Minimum graft volume for successful adult-to-adult living donor liver transplantation for fulminant hepatic failure

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.

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.

Minimally invasive donor hepatectomy, systemic review

Liver transplantation is a life-saving therapy for patients with end-stage liver disease. Living donation is a critical source of organs throughout the world. Reducing donor morbidity and mortality is of utmost importance while maintaining access to liver transplantation for recipients. While laparoscopy was more rapidly utilized in donor nephrectomy, laparoscopy has been slower to develop for living donor hepatectomies due to the concerns about hemostasis, safety of the donor and quality of the graft. Pure minimal invasive approach has become a standard of care for left lateral sectionectomy (LLS) for pediatric recipients. In the past few years, a number of centers with significant laparoscopic and living donor experience have reported fully minimally invasive approach to hemi-hepatectomies. In this manuscript we discuss the experiences, lessons learned and path forward for laparoscopic and minimal invasive surgery(MIS) in donor hepatectomies (DH).

Reproducibility and reliability of computed tomography volumetry in estimation of the right-lobe graft weight in adult-to-adult living donor liver transplantation: Cantlie's line vs portal vein territorialization

BACKGROUND/PURPOSE

In living-donor liver transplantation (LDLT), liver volume assessment is a mandatory step in determining donor appropriateness. This study aimed to compare reliability and reproducibility between two major methods to define virtual hepatectomy plane, based on Cantlie's line (CTV-Cantlie) and portal vein territorialization (CTV-PVT) for right-lobe graft weight estimation in LDLT.

METHODS

A total of 188 donors who underwent preoperative CT scans were included. The liver was divided into right and left lobes using CTV-Cantlie and CTV-PTV measurements by two readers. Intraclass correlation coefficient (ICC) was used to determine interreader variability of hepatic weight measured using each CTV method. Intraoperative graft weight (IOW) was used as reference standard of right-lobe graft weight. Pearson correlation test was performed to determine correlation coefficients between presumed graft weight by each CTV method and IOW.

RESULTS

Intraclass correlation coefficients for total liver weight were roughly equivalent between the two CTV methods (CTV-Cantlie: 0.965 [95% CI, 0.954-0.974], CTV-PVT: 0.977 [0.970-0.983]). However, ICCs of right-and left-lobe weights between two readers were higher with CTV-PVT (0.997 and 0.850) than with CTV-Cantlie (0.829 and 0.668). The IOW was 716.0 ± 162.0 g. Correlation coefficients between presumed graft weight by CTV-Cantlie or CTV-PVT and IOW were 0.722 and 0.807, respectively (both P < .001).

CONCLUSIONS

For estimation of the right-lobe graft weight in LDLT, CTV-PVT may provide higher reliability and reproducibility than CTV-Cantlie.

The Risk of Going Small: Lowering GRWR and Overcoming Small-For-Size Syndrome in Adult Living Donor Liver Transplantation

OBJECTIVE

The aim of this study was to determine the outcomes of living donor liver transplantation (LDLT) according to various graft-to-recipient weight ratio (GRWR).

BACKGROUND

The standard GRWR in LDLT is >0.8%. Our center accepted predicted GRWR ≥0.6% in selected patients.

METHODS

Data from patients who underwent LDLT from 2001 to 2017 were included. Patients were stratified according to actual GRWR (Group 1:GRWR ≤0.6%; Group 2: 0.6%<GRWR≤ 0.8%; Group 3:GRWR >0.8%).

RESULTS

There were 545 LDLT (group 1 = 39; group 2 = 159; group 3 = 347) performed. Pretransplant predicted GRWR showed good correlation to actual GRWR (R = 0.834) and these figures differed within a ± 10%margin (P = 0.034) using an equivalence test. There were more left lobe grafts in group 1 (33.3%) than group 2 (10.7%) and 3 (2.9%). Median donor age was <35 years and steatosis >10% was rare.There was no difference in postoperative complication, vascular and biliary complication rate between groups. Over one-fifth (20.5%) of group 1 patients required portal flow modulation (PFM) and was higher than group 2 (3.1%) and group 3 (4%) (P = 0.001). Twenty-six patients developed small-for-size syndrome (SFSS): 5 of 39 (12.8%) in group 1 and 21 of 159 (13.2%) in group 2 and none in group 3 (P < 0.001). There were 2 hospital mortalities; otherwise, the remaining patients [24/26 (92.3%)] survive with a functional liver graft. The 5-year graft survival rates were 85.4% versus 87.8% versus 84.7% for group 1, 2, and 3, respectively (P = 0.718). GRWR did not predict worse survivals in multivariable analysis.

CONCLUSIONS

Graft size in LDLT can be lowered to 0.6% after careful recipient selection, with low incidence of SFSS and excellent outcomes. Accurate graft weight prediction, donor-recipient matching, meticulous surgical techniques, appropriate use of PFM, and vigilant perioperative care is important to the success of such approach.

Conceptual changes in small-for-size graft and small-for-size syndrome in living donor liver transplantation

Early series in living donor liver transplantation (LDLT) in adults demonstrated a lower safe limit of graft volume standard liver volume ratio 25%–45%. A subsequent worldwide large LDLT series proposed a 0.8 graft recipient weight ratio (GRWR) to define small-for-size graft (SFSG) in adult LDLT. Thereafter, researchers identified innate and inevitable factors including changes in liver volume during imaging studies and graft shrinkage due to perfusion solution. Although the definition of small-for-size syndrome (SFSS) advocated in the 2000s was mainly based on prolonged cholestasis and ascites output, the term SFSS was inadequate to describe clinical manifestations possibly caused by multiple factors. Thus, the term “early allograft dysfunction (EAD),” characterized by total bilirubin >10 mg/dL or coagulopathy with international normalized ratio >1.6 on day 7, has become prevalent to describe graft dysfunction including SFSS after LDLT. Although various efforts have been made to overcome EAD in LDLT, graft selection to maintain an expected GRWR >0.8 and full venous drainage, as well as inflow modulation using splenic artery ligation, have become standard in recent LDLT.

