Pathophysiologic observations and histopathologic recognition of the portal hyperperfusion or small-for-size syndrome

Vascular damage and excessive proliferation compromise liver function after extended hepatectomy in mice

BACKGROUND AND AIMS

Surgical resection remains the gold standard for liver tumor treatment, yet the emergence of postoperative liver failure, known as the small-for-size syndrome (SFSS), poses a significant challenge. The activation of hypoxia sensors in an SFSS liver remnant initiated early angiogenesis, improving the vascular architecture, safeguarding against liver failure, and reducing mortality. The study aimed to elucidate vascular remodeling mechanisms in SFSS and their impact on hepatocyte function and subsequent liver failure.

APPROACH AND RESULTS

Mice underwent extended partial hepatectomy to induce SFSS, with a subset exposed to hypoxia immediately after surgery. Hypoxia bolstered posthepatectomy survival rates. The early proliferation of liver sinusoidal cells, coupled with recruitment of putative endothelial progenitor cells, increased vascular density, improved lobular perfusion, and limited hemorrhagic events in the regenerating liver under hypoxia. Administration of granulocyte colony-stimulating factor in hepatectomized mice mimicked the effects of hypoxia on vascular remodeling and endothelial progenitor cell recruitment but failed to rescue survival. Compared to normoxia, hypoxia favored hepatocyte function over proliferation, promoting functional preservation in the regenerating remnant. Injection of Adeno-associated virus serotype 8-thyroxine-binding globulin-hepatocyte nuclear factor 4 alpha virus for hepatocyte-specific overexpression of hepatocyte nuclear factor 4 alpha, the master regulator of hepatocyte function, enforced functionality in proliferating hepatocytes but did not rescue survival. The combination of hepatocyte nuclear factor 4 alpha overexpression and granulocyte colony-stimulating factor treatment rescued survival after SFSS-setting hepatectomy.

CONCLUSIONS

In summary, SFSS arises from an imbalance and desynchronized interplay between functional regeneration and vascular restructuring. To improve survival following SFSS hepatectomy, it is essential to adopt a 2-pronged strategy aimed at preserving the function of proliferating parenchymal cells and simultaneously attenuating vascular damage.

Molecular mechanisms in liver repair and regeneration: from physiology to therapeutics

Liver repair and regeneration are crucial physiological responses to hepatic injury and are orchestrated through intricate cellular and molecular networks. This review systematically delineates advancements in the field, emphasizing the essential roles played by diverse liver cell types. Their coordinated actions, supported by complex crosstalk within the liver microenvironment, are pivotal to enhancing regenerative outcomes. Recent molecular investigations have elucidated key signaling pathways involved in liver injury and regeneration. Viewed through the lens of metabolic reprogramming, these pathways highlight how shifts in glucose, lipid, and amino acid metabolism support the cellular functions essential for liver repair and regeneration. An analysis of regenerative variability across pathological states reveals how disease conditions influence these dynamics, guiding the development of novel therapeutic strategies and advanced techniques to enhance liver repair and regeneration. Bridging laboratory findings with practical applications, recent clinical trials highlight the potential of optimizing liver regeneration strategies. These trials offer valuable insights into the effectiveness of novel therapies and underscore significant progress in translational research. In conclusion, this review intricately links molecular insights to therapeutic frontiers, systematically charting the trajectory from fundamental physiological mechanisms to innovative clinical applications in liver repair and regeneration.

Serum Lactate Clearance as a Predictive Biomarker for Optimal Graft Perfusion in Living Donor Liver Transplantation

BACKGROUND

The optimal balance between the graft volume (GV) and portal venous flow (PVF) in living donor liver transplantation (LDLT) is unclear. As lactate is mainly metabolized in the liver, perioperative lactate levels are reportedly a useful biomarker for early graft dysfunction (EGD). The present study analyzed perioperative lactate levels according to the PVF.

METHODS

The PVF/GV (mL/min per 100 g GV) of 97 recipients from 1996 to 2022 was retrospectively classified as low (LPVF; PVF/GV ≤ 100, N = 29), moderate (MPVF; PVF/GV 100-250, N = 40), or high (HPVF; PVF/GV > 250, N = 28). Lactate levels were obtained preoperatively (L0), immediately after graft reperfusion (L1), 4 h after reperfusion (L2), and on postoperative day 3 (L3). The lactate clearances were then calculated.

RESULTS

The lower the PVF/GV ratio, the younger the age at LDLT and the higher the graft-to-recipient weight ratio. The median L2 and L3 in the HPVF group were significantly higher than those in the other groups (p = 0.019 and p = 0.003, respectively). The median ΔL1 in the HPVF group was lower than that in the LPVF and MPVF groups (0.23 vs. 0.50, p < 0.0001 and 0.23 vs. 0.41, p = 0.011, respectively). ΔL1 was negatively correlated with the PVF/GV. Although no patient had EGD, three patients with HPVF with low ΔL1 developed small-for-size syndrome.

CONCLUSIONS

Graft hyperperfusion may delay the recovery of the graft function and result in poor lactate clearance. The combination of the PVF/GV and lactate clearance may be useful as a prognostic marker for optimal graft perfusion in LDLT.

LEVEL OF EVIDENCE

IV.

Prediction and management of small-for-size syndrome in living donor liver transplantation

Small-for-size syndrome (SFSS) remains a critical challenge in living donor liver transplantation (LDLT), characterized by graft insufficiency due to inadequate liver volume, leading to significant postoperative morbidity and mortality. As the global adoption of LDLT increases, the ability to predict and manage SFSS has become paramount in optimizing recipient outcomes. This review provides a comprehensive examination of the pathophysiology, risk factors, and strategies for managing SFSS across the pre-, intra-, and postoperative phases. The pathophysiology of SFSS has evolved from being solely volume-based to incorporating portal hemodynamics, now recognized as small-for-flow syndrome. Key risk factors include donor-related parameters like age and graft volume, recipient-related factors such as MELD score and portal hypertension, and intraoperative factors related to venous outflow and portal inflow modulation. Current strategies to mitigate SFSS include careful graft selection based on graft-to-recipient weight ratio and liver volumetry, surgical techniques to optimize portal hemodynamics, and novel interventions such as splenic artery ligation and hemiportocaval shunts. Pharmacological agents like somatostatin and terlipressin have also shown promise in modulating portal pressure. Advances in 3D imaging and artificial intelligence-based volumetry further aid in preoperative planning. This review emphasizes the importance of a multifaceted approach to prevent and manage SFSS, advocating for standardized definitions and grading systems. Through an integrated approach to surgical techniques, hemodynamic monitoring, and perioperative management, significant strides can be made in improving the outcomes of LDLT recipients. Further research is necessary to refine these strategies and expand the application of LDLT, especially in challenging cases involving small-for-size grafts.

Clinical Significance of Grade A Small-for-size Syndrome After Living Donor Liver Transplantation Utilizing the New Definition of Diagnostic Criteria: An International Multicenter Study

BACKGROUND

New diagnostic criteria have recently been established to classify small-for-size syndrome (SFSS) after living donor liver transplantation into 3 groups based on severity. This study aimed to evaluate the clinical impact of grade A SFSS and identify the mortality risk.

