Portocaval Shunt Research Articles

Protocolo de monitorización hemodinámica hepática en el trasplante hepático de donante vivo en adultos

IntroductionThe recipient of an adult living donor liver transplant (ALDLT) is subjected to great haemodynamic changes that could lead to the appearance of a “small-for-size” syndrome in the post-operative period due to portal hyperflow. The aim of this article is to evaluate these changes, and try to correlate them with portal vein flow during reperfusion. Material and methodsA protocol for monitoring various liver haemodynamic data of the ALDLT recipient before, during and after surgery has been used since the year 2003. The haemodynamic outcome of the recipient after the transplant, as well as the correlation between the portal vein flow during reperfusion and the collected haemodynamic data is analysed. ResultsThere was no small for size syndrome. A significant relationship was found between the portal flow during reperfusion and the portal vein pressure at the beginning of the operation (r=0.46, P<.006) and with the portocaval shunt flow during the anhepatic phase (r=0.55, P<.001). The recipients showed a normal splanchnic hemodynamic state at 3 months after the transplant. ConclusionsHaemodynamic monitoring of the ALDLT recipient is essential to prevent portal hyperflow. The relationship between flow during reperfusion and flow through the portocaval shunt means that patients with a higher risk of hyperflow can be identified and can be modified before reperfusion.

Temporary intraoperative porto-caval shunt: useless or beneficial in piggy back liver transplantation?

The role of intraoperative porto-caval shunts in orthotopic liver transplantation (OLT) is controversial. Aim of this study was to analyze the effects of an intraoperative, porto-caval catheter-shunt on graft function and survival following cava sparing OLT. Four hundred and forty-eight piggy back liver transplantations with or without a temporary spontaneous porto-caval shunt between 1997 and 2010 were analyzed (shunt n=274 vs. no shunt n=174). Lab MELD scores and donor risk indices (DRI) were calculated. Hepatic injury (ALT, AST), -function (bilirubin, prothrombin ratio), postreperfusion liver blood flow and graft survival were registered [mean follow-up: 50.5 (0-163.0) months]. The impact of a shunt on graft survival was determined using multivariate analysis. Usage of a porto-caval shunt was associated with reduced hepatic injury (ALT, AST), whereas graft function was not affected. The shunt group showed a significantly increased portal venous blood flow after reperfusion. Retransplantation rate was decreased (7.7% vs. 20.1%, P=0.001) and long-term graft survival was significantly increased with a porto-caval shunt (hazard ratio 2.1, P<0.001). This effect was even more pronounced for marginal organs. Usage of intraoperative porto-caval catheter-shunts is beneficial in cava sparing OLT and is associated with reduced ischemia-reperfusion injury and improved organ survival in particular for recipients of marginal organs.

Hepatobiliary and Pancreatic: Abernethy malformation—congenital portocaval shunt

Hepatobiliary and Pancreatic: Abernethy malformation—congenital portocaval shunt

Side to Side Cavocavostomy in Piggy Back Adult Liver Transplantation

Aims: Retrospective study designed to describe results of the side-to-side cavo-cavostomy (STSCC) anastomosis through caval reconstruction, with particular emphasis on complications associated with this technique. All within a single Institution experience. Patients and methods: From June 1998 to January 2012, 577 cadaver liver transplants were performed at our Institution. 575 of which underwent STSCC in accordance with Belghiti's technique described elsewhere. Temporary porto-caval shunt was coupled to STSCC in 38 cases. Routine intraoperative Doppler ultrasonography was performed at the end of every procedure. Results: STSCC was feasible in all but 2 cases (99.66%) regardless of recipient's vena cava, anatomic factors, graft size or re-transplant status. Mean operative time for STSCC was 13 minutes (6-30 minutes). Though not necessarily considered a complication, there were 3 cases of caval stump thrombosis (0,52%). Complications strictly associated with this particular technique were limited to 4 patients (0,69%). The most significant one was the case of a patient that presented with acute post-operative Budd-Chiari syndrome that developed progressive deterioration due to liver failure. The patient could not be rescued with re-transplantation due to progressive brain damage and eventual cardiac arrest. The other three patients that developed direct complications attributed to STSCC were managed successfully. In one patient that developed outflow obstruction due to torsion from donor graft/recipient mismatch, the outflow was surgically improved by falciform ligament fixation. The second was only evident on biopsy by sinusoidal congestion and was managed non-operatively with measures to decrease central venous pressure. The third patient developed a pulmonary distress due to a decreased cardiac return consequence of a large sized graft, with subsequent severe haemodynamic instability requiring significant amount of pressors. The patient was managed non-operatively through a “positional” approach, by turning him 45 degree to the left in order to improve venous return to the heart. Twenty-five cases were done uneventfully with STSCC in patients undergoing re-transplantation. Conclusions: Side-to-Side Cavo-Cavostomy during piggyback liver transplantation has proven to be a safe and straightforward procedure, which can be performed even in a re-transplantation setting. In our experience this technique has shown a very low incidence of venous outflow obstruction. Maximal preservation of recipient inferior vena cava and temporary porto-caval shunt, improves decompression of inferior and splanchnic venous systems during the an-hepatic phase. In our opinion, STSCC helps overcome the outflow complications associated with traditional piggyback technique by using the orifices of one or more recipient hepatic veins as needed. Our study also indicates that donor graft to recipient mismatch is not an absolute contraindication when proper body size match is considered. A wide anastomosis with typical recipient hepatic veins inclusion and routine post-anastomotic Doppler Ultrasonography measurements are warranted.