Key roles of hepatologists in successful liver transplantation

Liver transplantation (LT) has been carried out for acute liver failure, end-stage liver disease, and congenital metabolic disease in more than 7000 cases in Japan. Liver transplantation has been established as a treatment option, and survival rates have improved. In 2016, a new registration/allocation policy and a new scoring system for deceased donor LT were established. The management of perioperative patients and preoperative therapy for liver failure, nutrition, and preventing infection were upgraded. Moreover, methods for preventing disease recurrence, and treating hepatitis C and B have been developed and are particularly crucial for good outcomes in LT. Treatment of the complications of obesity, lifestyle-related diseases, and malignancy is also required post-LT. Managing patients after LT contributes to better survival and quality of life. The role of hepatologists is becoming broader and more important.

Resection for Klatskin tumors: technical complexities and results

Klatskin's tumors, actually-redefined as perihilar cholangiocarcinoma (phCCA) do represent 50-70% of all CCAs and develop in a context of chronic inflammation and cholestasis of bile ducts. Surgical resection provides the only chance of cure for this disease but is technically challenging because of the complex, intimate and variable relationship between biliary and vascular structures at this location. Five years survival rates range between 25-45% (median 27-58 months) in case of R0 resection and 0-23% (median 12-21 months) in case of R1 resection respectively. It should be noted that the major costs of high radicality are represented by relative high morbidity and mortality rates (i.e., 20-66% and 0-9% respectively). Considering the fact that radical resection may represent the only curative treatment of phCCA, we focused our review on surgical planning and techniques that may improve resectability rates and outcomes for locally advanced phCCA. The surgical treatment of phCCA can be successful when following aspects have been fulfilled: (I) accurate preoperative diagnostic aimed to identify the tumor in all its details (localization and extension) and to study all the risk factors influencing a posthepatectomy liver failure (PHLF): i.e., liver volume, liver function, liver quality, haemodynamics and patient characteristics; (II) High end surgical skills taking in consideration the local extension of the tumor and the vascular invasion which usually require an extended hepatic resection and often a vascular resection; (III) adequate postoperative management aimed to avoid major complications (i.e., PHLF and biliary complications). These are technically challenging operations and must be performed in a high volume centres by hepato-biliary-pancreas (HBP)-surgeons with experience in microsurgical vascular techniques.

CT evaluation of living liver donor: Can 100-kVp plus iterative reconstruction protocol provide accurate liver volume and vascular anatomy for liver transplantation with reduced radiation and contrast dose?

We evaluated whether donor computed tomography (CT) with a combined technique of lower tube voltage and iterative reconstruction (IR) can provide sufficient preoperative information for liver transplantation.We retrospectively reviewed CT of 113 liver donor candidates. Dynamic contrast-enhanced CT of the liver was performed on the following protocol: protocol A (n = 70), 120-kVp with filtered back projection (FBP); protocol B (n = 43), 100-kVp with IR. To equalize the background covariates, one-to-one propensity-matched analysis was used. We visually compared the score of the hepatic artery (A-score), portal vein (P-score), and hepatic vein (V-score) of the 2 protocols and quantitatively correlated the graft volume obtained by CT volumetry (graft-CTv) under the 2 protocols with the actual graft weight.In total, 39 protocol-A and protocol-B candidates showed comparable preoperative clinical characteristics with propensity matching. For protocols A and B, the A-score was 3.87 ± 0.73 and 4.51 ± 0.56 (P < .01), the P-score was 4.92 ± 0.27 and 5.0 ± 0.0 (P = .07), and the V-score was 4.23 ± 0.78 and 4.82 ± 0.39 (P < .01), respectively. Correlations between the actual graft weight and graft-CTv of protocols A and B were 0.97 and 0.96, respectively.Liver-donor CT imaging under 100-kVp plus IR protocol provides better visualization for vascular structures than that under 120-kVp plus FBP protocol with comparable accuracy for graft-CTv, while lowering radiation exposure by more than 40% and reducing contrast-medium dose by 20%.

Patterns of Early Allograft Dysfunction in Adult Live Donor Liver Transplantation: The A2ALL Experience

BACKGROUND

Early allograft dysfunction (EAD) after living donor liver transplantation (LDLT) has often been attributed to inadequate graft size, and termed small-for-size syndrome. Early allograft dysfunction definitions include a variable constellation of findings, including hyperbilirubinemia, coagulopathy, encephalopathy, and ascites formation. Among putative causes of EAD after LDLT are excessive portal pressure and/or flow. Our objective was to evaluate patterns of EAD after LDLT.

METHODS

In this study, 631 LDLT recipients were monitored for complications, EAD (defined by postoperative day 7 bilirubin >10 mg/dL or international normalized ratio >1.6), and graft failure. Approximately 200 had portal venous and arterial pressure and flow measurements before and after LDLT. Portal inflow modification (splenic artery ligation, hemiportocaval shunt, or splenectomy) was performed at the discretion of the operating surgeon. Associations between EAD and recipient, donor, and transplant factors were examined using multivariable logistic regression.

RESULTS

Risk of EAD was associated with left lobe grafts, lower graft weight among left lobes, higher preoperative bilirubin, higher portal reperfusion pressure, higher donor age, and higher donor body mass index. The risk of graft loss within the first 90 days was 5.2 times higher for recipients with EAD versus those without EAD (P < 0.001).