METHODS

We collected data from 406 patients diagnosed with grade A SFSS after living donor liver transplantation. Grade A SFSS is characterized by total bilirubin >5 mg/dL on postoperative day (POD) 7 or total bilirubin >5 mg/dL or ascites >1 L/d on POD 14. After propensity score matching, 193 patients were categorized into the up-trend group, down-trend group, and ascites group, with 43 patients (22.3%) in the up-trend group (total bilirubin on POD 7 < POD 14), 107 patients (55.4%) in the down-trend group (total bilirubin on POD 7 > POD 14), and 43 patients (22.3%) in the ascites group (only satisfying ascites criteria).

RESULTS

There was no significant difference in survival between patients with grade A SFSS and those without SFSS ( P  = 0.152). The up-trend group showed a higher 90-d mortality rate than the down-trend and ascites groups ( P  = 0.025). The 1-y survival rate differed significantly between the groups (87.6%, 91.9%, and 97.7%, respectively; P  = 0.044). The independent risk factors for survival were up-trend of total bilirubin, recipient age (65 y and older), model for end-stage liver disease score (≥30), and ABO incompatibility. Patients with ≥2 risk factors had worse survival rates than those with none and only 1 risk factor ( P  < 0.001).

CONCLUSIONS

Although the survival rate was comparable between the grade A SFSS and non-SFSS cohorts, the up-trend group showed worse survival. Aggressive interventions should be considered for up-trend patients with risk factors.

Graft inflow modulation in recipients with portal hypertension

The extended application of living donor liver transplantation (LDLT) has revealed the problem of graft size mismatching, potentially leading to the "small-for-size syndrome" (SFSS). SFSS is a rare dysfunction that may affect a partial liver graft, characterized by coagulopathy, cholestasis, ascites, and encephalopathy. A key role in the physiopathology of SFSS is played by portal hypertension (PHT) to which a small allograft is submitted after reperfusion, 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. Thus, SFSS prevention relies not only on increasing graft volume (implementing the use of larger grafts or auxiliary/dual liver transplantation), but also on the control of the increased portal vein pressure (PVP) and portal vein flow (PVF). To this aim, surgical graft inflow modulation techniques (GIM) such as splenic artery ligation (SAL), splenectomy and hemiportocaval shunts, can be considered when an imbalance between the PVP and the hepatic arterial flow (HAF) is acknowledged. However, such strategies have their pros and cons, and a deep knowledge of the indications and complications is needed. Furthermore, pharmacological modulation has also been proposed. This review is aimed to update available literature on the current knowledge and strategies for modulating portal vein flow in LDLT.

Use of Intravoxel Incoherent Motion Diffusion-Weighted Imaging to Assess Mesenchymal Stromal Cells Promoting Liver Regeneration in a Rat Model

RATIONALE AND OBJECTIVES

Mesenchymal stem cells (MSCs) have the potential to promote liver regeneration, but the process is unclear. This study aims to explore the therapeutic effects and dynamic processes of MSCs in liver regeneration through intravoxel incoherent motion (IVIM) imaging.

ANIMAL MODEL

70 adult Sprague-Dawley rats were randomly divided into either the control or MSC group (n = 35/group). All rats received a partial hepatectomy (PH) with the left lateral and middle lobes removed. Each group was divided into seven subgroups: pre-PH and 1, 2, 3, 5, 7, and 14 days post-PH (n = 5 rats/subgroup). Magnetic resonance imaging (MRI) was performed before obtaining pathological specimens at each time point on postoperative days 1, 2, 3, 5, 7, and 14. The MRI parameters for the pure diffusion coefficient (D), pseudodiffusion coefficient (D*), and perfusion fraction (PF) were calculated. Correlation analysis was conducted for the biochemical markers (alanine transaminase [ALT], aspartate transaminase [AST], and total bilirubin [TBIL]), histopathological findings (hepatocyte size and Ki-67 proliferation index), liver volume (LV) and liver regeneration rate (LLR).

RESULTS

Liver D, D* , and PF differed significantly between the control and MSC groups at all time points (all P < 0.05). After PH, the D increased, then decreased, and the D* and PF decreased, then increased in both groups. The hepatocyte Ki-67 proliferation index of the MSC group was lower on day 2 post-PH, but higher on days 3 and 5 post-PH than that of the control group. Starting from day 3 post-PH, both the LV and LLR in the MSC group were greater than those in the control group (all P < 0.05). Hepatocytes were larger in the MSC group than in the control group on days 2 and 7 post-PH. In the MSC group, the D, D* , and PF were correlated with the AST levels, Ki-67 index and hepatocyte size (|r|=0.35-0.71; P < 0.05). In the control group, the D and D* were correlated with ALT levels, AST levels, Ki-67 index, LLR, LV, and hepatocyte size (|r|=0.34-0.95; P < 0.05).

CONCLUSION

Bone marrow MSC therapy can promote hepatocyte hypertrophy and prolong liver proliferation post-PH. IVIM parameters allow non-invasively evaluating the efficacy of MSCs in promoting LR.

"Reduced Size Liver Grafts in Pediatric Liver Transplantation; Technical Considerations"

Liver transplantation (LT) has become a vital treatment option for children with end-stage liver disease. Left lateral segment (LLS) grafts are particularly common in split and living donor LT for pediatric patients. However, challenges arise in small infants receiving LLS grafts, primarily due to graft-size mismatches, resulting in "large-for-size" grafts. To overcome this issue, the practice of further reducing grafts from the LLS to diminish graft thickness has been explored. Currently, the indication for reducing the thickness of LLS grafts includes recipients with a body weight (BW) under 5.0 kg, neonates with acute liver failure, or those with metabolic liver disease. At the National Center for Child Health and Development in Tokyo, Japan, among 131 recipients of reduced-size LLS grafts, a remarkable 15-year graft survival rate of 89.9% has been achieved in small infants. This success indicates that with experience and refinement of the technique, there's a trend towards improved graft survival in recipients with reduced-thickness LLS grafts. This advancement underscores the importance of BW-appropriate methods in graft selection to ensure exceptional outcomes in vulnerable pediatric patients in need of LT. These techniques' ongoing development and refinement are crucial in enhancing the survival rates and overall outcomes for these young patients.

Three Dimensional Bioprinting for Hepatic Tissue Engineering: From In Vitro Models to Clinical Applications

Fabrication of functional organs is the holy grail of tissue engineering and the possibilities of repairing a partial or complete liver to treat chronic liver disorders are discussed in this review. Liver is the largest gland in the human body and plays a responsible role in majority of metabolic function and processes. Chronic liver disease is one of the leading causes of death globally and the current treatment strategy of organ transplantation holds its own demerits. Hence there is a need to develop an in vitro liver model that mimics the native microenvironment. The developed model should be a reliable to understand the pathogenesis, screen drugs and assist to repair and replace the damaged liver. The three-dimensional bioprinting is a promising technology that recreates in vivo alike in vitro model for transplantation, which is the goal of tissue engineers. The technology has great potential due to its precise control and its ability to homogeneously distribute cells on all layers in a complex structure. This review gives an overview of liver tissue engineering with a special focus on 3D bioprinting and bioinks for liver disease modelling and drug screening.

Post-hepatectomy liver failure: A timeline centered review

BACKGROUND

Post-hepatectomy liver failure (PHLF) is a leading cause of postoperative mortality after liver surgery. Due to its significant impact, it is imperative to understand the risk stratification and preventative strategies for PHLF. The main objective of this review is to highlight the role of these strategies in a timeline centered way around curative resection.