Small-Intestinal Variceal Hemorrhage: Successful Treatment with Transjugular Intrahepatic Portosystemic Shunt

Purpose: A 48 y/o female with a history of alcoholic cirrhosis and portal hypertension presented with 2 episodes of large hematochezia with severe epigastric and periumbilical abdominal pain. Labs revealed an acute decline in hemoglobin (Hgb) from 11 to 8 gm/dL. An abdominal CT obtained to evaluate her abdominal pain revealed changes suggestive of portal hypertension including multiple collaterals, small intestinal (SI) varices, splenorenal shunting, and a recanalized paraumbilical vein. Intraluminal blood in the distal SI was noted, thought to be in the region of a SI varix and potentially the etiology of her symptoms. Fluid resuscitation, blood transfusion, IV proton pump inhibitor and octreotide therapy were initated. However, she continued to have persistent hematochezia with a further drop in Hgb to 6.3 gm/dL. Emergent EGD did not demonstrate any lesion as a source of bleeding. Subsequent CT angiography showed pooling of contrast in the distal loop of ileum with large SI varices. Attempts at angiographically controlling bleeding were unsuccessful. Given the findings of portal enteropathy with large SI varices, emergent therapeutic TIPS was performed for acute control of SI bleeding. Post-TIPS HVPG was documented as 7 mmHg. Subsequently, her bleeding stopped and her Hgb improved. Overall, she received 10 units of packed RBC, 6 units of FFP and 4 units of platelet transfusion. Portal hypertension, usually a complication of cirrhosis, presents as ascites, splenomegaly, and bleeding from esophageal, gastric, and ectopic varices. Ectopic enteric varices including duodenal, mesenteric, anorectal, peristomal, and rarely ileal varices are an unusual cause of GI bleeding accounting for 1-5% of all variceal bleeding. While the incidence of bleeding is low, this may result in severe, life threatening hemorrhage with a mortality approaching 40%. Therapeutic options for variceal bleeding include endoscopic sclerotherapy, vasoactive drugs, segmental bowel resection, portosystemic shunt surgery, oversewing of varices, and TIPS procedures with or without focal variceal embolization. Endoscopic management is limited as very often visualization of SI varices is not achieved because of their distal location and relatively small size. Unless the underlying portal hypertension is treated, suture ligation of varices as well as sclerotherapy have high rebleeding rates. Surgical portocaval shunting is effective with low rebleeding rates, but is only recommended in patients who can tolerate a major surgical procedure. TIPS can effectively reduce the portocaval gradient, and consequently, the risks of bleeding decrease drastically. This is especially indicated for patients that are poor surgical candidates.