CONCLUSIONS

Early allograft dysfunction can be defined using postoperative day 7 laboratory values that are highly predictive of early graft failure within 90 days. Risk factors associated with EAD after LDLT include: graft type and size, preoperative bilirubin, portal reperfusion pressure, donor age, and donor body mass index.

Adult-to-adult living donor liver transplantation: Operative techniques to optimize the recipient's outcome

Adult-to-adult living donor liver transplantation (LDLT) is widely accepted today with good outcomes and safety reported worldwide for both donor and recipient. Nonetheless, it remained a highly demanding technical and complex surgery if undertaken. The last two decades have seen an increased in adult-to-adult LDLT following our first report of right lobe LDLT in overcoming graft size limitation in adults. In this article, we discussed the operative techniques and challenges of adult right lobe LDLT incorporating the middle hepatic vein, which is practiced in our center for the recipient operation. The various issues and challenges faced by the transplant surgeon in ensuring good recipient outcome are explored and discussed here as well. Hence, it is important to understand that a successful recipient operation is dependent of multifactorial events starting at the preoperative stage of planning, understanding the intraoperative technical challenges and the physiology of flow modulation that goes hand-in-hand with the operation. Therefore, one needs to arm oneself with all the possible knowledge in overcoming these technical challenges and the ability to be flexible and adaptable during LDLT by tailoring the needs of each patient individually.

Bone marrow-derived progenitor cells in de novo liver regeneration in liver transplant

The study was designed (1) to examine the hypothesis that circulating progenitor cells play a role in the process of de novo regeneration in human liver transplants and that these cells arise from a cell population originating in, or associated with, the bone marrow and (2) to investigate whether the transplanted liver volume has an effect on the circulating recipient-derived progenitor cells that generate hepatocytes during this process. Clinical data and liver tissue characteristics were analyzed in male individuals who underwent sex-mismatched adult-to-adult living donor liver transplantation using dual left lobe grafts. Dual left lobe grafts were examined at the time of transplantation and 19 to 27 days after transplantation. All recipients showed recovery of normal liver function and a significant increase in the volume of the engrafted left lobes after transplantation. Double staining for a Y-chromosome probe and the CD31 antigen showed the presence of hybrid vessels composed of recipient-derived cells and donor cells within the transplanted liver tissues. Furthermore, CD34-expressing cells were observed commingling with Y-chromosome+ cells. The ratio of recipient-derived vessels and the number of Y+ CD34+ cells tended to be higher when smaller graft volumes underwent transplantation. These findings suggest that the recruitment of circulating bone marrow-derived progenitor cells could contribute to vessel formation and de novo regeneration in human liver transplants. Moreover, graft volume may be an important determinant for the active mobilization of circulating recipient-derived progenitor cells and their contribution to liver regeneration.

A complete treatment of adult living donor liver transplantation: a review of surgical technique and current challenges to expand indication of patients

The growing disparity between the number of liver transplant candidates and the supply of deceased donor organs has motivated the development of living donor liver transplantation (LDLT). Over the last two decades, the operation has been markedly improved by innovations rendering modern results comparable with those of deceased donor liver transplantation (DDLT). However, there remains room for further innovation, particularly in adult living donor liver transplantation (ALDLT). Unlike whole-size DDLT and pediatric LDLT, size-mismatching between ALDLT graft and recipient body weight and changing dynamics of posttransplant allograft regeneration have remained major challenges. A better understanding of the complex surgical anatomy and physiologic differences of ALDLT helps avoid small-for-size graft syndrome, graft congestion from outflow obstruction and graft hypoperfusion from portal flow steal. ALDLT for high-urgency patients (Model for End-Stage Liver Disease score >30) can achieve results comparable to DDLT in high volume centers. Size limitations of partial grafts and donor safety issues can be overcome with dual grafts and modified right-lobe grafts that preserve the donor's middle hepatic vein trunk. Extended application of LDLT for unresectable hepatocellular carcinoma above Milan criteria is an optional strategy at the cost of slightly compromised survival. ABO-blood group incompatibility obstacles have been broken down by introducing a paired donor exchange program and refined peri-operative management of ABO-incompatible ALDLT. This review focuses on recent innovations of surgical techniques, safe donor selection, current strategies to expand ALDLT with broadened patient selection criteria and important aspects of teamwork required for success.

New perspectives in the assessment of future remnant liver

In order to achieve microscopic radical resection margins and thus better survival, surgical treatment of hepatic tumors has become more aggressive in the last decades, resulting in an increased rate of complex and extended liver resections. Postoperative outcomes mainly depend on the size and quality of the future remnant liver (FRL). Liver resection, when performed in the absence of sufficient FRL, inevitably leads to postresection liver failure. The current gold standard in the preoperative assessment of the FRL is computed tomography volumetry. In addition to the volume of the liver remnant after resection, postoperative function of the liver remnant is directly related to the quality of liver parenchyma. The latter is mainly influenced by underlying diseases such as cirrhosis and steatosis, which are often inaccurately defined until microscopic examination after the resection. Postresection liver failure remains a point of major concern that calls for accurate methods of preoperative FRL assessment. A wide spectrum of tests has become available in the past years, attesting to the fact that the ideal methodology has yet to be defined. The aim of this review is to discuss the current modalities available and new perspectives in the assessment of FRL in patients scheduled for major liver resection.