DATA SOURCES

This review includes studies on both humans and animals, where they addressed PHLF. A literature search was conducted across the Cochrane Library, Embase, MEDLINE/PubMed, and Web of Knowledge electronic databases for English language studies published between July 1997 and June 2020. Studies presented in other languages were equally considered. The quality of included publications was assessed using Downs and Black's checklist. The results were presented in qualitative summaries owing to the lack of studies qualifying for quantitative analysis.

RESULTS

This systematic review with 245 studies, provides insight into the current prediction, prevention, diagnosis, and management options for PHLF. This review highlighted that liver volume manipulation is the most frequently studied preventive measure against PHLF in clinical practice, with modest improvement in the treatment strategies over the past decade.

CONCLUSIONS

Remnant liver volume manipulation is the most consistent preventive measure against PHLF.

Optimal graft size in pediatric living donor liver transplantation: How are children different from adults?

BACKGROUND

Pediatric liver transplantation is an established treatment for end-stage liver disease in children. However, it is still posing relevant challenges, such as optimizing the graft selection according to the recipient size. Unlike adults, small children tolerate large-for-size grafts and insufficient graft volume might represent an issue in adolescents when graft size is disproportionate.

METHODS

Graft-size matching strategies over time were examined in pediatric liver transplantation. This review traces the measures/principles put in place to prevent large-for-size or small-for-size grafts in small children to adolescents with a literature review and an analysis of the data issued from the National Center for Child Health and Development, Tokyo, Japan.

RESULTS

Reduced left lateral segment (LLS; Couinaud's segment II and III) was widely applicable for small children less than 5 kg with metabolic liver disease or acute liver failure. There was significantly worse graft survival if the actual graft-to-recipient weight ratio (GRWR) was less than 1.5% in the adolescent with LLS graft due to the small-for-size graft. Children, particularly adolescents, may then require larger GRWR than adults to prevent small-for-size syndrome. The suggested ideal graft selections in pediatric LDLT are: reduced LLS, recipient body weight (BW) < 5.0 kg; LLS, 5.0 kg ≤ BW < 25 kg; left lobe (Couinaud's segment II, III, IV with middle hepatic vein), 25 kg ≤ BW < 50 kg; right lobe (Couinaud's segment V, VI, VII, VIII without middle hepatic vein), 50 kg ≤ BW. Children, particularly adolescents, may then require larger GRWR than adults to prevent small-for-size syndrome.

CONCLUSION

Age-appropriate and BW-appropriate strategies of graft selection are crucial to secure an excellent outcome in pediatric living donor liver transplantation.

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.

The Role of Endoplasmic Reticulum Stress Response in Liver Regeneration

Exposure to hepatotoxic chemicals is involved in liver disease-related morbidity and mortality worldwide. The liver responds to damage by triggering compensatory hepatic regeneration. Physical agent or chemical-induced liver damage disrupts hepatocyte proteostasis, including endoplasmic reticulum (ER) homeostasis. Post-liver injury ER experiences a homeostatic imbalance, followed by active ER stress response signaling. Activated ER stress response causes selective upregulation of stress response genes and downregulation of many hepatocyte genes. Acetaminophen overdose, carbon tetrachloride, acute and chronic alcohol exposure, and physical injury activate the ER stress response, but details about the cellular consequences of the ER stress response on liver regeneration remain unclear. The current data indicate that inhibiting the ER stress response after partial hepatectomy-induced liver damage promotes liver regeneration, whereas inhibiting the ER stress response after chemical-induced hepatotoxicity impairs liver regeneration. This review summarizes key findings and emphasizes the knowledge gaps in the role of ER stress in injury and regeneration.

Surgical Models of Liver Regeneration in Pigs: A Practical Review of the Literature for Researchers

The remarkable capacity of regeneration of the liver is well known, although the involved mechanisms are far from being understood. Furthermore, limits concerning the residual functional mass of the liver remain critical in both fields of hepatic resection and transplantation. The aim of the present study was to review the surgical experiments regarding liver regeneration in pigs to promote experimental methodological standardization. The Pubmed, Medline, Scopus, and Cochrane Library databases were searched. Studies evaluating liver regeneration through surgical experiments performed on pigs were included. A total of 139 titles were screened, and 41 articles were included in the study, with 689 pigs in total. A total of 29 studies (71% of all) had a survival design, with an average study duration of 13 days. Overall, 36 studies (88%) considered partial hepatectomy, of which four were an associating liver partition and portal vein ligation for staged hepatectomy (ALPPS). Remnant liver volume ranged from 10% to 60%. Only 2 studies considered a hepatotoxic pre-treatment, while 25 studies evaluated additional liver procedures, such as stem cell application, ischemia/reperfusion injury, portal vein modulation, liver scaffold application, bio-artificial, and pharmacological liver treatment. Only nine authors analysed how cytokines and growth factors changed in response to liver resection. The most used imaging system to evaluate liver volume was CT-scan volumetry, even if performed only by nine authors. The pig represents one of the best animal models for the study of liver regeneration. However, it remains a mostly unexplored field due to the lack of experiments reproducing the chronic pathological aspects of the liver and the heterogeneity of existing studies.

Current evidence on posthepatectomy liver failure: comprehensive review

INTRODUCTION

Despite important advances in many areas of hepatobiliary surgical practice during the past decades, posthepatectomy liver failure (PHLF) still represents an important clinical challenge for the hepatobiliary surgeon. The aim of this review is to present the current body of evidence regarding different aspects of PHLF.

METHODS

A literature review was conducted to identify relevant articles for each topic of PHLF covered in this review. The literature search was performed using Medical Subject Heading terms on PubMed for articles on PHLF in English until May 2022.

RESULTS

Uniform reporting on PHLF is lacking due to the use of various definitions in the literature. There is no consensus on optimal preoperative assessment before major hepatectomy to avoid PHLF, although many try to estimate future liver remnant function. Once PHLF occurs, there is still no effective treatment, except liver transplantation, where the reported experience is limited.

DISCUSSION

Strict adherence to one definition is advised when reporting data on PHLF. The use of the International Study Group of Liver Surgery criteria of PHLF is recommended. There is still no widespread established method for future liver remnant function assessment. Liver transplantation is currently the only effective way to treat severe, intractable PHLF, but for many indications, this treatment is not available in most countries.

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.

Gene expression profile in experimental frozen-thawed ovarian grafts treated with scaffold-base delivery of adipose tissue-derived stem cells

PURPOSE

Gelfoam scaffold is a feasible and safe non-invasive technique for Adipose tissue-derived Stem Cell (ASC)-delivery in the treatment of frozen-thawed ovarian autografts. This study seeks to analyze the genes expression profile of rat frozen-thawed ovarian autografts treated with scaffold-based delivery of adipose tissue-derived stem cells.

METHODS

Eighteen adult Wistar rats were distributed into three groups: Control (frozen-thawed only); Group 1 (G1) and Group 2 (G2) (frozen-thawed ovaries treated with culture medium or ASC, respectively). Both treatments were performed immediately after autologous retroperitoneal transplant with scaffold-based delivery. The ovarian grafts were retrieved 30 days after transplantation. Quantitative gene expression (qPCR) for apoptosis, angiogenesis, and inflammatory cytokines (84 genes in each pathway) were evaluated by RT-PCR. Graft morphology (HE), apoptosis (cleaved-caspase-3), neoangiogenesis (VEGF), and cellular proliferation (Ki-67) were assessed.

