Significance of portal venous flow in graft regeneration after living related liver transplantation

Volumetric graft changes after liver transplantation: evidence of adaptation to recipient body size

It is believed that whole liver grafts adjust their size to fit the body size of the recipient after transplantation, despite a lack of evidence. The aim of this study was to test this hypothesis. This was a retrospective cohort study of 113 liver transplantations performed at Karolinska University Hospital. The cohort was divided based on graft volume-to-standard liver volume ratio (GV/SLV) into quartiles of small, mid, and large grafts. Serial volumetric assessment was performed on the day of transplantation and at posttransplant check-ups early (<2 mo) and late (9-13 mo) after transplantation using computed tomography (CT) volumetry. Change in GV/SLV ratio over time was analyzed with ANOVA repeated measures. A multiple regression model was used to investigate the influence of intraoperative blood flow, recipient body size, age, and relative sickness on graft volume changes. Between the three time points, mean GV/SLV ratio adapted to 0.55-0.94-1.00 in small grafts (n = 29, P < 0.001); 0.87-1.18-1.13 in midgrafts (n = 56, P < 0.001); 1.11-1.51-1.18 in large grafts (n = 28, P < 0.001). Regression analysis showed a positive correlation between posttransplant graft growth and portal flow (β = 1.18, P = 0.005), arterial flow (β = 0.17, P = 0.001), and recipient body surface area (β = 59.85, P < 0.001). A negative correlation was observed for graft weight-to-recipient weight ratio (GRWR; β = -33.12, P < 0.001). Grafts with initial GV/SLV-ratio < 0.6 adapt toward the ideal volume for recipient body size 1 year after transplantation. The disparity between graft size relative to recipient body size, and the portal and arterial perfusion, influence volumetric graft changes.NEW & NOTEWORTHY This is the first and largest human study to verify the hypothesis that whole liver grafts adjust their size to match recipient body size 1 year after transplantation-a phenomenon that has previously only been observed in experimental animal studies and human case reports. The direction of volumetric changes is driven by the disparity between graft size relative to recipient body surface area and weight, as well as the intraoperative portal- and arterial graft perfusion.

Preoperative Alanine Aminotransferase and Remnant Liver Volume Predict Liver Regeneration After Live Donor Hepatectomy

BACKGROUND

Regeneration of the remnant liver in early postoperative period determines the outcome in live liver donors (LLDs). The aim of the current study is to evaluate the factors that influence liver regeneration following live donor hepatectomy.

METHODS

Total liver volume (TLV), estimated graft volume (EGV), and remnant liver volume (RLV) were calculated preoperatively in a prospective study of 154 LLDs. Absolute and percentage growth of remnant liver (regeneration index) in donor was estimated at 7th postoperative day (POD) by computed tomography (CT) volumetric analysis.

RESULTS

One hundred eighteen donors underwent right hepatectomy (RH), 29 underwent left hepatectomy (LH), 6 donors had left lateral sectionectomy (LLS), and one had right posterior sectionectomy. The median percentage growth of remnant liver at the end of the first week was 46.14% (51.74%, 35.32%, and 17.38% for RH, LH, and LLS, respectively). On univariate analysis, female donors (p = 0.051), RH graft (p = 0.001), no steatosis on ultrasonography (p = 0.042), lower TLV (p = 0.029), RLV (p = < 0.001), RLV-to-body weight ratio (RLVBWR) (p = < 0.001), preoperative alanine aminotransferase (ALT) level (p = 0.017), aspartate aminotransferase (AST) (p = 0.035) and higher POD 7 alkaline phosphatase (ALP) (p = 0.033), and POD 7 gamma-glutamyl transferase GGT (p = 0.006) were found to be predictors of greater liver regeneration. Among them, lower RLV (P = 0.008), RLVBWR (p = 0.011), and preoperative ALT level (p = 0.021) were most significant factors predictive of liver regeneration on logistic regression analysis with backward elimination.

CONCLUSION

The liver regenerates rapidly in LLDs following hepatectomy. Low RLV, RLVBWR, and preoperative ALT levels were predictors of liver regeneration in the first week following donor hepatectomy.

Baicalin attenuates liver hypoxia/reoxygenation injury by inducing autophagy

The aim of the present study was to explore the effect of baicalin on liver hypoxia/reoxygenation (H/R) injury and the possible mechanism involved. A cellular H/R model was established and cells were treated with 50, 100 and 200 µmol/l baicalin. Following reoxygenation for 6 h, cell viability, lactate dehydrogenase (LDH), B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), caspase 3 and cleaved caspase 3 were assessed. Furthermore, levels of endoplasmic reticulum stress markers binding of immunoglobulin protein (BIP) and CCAAT/enhancer-binding protein homologous protein (CHOP) and autophagy markers microtubule-associated proteins 1A/1B light chain 3B (LC3) and beclin 1 were measured. To confirm the involvement of autophagy in baicalin-mediated attenuation of H/R injury, the autophagy inhibitor 3-methyladenine (3-MA) was administered. The results revealed that baicalin administration increased cell viability and decreased LDH levels, most notably at a dosage of 100 µmol/l. Baicalin pretreatment also downregulated the expression of caspase 3, cleaved caspase 3 and Bax, while upregulating the expression of Bcl-2. Furthermore, BIP and CHOP were decreased while LC3 and beclin-1 were significantly increased by baicalin pretreatment. Inhibiting autophagy using 3-MA, resulted in a significant decrease in LC3-II, beclin-1 and LDH, as well as increase in the expression of BIP, CHOP, caspase 3, cleaved caspase 3 and Bax. Bcl-2 and cell viability were also decreased. In conclusion, the results of the present study indicate that baicalin exerts a protective effect on liver H/R injury and this may be achieved via the induction of autophagy.