Small-for-size syndrome in living-donor liver transplantation using a left lobe graft

In living-donor liver transplantation with a left lobe graft, which can reduce the burden on the donor compared to right lobe graft, the main problem is small-for-size (SFS) syndrome. SFS syndrome is a multifactorial disease that includes aspects related to the graft size, graft quality, recipient factors and even technical issues. The main pathophysiology of SFS syndrome is the sinusoidal microcirculatory disturbance induced by shear stress, which is caused by excessive portal inflow into the smaller graft. The donor age, the presence of steatosis of the graft and a poor recipient status are all risk factors for SFS syndrome. To resolve SFS syndrome, portal inflow modulation, splenectomy, splenic artery modulation and outflow modulation have been developed. It is important to establish strict criteria for managing SFS syndrome. Using pharmacological interventions and/or therapeutic approaches that promote liver regeneration could increase the adequate outcomes in SFS liver transplantation. Left lobe liver transplantation could be adopted in Western countries to help resolve the organ shortage.

Living donor liver transplantation for obese patients: challenges and outcomes

Living donor liver transplantation (LDLT) is an accepted option for end-stage liver disease, particularly in countries in which there are organ shortages. However, little is known about LDLT for obese patients. We sought to determine the effects of obesity on pretransplant living donor selection for obese recipients and their outcomes. On the basis of body mass index (BMI) values, 148 patients were classified as normal weight (N), 148 were classified as overweight (OW), and 74 were classified as obese (O). O recipients had significantly greater BMI values (32.1 ± 1.6 versus 23.2 ± 1.9 kg/m(2), P < 0.001) and received larger actual grafts (918.9 ± 173 versus 839.4 ± 162 g, P = 0.002) than recipients with normal BMI values. Donors who donated to O recipients had a greater mean BMI (26.3 ± 3.8 kg/m(2)) than those who donated to N recipients (24.4 ± 3.2 kg/m(2), P = 0.001). Although O recipients were more likely to face some challenges in finding a suitable living donor, there were no differences in graft survival [hazard ratio (HR) = 0.955, 95% confidence interval (CI) = 0.474-1.924, P = 0.90] or recipient survival (HR = 0.90, 95% CI = 0.56-1.5, P = 0.67) between the 3 groups according to an adjusted Cox proportional hazards model. There were no significant differences in posttransplant complication rates between the 3 recipient groups or in the morbidity rates for the donors who donated to O recipients versus the donors who donated to OW and N recipients (P = 0.26). Therefore, we recommend that obese patients undergo pretransplant evaluations. If they are adequately evaluated and selected, they should be considered for LDLT.

Acute liver failure and liver transplantation

Acute liver failure (ALF) is defined by the presence of coagulopathy (International Normalized Ratio ≥ 1.5) and hepatic encephalopathy due to severe liver damage in patients without pre-existing liver disease. Although the mortality due to ALF without liver transplantation is over 80%, the survival rates of patients have considerably improved with the advent of liver transplantation, up to 60% to 90% in the last two decades. Recent large studies in Western countries reported 1, 5, and 10-year patient survival rates after liver transplantation for ALF of approximately 80%, 70%, and 65%, respectively. Living donor liver transplantation (LDLT), which has mainly evolved in Asian countries where organ availability from deceased donors is extremely scarce, has also improved the survival rate of ALF patients in these regions. According to recent reports, the overall survival rate of adult ALF patients who underwent LDLT ranges from 60% to 90%. Although there is still controversy regarding the graft type, optimal graft volume, and ethical issues, LDLT has become an established treatment option for ALF in areas where the use of deceased donor organs is severely restricted.

Estimation of the congestion area volume in potential living donor remnant livers

BACKGROUND

Living donor liver transplantation is widely performed in adult patients. One of the problems in this setting is a small-for-size graft, which results in dysfunction and poor prognosis of a transplantation. A right liver graft was devised to overcome this problem; furthermore, inclusion of the middle hepatic vein (MHV) has been suggested to greatly improve recipient outcomes. However, extended right hepatectomy involves a surgical risk for the living donor in terms of congestion of the left paramedian sector. The volume of the venoocclusive region of a living donor liver possibly varies depending on the collateral patterns of veins draining the cranial part of segment 4 (S4).

PATIENTS AND METHODS

We were analyzed the normal livers of 50 patients who underwent triphasic contrast-enhanced multidetector row computed tomography during preoperative and postoperative examinations. The patient pathologies consisted of gastric cancer (n = 25), colon cancer (n = 1), or renal cancer (n = 24). We calculated the volume of the entire liver as well as those of the right graft and left remnant lobes for comparison with the drainage volume of each hepatic vein and its branches.

RESULTS

On the basis of the anatomic venous drainage of the cranial part of S4 (V4sup), we classified hepatic veins as group A (n = 31), the V4sup joined the left hepatic vein or the MHV distal to the vein draining S8 area (MV8), or group B (n = 19), V4sup joined the MHV proximal to MV8. The mean volume of the congested area was 6.9% in group A and 15.9% in group B. The venoocclusive areas in the remnant livers were estimated to be larger in group B (P < .001).

CONCLUSION

The collateral pattern of V4sup and MV8 as well as preoperative volumetric analysis are important for graft selection to decide the line of transection.

Adult-to-adult living donor liver transplantation for acute liver failure in China

AIM: To investigate the long-term outcome of recipients and donors of adult-to-adult living-donor liver transplantation (AALDLT) for acute liver failure (ALF).

METHODS: Between January 2005 and March 2010, 170 living donor liver transplantations were performed at West China Hospital of Sichuan University. All living liver donor was voluntary and provided informed consent. Twenty ALF patients underwent AALDLT for rapid deterioration of liver function. ALF was defined based on the criteria of the American Association for the Study of Liver Diseases, including evidence of coagulation abnormality [international normalized ratio (INR) ≥ 1.5] and degree of mental alteration without pre-existing cirrhosis and with an illness of < 26 wk duration. We reviewed the clinical indications, operative procedure and prognosis of AALDTL performed on patients with ALF and corresponding living donors. The potential factors of recipient with ALF and corresponding donor outcome were respectively investigated using multivariate analysis. Survival rates after operation were analyzed using the Kaplan-Meier method. Receiver operator characteristic (ROC) curve analysis was undertaken to identify the threshold of potential risk factors.