RESULTS

In grafts treated with ASC, the apoptosis pathway showed the highest number of genes over-regulated - 49 genes - compared to inflammation cytokines and angiogenesis pathway - 36 and 23 genes respectively, compared to grafts treated with culture medium. Serpinb5 family was highlighted in the angiogenesis pathway and Cxcl6 in the inflammation cytokines pathway. In the apoptosis pathway, the most over-regulated gene was Capsase14. ASC treatment promoted the reduction of cleaved caspase-3 in the theca internal layer and increased cell proliferation by Ki-67 in the granulosa layer without altering VEGF. A mild inflammatory infiltrate was observed in both groups.

CONCLUSION

ASC therapy in rat frozen-thawed ovarian autografts promoted an abundance of genes involved with apoptosis and inflammatory cytokines without compromising the ovary graft morphology and viability for short time. Further studies are necessary to evaluate the repercussion of apoptosis and inflammation on the graft in the long term.

Critical Role of LSEC in Post-Hepatectomy Liver Regeneration and Failure

Liver sinusoids are lined by liver sinusoidal endothelial cells (LSEC), which represent approximately 15 to 20% of the liver cells, but only 3% of the total liver volume. LSEC have unique functions, such as fluid filtration, blood vessel tone modulation, blood clotting, inflammatory cell recruitment, and metabolite and hormone trafficking. Different subtypes of liver endothelial cells are also known to control liver zonation and hepatocyte function. Here, we have reviewed the origin of LSEC, the different subtypes identified in the liver, as well as their renewal during homeostasis. The liver has the exceptional ability to regenerate from small remnants. The past decades have seen increasing awareness in the role of non-parenchymal cells in liver regeneration despite not being the most represented population. While a lot of knowledge has emerged, clarification is needed regarding the role of LSEC in sensing shear stress and on their participation in the inductive phase of regeneration by priming the hepatocytes and delivering mitogenic factors. It is also unclear if bone marrow-derived LSEC participate in the proliferative phase of liver regeneration. Similarly, data are scarce as to LSEC having a role in the termination phase of the regeneration process. Here, we review what is known about the interaction between LSEC and other liver cells during the different phases of liver regeneration. We next explain extended hepatectomy and small liver transplantation, which lead to "small for size syndrome" (SFSS), a lethal liver failure. SFSS is linked to endothelial denudation, necrosis, and lobular disturbance. Using the knowledge learned from partial hepatectomy studies on LSEC, we expose several techniques that are, or could be, used to avoid the "small for size syndrome" after extended hepatectomy or small liver transplantation.

Intraoperative Increase of Portal Venous Pressure is an Immediate Predictor of Posthepatectomy Liver Failure After Major Hepatectomy: A Prospective Study

OBJECTIVES

The aim of this study was to assess intraoperative changes of hepatic macrohemodynamics and their association with ascites and posthepatectomy liver failure (PHLF) after major hepatectomy.

SUMMARY OF BACKGROUND DATA

Large-scale ascites and PHLF remain clinical challenges after major hepatectomy. No study has concomitantly evaluated arterial and venous liver macrohemodynamics in patients undergoing liver resection.

METHODS

Portal venous pressure (PVP), portal venous flow (PVF), and hepatic arterial flow (HAF) were measured intraoperatively pre- and postresection in 67 consecutive patients with major hepatectomy (ie, resection of ≥3 liver segments). A group of 30 patients with minor hepatectomy served as controls. Liver macrohemodynamics and their intraoperative changes (ie, Δ) were analyzed as predictive biomarkers of ascites and PHLF using Fisher exact, t test, or Wilcoxon rank sum test for univariate and logistic regression for multivariate analyses.

RESULTS

Major hepatectomy increased PVP by 26.9% (P = 0.001), markedly decreased HAF by 40.7% (P < 0.001), and slightly decreased PVF by 13.4% (P = 0.011). Minor resections had little effects on hepatic macrohemodynamics. There was no significant association of liver macrohemodynamics with ascites. While middle hepatic vein resection caused higher postresection PVP after right hepatectomy (P = 0.04), the Pringle maneuver was associated with a significant PVF (P = 0.03) and HAF reduction (P = 0.03). Uni- and multivariate analysis revealed an intraoperative PVP increase as an independent predictor of PHLF (P = 0.025).

CONCLUSION

Intraoperative PVP kinetics serve as independent predictive biomarker of PHLF after major hepatectomy. These data highlight the importance to assess intraoperative dynamics rather than the pre- and postresection PVP values.

The beneficial impacts of splanchnic vasoactive agents on hepatic functional recovery in massive hepatectomy porcine model

Background

Excessive portal pressure after massive hepatectomy can cause hepatic sinusoidal injury and have deleterious impacts on hepatic functional recovery, contributing to developing post-hepatectomy liver failure. This study aimed to assess the effects of splanchnic vasoactive agents on hepatic functional recovery and regeneration while clarifying the underlying mechanism, using a 70% hepatectomy porcine model.

Methods

Eighteen pigs undergoing 70% hepatectomy were involved in this study and divided into three groups: control (n=6), terlipressin (n=6), and octreotide (n=6). Terlipressin (0.5 mg) and octreotide (0.2 mg) were administered 3 times a day for each group with the first dose starting just before surgery until the 7th postoperative day, at which time the surviving pigs were sacrificed. During the period, portal pressure, liver weight, biochemical analysis, histological injury score, and molecular markers were evaluated and compared between groups.

Results

The 7-day survival rates in the octreotide, terlipressin, and control groups were 100%, 83.3%, and 66.7%, respectively. The portal pressures decreased in both terlipressin and octreotide groups than the control group at 30 minutes, 1 hour and 6 hours after hepatectomy. The amount of regeneration measured by liver weight to body weight ratio at the time of sacrifice in the terlipressin group was smaller than that in the control group (117% vs. 129%, P=0.03). Serum aspartate aminotransferase (AST) and total bilirubin levels at 1 and 6 hours after hepatectomy and prothrombin time/international normalized ratio (PT/INR) at 6 hours after hepatectomy were significantly improved in the terlipressin and octreotide groups compared to the control group. Serum endothelin-1 (ET-1) was significantly lower in the terlipressin group than that in the control group 6 hours after hepatectomy (P<0.01). The histological injury score in the control group was significantly higher than that in the terlipressin group on the 7th postoperative day (P<0.01).

Conclusions

Splanchnic vasoactive agents, such as terlipressin and octreotide, could effectively decrease portal pressure and attenuate liver injury after massive hepatectomy.