Significance of Portal Venous Velocity in Short-term Graft Function in Living Donor Liver Transplantation

BACKGROUND

Graft regeneration and functional recovery after reperfusion of transplanted graft are very important for successful living donor liver transplantation (LDLT). The aim of this study was to evaluate the significance of postoperative portal venous velocity (PVV) in short-term recovery of graft function in LDLT.

PATIENTS AND METHODS

From February 2007 through December 2015, we performed 17 primary LDLTs, which were included in the present study. The patients ranged in age from 12 to 65 years (mean: 50 years), and 11 were female patients. Postoperatively, Doppler ultrasonography was performed daily to measure PVV (cm/s), and liver function parameters were measured daily. The change in PVV (ΔPVV) was defined as follows: ΔPVV = PVV on postoperative day (POD) 1 - PVV on POD 7. Maximal value of serum aspartate aminotransferase (ASTmax) and maximal value of serum alanine transaminase (ALTmax) at 24 hours after graft reperfusion were used as parameters of reperfusion injury. Correlation analyses were performed as follows: (1) correlation of ΔPVV and PVV on POD 1 (PVV-POD 1) with the values such as ASTmax, ALTmax, other liver function parameters on POD 7 and graft regeneration rate; (2) correlation of ASTmax and ALTmax with other liver function parameters on POD 7.

RESULTS

ΔPVV significantly correlated with the values of serum total bilirubin (P < .01), prothrombin time (P < .01), and platelet count (P < .05), and PVV-POD 1 significantly correlated with the values of serum total bilirubin (P < .05) and prothrombin time (P < .05).

CONCLUSION

ΔPVV and PVV-POD 1 may be useful parameters of short-term functional recovery of the transplant liver in LDLT.

Impact of Portal Hemodynamic Changes in Partial Liver Grafts on Short-Term Graft Regeneration in Living Donor Liver Transplantation

BACKGROUND

Regeneration of partial liver grafts is critical for successful living donor liver transplantation (LDLT), especially in adult recipients. The purpose of this study was to investigate the intraoperative hemodynamic changes in partial liver grafts and characterize their potential impact on post-transplant liver regeneration in LDLT.

METHODS

We examined the portal venous flow (PVF) and hepatic arterial flow (HAF) to partial liver grafts by means of ultrasonic transit time flowmeter of donors immediately before graft retrieval and of the corresponding recipients after vascular reconstruction in 48 LDLT cases. We evaluated post-transplant liver regeneration according to the changes in graft liver volume between the time of transplantation and the 7th post-transplant day.

RESULTS

There was a significant increase in PVF to the partial liver grafts in recipients (rPVF) compared with that in donors. In contrast, graft HAF in recipients significantly decreased compared with that in donors. The rPVF inversely correlated with graft weight (GW)-recipient body weight ratio (GRWR), whereas HAF volume showed no significant correlation. The rPVF/GW positively correlated with the rate of liver regeneration (GRR), which inversely correlated with GRWR. The rPVF/GW was significantly higher, and GRR tended to be larger in the small graft group than in the non-small graft group.

CONCLUSIONS

Intraoperative portal hemodynamic changes in partial liver grafts strongly affect their post-transplant regeneration. In particular, in small liver grafts, an immediate and remarkable increase in graft PVF may contribute to rapid liver regeneration after LDLT if the increased PVF remains within a safe range.

Graft inflow modulation in adult-to-adult living donor liver transplantation: A systematic review

INTRODUCTION

Small-for-size syndrome (SFSS) has an incidence between 0 and 43% in small-for-size graft (SFSG) adult living donor liver transplantation (LDLT). Portal hypertension following reperfusion and the hyperdynamic splanchnic state are reported as the major triggering factors of SFSS. Intra- and postoperative strategies to prevent or to reduce its onset are still under debate. We analyzed graft inflow modulation (GIM) during adult LDLT considering the indications, efficacy of the available techniques, changes in hemodynamics and outcomes.

MATERIALS AND METHODS

A systematic literature search was performed using PubMed, EMBASE, Scopus and the Cochrane Library Central. Treatment outcomes including in-hospital mortality and morbidity, re-transplantation rate, 1-, 3-, and 5-year patient overall survival and 1-, 3-, and 5-year graft survival rates, hepatic artery and portal vein flows and pressures before and after inflow modulation were analyzed.

