are available to reduce portal congestion and reverse SFSS.

Long-term Functional Maintenance of Exteriorized Portal Venous Catheters in a Porcine Animal Model

BACKGROUND

Portal venous access for blood sampling, infusion therapy, and measurement of portal venous pressure is of special interest for experimental studies in surgery, pharmacology, and hepatology. Chronic animal models with continuous portal venous access are rare and especially thrombosis or clotting of permanent catheters is a frequent complication. Aim of this study was to establish a preclinical pig model with a permanent portal venous catheter (PVC).

MATERIALS AND METHODS

PVC implantation was performed in 21 LEWE mini pigs. The catheter was inserted in the distal part of the superior mesenteric vein and fixated with a tobacco-pouch suture. Animals were followed up for 4 wk, directly after implantation of the PVC. Blood gas analyses and portal venous pressures were recorded. Three different groups with continuous infusion via the catheters were defined: NaCl solution (2 mL/h) (group 1), NaCl solution (2 mL/h) + enoxaparin sodium injection (anti-Xa levels of 0.3-0.8 U/mL) (group 2) and heparinized NaCl (2 I.E./mL, 2 mL/h) (group 3).

RESULTS

All 21 PVC implantations were performed without any complications. Application of continuous perfusion with heparinized NaCl (group 3) enabled portal venous access for the entire experiment in 8 of 10 cases (mean of 23.7 d) without any signs of dysfunction. However, for use of NaCl alone or in combination with enoxaparin sodium, catheters were only functional for 6.8 d and 6.9 d, respectively.

CONCLUSIONS

Permanent portal venous access through PVC in mini pigs is achievable by continuous infusion of low-dose heparinized NaCl solution.

Is Portal Inflow Modulation Always Necessary for Successful Utilization of Small Volume Living Donor Liver Grafts?

Although the well-accepted lower limit of the graft-to-recipient weight ratio (GRWR) for successful living donor liver transplantation (LDLT) remains 0.80%, many believe grafts with lower GRWR may suffice with portal inflow modulation (PIM), resulting in equally good recipient outcomes. This study was done to evaluate the outcomes of LDLT with small-for-size grafts (GRWR <0.80%). Of 1321 consecutive adult LDLTs from January 2012 to December 2017, 287 (21.7%) had GRWR <0.80%. PIM was performed (hemiportocaval shunt [HPCS], n = 109; splenic artery ligation [SAL], n = 14) in 42.9% patients. No PIM was done if portal pressure (PP) in the dissection phase was <16 mm Hg. Mean age of the cohort was 49.3 ± 9.1 years. Median Model for End-Stage Liver Disease score was 14, and the lowest GRWR was 0.54%. A total of 72 recipients had a GRWR <0.70%, of whom 58 underwent HPCS (1 of whom underwent HPCS + SAL) and 14 underwent no PIM, whereas 215 had GRWR between 0.70% and 0.79%, of whom 51 and 14 underwent HPCS and SAL, respectively. During the same period, 1034 had GRWR ≥0.80% and did not undergo PIM. Small-for-size syndrome developed in 2.8% patients. Three patients needed shunt closure at 1 and 4 weeks and 60 months. The 1-year patient survival rates were comparable. In conclusion, with PIM protocol that optimizes postperfusion PP, low-GRWR grafts can be used for appropriately selected LDLT recipients with acceptable outcomes.

Impact of imbalanced graft-to-spleen volume ratio on outcomes following living donor liver transplantation in an era when simultaneous splenectomy is not typically indicated

The impact of an imbalanced graft-to-spleen volume ratio (GSVR) on posttransplant outcomes other than postreperfusion portal hypertension remains unknown. The importance of GSVR might vary according to whether simultaneous splenectomy (SPX) is performed. This retrospective study divided 349 living donor liver transplantation (LDLT) recipients from 2006 to 2017 into 2 groups: low GSVR (≤0.70 g/mL) and normal GSVR (>0.70 g/mL). The cutoff value of GSVR was set based on the first quartile of the distributed data. Graft survival and associations with various clinical factors were investigated between the groups according to whether SPX was performed. Low GSVR did not affect outcomes when SPX was performed. In contrast, it was associated with an increased incidence of early graft loss (EGL) and poor graft survival by presenting posttransplant thrombocytopenia, cholestasis, coagulopathy, and massive ascites when the spleen was preserved. Among patients with a preserved spleen, the multivariable analysis results revealed that older donor age and low GSVR were independent risk factors for graft loss. In conclusion, low GSVR was an independent predictor of graft loss after LDLT when the spleen was preserved. Preserved spleen with extremely low GSVR may be related to persistent hypersplenism, impaired graft function, and consequent EGL.