Liver regeneration: biological and pathological mechanisms and implications

The liver is the only solid organ that uses regenerative mechanisms to ensure that the liver-to-bodyweight ratio is always at 100% of what is required for body homeostasis. Other solid organs (such as the lungs, kidneys and pancreas) adjust to tissue loss but do not return to 100% of normal. The current state of knowledge of the regenerative pathways that underlie this 'hepatostat' will be presented in this Review. Liver regeneration from acute injury is always beneficial and has been extensively studied. Experimental models that involve partial hepatectomy or chemical injury have revealed extracellular and intracellular signalling pathways that are used to return the liver to equivalent size and weight to those prior to injury. On the other hand, chronic loss of hepatocytes, which can occur in chronic liver disease of any aetiology, often has adverse consequences, including fibrosis, cirrhosis and liver neoplasia. The regenerative activities of hepatocytes and cholangiocytes are typically characterized by phenotypic fidelity. However, when regeneration of one of the two cell types fails, hepatocytes and cholangiocytes function as facultative stem cells and transdifferentiate into each other to restore normal liver structure. Liver recolonization models have demonstrated that hepatocytes have an unlimited regenerative capacity. However, in normal liver, cell turnover is very slow. All zones of the resting liver lobules have been equally implicated in the maintenance of hepatocyte and cholangiocyte populations in normal liver.

Posthepatectomy liver failure

Liver surgery is one of the most complex surgical interventions with high risk and potential for complications. Posthepatectomy liver failure (PHLF) is a serious complication of liver surgery that occurs in about 10% of patients undergoing major liver surgery. It is the main source of morbidity and mortality. Appropriate surgical techniques and intensive care management are important in preventing PHLF. Early start of the liver support systems is very important for the PHLF patient to recover, survive, or be ready for a liver transplant. Nonbiological and biological liver support systems should be used in PHLF to prepare for treatment or organ transplantation. The definition of the state, underlying pathophysiology and treatment strategies will be reviewed here.

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.

A Novel Method for the Prevention and Treatment of Small-for-Size Syndrome in Liver Transplantation

BACKGROUND

Currently there is no consensus on the optimal management of small-for-size syndrome following liver transplantation. Here we describe a technique to alleviate portal hypertension and improve the hepatocyte reperfusion in small-for-size liver transplantation in a Lewis rat model.

METHODS

The rats underwent trans-portal vein intra-hepatic portosystemic shunt using a self-developed porous conical tube (TPIPSS: Fig. 1) on small-for-size liver transplants (SFS) with right lobe graft. The treatment effect was evaluated by comparing hemodynamic parameters, morphological changes, serum parameters, ET-1 and eNOS expression, hepatocyte proliferation and apoptosis, CYP3A2 levels, postoperative complications, and survival between the two groups with SFS liver transplants.

RESULTS

Porous conical prosthesis prolonged the filling time of small-for-size grafts. Moreover, grafts with TPIPSS showed a lower portal vein pressure, improved microcirculatory flow, alleviated histological changes, decreased ET-1 and increased eNOS expressions, and significantly less damage to liver function comparing to grafts without TPIPSS. Mean survival and overall 30-day survival were significantly higher in the TPIPSS group.

CONCLUSIONS

These results demonstrate that porous conical tube as trans-portal vein intra-hepatic portosystemic shunt device is an effective way to alleviate portal vein hypertension and improve hepatocyte reperfusion after small-for-size liver transplantation.

Small-for-size syndrome in liver transplantation: Definition, pathophysiology and management

BACKGROUND

Since the first success in an adult patient, living donor liver transplantation (LDLT) has become an universally used procedure. Small-for-size syndrome (SFSS) is a well-known complication after partial LT, especially in cases of adult-to-adult LDLT. The definition of SFSS slightly varies among transplant physicians. The use of a partial liver graft has risks of SFSS development. Persistent portal vein (PV) hypertension and PV hyper-perfusion after LT were identified as the main factors. Hence, various approaches were explored to modulate PV flow and decrease PV pressure in order to alleviate this syndrome. Herein, the definition, clinical symptoms, pathophysiology, basic research, as well as preventive and treatment strategies for SFSS are reviewed based on an extensive review of the literature and on our own experiences.

DATA SOURCES

The articles were collected through PubMed using search terms "liver transplantation", "living donor liver transplantation", "living liver donation", "partial graft", "small-for-size graft", "small-for-size syndrome", "graft volume", "remnant liver", "standard liver volume", "graft to recipient body weight ratio", "sarcopenia", "porcine", "swine", and "rat". English publications published before March 31, 2020 were included in this review.

RESULTS

Many transplant surgeons performed PV flow modulation, including portocaval shunt, splenic artery ligation and splenectomy. With these techniques, patient outcome has been improved even when using a "small" graft. Other factors, such as preoperative recipients' nutritional and skeletal muscle status, graft congestion, and donor factors, were also identified as risk factors which all have been addressed using various strategies.

CONCLUSIONS

The surgical approach controlling PV flow and pressure could help to prevent SFSS especially in severely ill recipients. In the absence of efficacious medications to resolve SFSS, conservative treatments, including aggressive fluid balance correction for massive ascites, anti-microbiological therapy to prevent or control sepsis and intensive nutritional therapy, are all required if SFSS could not be prevented.

"Small-for-Flow" Syndrome: Concept Evolution

BACKGROUND

The "Small-for-Size" syndrome is defined as a liver failure after a liver transplant with a reduced graft or after a major hepatectomy. The later coined "Small-for-Flow" syndrome describes the same situation in liver resections but based on hemodynamic intraoperative parameters (portal pressure > 20 mmHg and/or portal flow > 250 ml/min/100 g). This focuses on the damage caused by the portal hyperafflux related to the volume of the remnant.

METHODS

Relevant studies were reviewed using Medline, PubMed, and Springer databases.

RESULTS

Portal hypertension after partial hepatectomies also leads to a higher morbidity and mortality. There are plenty of experimental studies focusing on flow rather than size. Some of them also perform different techniques to modulate the portal inflow. The deleterious effect of high posthepatectomy portal venous pressure is known, and that is why the idea of portal flow modulation during major hepatectomies in humans is increasing in everyday clinical practice.

CONCLUSIONS

Considering the extensive knowledge obtained with the experimental models and good results in clinical studies that analyze the "Small-for-Flow" syndrome, we believe that measuring portal flow and portal pressure during major liver resections should be performed routinely in extended liver resections. Applying these techniques, the knowledge of hepatic hemodynamics would be improved in order to advance against posthepatectomy liver failure.

Effects of Trendelenburg position and increased airway pressure on hepatic regional blood flow of normal and resected liver

High portal venous blood flow (Qpv) may contribute to posthepatectomy liver failure. Both Trendelenburg position (TP) and elevated airway pressure (Paw) increase backpressure to venous return and may thereby reduce Qpv. The aim of this study was to evaluate the effects of TP and increased Paw on hepatosplanchnic hemodynamics before and after major liver resection. Arterial and venous blood pressures, Qpv, extrasplanchnic inferior vena cava (Qivc), superior mesenteric (Qsma), hepatic (Qha), and carotid artery blood flows (Qca) were measured in 14 anesthetized and mechanically ventilated pigs in supine and 30° TP during end-expiratory hold at 5 cmH2O positive end-expiratory pressure (PEEP) and during inspiratory hold with Paw of 15, 20, 25, and 30 cmH2O. After major liver resection, the interventions were repeated in seven randomly selected animals. At baseline, TP increased right atrial pressure (Pra) and Qpv but not Qivc or Qsma. With increased Paw in the supine position, Pra increased and all regional blood flows decreased. TP during increasing Paw attenuated the decrease in Qpv, Qsma, and Qivc but not in Qha or Qca. After liver resection, the effects of TP during increasing Paw remained, albeit at higher portal vein pressures. However, TP alone did not increase IVC venous return. Increasing Paw in supine position reduces Qpv and all other regional flows, while the reduction in Qpv is attenuated in TP, suggesting partly preserved liver waterfall or decreased intrahepatic resistance. Liver resection, despite resulting in major intrahepatic blood flow changes, does not fundamentally influence the interaction of increasing Paw and TP on regional perfusion.