RESULTS

From 563 articles, 12 studies dated between 2003 and 2014 fulfilled the selection criteria and were therefore included in the study. These comprised a total of 449 adult patients who underwent inflow modulation during adult-to-adult LDLT. Types of GIM described were splenic artery ligation, splenectomy, meso-caval shunt, spleno-renal shunt, portocaval shunt, and splenic artery embolization. Mortality and morbidity ranged between 0 and 33% and 17% and 70%, respectively. Re-transplantation rates ranged between 0% and 25%. GIM was associated with good survival for both graft and recipients, reaching an 84% actuarial rate at 5 years. Through the use of GIM, irrespective of the technique, a statistically significant reduction of PVF and PVP was obtained.

CONCLUSIONS

GIM is a safe and efficient technique to avoid or limit portal hyperperfusion, especially in cases of SFSG, decreasing overall morbidity and improving outcomes.

Size mismatch in liver transplantation

Size mismatch is an unique and inevitable but critical issue in live donor liver transplantation. Unmatched metabolic demand of recipient as well as physiologic mismatch aggravates the damage to liver graft, inevitably leading to graft failure on recipient. Also, an excessive resection of liver graft for better recipient outcome in live donor liver transplant may jeopardize the healthy donor well-being and even put donor life in danger. There is a fine balance between resected graft volume required to meet the recipient's metabolic demand and residual graft volume required for donor safety. The obvious clinical necessity of finding that balance has prompted a clinical need and promoted the improvement of knowledge and development of management strategies for size-mismatched transplants. The development of the size-matching methodology has significantly improved graft outcome and recipient survival in live donor liver transplants. On the other hand, the effect of size mismatch in cadaveric transplants has never been observed as being so pronounced. The importance of matching of the donor recipient size has been unrecognized in cadaveric liver transplant. In this review, we attempt to summarize the current most updated knowledge on the subject, particularly addressing the definition and complications of size-mismatched cadaveric liver transplant, as well as management strategies.

The Correlation of Hepatic and Systemic Hemodynamics During Liver Transplantation: Quantification of Hepatic Resistance as an Actual Value

The correlation between portal vein pressure (PVP) and flow (PVF) has not been established, and there is still lack of consensus about the optimal hemodynamics during liver transplantation (LT). We aimed to establish the correlation between systemic and hepatic hemodynamics during LT by applying the hepatokinetic power hypothesis, based on the law of energy conservation and hydrodynamics.A total of 103 adult liver transplant recipients were enrolled in this study from September 2012 to December 2014. Systemic and hepatic hemodynamics were assessed intraoperatively to calculate the hepatokinetic power status. Severe surgical complications (Clavien-Dindo grade ≥III) were recorded as the main outcome measure, and potential covariates were evaluated including recipient, donor, donor-recipient match, surgery-related factors, conventional hemodynamics, and the intraoperative hepatokinetic power profile.In multivariate analysis, hepatokinetic power gradient >4260 mL mmHg min100 g graft weight (P = 0.001), 2.2 < ratio of hepatokinetic power from the portal vein to the hepatic artery ≤8.7 (P = 0.012), and hepatic resistance of partial grafts ≤0.006 or >0.015 min mmHg mL (P = 0.012) were associated with a higher risk. None of the conventional hemodynamic parameters, such as PVP, PVF, and hepatic venous pressure gradient, entered into this regression model (c-statistic = 0.916) when competing with hepatokinetic power indexes.The hepatokinetic power hypothesis clarifies the correlation of systemic and hepatic hemodynamics in a simple, rational manner. The hepatic resistance, derived from the hepatokinetic power equation, can be quantified and has an effect on the incidence of severe surgical complications. This finding offers a new objective clinical approach to evaluate graft quality during transplantation.

Optimal central venous pressure during the neohepatic phase to decrease peak portal vein flow velocity for the prevention of portal hyperperfusion in patients undergoing living donor liver transplantation

BACKGROUND

The association between intraoperative systemic hemodynamic status and preventing portal hyperperfusion, which induces shear stress on the sinusoidal endothelial cells of liver grafts, resulting in poor graft function in live-donor recipients, has not been identified. This study evaluates the effects of systemic hemodynamic parameters (SHPs) during the neohepatic phase on changes in hepatic hemodynamic parameters (HHPs) between the neohepatic phase and the 1st postoperative day.

METHODS

Thirty-eight patients undergoing living donor liver transplantation (LDLT) were enrolled in this study. HHPs (flow velocities of portal vein and hepatic artery) were measured immediately after hepatic artery and bile duct reconstruction and on the first postoperative day. SHPs (mean arterial pressure, central venous pressure [CVP], cardiac index, stroke volume variation, stroke volume index, systemic vascular resistance index, and central venous oxygen saturation) were recorded and averaged for 5 minutes after the measurement of HHPs. The relationships between the SHPs and HHPs were assessed using linear or quadratic regression analysis.

RESULTS

Peak portal vein flow velocity (PVV) decreased on the 1st postoperative day in 24 patients (63%). There was an inverted-U relationship between CVP and the percentage change in PVV (R(2) = 0.241, P = .008). According to the quadratic regression model, the PVV maximally decreased at a CVP of 7.8 mm Hg. No significant correlations were found between the other SHPs and HHPs.