Older Donor Age Is a Risk Factor for Negative Outcomes After Adult Living Donor Liver Transplantation Using Small-for-Size Grafts

Adult-to-adult living donor liver transplantation (ALDLT) using small-for-size grafts (SFSGs), ie, a graft with a graft-to-recipient weight ratio (GRWR) <0.8%, has been a challenge that should be carefully dealt with, and risk factors in this category are unclear. Therefore, we aimed to examine the risk factors and outcomes of ALDLT using SFSGs over a 13-year period in 121 patients who had undergone their first ALDLT using SFSGs. Small-for-size syndrome (SFSS), early graft loss, and 1-year mortality were encountered in 21.6%, 14.9%, and 18.4% of patients, respectively. By multivariate analysis, older donor age (≥45 years) was an independent risk factor for SFSS (odds ratio [OR], 4.46; P = 0.004), early graft loss (OR, 4.11; P = 0.02), and 1-year mortality (OR, 3.76; P = 0.02). Child-Pugh C class recipients were associated with a higher risk of SFSS development (P = 0.013; OR, 7.44). Despite no significant difference between GRWR categories in the multivariate outcome analysis of the whole population, in the survival analysis of the 2 donor age groups, GRWR <0.6% was associated with significantly lower 1-year survival than the other GRWR categories in the younger donor group. Moreover, in the high final portal venous pressure (PVP) group (>15 mm Hg), younger ABO-compatible donors showed 100% 1-year survival with a significant difference from the group of other donors. Older donor age was an independent risk factor for SFSS, early graft loss, and 1-year mortality after ALDLT using SFSGs. GRWR should not be <0.6%, and PVP modulation is indicated when grafts from older or ABO-incompatible donors are used.

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.

Quantitative study of liver hemodynamic changes in rats with small-for-size syndrome by the 4D-CT perfusion technique

OBJECTIVE

The microcirculatory hemodynamic changes of small-for-size syndrome (SFSS) are still unclear. In this study, they were investigated by four-dimensional CT perfusion (4D-CTP) technique.

METHODS

The sham group, 50, 60, 70 and 80 % partial hepatectomy (PH) rat groups were established. At 1 hour (1 h), 1 day (1 d), 3 days (3 d) and 7 days (7 d) post-operation, serological examination, 4D-CTP scan and histopathological examination were performed. One-way analysis of variance and the Kruskal-Wallis test were used for the comparison.

RESULTS

Based on the diagnostic criteria of SFSS, the 80 % group was considered to be a successful model. In all the PH groups, portal vein perfusion and total liver perfusion peaked at 1 h and declined at 1d and 3d. Both portal vein perfusion and total liver perfusion were significantly higher in the 80 % group than the sham group, 50 and 60% groups at 1 h (p < 0.05), and 80 % group at 3d and 7d (p < 0.05). In the 50 and 60 % groups, hepatic artery perfusion decreased at 1 h and maintained at a lower level until at 7 d; whereas, in the 70 and 80% groups, it increased at 1 h, then decreased and reached the lowest level at 7 d. No significant difference appeared in hepatic artery perfusion between any two groups at any time points. At all time points, hepatic perfusion index was lower in all the PH groups than the sham group. Significant differences in hepatic perfusion index appeared between the 80% group and the sham group at 1 h and 1 d (p < 0.05).

CONCLUSIONS

The CTP parameters quantitatively revealed the microcirculatory hemodynamic changes in SFSS, which were further confirmed to be associated with histopathological injury. It is suggested that the hemodynamic changes in SFSS remnant liver can provide useful information for further revealing the mechanism of SFSS and may help for guiding the treatments.

ADVANCES IN KNOWLEDGE

By using the 4D-CTP technique, the hepatic microcirculatory hemodynamic changes could be quantitatively measured in vivo for small animal research.