NEW & NOTEWORTHY In Trendelenburg position (TP), liver blood flow is the only contributor to increased venous return measured in the inferior vena cava (IVC), which attenuates the decreased IVC venous return induced by increasing airway pressure. After liver resection, TP similarly attenuated effects of increasing airway pressure.

Role of interleukin 6 in liver cell regeneration after hemi-hepatectomy, correlation with liver enzymes and flow cytometric study

Aim of the study

Liver regeneration after hemi-hepatectomy may be affected by several growth factors and cytokines. The aim is to evaluate the importance of interleukin 6 (IL-6) in the induction of liver cell regeneration and find correlations with other parameters such as liver enzymes, and DNA analysis by flow cytometric studies.

Material and methods

80 adult male Sprague-Dawley rats were obtained and divided into two equal groups (n = 40 rats) to undergo 70% partial hepatectomy: group 1 - untreated (control) group; 40 rats not treated; and group 2 - treated group, 40 rats treated with IL-6 35 μg/100 gm body weight according to a lethality study for a period of 4 days, then hepatic resection was carried out according to the steps of Higgins and Anderson. Assessment of liver enzymes and bilirubin level was done. Flow cytometric study was done using a flow cytometer (FACSCalibur; Becton Dickinson) and DNA content was estimated with CellQuest software (Becton Dickinson).

Results

The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were significantly higher in the untreated group of rats with liver resection. A higher value of bilirubin was observed in the treated group. Rat weight at sacrification was significantly lower in the group of rats treated with IL-6 than those without treatment, p < 0.001. Liver weight at sacrification was significantly higher in the group of rats treated with IL-6 (p < 0.001). The percentage of apoptotic cells with hypodiploid DNA content was determined from DNA histograms. Untreated rat resected liver showed a peak pattern that represented liver damage with high damage of 73.4%.

Conclusions

Interleukin 6 is of value in induction of liver cell regeneration after seventy percent hemi-hepatectomy as evident by increased liver cell mass, liver enzymes and flow cytometric analysis.

Clinical translation of liver regeneration therapies: A conceptual road map

The increasing incidence of severe liver diseases worldwide has resulted in a high demand for curative liver transplantation. Unfortunately, the need for transplants by far eclipses the availability of suitable grafts leaving many waitlisted patients to face liver failure and often death. Routine use of smaller grafts (for example left lobes, split livers) from living or deceased donors could increase the number of life-saving transplants but is often limited by the graft versus recipient weight ratio defining the safety margins that minimize the risk of small for size syndrome (SFSS). SFSS is a severe complication characterized by failure of a small liver graft to regenerate and occurs when a donor graft is insufficient to meet the metabolic demand of the recipient, leading to liver failure as a result of insufficient liver mass. SFSS is not limited to transplantation but can also occur in the setting of hepatic surgical resections, where life-saving large resections of tumors may be limited by concerns of post-surgical liver failure. There are, as yet no available pro-regenerative therapies to enable liver regrowth and thus prevent SFSS. However, there is optimism around targeting factors and pathways that have been identified as regulators of liver regeneration to induce regrowth in vivo and ex vivo for clinical use. In this commentary, we propose a roadmap for developing such pro-regenerative therapy and for bringing it into the clinic. We summarize the clinical indications, preclinical models, pro-regenerative pathways and safety considerations necessary for developing such a drug.

Impact of cirrhosis in patients undergoing laparoscopic liver resection in a nationwide multicentre survey

BACKGROUND

The aim was to analyse the impact of cirrhosis on short-term outcomes after laparoscopic liver resection (LLR) in a multicentre national cohort study.

METHODS

This retrospective study included all patients undergoing LLR in 27 centres between 2000 and 2017. Cirrhosis was defined as F4 fibrosis on pathological examination. Short-term outcomes of patients with and without liver cirrhosis were compared after propensity score matching by centre volume, demographic and tumour characteristics, and extent of resection.

RESULTS

Among 3150 patients included, LLR was performed in 774 patients with (24·6 per cent) and 2376 (75·4 per cent) without cirrhosis. Severe complication and mortality rates in patients with cirrhosis were 10·6 and 2·6 per cent respectively. Posthepatectomy liver failure (PHLF) developed in 3·6 per cent of patients with cirrhosis and was the major cause of death (11 of 20 patients). After matching, patients with cirrhosis tended to have higher rates of severe complications (odds ratio (OR) 1·74, 95 per cent c.i. 0·92 to 3·41; P = 0·096) and PHLF (OR 7·13, 0·91 to 323·10; P = 0·068) than those without cirrhosis. They also had a higher risk of death (OR 5·13, 1·08 to 48·61; P = 0·039). Rates of cardiorespiratory complications (P = 0·338), bile leakage (P = 0·286) and reoperation (P = 0·352) were similar in the two groups. Patients with cirrhosis had a longer hospital stay than those without (11 versus 8 days; P = 0·018). Centre expertise was an independent protective factor against PHLF in patients with cirrhosis (OR 0·33, 0·14 to 0·76; P = 0·010).

CONCLUSION

Underlying cirrhosis remains an independent risk factor for impaired outcomes in patients undergoing LLR, even in expert centres.

Liver Transplantation

The field of liver transplantation has changed since the MELD scoring system became the most widely used donor allocation tool. Due to the MELD-based allocation system, sicker patients with higher MELD scores are being transplanted. Persistent organ donor shortages remain a challenging issue, and as a result, the wait-list mortality is a persistent problem for most of the regions. This chapter focuses on deceased donor and live donor liver transplantation in patients with complications of portal hypertension. Special attention will also be placed on donor-recipient matching, perioperative management of transplant patients, and the impact of hepatic hemodynamics on transplantation.

Comprehensive Characterization of a Porcine Model of The "Small-for-Flow" Syndrome

INTRODUCTION

The term "Small-for-Flow" reflects the pathogenetic relevance of hepatic hemodynamics for the "Small-For-Size" syndrome and posthepatectomy liver failure. We aimed to characterize a large-animal model for studying the "Small-for-Flow" syndrome.

METHODS

We performed subtotal (90%) hepatectomies in 10 female MiniPigs using a simplified transection technique with a tourniquet. Blood tests, hepatic and systemic hemodynamics, and hepatic function and histology were assessed before (Bas), 15 min (t-15 min) and 24 h (t-24 h) after the operation. Some pigs underwent computed tomography (CT) scans for hepatic volumetry (n = 4) and intracranial pressure (ICP) monitoring (n = 3). Postoperative care was performed in an intensive care unit environment.

RESULTS

All hepatectomies were successfully performed, and hepatic volumetry confirmed liver remnant volumes of 9.2% [6.2-11.2]. The hepatectomy resulted in characteristic hepatic hemodynamic alterations, including portal hyperperfusion, relative decrease of hepatic arterial blood flow, and increased portal pressure (PP) and portal-systemic pressure gradient. The model reproduced major diagnostic features including the development of cholestasis, coagulopathy, encephalopathy with increased ICP, ascites, and renal failure, hyperdynamic circulation, and hyperlactatemia. Two animals (20%) died before t-24 h. Histological liver damage was observed at t-15 min and at t-24 h. The degree of histological damage at t-24 h correlated with intraoperative PP (r = 0.689, p = 0.028), hepatic arterial blood flow (r = 0.655, p = 0.040), and hepatic arterial pulsatility index (r = 0.724, p = 0.066). All animals with intraoperative PP > 20 mmHg presented liver damage at t-24 h.