Revisiting the Rare Cause of Non-Cirrhotic Portal Hypertension in West

Purpose: A 45-year-old man with a presumed diagnosis of cryptogenic liver cirrhosis came to our institution for a second opinion regarding need for liver transplantation. He had prior episodes of rectal bleeding. He had undergone extensive evaluation, and liver transplantation was suggested to him. He was born and raised in Egypt and moved to the United States at age 24. His physical exam was only significant for splenomegaly. His calculated MELD score was 9. Additional laboratory testing included negative serological tests for viral hepatitis, autoimmune hepatitis, PBC, PSC and normal iron studies, ceruloplasmin, and alpha-1 antitrypsin values. Serum IgG for Schistosoma mansoni was performed and returned positive (5.66, normal value < 1.0). Outside liver biopsy reviewed at our center showed non-caseating granulomas, minimal fibrosis stage 0-1. He was therefore diagnosed with non-cirrhotic portal hypertension related to schistosomiasis. He was treated with oral praziquantel. Despite prophylaxis with propranolol, the patient continued to have episodes of gastrointestinal bleeding and underwent porto-caval shunt with excellent clinical response. Liver biopsy at time of surgery revealed concentric fibrosis around bile ducts (Symmer's pipe stem fibrosis) (Figure 1) and multiple small non-caseating granulomas with eosinophils in liver parenchyma. Trichrome stain revealed subcapsular bridging fibrosis. Schistosomiasis is the second most prevalent tropical disease affecting humans, although rarely observed in the United States. It is acquired by penetration of broken skin by the parasite when in contact with contaminated fresh water. Initial infections can be asymptomatic until organ damage has occurred several years later. Adult worms lay eggs in intestinal venous drainage which migrate to the liver via the portal circulation. Granulomatous inflammation and fibrosis secondary to infection can lead to portal hypertension. The treatment of choice is oral praziquantel, but this does not reverse the fibrosis that has already developed. It is imperative to consider schistosomiasis as an etiology of liver disease in patients who originate from endemic regions and provide early treatment in order to prevent complications such as portal hypertension.Figure: No Caption available.

Side-to-Side Cavocavostomy in Adult Piggyback Liver Transplantation

ObjectiveOur objective was to perform a retrospective study that described the anastomosis technique as well as the complications of side-to-side cavo-caval reconstruction. Patients and MethodsFrom June 1998 to April 2011, we performed 284 liver transplantations including 10 adults with live donor organs. In all cases but 2 (272), cavo-caval reconstruction was performed using side-to-side cavo-caval (STSCC) anastomosis. In 19 cases (6.9%), we also carried out an end-to-side temporary porto-caval shunt (TPCS). In 17 cases (6.2%) the technique was performed for retransplantation. ResultsSTSCC anastomosis was technically feasible in all but 2 cases, regardless of the recipient's vena cava, anatomic factors, or graft size. Mean operative time for the STSCC was 13 minutes (range, 6–25). Routine Doppler ultrasonography was performed intraoperatively at the end of the surgery. There was no case of cava stump thrombosis. Complications associated with this technique were limited to 2 patients. One complication was torsion due to donor graft/recipient mismatch, which was successfully treated surgically by falciform ligament fixation. The second complication was only evident by sinusoidal congestion and was managed nonoperatively. Seventeen cases were uneventful for retransplant recipients. ConclusionsSTSCC during piggyback liver transplantation is safe and can be performed in the retransplantation setting, with a low incidence of venous outflow obstruction that can be associated with the traditional piggyback technique. Our data suggest that donor graft to recipient mismatch is not an absolute contraindication when proper body size match is considered. A wide anastomosis with typical recipient hepatic vein inclusion is warranted with routine postanastomotic Doppler ultrasonography.

Distribution of extrahepatic congenital portosystemic shunt morphology in predisposed dog breeds

BackgroundAn inherited basis for congenital extrahepatic portosystemic shunts (EHPSS) has been demonstrated in several small dog breeds. If in general both portocaval and porto-azygous shunts occur in breeds predisposed to portosystemic shunts then this could indicate a common genetic background. This study was performed to determine the distribution of extrahepatic portocaval and porto-azygous shunts in purebred dog populations.ResultsData of 135 client owned dogs diagnosed with EHPSS at the Faculty of Veterinary Medicine of Utrecht University from 2001 – 2010 were retrospectively analyzed. The correlation between shunt localization, sex, age, dog size and breed were studied. The study group consisted of 54 males and 81 females from 24 breeds. Twenty-five percent of dogs had porto-azygous shunts and 75% had portocaval shunts. Of the dogs with porto-azygous shunts only 27% was male (P = 0.006). No significant sex difference was detected in dogs with a portocaval shunt. Both phenotypes were present in almost all breeds represented with more than six cases. Small dogs are mostly diagnosed with portocaval shunts (79%) whereas both types are detected. The age at diagnosis in dogs with porto-azygous shunts was significantly higher than that of dogs with portocaval shunts (P < 0.001).ConclusionThe remarkable similarity of phenotypic variation in many dog breeds may indicate common underlying genes responsible for EHPSS across breeds. The subtype of EHPSS could be determined by a minor genetic component or modulating factors during embryonic development.