CONCLUSIONS

Maintaining CVP (approximately 8 mm Hg) during the neohepatic phase was clinically beneficial in decreasing PVV to prevent portal hyperperfusion in the early postoperative period of LDLT.

Analysis of unique liver volume restoration after laparoscopic fenestration of liver cysts

INTRODUCTION

Laparoscopic fenestration is a standard procedure for the treatment of non-parasitic liver cysts. After fenestration, the remnant liver often restores its volume. However, no systematic analysis of the phenomenon exists. In the present study, the pattern of liver volume restoration after laparoscopic fenestration of liver cysts was analyzed, and the mechanism for the unique restoration was investigated.

METHODS

Seven patients with giant non-parasitic liver cysts underwent laparoscopic fenestration. Liver volume restoration in each section and changes in the diameter of the portal branch were analyzed after fenestration with CT or MRI. In two patients, regional liver volume restoration was assessed in detail using region-growing software, and change in portal flow distribution was estimated using computational fluid dynamics. Then, the regional liver volume restoration rate was compared with the portal hemodynamic changes.

RESULTS

Liver volume restoration after fenestration was dependent on the size and position of the cysts; it not uniform throughout the remnant liver. The liver volume restoration in sections that had been compressed by giant cysts was significantly greater than in other areas after fenestration. This volume restoration was accompanied by an increase in the diameters of the portal branches in these sections. In addition, a strong correlation between the regional liver volume restoration rate and the changes in portal flow distribution existed in the computationally analyzed cases.

CONCLUSION

Liver volume restoration after the fenestration of giant liver cysts non-uniformly occurs in the remnant liver. Improved portal vein circulation in the hepatic area adjacent to the excised giant liver cysts most likely regulates the greater regional volume restoration rate in the area.

Mesenchymal stem cells support hepatocyte function in engineered liver grafts

Recent studies suggest that organ decellularization is a promising approach to facilitate the clinical application of regenerative therapy by providing a platform for organ engineering. This unique strategy uses native matrices to act as a reservoir for the functional cells which may show therapeutic potential when implanted into the body. Appropriate cell sources for artificial livers have been debated for some time. The desired cell type in artificial livers is primary hepatocytes, but in addition, other supportive cells may facilitate this stem cell technology. In this context, the use of mesenchymal stem cells (MSC) is an option meeting the criteria for therapeutic organ engineering. Ideally, supportive cells are required to (1) reduce the hepatic cell mass needed in an engineered liver by enhancing hepatocyte function, (2) modulate hepatic regeneration in a paracrine fashion or by direct contact, and (3) enhance the preservability of parenchymal cells during storage. Here, we describe enhanced hepatic function achieved using a strategy of sequential infusion of cells and illustrate the advantages of co-cultivating bone marrow-derived MSCs with primary hepatocytes in the engineered whole-liver scaffold. These co-recellularized liver scaffolds colonized by MSCs and hepatocytes were transplanted into live animals. After blood flow was established, we show that expression of adhesion molecules and proangiogenic factors was upregulated in the graft.

Portal flow is the main predictor of early graft dysfunction regardless of the GRWR status in living donor liver transplantation - a retrospective analysis of 134 patients

BACKGROUND

Sometimes even in adequate graft to recipient weight ratio (GRWR) settings and after ruling out all other causes, recipients still show features of the small for size syndrome. The purpose of this study was to evaluate all causative factors responsible for early graft dysfunction fulfilling the definition of the small for size syndrome, regardless of the GRWR status, and with particular emphasis on portal flow (ml/min/100 g). We also tried to establish whether a high portal flow on intraoperative Doppler study immediately after reperfusion can predict graft dysfunction.

MATERIAL AND METHODS

Early graft dysfunction was defined according to the definitions given for the small for size syndrome by the Kyushu University Group. Patients undergone living donor liver transplantations between January 2010 and December 2012 were analyzed. We routinely do Doppler ultrasound (USG) immediately after reperfusion and daily for 5 days. The portal vein flow after routine Doppler examination immediately after reperfusion was noted as the portal vein flow at day 0.

RESULTS

19 of 134 patients showed features of early graft dysfunction as defined. On univariate analysis, hepatitis C virus (HCV) and portal vein flow immediately after reperfusion were significant predictors of postoperative graft dysfunction. (p = 0.008 and p < 0.0001). On multivariate logistic regression, only portal vein flow after reperfusion (p = 0.002) remained as the significant predictor of postoperative graft dysfunction. A portal flow of greater than 190 (ml/min/100 g) was significant in predicting graft dysfunction (p < 0.0001) with an AUROC of 0.709. GRWR was not a significant predictor.

CONCLUSION

A portal vein flow immediately after reperfusion >190/ml/min/100 g. reliably predicted whether a graft would behave as small for size or not, regardless of the GRWR status. Portal vein flow was the most significant predictor of graft dysfunction.

Regional hepatic regeneration after liver resection correlates well with preceding changes in the regional portal circulation in humans

BACKGROUND AND AIMS

While portal hemodynamics largely affects the liver regeneration after partial hepatectomy, whether the remnant liver homogeneously regenerates is unclear, especially in humans. We hypothesized that change in flow distribution varies in each remnant portal branch after liver resection in humans and the liver consequently regenerates heterogeneously.