RESULTS: The causes of ALF were hepatitis B (n = 18), drug-induced (n = 1) and indeterminate (n = 1). The score of the model for end-stage liver disease was 37.1 ± 8.6, and the waiting duration of recipients was 5 ± 4 d. The graft types included right lobe (n = 17) and dual graft (n = 3). The mean graft weight was 623.3 ± 111.3 g, which corresponded to graft-to-recipient weight ratio of 0.95% ± 0.14%. The segment Vor VIII hepatic vein was reconstructed in 11 right-lobe grafts. The 1-year and 3-year recipient’s survival and graft survival rates were 65% (13 of 20). Postoperative results of total bilirubin, INR and creatinine showed obvious improvements in the survived patients. However, the creatinine level of the deaths was increased postoperatively and became more aggravated compared with the level of the survived recipients. Multivariate analysis showed that waiting duration was independently correlated with increased mortality (P = 0.014). Furthermore, ROC curve revealed the cut-off value of waiting time was 5 d (P = 0.011, area under the curve = 0.791) for determining the mortality. The short-term creatinine level with different recipient’s waiting duration was described. The recipients with waiting duration ≥ 5 d showed the worse renal function and higher mortality than those with waiting duration < 5 d (66.7% vs 9.1%, P = 0.017). In addition, all donors had no residual morbidity. Furthermore, univariate analysis did not show that short assessment time induced the high morbidity (P = 0.573).

CONCLUSION: Timely AALDLT for patients with ALF greatly improves the recipient survival. However, further systemic review is needed to investigate the optimal treatment strategy for ALF.

[Small-for-size: experimental findings for liver surgery]

The characteristics of the hepatic macrocirculation, i.e., the parallel portal-venous and arterial blood supply, is of utmost relevance for liver surgery. With extended hepatectomy or transplantation of a reduced-size liver the remaining or transplanted liver tissue is overperfused because the liver fails to regulate the portal-venous inflow. This portal hyperperfusion is responsible for the initiation of liver cell proliferation but represents at the same time one of the substantial events in the pathogenesis of the small-for-size syndrome. Portal-venous hyperperfusion, the so-called hepatic arterial buffer response, which describes the semi-reciprocal relationship between the portal-venous and hepatic arterial blood flows, leads to an arterial hypoperfusion of the small-for-size liver. In this article experimental and clinical data are discussed which underline the high but so far overseen relevance of this arterial underperfusion in the development of a small-for-size syndrome.

Adult living-related liver donation for acute liver failure: is it ethically appropriate?

Acute liver failure (ALF) results in the annual death of approximately 3.5 per million people in the United States. Unfortunately, given the marked shortage of cadaveric liver donations and the ethical questions that plague utilization of living donor liver transplantation (LDLT) for ALF, many patients with ALF die before a liver is allocated to them. In this review, we discuss how the consistent utilization of LDLT for ALF could decrease the mortality rate of ALF. Additionally, we examine a key underlying issue: is LDLT for ALF ethically appropriate?

Safety of small-for-size grafts in adult-to-adult living donor liver transplantation using the right lobe

The problem of graft size is one of the critical factors limiting the expansion of adult-to-adult living donor liver transplantation (LDLT). We compared the outcome of LDLT recipients who received grafts with a graft-to-recipient weight ratio (GRWR) < 0.8% or a GRWR > or = 0.8%, and we analyzed the risk factors affecting graft survival after small-for-size grafts (SFSGs) were used. Between June 1997 and April 2008, 427 patients underwent LDLT with right lobe grafts at the Department of Surgery of Samsung Medical Center. Recipients were divided into 2 groups: group A with a GRWR < 0.8% (n = 35) and group B with a GRWR > or = 0.8% (n = 392). We retrospectively evaluated the recipient factors, donor factors, and operative factors through the medical records. Small-for-size dysfunction (SFSD) occurred in 2 of 35 patients (5.7%) in group A and in 14 of 392 patients (3.6%) in group B (P = 0.368). Graft survival rates at 1, 3, and 5 years were not different between the 2 groups (87.8%, 83.4%, and 74.1% versus 90.7%, 84.5%, and 79.4%, P = 0.852). However, when we analyzed risk factors within group A, donor age and middle hepatic vein tributary drainage were significant risk factors for graft survival according to univariate analysis (P = 0.042 and P = 0.038, respectively). Donor age was the only significant risk factor for poor graft survival according to multivariate analysis. The graft survival rates of recipients without SFSD tended to be higher than those of recipients with SFSD (85.3% versus 50.0%, P = 0.074). The graft survival rates of recipients with grafts from donors < 44 years old were significantly higher than those of recipients with grafts from donors > or = 44 years old (92.2% versus 53.6%, P = 0.005). In conclusion, an SFSG (GRWR < 0.8%) can be used safely in adult-to-adult right lobe LDLT when a recipient is receiving the graft from a donor younger than 44 years.

Right lobe estimated blood-free weight for living donor liver transplantation: accuracy of automated blood-free CT volumetry--preliminary results

PURPOSE

To determine the relative accuracy of automated blood-free to blood-filled computed tomographic (CT) volumetry for estimation of right-lobe weight in living donor liver transplantation.