Portal Hypertension and Ascites in Extramedullary Hematopoiesis

Myeloproliferative diseases (MPD) are clonal stem cell disorders which mainly include polycythemia vera (PV), essential thrombocythemia (ET), and idiopathic myelofibrosis (IMF). They are characterized by leucocytosis, thrombocytosis, erythrocytosis, splenomegaly, and bone marrow hypercellularity. This might also result in extramedullary hematopoiesis. Abdominal manifestation has been recognized as a feature of these disorders. Splenomegaly and hepatomegaly are fairly common as opposed to ascites which is rare. The MPDs mainly affect the hepatic circulatory systems. The common hepatic manifestations are Budd-Chiari syndrome (BCS), portal vein thrombosis (PVT), and nodular regenerative hyperplasia. A few other features seen in MPDs are caused by extramedullary hematopoiesis, increased hepatic blood flow, and secondary hemosiderosis from multiple blood transfusions. Portal hypertension is found in up to 7% of patients. We report a case of portal hypertension with ascites in a patient with extramedullary hematopoiesis treated with transjugular intrahepatic portocaval shunt (TIPS).

Effect of Portal Haemodynamics on Liver Graft and Intestinal Mucosa after Small-for-Size Liver Transplantation in Swine

Background: After small-for-size graft (SFSG) transplantation, elevated portal venous pressure (PVP) may lead to postoperative liver damage. Herein we evaluated the impact of portocaval shunt (PCS) to control PVP on liver grafts and intestine following SFSG transplantation. Methods: Nineteen SFSG transplantations were performed with 30% of native liver in swine. Swine were divided into 3 groups: a high-flow shunt group (HS: n = 7), in which portal venous flow (PVF) was reduced with a 10-mm diameter PCS; a low-flow shunt group (LS: n = 6), in which PVF was reduced with a 5-mm diameter PCS, and a no-shunt group (NS: n = 6), in which no PCS was placed. Results: Seven-day survivals were 83.3% in NS, 100% in LS and 0% in HS (p = 0.0088). PVP was significantly higher in the NS group (p = 0.0001; mean ± SEM NS/LS/HS: 20.5 ± 0.7/14.0 ± 1.2/11.6 ± 0.5 mm Hg). The LS group exhibited the highest compliance (PVF/PVP; NS/LS/HS 42.7 ± 10.9/44.6 ± 4.9/37.7 ± 8.3 ml/min/mm Hg; p = 0.009), the lowest aspartate aminotransferase (NS/LS/HS 562 ± 18/370 ± 55/720 ± 130 IU/l; p = 0.0493), and suppressed deleterious alternations of the hepatic parenchyma and intestinal mucosa. Conclusions: Portal hypertension after SFSG transplantation impaired liver and intestinal mucosa; however, inadequate portal flow impaired not only the liver, but also survival.

Left lobe adult-to-adult living donor liver transplantation: Should portal inflow modulation be added?

Recently, the successful application of portal inflow modulation has led to renewed interest in the use of left lobe grafts in adult-to-adult living donor liver transplantation (LDLT). However, data on the hepatic hemodynamics supporting portal inflow modulation are limited, and the optimal portal circulation for a liver graft is still unclear. We analyzed 42 consecutive adult-to-adult left lobe LDLT cases without splenectomy or a portocaval shunt. The mean actual graft volume (GV)/recipient standard liver volume (SLV) ratio was 39.8% ± 5.7% (median = 38.9%, range = 26.1%-54.0%). The actual GV/SLV ratio was less than 40% in 24 of the 42 cases, and the actual graft-to-recipient weight ratio was less than 0.8% in 17 of the 42 recipients. The mean portal vein pressure (PVP) was 23.9 ± 7.6 mm Hg (median = 23.5 mm Hg, range = 9-38 mm Hg) before transplantation and 21.5 ± 3.6 mm Hg (median = 22 mm Hg, range = 14-27 mm Hg) after graft implantation. The mean portal pressure gradient (PVP - central venous pressure) was 14.5 ± 6.8 mm Hg (median = 13.5 mm Hg, range = 3-26 mm Hg) before transplantation and 12.4 ± 4.4 mm Hg (median = 13 mm Hg, range = 1-21 mm Hg) after graft implantation. The mean posttransplant portal vein flow was 301 ± 167 mL/minute/100 g of liver in the 38 recipients for whom it was measured. None of the recipients developed small-for-size syndrome, and all were discharged from the hospital despite portal hyperperfusion. The overall 1-, 3-, and 5-year patient and graft survival rates were 100%, 97%, and 91%, respectively. In conclusion, LDLT with a left liver graft without splenectomy or a portocaval shunt yields good long-term results for adult patients with a minimal donor burden.