METHODS

Twenty-two patients who underwent anatomical hepatic resection preserving intact drainage veins were analyzed. Based on perioperative contrast-enhanced computed tomography, the regional hepatic regeneration in each segment was analyzed using a region growing software. The perioperative change in the distribution of blood flow in each portal branch was assessed using the computational flow dynamics technique. The correlation between the change in the portal flow distribution and the later regional hepatic regeneration was investigated.

RESULTS

The distribution of portal blood flow in each remnant branch largely changed at 2 weeks (71-389 %). Each remnant segment also heterogeneously regenerated at 3 months (85-204 %). Meanwhile, a good correlation between the regional regeneration rate at 3 months and the relative change in the flow distribution in each circulating portal branch at 2 weeks was detected in each patient (r = 0.74-0.99).

CONCLUSIONS

After partial hepatectomy, the change in blood flow varies in each remnant portal branch and the liver heterogeneously regenerates in humans. The good correlation between the earlier change in the portal flow distribution and the later regional hepatic regeneration strongly suggests that the portal venous flow most likely regulates the non-uniform liver regeneration after hepatic resection in humans.

Small-for-size syndrome in living donor liver transplantation

When the graft volume is too small to satisfy the recipient's metabolic demand, the recipient may thus experience small-for-size syndrome (SFSS). Because the occurrence of SFSS is determined by not only the liver graft volume but also a combination of multiple negative factors, the definitions of small-for-size graft (SFSG) and SFSS are different in each institute and at each time. In the clinical setting, surgical inflow modulation and maximizing the graft outflow are keys to overcoming SFSS. Accordingly, relatively smaller-sized grafts can be used with surgical modification and pharmacological manipulation targeting portal circulation and liver graft quality. Therefore, the focus of the SFSG issue is now shifting from how to obtain a larger graft from the living donor to how to manage the use of a smaller graft to save the recipient, considering donor safety to be a priority.

Increasing donor body weight to prevent small-for-size syndrome in living donor liver transplantation

BACKGROUND

This study was designed to evaluate the possibility of avoiding small-for-size syndrome (SFSS) in living donor liver transplantation (LDLT) by increasing the donor's body weight (BW) before liver donation.

METHODS

Nineteen participants, including 15 volunteers and 4 liver donors, were enrolled in this study to increase their BW by 1.5-5 kg within 3 months by eating a high-protein and high-carbohydrate diet according to a flexible formula to increase calorie intake.

RESULTS

Fifteen participants, including 12 volunteers and 3 live liver donors, successfully increased their BW by 1.5-5 kg within 3 months (failure rate, 21%). The actual liver weight (LW) gain was more than the expected LW gain using the formula for calculating standard liver volume (2.77- to 8.94-fold; median, 4.49-fold; mean, 4.45-fold, P < 0.005) and using the ratio of liver weight to body weight (1.36- to 4.49-fold; median, 2.01-fold; mean, 2.06-fold, P < 0.005). The enlargement of the livers was symmetrical without significant fatty change. The graft-versus-recipient weight ratio increased 0.17%, 0.07%, and 0.08%, respectively, for the three live liver donors and successful LDLTs were performed.

CONCLUSIONS

By having liver donors eat a high-protein, high-carbohydrate diet to increase their BW in a short period of time, the actual LW may increase more than the expected LW gain without fatty change. This method of increasing LW may be used in selected cases of LDLT to avoid SFSS.

Changes in mitochondrial respiratory enzyme activity after ischemia-reperfusion injury in living-donor liver transplantation

BACKGROUND

Ischemia-reperfusion (I-R) injury plays an important role in the immediate graft function in living-donor liver transplantation (LDLT). There is growing evidence that mitochondria play a pivotal role in I-R injury. Our aim was to evaluate changes in mitochondrial respiratory enzyme activities after I-R injury in LDLT.

METHODS

Specimens from 8 donor recipient pairs enrolled in this study were obtained from the donor livers before harvest (before I-R injury) and after vascular anastomosis in the recipient (after I-R injury). Histidine-tryptophan-ketoglutarate solution was used to perfuse the organ during the cold ischemic period between harvesting and transplantation. We correlated changes in mitochondrial respiratory enzyme complex activity (succinate cytochrome c reductase [SCCR]; NADH cytochrome c reductase [NCCR]) after I-R injury with clinical data and graft status.

RESULTS

NCCR and SCCR activities did not uniformly decrease after I-R injury. Two of 8 recipients experienced graft dysfunction after transplantation. The decrease in neither NCCR nor SCCR activity correlated with graft dysfunction in these 2 patients. Among the clinical factors, grafts from older donors tended to show decreased NCCR activity after I-R injury.

CONCLUSIONS

In this study, changes in mitochondrial respiratory enzyme activity failed to predict the severity of I-R injury in LDLT. The organ preservation solution may play a protective role on mitochondrial respiratory enzymes during I-R injury.