MATERIALS AND METHODS

This retrospective study was approved by the institutional review board; informed consent was waived. Between October 1, 2008, and April 30, 2009, 88 live liver donors (54 men, 34 women; mean age, 26.1 years +/- 6.9 [standard deviation]) who underwent CT and had their right lobes procured in the study institution were included. Automated measurement of blood-filled volume (V(BFill)) and blood-free volume (V(BFree)) of the right lobe was performed by using 16-row multidetector CT performed with 5-mm intervals. Actual hepatic weight was measured blood free during surgery. Percentage blood volume, %V(B), was calculated as follows: %V(B) = V(BFill) - V(BFree)/V(BFill) . 100. Pearson tests were performed to determine correlation coefficients between V(BFill)/1.22 or V(BFree) and weight. Percentage deviation and percentage absolute deviation of V(BFree) from weight were compared with those of V(BFill)/1.22 by using a paired t test or Wilcoxon rank sum test. Regression analysis was performed between V(BFree) and weight.

RESULTS

Mean V(BFill), V(BFree), and weight were 789.0 mL +/- 126.4, 713.9 mL +/- 114.4, and 717.8 g +/- 110.4. Percentage blood volume varied from 6.5% to 19.8% (mean, 9.5%). Compared with weight, the correlation coefficient was slightly higher with V(BFree) (r = 0.9140) than with V(BFill)/1.22 (r = 0.8909). Mean percentage deviation and percentage absolute deviation were significantly smaller with V(BFree) (-0.4% +/- 6.3, 5.0% +/- 3.8; P < .001) than with V(BFill)/1.22 (-9.8% +/- 6.5, 10.2% +/- 7.3; P < .001). The equation relating V(BFree) and weight, W, was as follows: W = (0.8815 . V(BFree)) + 88.5117, with R(2) of 0.8355 (P < .001).

CONCLUSION

At automated CT volumetry in live liver donors, the percentage blood volume varies. The V(BFree) is more accurate than is V(BFill)/1.22 in estimation of hepatic weight.

Alleviating the burden of small-for-size graft in right liver living donor liver transplantation through accumulation of experience

The issue of small-for-size graft (SFSG) containing the middle hepatic vein in right liver living donor liver transplantation from 1996 to 2008 (n = 320) was studied. Characteristics of donors, grafts and recipients were comparable between Era I (first 50 cases) and Era II (next 270 cases) except that the median model for end-stage liver disease (MELD) score was higher in Era I (29 vs. 24; p = 0.024). The median graft to standard liver volume ratio (G/SLV) in Era I was 49.0% (range, 32.8-86.2%), versus 49.3% (range, 28.4-89.4%) in Era II (p = 0.498). Hospital mortality rate, the study endpoint, dropped from 16.0% (8/50) in Era I to 2.2% (6/270) in Era II (p = 0.000). Univariate analysis showed that MELD score (p = 0.002), pretransplant hepatorenal syndrome (p = 0.000) and Era I (p = 0.000) were significant in hospital mortality. Logistic regression analysis showed that only Era I (relative risk 9.758; 95% confidence interval, 2.885-33.002; p = 0.000) was significant. In Era I, G/SLV<40% had a relative risk of 7.8 (95% confidence interval, 1.225-49.677; p = 0.030). The hospital mortality rates for G/SLV<40% were 50% (3/6) and 1.9% (1/52) in Era I and II respectively. In conclusion, through accumulation of experience, SFSG became less important as a factor in hospital mortality.

Adenosine restores the hepatic artery buffer response and improves survival in a porcine model of small-for-size syndrome

The aim of the study is to define the role of the HABR in the pathophysiology of the SFS liver graft and to demonstrate that restoration of hepatic artery flow (HAF) has a significant impact on outcome and improves survival. Nine pigs received partial liver allografts of 60% liver volume, Group 1; 8 animals received 20% LV grafts, Group 2; 9 animals received 20% LV grafts with adenosine infusion, Group 3. HAF and portal vein flow (PVF) were recorded at 10 min, 60 min and 90 min post reperfusion, on POD 3 and POD 7 in Group 1, and daily in Group 2 and 3 up to POD 14. Baseline HAF and PVF (ml/100 g/min) were 29 +/- 12 (mean +/- SD) and 74 +/- 8 respectively, with 28% of total liver blood flow (TLBF) from the HA and 72% from the PV. PVF peaked at 10 mins in all groups, increasing by a factor of 3.8 in the 20% group compared to an increase of 1.9 in the 60% group. By POD 7-14 PVF rates approached baseline values in all groups. The HABR was intact immediately following reperfusion in all groups with a reciprocal decrease in HAF corresponding to the peak PVF at 10 min. However in the 20% group HAF decreased to 12 +/- 8 ml/100 g/min at 90 min and remained low out to POD 7-14 despite restoration of normal PVF rates. Histopathology confirmed evidence of HA vasospasm and its consequences, cholestasis, centrilobular necrosis and biliary ischemia in Group 2. HA infusion of adenosine significantly improved HAF (p < .0001), reversed pathological changes and significantly improved survival (p = .05). An impaired HABR is important in the pathophysiology of the SFSS. Reversal of the vasospasm significantly improves outcome.

[How can the number of liver transplantations be increased?]

The number of patients suitable for liver transplantation is progressively increasing due to the excellent results achieved with this procedure, giving rise to a growing imbalance in the number of candidates on the waiting list and the number of donors. This situation has prompted transplant teams to search for alternatives to increase the number of liver grafts. On the one hand, the criteria for donation have been broadened to include donors with advanced age, liver steatosis, hepatitis B and C viruses, neoplasms, and benign underlying diseases. On the other hand, new transplant techniques have been used with grafts from split livers, living donors, sequential or domino transplants and non-heart-beating donors. Other options such as xenotransplantation and hepatocyte transplants currently lack clinical applicability.