Hepatic myelopathy in a patient with decompensated alcoholic cirrhosis and portal colopathy.

Cirrhotic or hepatic myelopathy is a rare neurological complication of chronic liver disease usually seen in adults and presents as a progressive pure motor spastic paraparesis which is usually associated with overt liver failure and a surgical or spontaneous systemic portocaval shunt. We describe the development of progressive spastic paraparesis, in a patient with alcoholic cirrhosis with portal hypertension and portal colopathy who presented with the first episode of hepatic encephalopathy. The patient had not undergone any shunt procedure.

Balloon-occluded Retrograde Transvenous Obliteration for Portocaval Shunt Except Gastrorenal Shunt

Balloon-occluded Retrograde Transvenous Obliteration for Portocaval Shunt Except Gastrorenal Shunt

Abernethy malformation complicated by hepatopulmonary syndrome and a liver mass successfully treated by liver transplantation

A seven-yr-old boy presented with persistent oxygen requirement following a respiratory infection. Physical exam was remarkable for orthodeoxia and digital clubbing. Laboratory evaluation showed elevated A-a oxygen gradient of 48 mmHg and mildly elevated transaminases. Sonography showed a 13 cm multilobulated liver mass and a biopsy revealed histological findings consistent with focal nodular hyperplasia. MAA scan revealed 23% right to left shunting. Abdominal CTA and MRV demonstrated the absence of the intrahepatic portal vein with an extrahepatic portocaval shunt. Abernethy malformation is a rare anomalous intra- or extrahepatic communication between portal blood flow and systemic venous return. In rare cases, Abernethy malformation results in HPS. Ours is the sixth case report to describe the co-existence of these two entities. Surgical correction of anomalous hepatic vasculature or liver transplant is imperative to restoration of lung function and also to prevent progression of possible malignant liver tumors. We describe the second patient with Abernethy and HPS who underwent liver transplant with complete resolution of HPS.

Large focal nodular hyperplasia and extrahepatic portosystemic shunt in a male patient: Multi-modality imaging features

Congenital extrahepatic portocaval shunt is a rare condition that is described mostly in female patients. We report an unusual case of a young adult male patient with type 1 congenital extrahepatic portocaval shunt with associated development of a focal nodular hyperplasia on a background of regenerative nodules. With multi-slice CT utilisation, there is increased detection of portocaval malformation in asymptomatic patients. This congenital variant is clinically significant with associated development of hepatocellular lesions, hepatic dysfunction and/or encephalopathy.

Liver impairment after portacaval shunt in the rat: The loss of protective role of mast cells?

Mast cells are involved in various liver diseases and appear to play a broader pathogenic role than originally thought. They may participate in the splanchnic alterations related to a porto-systemic shunt. To verify this hypothesis we studied the serum and hepatic histological changes in rats four weeks after an end-to-side portacaval shunt. In this experimental model of chronic liver insufficiency we also assessed the mucosal mast cells (MMC) and connective tissue mast cells (CTMC) in the liver, mesenteric lymph nodes and small intestine, as well as the serum levels of rat mast cell protease-II (RMCP-II). The results show liver and testes atrophy, with hypoalbuminemia (p=0.0001), hyperbilirubinemia (p=0.0001) and increase in aspartate aminotransferase (p=0.004) and alanine aminotransferase (p=0.0001). Hepatic histopathology demonstrates hepatocytic necrosis and apoptosis, portal inflammation, biliary proliferation, steatosis and fibrosis. There is a decrease of MMCs and CTMCs in the liver, while in the ileum CTMCs increase and MMCs decrease. These results suggest the involvement of mast cells in the pathophysiological splanchnic impairments in this experimental model. In particular, the decreased number of liver mast cells may be associated with the hepatic atrophy. If this is the case, we propose that the disruption of the hepato-intestinal axis after a portocaval shunt in the rat could inhibit the ability of the liver to developing an appropriate repair response mediated by mast cells.