Liver regeneration in donors and adult recipients after living donor liver transplantation

In living donor liver transplantation, the safety of the donor operation is the highest priority. The introduction of the right lobe graft was late because of concerns about donor safety. We investigated donor liver regeneration by the types of resected segments as well as recipients to assess that appropriate regeneration was occurring. Eighty-seven donors were classified into 3 groups: left lateral section donors, left lobe donors, and right lobe donors. Forty-seven adult recipients were classified as either left or right lobe grafted recipients. Volumetry was retrospectively performed at 1 week, 1, 2, 3, and 6 months, and 1 year after the operation. In the right lobe donor group, the remnant liver volume was 45.4%, and it rapidly increased to 68.9% at 1 month and 89.8% at 6 months. At 6 months, the regeneration ratios were almost the same in all donor groups. The recipient liver volume increased rapidly until 2 months, exceeding the standard liver volume, and then gradually decreased to 90% of the standard liver volume. Livers of the right lobe donor group regenerated fastest in the donor groups, and the recipient liver regenerated faster than the donor liver. Analyzing liver regeneration many times with a large number of donors enabled us to understand the normal liver regeneration pattern. Although the donor livers did not reach their initial volume, the donors showed normal liver function at 1 year. The donors have returned to their normal daily activities. Donor hepatectomy, even right hepatectomy, can be safely performed with accurate preoperative volumetry and careful decision-making concerning graft-type selection.

Different hemodynamic patterns of alcoholic and viral endstage cirrhosis: analysis of explanted liver weight, degree of fibrosis and splanchnic Doppler parameters

OBJECTIVE

In cirrhosis, portal hemodynamics is usually considered independently of the disease etiology. The objective of this study was to investigate the role of the etiology of liver disease on the relationship between liver blood flow and liver pathology in endstage cirrhosis.

MATERIAL AND METHODS

Portal blood velocity and volume, congestion index of the portal vein, and hepatic and splenic pulsatility indices were evaluated with echo-Doppler in cirrhotic patients immediately before liver transplantation. When a patent paraumbilical vein was present, its blood flow was measured and effective portal liver perfusion was calculated as portal blood flow minus paraumbilical blood flow. The hemodynamic parameters were correlated with liver weight and the pattern of the liver fibrosis morphometrically assessed in explanted livers. A total of 131 patients with alcoholic or viral cirrhosis were included in the study.

RESULTS

In alcoholic cirrhosis, liver weight was higher than that in viral disease (1246+/-295 g versus 1070+/-254 g, p=0.001), portal liver perfusion per gram of liver tissue was lower (0.49+/-0.36 ml g(-1) min(-1) versus 0.85+/-0.56 ml g(-1) min(-1), p=0.004) and hepatic pulsatility indices were higher (1.45+/-0.31 versus 1.26+/-0.30, p=0.018). The degree of liver fibrosis was similar in alcoholic and viral cirrhosis (11.7+/-5.5% versus 11.0+/-4.4%, p=NS). An inverse relationship between liver weight and Child-Pugh score was disclosed in viral (p<0.001) but not in alcoholic disease.

CONCLUSIONS

A different hemodynamic pattern characterizes the advanced stage of cirrhosis of alcoholic and viral origin. A more severe alteration of intrahepatic portal perfusion, probably coexisting with a more severe hepatocyte dysfunction, and a higher liver weight can be detected in alcoholic cirrhosis.

Optimal portal venous circulation for liver graft function after living-donor liver transplantation

BACKGROUND

Previous studies have shown poor outcome after living-donor liver transplantation (LDLT) as a result of excessive portal venous pressure (PVP), excessive portal venous flow (PVF), or inadequate PVF. We investigated optimal portal venous circulation for liver graft function after LDLT in adult recipients retrospectively.

METHODS

Between June 2003 and November 2004, 28 adult patients underwent LDLT in our institution. We modulated PVP under 20 mmHg in these 28 cases by performing a splenectomy (n=4) or splenorenal shunt (n=1). The PVF and PVP were measured at the end of the operation. Compliance was calculated by dividing PVF by PVP.

RESULTS

PVF and compliance showed a significant inverse correlation with peak billirubin levels after LDLT (r = -0.63: r=-0.60, P<0.01), and with peak international normalized ratio after LDLT (r=-0.41: r=-0.51, P<0.05). Compliance was higher in right-lobe graft with middle hepatic vein cases (148+/-27 ml/min/mmHg), and lower in left-lobe graft cases (119+/-50 ml/min/mmHg).

CONCLUSIONS

Liver graft function was better when PVF and graft compliance were higher and PVP was maintained under 20 mmHg.

The 'small for size' liver syndrome

PURPOSE OF REVIEW

Small-for-size syndrome (SFSS) is a clinical syndrome described following liver transplantation (LT) and extended hepatectomy. New evidence has emerged documenting the importance of preoperative evaluation of functional liver mass, liver quality, influence of portal hypertension, and variations in surgical technique to improve outcome.