Exact CT-based liver volume calculation including nonmetabolic liver tissue in three-dimensional liver reconstruction

Exact preoperative determination of the liver volume is of great importance prior to hepatobiliary surgery, especially in living donated liver transplantation (LDLT) and extended hepatic resections. Modern surgery-planning systems estimate these volumes from segmented image data. In an experimental porcine study, our aim was (1) to analyze and compare three volume measurement algorithms to predict total liver volume, and (2) to determine vessel tree volumes equivalent to nonmetabolic liver tissue. Twelve porcine livers were examined using a standardized three-phase computed tomography (CT) scan and liver volume was calculated computer-assisted with the three different algorithms. After hepatectomy, livers were weighed and their vascular system plasticized followed by CT scan, CT reconstruction and re-evaluation of total liver and vessel volumes with the three different algorithms. Blood volume determined by the plasticized model was at least 1.89 times higher than calculated by multislice CT scans (9.7% versus 21.36%, P=0.028). Analysis of 3D-CT-volumetry showed good correlation between the actual and the calculated liver volume in all tested algorithms with a high significant difference in estimating the liver volume between Heymsfield versus Heidelberg (P=0.0005) and literature versus Heidelberg (P=0.0060). The Heidelberg algorithm reduced the measuring error with deviations of only 1.2%. The present results suggest a safe and highly predictable use of 3D-volumetry in liver surgery for evaluating liver volumes. With a precise algorithm, the volume of remaining liver or single segments can be evaluated exactly and potential operative risks can therefore be better calculated. To our knowledge, this study implies for the first time a blood pool, which corresponds to nonmetabolic liver tissue, of more than 20% of the whole liver volume.

Seeking beyond rejection: an update on the differential diagnosis and a practical approach to liver allograft biopsy interpretation

Pathologic evaluation of liver allograft biopsies plays an integral role in the management of patients after liver transplantation. This review summarizes the clinical context and classical histology of different types of allograft rejection and also the common entities that enter the differential diagnosis of allograft rejection, and provides practical approaches to liver allograft biopsy interpretation. In addition, some of the new developments in the field of liver transplant pathology are updated. The purpose of this review is to provide guidance for pathologists interpreting liver allograft biopsies, particularly those interested in developing expertise in the field of liver transplant pathology.

Acute liver failure and living donor liver transplantation

Acute liver failure (ALF) is defined by the presence of hepatic encephalopathy due to severe liver damage in patients without pre-existing liver disease. Although the mortality of ALF without liver transplantation is over 80%, the survival rates of ALF patients have improved considerably with the advent of liver transplantation, up to 60-80% in the last decade. Living donor liver transplantation (LDLT), which has mainly evolved in Asian countries where organ availability from deceased donors is extremely scarce, has also improved the survival rate of ALF patients. According to recent reports, the overall survival rate of adult ALF patients who underwent LDLT is 60% to 90%. Although there is still controversy regarding the graft type, the optimal graft volume, and ethical issues of defining the indications for LDLT in ALF patients with respect to donor risk, LDLT has become an established treatment option for ALF in areas where the use of deceased donors organs is severely restricted.

Current concept of small-for-size grafts 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 (SFS) graft syndrome." The initial trials to resolve this problem involved increasing the procured graft size, from left to right, and even extension 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 such as auxiliary or dual liver transplantation, but also control of the increased portal pressure caused by an SFS graft, such as a portosystemic shunt or splenectomy, have been trialed with some positive results. To establish an effective strategy for transplanting SFS grafts and preventing SFS graft syndrome, it is essential to have precise knowledge and tactics to evaluate graft quality and graft volume, when performing these LDLTs with portal pressure control. We reviewed the updated literature on the pathogenesis of and strategies for using SFS grafts.

Historical perspective of living donor liver transplantation

Living donor liver transplantation (LDLT) has gone through its formative years and established as a legitimate treatment when a deceased donor liver graft is not timely or simply not available at all. Nevertheless, LDLT is characterized by its technical complexity and ethical controversy. These are the consequences of a single organ having to serve two subjects, the donor and the recipient, instantaneously. The transplant community has a common ground on assuring donor safety while achieving predictable recipient success. With this background, a reflection of the development of LDLT may be appropriate to direct future research and patient-care efforts on this life-saving treatment alternative.

Remnant liver volume to body weight ratio > or =0.5%: A new cut-off to estimate postoperative risks after extended resection in noncirrhotic liver

BACKGROUND

Before extended hepatectomy of five or more segments, the remnant liver volume (RLV) is usually calculated as a ratio of RLV to total liver volume (RLV-TLV) and must be >20% to 25%. This method can lead to compare parts of normal liver parenchyma to others compromised by biliary or vascular obstruction or by portal vein embolization. Extrapolating from living-donor liver transplantation, we hypothesized that RLV to body weight ratio (RLV-BWR) could accurately assess the functional limit of hepatectomy.

STUDY DESIGN

From September 2000 to December 2004, volumetric measurements of RLV using computed tomography were obtained before right-extended hepatectomy in 31 patients. RLV-BWR of 0.5% as a critical point for patient course was compared with stratification by RLV-TLV (< or =25% or >25% and < or =20% or >20%).

RESULTS

Three-month morbidity and mortality were not significantly different between groups RLV-TLV < or = and >25% and between groups RLV-TLV < or = and >20%, but increased significantly in group RLV-BWR < or = 0.5% compared with group RLV-BWR > 0.5% (p = 0.038 and p = 0.019, respectively) with an non-significant increase in death from liver failure (p = 0.077).

CONCLUSIONS

RLV-BWR was more specific than RLV-TLV in predicting postoperative course after extended hepatectomy. Patients with an anticipated RLV < or = 0.5% of body weight are at considerable risk for hepatic dysfunction and postoperative mortality.