CONCLUSION

The present 90% hepatectomy porcine experimental model is a feasible and reproducible model for investigating the "Small-for-Flow" syndrome.

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.

Portal Inflow Modulation by Somatostatin After Major Liver Resection: A Pilot Study

: Major hepatectomy (MH) can lead to an increasing portal vein pressure (PVP) and to lesions of the hepatic parenchyma. Several reports have assessed the deleterious effect of a high posthepatectomy PVP on the postoperative course of MH. Thus, several surgical modalities of portal inflow modulation (PIM) have been described. As for pharmacological modalities, experimental studies showed a potential efficiency of Somatostatin to reduce PVP and flow. To our knowledge, no previous clinical reports of PIM using somatostatin are available. Herein, we report the results of PIM using somatostatin in 10 patients who underwent MH with post-hepatectomy PVP > 20 mmHg. Our results suggest Somatostatin could be considered as an efficient reversible PIM when PVP decrease is above 2.5 mmHg.

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.

Somatostatin and the "Small-For-Size" Liver

"Small-for-size" livers arising in the context of liver resection and transplantation are vulnerable to the effects of increased portal flow in the immediate postoperative period. Increased portal flow is an essential stimulus for liver regeneration. If the rise in flow and stimulus for regeneration are excessive; however, liver failure and patient death may result. Somatostatin is an endogenous peptide hormone that may be administered exogenously to not only reduce portal blood flow but also offer direct protection to different cells in the liver. In this review article, we describe key changes that transpire in the liver following a relative size reduction occurring in the context of resection and transplantation and the largely beneficial effects that peri-operative somatostatin therapy may help achieve in this setting.

The Impact of a Nitric Oxide Synthase Inhibitor (L-NAME) on Ischemia⁻Reperfusion Injury of Cholestatic Livers by Pringle Maneuver and Liver Resection after Bile Duct Ligation in Rats

The Pringle maneuver (PM) has been widely used to control blood loss during liver resection. However, hepatic inflow occlusion can also result in hepatic ischemia–reperfusion injury (IRI), especially in patients with a cholestatic, fibrotic, or cirrhotic liver. Here we investigate a nitric oxide synthase (NOS) inhibitor N-Nitroarginine methyl ester (L-NAME) on IRI after the PM and partial hepatectomy of cholestatic livers induced by bile duct ligation (BDL) in rats. Control group (non-BDL/no treatment), BDL + T group (BDL/L-NAME treatment) and BDL group (BDL/no treatment) were analyzed. Cholestasis was induced by BDL in the L-NAME and BDL group and a 50% partial hepatectomy with PM was performed. L-NAME was injected before PM in the BDL + T group. Hepatocellular damage, portal venous flow, microcirculation, endothelial lining, and eNOS, iNOS, interleukin (IL)-6, and transforming growth factor-β (TGF-β) were evaluated. Microcirculation of the liver in the BDL + T group tended to be higher. Liver damage and apoptotic index were significantly lower and Ki-67 labeling index was higher in the BDL + T group while iNOS and TGF-β expression was decreased. This was corroborated by a better preserved endothelial lining. L-NAME attenuated IRI following PM and improved proliferation/regeneration of cholestatic livers. These positive effects were considered as the result of improved hepatic microcirculation, prevention of iNOS formation, and TGF-β mRNA upregulation.

The effects of terlipressin and direct portacaval shunting on liver hemodynamics following 80% hepatectomy in the pig

Liver failure is the major cause of death following liver resection. Post-resection portal venous pressure (PVP) predicts liver failure, is implicated in its pathogenesis, and when PVP is reduced, rates of liver dysfunction decrease. The aim of the present study was to characterize the hemodynamic, biochemical, and histological changes induced by 80% hepatectomy in non-cirrhotic pigs and determine if terlipressin or direct portacaval shunting can modulate these effects. Pigs were randomized (n=8/group) to undergo 80% hepatectomy alone (control); terlipressin (2 mg bolus + 0.5-1 mg/h) + 80% hepatectomy; or portacaval shunt (PCS) + 80% hepatectomy, and were maintained under terminal anesthesia for 8 h. The primary outcome was changed in PVP. Secondary outcomes included portal venous flow (PVF), hepatic arterial flow (HAF), and biochemical and histological markers of liver injury. Hepatectomy increased PVP (9.3 ± 0.4 mmHg pre-hepatectomy compared with 13.0 ± 0.8 mmHg post-hepatectomy, P<0.0001) and PVF/g liver (1.2 ± 0.2 compared with 6.0 ± 0.6 ml/min/g, P<0.0001) and decreased HAF (70.8 ± 5.0 compared with 41.8 ± 5.7 ml/min, P=0.002). Terlipressin and PCS reduced PVP (terlipressin = 10.4 ± 0.8 mmHg, P=0.046 and PCS = 8.3 ± 1.2 mmHg, P=0.025) and PVF (control = 869.0 ± 36.1 ml/min compared with terlipressin = 565.6 ± 25.7 ml/min, P<0.0001 and PCS = 488.4 ± 106.4 ml/min, P=0.002) compared with control. Treatment with terlipressin increased HAF (73.2 ± 11.3 ml/min) compared with control (40.3 ± 6.3 ml/min, P=0.026). The results of the present study suggest that terlipressin and PCS may have a role in the prevention and treatment of post-resection liver failure.

Transit time ultrasound perivascular flow probe technology is superior to MR imaging on hepatic blood flow measurement in a porcine model

BACKGROUND

The hepatic hemodynamics is an essential parameter in surgical planning as well as in various disease processes. The transit time ultrasound (TTUS) perivascular flow probe technology is widely used in clinical practice to evaluate the hepatic inflow, yet invasive. The phase-contrast-MRI (PC-MRI) is not invasive and potentially applicable in assessing the hepatic blood flow. In the present study, we compared the hepatic inflow rates using the PC-MRI and the TTUS probe, and evaluated their predictive value of post-hepatectomy adverse events.

METHODS

Eighteen large white pigs were anaesthetized for PC-MRI and approximately 75% hepatic resection was performed under a unified protocol. The blood flow was measured in the hepatic artery (Qha), the portal vein (Qpv), and the aorta above the celiac trunk (Qca) using PC-MRI, and was compared to the TTUS probe. The Bland-Altman method was conducted and a partial least squares regression (PLS) model was implemented.

RESULTS

The mean Qpv measured in PC-MRI was 0.55 ± 0.12 L/min, and in the TTUS probe was 0.74 ± 0.17 L/min. Qca was 1.40 ± 0.47 L/min in the PC-MRI and 2.00 ± 0.60 L/min in the TTUS probe. Qha was 0.17 ± 0.10 L/min in the PC-MRI, and 0.13 ± 0.06 L/min in the TTUS probe. The Bland-Altman method revealed that the estimated bias of Qca in the PC-MRI was 32% (95% CI: -49% to 15%); Qha 17% (95% CI: -15% to 51%); and Qpv 40% (95% CI: -62% to 18%). The TTUS probe had a higher weight in predicting adverse outcomes after 75% resection compared to the PC-MRI (β= 0.35 and 0.43 vs β = 0.22 and 0.07, for tissue changes and premature death, respectively).