RECENT FINDINGS

SFSS is characterized by postoperative coagulopathy and liver dysfunction due to insufficient functional liver mass. Recent radiologic advances allow accurate preoperative estimation of total, graft, and remnant liver volume (RLV). In adult-to-adult living donor liver transplantation (LDLT), a graft-to-recipient body weight ratio > or = 0.8% or graft weight ratio > or = 30% are important to avoid SFSS. Minimal functional RLV following extended hepatectomy is > or = 25% in a normal liver, and > or = 40% with preoperative liver dysfunction. Preoperative portal vein or hepatic artery embolization to increase RLV and function after extended hepatectomy, and the increasing use of parenchymal-sparing segmental resections have improved outcome. In LT, the evolving use of split livers, LDLT and marginal grafts has resulted in increased recognition of SFSS. This has led to a renewed interest in defining the pathophysiology, and the development of new surgical techniques to reduce its incidence.

SUMMARY

Current radiologic imaging techniques can be used to evaluate liver volume and the risk of SFSS following LT and extended hepatectomy. Intraoperative techniques to predict postoperative dysfunction are emerging, and may be helpful in directing the use of pre-emptive surgical interventions. The future lies in the development of perioperative liver protection and support in predicted SFSS, and enhancement of healthy liver regeneration.

Living donor liver transplantation with left liver graft

Small-for-size syndrome in LDLT is associated with graft exposure to excessive portal perfusion. Prevention of graft overperfusion in LDLT can be achieved through intraoperative modulation of portal graft inflow. We report a successful LDLT utilising the left lobe with a GV/SLV of only 20%. A 43 year-old patient underwent to LDLT at our institution. During the anhepatic phase a porto-systemic shunt utilizing an interposition vein graft anastomosed between the right portal branch and the right hepatic vein was performed. After graft reperfusion splenectomy was also performed. Portal vein pressure, portal vein flow and hepatic artery flow were recorded. A decrease of portal vein pressure and flow was achieved, and the shunt was left in place. The recipient post-operative course was characterized by good graft function. Small-for-size syndrome by graft overperfusion can be successfully prevented by utilizing inflow modulation of the transplanted graft. This strategy can permit the use of left lobe in adult-to-adult living donor liver transplantation.

Porcine partial liver transplantation: a novel model of the "small-for-size" liver graft

Increasing shortage of cadaveric grafts demands the utilization of living donor and split liver grafts. The purpose of this study was to 1) define the "small-for-size" graft in a pig liver transplant model 2) evaluate pathological changes associated with small-for-size liver transplantation. Pigs were divided into four groups based on the volume of transplanted liver: (a) control group (n=4), 100% liver volume (LV) (b) group I (n=8), 60% LV (c) group II (n=8), 30% LV (d) group III (n=15), 20% LV. Tacrolimus and methyl prednisone were administered as immunosuppression. Animals were followed for 5 days with daily serum biochemistry, liver biopsies on day 3 and 5 for light microscopy, and tissue levels of thymidine kinase (TK) and ornithine decarboxylase (ODC). Liver grafts were weighed pretransplant and at sacrifice. All the recipients of 100%, 60%, and 30% grafts survived. Transplantation of 20% grafts (group III) resulted in a 47% mortality rate. Group III animals showed significantly prolonged prothrombin times (p<0.05), elevated bilirubin levels (p<0.05), and ascites. The rate of regeneration, as indicated by TK activity and graft weight was inversely proportional to the size of the transplanted graft. The severity of the microvascular injury was inversely proportional to graft size and appeared to be the survival-limiting injury. Frank rupture of the sinusoidal lining, parenchymal hemorrhage, and portal vein injury were prominent in group III animals 1 hour following reperfusion. This study established a reproducible large animal model of partial liver grafting; it defined the small-for-size syndrome in this model and described the associated microvascular injury.

Clinical relevance of adapting portal vein flow in living donor liver transplantation in adult patients

Size mismatching is a major concern in adult living donor liver transplantation (ALDLT). Graft hyperperfusion in these grafts is considered the main factor leading to graft dysfunction and poor survival. We describe the clinical significance of graft inflow modification (GIM) by splenic artery ligation in a series of 24 consecutive ALDLT. Between September 1999 and December 2001, 24 patients underwent ALDLT at our institution. Patients were divided into two groups: G1, n = 11 without GIM, and G2, n = 13 with GIM. Both groups were equivalent in terms of preoperative clinical state, graft characteristics, and surgical technique. Graft hyperperfusion was noticed overall, especially in small grafts (graft-to-recipient body weight ratio <0.8), with mean recipient portal vein (rPVF) values at least three times greater than those recorded in the donors. GIM permitted in G2 a significant decrease in rPVF. Small-for-size syndrome (SFSS) occurred in three (27%) patients in G1 with small grafts showing graft hyperperfusion and necessitating a retransplantation. SFSS did not occur in G2. One-year overall survival was 62% and 93% respectively for G1 and G2. It is concluded that when small-for-size grafts are accompanied by graft hyperperfusion, the rPVF should be lowered to avoid the SFSS and to improve the outcome.