Live donor liver transplantation in adults

Live donor liver transplantation (LDLT) was initiated in 1988 for children recipients. Its application to adult recipients was limited by graft size until the first right liver LDLT was performed in Hong Kong in 1996. Since then, right liver graft has become the major graft type. Despite rapid adoption of LDLT by many centers, many controversies on donor selection, indications, techniques, and ethics exist. With the recent known 11 donor deaths around the world, transplant surgeons are even more cautious than the past in the evaluation and selection of donors. The need for routine liver biopsy in donor evaluation is arguable but more and more centers opt for a policy of liberal liver biopsy. Donation of the middle hepatic vein (MHV) in the right liver graft was considered unsafe but now data indicate that the outcome of donors with or without MHV donation is about equal. Right liver LDLT has been shown to improve the overall survival rate of patients with chronic liver disease, acute or acute-on-chronic liver failure and hepatocellular carcinoma waiting for liver transplantation. The outcome of LDLT is equivalent to deceased donor liver transplantation despite a smaller graft size and higher technical complexity.

Preoperative Helical Computerized Tomography Estimation of Donor Liver Volume

BACKGROUND

The purpose of this study was to evaluate the accuracy of spiral computed tomography (CT) and 3-D imaging models in measuring total and segmental liver volume in potential living donors.

METHODS

A prospective study was undertaken to assess the correlation between the volumes of potential donor livers determined via helical CT and the actual volumes measured during operation in 150 donor candidates. Left-lateral segment (S2,3) or left-lobe (S2,3,4) transplantation was performed in 36 cases with 96 right-lobe liver transplants (S5,6,7,8). Ten donor candidates were refused owing to inadequate liver volumes, and 8 for other reasons.

RESULTS

The regression analysis model showed a significant correlation between the preoperative CT estimates of graft volume and intraoperative weight measurement of harvested grafts in living liver donors (F: 5525.37; P < .05); 97.7% of changes in CT volume were explained by differences in graft mass (R2: 0.977).

CONCLUSION

Preoperative estimation of segmental volumes of the donor liver is necessary to avoid donor-recipient size disparity, thereby preventing hepatic failure of donors after harvesting. It has a major impact on donor selection and type of surgical management. The accuracy of helical CT was high to determine total and segmental liver volumes.

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

In an attempt to more completely define the histopathologic features of the portal vein hyperperfusion or small-for-size syndrome (PHP/SFSS), we strictly identified 5 PHP/SFSS cases among 39 (5/39; 13%) adult living donor liver transplants (ALDLT) completed between 11/01 and 09/03. Living donor segments consisting of 3 right lobes, 1 left lobe, and 1 left lateral segment, with a mean allograft-to-recipient weight ratio (GRWR) of 1.0 +/- 0.3 (range 0.6 to 1.4), were transplanted without complications, initially, into 6 relatively healthy 25 to 63-year-old recipients. However, all recipients developed otherwise unexplained jaundice, coagulopathy, and ascites within 5 days after transplantation. Examination of sequential posttransplant biopsies and 3 failed allografts with clinicopathologic correlation was used in an attempt to reconstruct the sequence of events. Early findings included: (1) portal hyperperfusion resulting in portal vein and periportal sinusoidal endothelial denudation and focal hemorrhage into the portal tract connective tissue, which dissected into the periportal hepatic parenchyma when severe; and (2) poor hepatic arterial flow and vasospasm, which in severe cases, led to functional dearterialization, ischemic cholangitis, and parenchymal infarcts. Late sequelae in grafts surviving the initial events included small portal vein branch thrombosis with occasional luminal obliteration or recanalization, nodular regenerative hyperplasia, and biliary strictures. These findings suggest that portal hyperperfusion, venous pathology, and the arterial buffer response importantly contribute to early and late clinical and histopathologic manifestations of the small-for-size syndrome.

Excessive portal flow causes graft failure in extremely small-for-size liver transplantation in pigs

AIM

To evaluate the effects of a portocaval shunt on the decrease of excessive portal flow for the prevention of sinusoidal microcirculatory injury in extremely small-for-size liver transplantation in pigs.

METHODS

The right lateral lobe of pigs, i.e. the 25% of the liver, was transplanted orthotopically. The pigs were divided into two groups: graft without portocaval shunt (n = 11) and graft with portocaval shunt (n = 11). Survival rate, portal flow, hepatic arterial flow, and histological findings were investigated.

RESULTS

In the group without portocaval shunt, all pigs except one died of liver dysfunction within 24 h after transplantation. In the group with portocaval shunt, eight pigs survived for more than 4 d. The portal flow volumes before and after transplantation in the group without portocaval shunt were 118.2+/-26.9 mL/min/100 g liver tissue and 270.5+/-72.9 mL/min/100 g liver tissue, respectively. On the other hand, in the group with portocaval shunt, those volumes were 124.2+/-27.8 mL/min/100 g liver tissue and 42.7+/-32.3 mL/min/100 g liver tissue, respectively (P<0.01). As for histological findings in the group without portocaval shunt, destruction of the sinusoidal lining and bleeding in the peri-portal areas were observed after reperfusion, but these findings were not recognized in the group with portocaval shunt.

CONCLUSION

These results suggest that excessive portal flow is attributed to post transplant liver dysfunction after extreme small-for-size liver transplantation caused by sinusoidal microcirculatory injury.

Acute liver failure: a review

Since publication of the first descriptions of acute liver failure (ALF) as a distinct clinical entity in the 1950's, the understanding of the pathophysiologic mechanisms involved and the management options have increased substantially. ALF still represents a major challenge for todays hepatologists, because it can rapidly lead to multiorgan failure and death that may be preventable with appropriate intervention. This article summarizes the basic patho-physiology underlying ALF, compares epidemiologic trends in the United States, the United Kingdom, and the Far East, and reviews prognostic markers and treatment options for ALF.