CONCLUSIONS

There is a tendency of the PC-MRI to underestimate the flow measured by the TTUS probes. The TTUS probe measures are more predictive of relevant post-hepatectomy outcomes.

Cell-free therapy with the secretome of adipose tissue-derived stem cells in rats' frozen-thawed ovarian grafts

The use of secretome may be a new strand of cell therapy, which is equal to or even superior to the injection of live cells, called cell-free therapy. In ovarian transplantation, this approach may be a therapeutic possibility for the ovarian graft in hypoxia. We designed the present study to evaluate whether the cell-free therapy with the secretome of adipose tissue-derived stem cells (ASCs) in rat frozen-thawed ovarian grafts could protect a graft against ischemic injury. A single dose of rat ASCs secretome or vehicle was injected into the bilateral frozen-thawed ovaries of 18 adult female rats immediately after an autologous transplant. Nine animals were used to control the cryopreservation protocol and were evaluated before and after the cryopreservation process. Daily vaginal smears were performed for estrous cycle evaluation until euthanasia on postoperative day 30. Follicle viability by trypan blue, graft morphology by HE, and apoptosis by TUNEL and cleaved-caspase-3 were assessed. No differences were found with respect to estrous cycle resumption and follicle viability (p > 0.05). However, compared with the vehicle-treated grafts, the morphology of the secretome-treated grafts was impaired, showing reduced follicular population and increased apoptosis (p < 0.05). ASC secretome impaired the rat frozen-thawed ovarian graft from ischemic injury. However, more studies are needed to evaluate the factors involved and the possibility of applying the secretome in scaffolds to optimize its use.

Graft Dysfunction and Management in Liver Transplantation

Graft dysfunction of the liver allograft manifests across a spectrum in both timing posttransplantation and clinical presentation. This can range from mild transient abnormalities of liver tests to acute liver failure potentially leading to graft failure. The causes of graft dysfunction can be divided into those resulting in early and late graft dysfunction. Although nonspecific, liver biochemistry abnormalities are still the mainstay investigation used in monitoring for dysfunction. This article provides a summary of the main causes and management strategies for liver graft dysfunction in the early through late posttransplant stages.

Vascular tumours of the liver: a particular story

Vascular tumours of the liver represent an underrated chapter of medical and surgical hepatology. These tumours cover a wide spectrum ranging from the frequent and most benign hepatic haemangioma (HH), via the rare and intermediately aggressive hepatic epithelioid haemangioendothelioma (HEHE) to the rare and most malignant hepatic haemangiosarcoma (HHS). In contrast to the treatment algorithms for hepatocellular and cholangiocellular cancer, the diagnostic and therapeutic approaches to HEHE and HHS are not well developed. The related uncertainty is explained by their rare occurrence and their protean clinical, morphological (imaging) and histopathological presentation and behaviour. This article gives an update about these particular tumours based on the analysis of the recent literature and of the studies on vascular tumours published by the European Liver Intestine Transplantation Association (ELITA)-European Liver Transplant Registry (ELTR). It focuses also on the place of liver transplantation (LT) in the respective therapeutic algorithms. The differential diagnosis between these vascular and other tumour types may be very difficult. Correct diagnosis is of utmost importance and is based on a high index of clinical suspicion and on the integration of clinical, radiological, histological [including immunohistochemistry (IHC) and molecular biology findings]. Surgery, be it partial or total hepatectomy (LT), should be proposed whenever possible, because it is the therapeutic mainstay. In HEHE, LT provides excellent results, with long-term disease-free survivals (DFS) reaching 75%. Good results can be obtained even in case of (frequent) extrahepatic spread. Based on the extensive ELITA-ELTR study a HEHE-LT prognostic score has been proposed in order to estimate the risk of recurrence after LT. In contrast, results of surgery and LT are extremely poor for HHS, for the almost invariably rapid recurrence (within 6 months) and related death within 2 years. LT remains a contraindication for HHS. Due to the still important recurrence rate after surgical resection (25% in HEHE and almost 100% in HHS), there is an urgent need to develop pharmacological treatments targeting angiogenic and non-VEGF angiogenic pathways. To date, some prospective pilot studies and case reports have shown some short-term stabilisation of the disease in small groups of patients. In order to make progress, combination of surgery, anti-angiogenic and immunotherapy seems worthwhile. To complete the panel of vascular liver tumours, infantile haemangioendothelioma, haemangiopericytoma, nodular regenerative hyperplasia (NRH) and hepatic small vessel neoplasms (HSVN) are also discussed.

The role of imaging in prediction of post-hepatectomy liver failure

Post-hepatectomy liver failure (PHLF) is not only a leading cause of mortality but also a leading cause of life-threatening complications in patients undergoing liver resection. The ability to accurately detect the emergence of PHLF represents a crucially important step. Currently, PHLF can be predicted by a comprehensive evaluation of biological, clinical, and anatomical parameters. With the development of new technologies, imaging methods including elastography, diffusion-weighted magnetic resonance imaging, and gadolinium ethoxybenzyl diethylenetriaminepentaacetic acid-enhanced MRI play a more significant role in the pre-operative prediction and assessment of PHLF. In this review, we summarize the mainstream studies, with the aim of evaluating the role of imaging and improving the clinical value of existing scoring systems for predicting PHLF.

Modulating Portal Hemodynamics With Vascular Ring Allows Efficient Regeneration After Partial Hepatectomy in a Porcine Model

OBJECTIVE

To investigate safety and efficacy of temporary portal hemodynamics modulation with a novel percutaneously adjustable vascular ring (MID-AVR) onto a porcine model of 75% hepatectomy.

BACKGROUND

Postoperative liver failure is a leading cause of mortality after major hepatectomy. Portal flow modulation is an increasingly accepted concept to prevent postoperative liver failure. Nonetheless, the current strategies have shortcomings.

METHODS

Resection was performed under hemodynamic monitoring in 17 large, white pigs allocated into 2 groups. Eight pigs had ring around the portal vein for 3 days with the aim of reducing changes in hemodynamics due to hepatectomy. Analysis of hemodynamics, laboratory, and histopathological parameters was performed.

RESULTS

Percutaneous inflation, deflation, and removal of the MID-AVR were safe. Two (25%) pigs in the MID-AVR group and 4 (45%) controls died before day 3 (P = NS). A moderate increase of portal flow rate per liver mass after resection was associated with better survival (P = 0.017). The portocaval pressure gradient was lower after hepatectomy in the MID-AVR group (P = 0.001). Postoperative serum bilirubin levels were lower in the MID-AVR group (P = 0.007 at day 5). In the MID-AVR group, the Ki67 index was significantly higher on day 3 (P = 0.043) and the architectural derangement was lower (P < 0.05). Morphometric quantification of the bile canaliculi revealed a significantly lower number of intersection branches (P < 0.05) and intersection nodes (P < 0.001) on day 7 compared with the preoperative specimen, in the control group. These differences were not found in the ring group.

CONCLUSIONS

MID-AVR is safe for portal hemodynamics modulation. It might improve liver regeneration by protecting liver microarchitecture.