Results of a newborn liver transplant program in the era of piggyback technique and extended donor criteria in Italy

The aim of this study was to critically analyze the early and long-term results of a newborn liver transplantation (LTx) centre using piggyback technique (PT) without venovenous bypass and portocaval shunt in the era of extended criteria donors (ECDs). Between 2002 and 2010, a total of 229 LTx were performed in 225 patients, with the shortest as possible cold ischemia time (CIT) policy. The charts of the donors and recipients and the intraoperative data were retrospectively reviewed in order to define the feasibility of PT and surgical outcome, and long-term graft and patient survival. PT feasibility rate was 100%, with a median duration of surgery of 390min (range 210-630) and median unit of packed RBC transfused intraoperatively of 1U (range 1-10). Median CIT was 400min (range 130-870), and median AST peak was 403 mmol/L (range 48-16,900). ECDs graft rate was 85%. Over all primary dysfunction and non-function (PNF) rates were 7.4 and 2.2%, respectively and increased with graft steatosis >30% (P<0.004). Mortality, morbidity, re-operation and re-LTx rates were 4.4, 25, 6.1 and 1.3%, respectively, and median hospital stay was 18days (range 8-150). On the long term, graft and patient 5-year overall survival were 72 and 74%, respectively, and re-LTx rate was 0.4%. Survival was significantly affected by recipient HCV-Ab seropositive status (67 vs. 85%, P=0.023). Liver transplantation can be performed with low morbidity and mortality rates, despite ECDs. PT is a safe and effective procedure that, combined with short CIT, entailed prompt early functional recovery of the grafts and positive long-term results.

Response to Minou: “Does the temporary porto-caval shunt have any beneficial impact in orthotopic liver transplantation?”*

Response to Minou: “Does the temporary porto-caval shunt have any beneficial impact in orthotopic liver transplantation?”*

Does the temporary porto-caval shunt have any beneficial impact in orthotopic liver transplantation?

Does the temporary porto-caval shunt have any beneficial impact in orthotopic liver transplantation?

Decompression of the Portal Bed and Twice-Baseline Portal Inflow Are Necessary for the Functional Recovery of a “Small-for-Size” Graft

In partial liver transplant, a reduction in the intrahepatic vascular bed produces a rise in the portal vein flow and the portal venous pressure gradient, leading to endothelial and, thereby, hepatocellular injury and death in a process known as "small-for-size" (SFS) syndrome. To demonstrate that a calibrated portocaval shunt prevents superfluous inflow in a porcine model of SFS transplant. Donor pigs (15-20 kg) underwent 70% hepatectomy. In 2 groups, a 6 mm (S6) (n = 6) or 12 mm (S12) (n = 6) Gore-Tex shunt was placed between the portal vein and infrahepatic inferior vena cava. In a third group, no portocaval shunt was placed (SFS) (n = 17). Grafts were stored for 5 hours at 4°C and then transplanted into recipients (30-35 kg). Five-day survival was 29% in SFS, 100% in S6, and 0 in S12. Postreperfusion portal vein flow was 4-, 2-, and 1-times flow at baseline in SFS, S6, and S12, respectively. With respect to portal venous pressure gradient, both the 6- and 12-mm shunts effectively decompressed the portal bed. Aspartate aminotransferase and bilirubin rose and the Quick prothrombin time fell in all animals after reperfusion but improved significantly by day 5 in S6. Serum levels of endothelin-1 remained elevated in SFS and S12 but returned to baseline by 12 hours in S6: 2.76 (2.05-4.08) and 2.04 (1.97-2.12) versus 0.43 (0.26-0.50) pg/mL, respectively (P < 0.05 for both comparisons). A calibrated portocaval shunt that maintains portal vein flow about twice its baseline value produces a favorable outcome after SFS liver transplantation, avoiding endothelial injury due to portal hyperperfusion or to hypoperfusion because of excess shunting.