Relationship between portal venous flow and liver regeneration in patients after living donor right-lobe liver transplantation

The purpose of this study is to evaluate the relationship between portal venous (PV) velocity and degree of liver regeneration in humans after living donor liver transplantation (LDLT). Between July 1997 and September 2002, a total of 15 adult-to-adult LDLTs with right-lobe grafts were performed, and 13 of these patients were enrolled in this study. Postoperative PV dynamics differed according to the primary liver disease; therefore, patients were divided into two groups: a fulminant hepatic failure (FHF) group (n = 4) and a liver cirrhosis (LC) group (n = 9). Right-lobe donors (n = 13; D group) were used as controls. Doppler ultrasound was used to measured changes in PV velocity preoperatively; postoperative days (PODs) 1, 3, 7, 14, and 28; and 3 months after LDLT. To assess hepatic regeneration, the increase in liver volume ratio (postoperative liver volume to standard liver volume [SLV]) was measured. PV velocity after LDLT in the LC group increased sharply until POD 7, whereas those in the FHF and D groups were constant. In the first 3 months after LDLT, mean PV velocity was greater in the LC group than the other groups, reflecting the persistent hyperdynamic state in chronic end-stage liver disease. Liver regeneration also was more rapid in the LC group than the FHF and D groups and reached 100% as early as 2 weeks posttransplantation, whereas both the FHF and D livers reached approximately 80% of SLV at 3 months. PV velocity POD 7 correlated significantly with regeneration of the partial-liver allograft at 1 month (r = 0.84; P =.0091). In conclusion, the PV persistent hyperdynamic state in the LC group could directly trigger early liver regeneration in partial-liver allografts after LDLT.

Modulation of portal graft inflow: a necessity in adult living-donor liver transplantation?

OBJECTIVE

To evaluate the clinical significance of modulating the recipient portal inflow (rPVF) through perioperative ligation of the splenic artery in adult living-donor liver transplantation (ALDLTx) by focusing on vascular complications, intractable ascites production, and the prevention of small-for-size syndrome (SFSS).

SUMMARY BACKGROUND DATA

In ALDLTx, portal graft flow is enhanced to at least twice the donor value, raising the total liver inflow. Recipient hepatic arterial flow (rHAF) is lower than expected. Portal hyperperfusion of small grafts in larger recipients is thought to be one of the main causes of posttransplant graft dysfunction/SFSS.

METHODS

Seventeen ALDLTx were reviewed for a minimum of 2 months. Patients were divided retrospectively into two groups: G1 (n = 7), without modulation of rPVF, and G2 (n = 10), with splenic artery ligation to decrease rPVF perioperatively. Donor and recipient hepatic hemodynamics were evaluated against graft function and outcome, including correlations between rPVF, graft weight, graft:recipient body weight ratio, and recipient weight.

RESULTS

Following portal and arterial reperfusion, mean rPVF and rPVF/graft weight were much higher than in the donors, whereas mean rHAF and rHAF/graft weight were much lower. No differences were found between groups, except for rPVF and rHAF, which were much more higher and lower, respectively, before splenic artery ligation. In G1 patients, SFSS was seen in two patients and vascular complications occurred in two others. In G2 patients, splenic artery ligation permitted a significant decrease in rPVF, an improvement in rHAF, and the resolution of refractory ascites. Neither SFSS nor vascular complications were seen in G2 patients.

CONCLUSIONS

When a suboptimal graft:recipient body weight ratio is accompanied by high rPVF in ALDLTx, the portal flow should be modulated perioperatively; splenic artery ligation is a simple and safe method that is sufficient to allow this modulation in most patients.

Modulation of portal graft inflow: a necessity in adult living-donor liver transplantation?

OBJECTIVE

To evaluate the clinical significance of modulating the recipient portal inflow (rPVF) through perioperative ligation of the splenic artery in adult living-donor liver transplantation (ALDLTx) by focusing on vascular complications, intractable ascites production, and the prevention of small-for-size syndrome (SFSS).

SUMMARY BACKGROUND DATA

In ALDLTx, portal graft flow is enhanced to at least twice the donor value, raising the total liver inflow. Recipient hepatic arterial flow (rHAF) is lower than expected. Portal hyperperfusion of small grafts in larger recipients is thought to be one of the main causes of posttransplant graft dysfunction/SFSS.

METHODS

Seventeen ALDLTx were reviewed for a minimum of 2 months. Patients were divided retrospectively into two groups: G1 (n = 7), without modulation of rPVF, and G2 (n = 10), with splenic artery ligation to decrease rPVF perioperatively. Donor and recipient hepatic hemodynamics were evaluated against graft function and outcome, including correlations between rPVF, graft weight, graft:recipient body weight ratio, and recipient weight.

RESULTS

Following portal and arterial reperfusion, mean rPVF and rPVF/graft weight were much higher than in the donors, whereas mean rHAF and rHAF/graft weight were much lower. No differences were found between groups, except for rPVF and rHAF, which were much more higher and lower, respectively, before splenic artery ligation. In G1 patients, SFSS was seen in two patients and vascular complications occurred in two others. In G2 patients, splenic artery ligation permitted a significant decrease in rPVF, an improvement in rHAF, and the resolution of refractory ascites. Neither SFSS nor vascular complications were seen in G2 patients.

CONCLUSIONS

When a suboptimal graft:recipient body weight ratio is accompanied by high rPVF in ALDLTx, the portal flow should be modulated perioperatively; splenic artery ligation is a simple and safe method that is sufficient to allow this modulation in most patients.