Percutaneous recanalization of non-cirrhotic extrahepatic portal vein obstruction in children: technical considerations in a preliminary cohort.

OBJECTIVES: Portal hypertension resulting from non-cirrhotic extrahepatic portal vein obstruction (EHPVO) in children has been primarily managed with the Meso-Rex bypass, but only a few patients have a viable Rex recessus, required by surgery. This study reports a preliminary series of patients who underwent interventional radiology attempts at portal vein recanalization (PVR), with a focus on technical aspects and safety. METHODS: A retrospective review of consecutive patients with severe portal hypertension due to non-cirrhotic EHPVO at a single institution from 2022, who underwent percutaneous attempts at PVR, was performed. Technical and clinical data including fluoroscopy time, radiation exposure, technical and clinical success, complications and follow-up were recorded. RESULTS: Eleven patients (6 males and 5 females; median age 7 years, range 1-14) underwent 15 percutaneous transhepatic (n = 1), transplenic (n = 11), or simultaneous transhepatic/transplenic (n = 3) procedures. Rex recessus was patent in 4/11 (36%). Fluoroscopy resulted in a high median total dose area product (DAP) of 123 Gycm2 (range 17-788 Gycm2) per procedure. PVR was achieved in 5/11 patients (45%), 3/5 with obliterated Rex recessus. Two adverse events of grade 2 and grade 3 occurred without sequelae. After angioplasty, 4/5 patients required stenting to obtain sustained patency, as demonstrated by colour-Doppler ultrasound in all PVR after a median follow-up of 6 months (range 6-14). CONCLUSION: Our preliminary experience suggests that 45% of children with non-cirrhotic EHPVO can restore portal flow even with obliterated Rex recessus. In non-cirrhotic EHPVO, PVR may be an option, if a Meso-Rex bypass is not feasible, although the radiation exposure deserves attention. CLINICAL RELEVANCE STATEMENT: Innovative percutaneous procedures may have the potential to be an alternative option to the traditional surgical approach in the management of non-cirrhotic EHPVO and its complications in children not eligible for Meso-Rex bypass surgery. KEY POINTS: Non-cirrhotic portal hypertension in children has been traditionally managed by surgery with Meso-Rex bypass creation. Percutaneous PVR may restore the patency of the native portal system even when the Rex recessus is obliterated and surgery has been excluded. Interventional radiological techniques may offer a minimally invasive solution in complex cases of EHPVO in children when Meso-Rex bypass is not feasible.

Portal vein stenting blocked the inflow tract and completely resolved bile duct varices, formed by cavernous transformation of the portal vein.

There is no established treatment for bleeding bile duct varices (BDVs). We report the first case of portal vein (PV) stenting completely eradicating bleeding BDVs. A 70-year-old male with malignant lymphoma developed BDVs due to PV obstruction, which had caused compression and stricture of the distal bile duct. Endoscopic retrograde cholangiography was performed to evaluate the stricture and bleeding from the ruptured BDV was observed. Endoscopic hemostasis was difficult, requiring reopening of the extra-hepatic PV and reducing the blood flow to the BDVs for hemostasis. Therefore, PV stenting was performed. During the procedure, portal angiography confirmed an inflow tract to the BDVs. Therefore, covered stents were placed in the PV and adjusted to block the inflow tract to the BDVs at the distal end. After stenting, the BDVs were successfully blocked and all PV blood flowed through the stent placed in the extra-hepatic PV. Two weeks after stenting, the BDVs had disappeared completely and the bleeding has not recurred for months. We experienced a case in which PV stenting not only reopened an obstructed PV but also successfully occluded the inflow tract. This case demonstrates the potential of PV stenting for the treatment of hemorrhagic BDVs.

Beyond the Rex: an innovative meso-intrahepatic portal vein bypass for late-onset extrahepatic portal vein occlusion after living donor liver transplantation.

The Meso-Rex bypass (MRB) is recognized as an effective treatment for portal hypertension secondary to extrahepatic portal vein occlusion (EHPVO) both in the pediatric and adult population, within or outside the context of liver transplantation. It is the preferred surgical treatment in most centers because not only does it addresses the portal hypertension, but also restores physiologic portal hepatopetal flow. However, the Rex recess, the landmark for this technique, may not be safely accessible in some patients. We present a 22-year-old male who underwent living donor liver transplant (LDLT) for neonatal hepatitis. He presented with variceal bleeding due to EHPVO at 13 years after transplant. Various endoscopic, radiologic, and surgical interventions were employed to address the recurrent gastrointestinal bleeding, but results have been unsatisfactory. We performed a meso-intrahepatic portal vein bypass (MIPVB), an innovative alternative to the MRB, for this patient with extensive post-operative adhesions, perihilar collaterals, and cavernous transformation. MIPVB creation in patients where the Rex recess is inaccessible is technically challenging. But with a multidisciplinary team approach, meticulous preoperative planning, and close follow-up, the authors have demonstrated that it is a safe and feasible option for patients with late-onset EHPVO after liver transplantation.

Wedged hepatic vein portovenography for assessment of Rex vein patency in children with extrahepatic portal venous obstruction.

BACKGROUND: Meso-Rex bypass is the surgical intervention of choice for children with extrahepatic portal vein obstruction (EHPVO). Patency of Rex vein, umbilical recessus of the portal vein, is a prerequisite for this surgery. Conventional diagnostic modalities poorly detect patency, while transjugular wedged hepatic vein portography (WHVP) accurately detects patency in 90%. OBJECTIVES: We aimed to assess Rex vein patency and portal vein branching pattern in children with EHPVO using transjugular WHVP and to identify factors associated with Rex vein patency. METHODS: Transjugular WHVP was performed in 31 children with EHPVO by selective cannulation of left and right hepatic veins. Rex vein patency, type of intrahepatic portal venous anatomy (Types A-E), and factors associated with patency of Rex vein were studied. RESULTS: The patency of Rex recess on transjugular WHVP was 29%. Complete obliteration of intrahepatic portal venous radicles was the commonest pattern (Type E, 38.7%) while Type A, the favorable anatomy for meso-Rex bypass, was seen in only 12.9%. Patency of the Rex vein, but not the anatomical pattern, was associated with younger age at evaluation (patent Rex: 6.6 ± 4.9 years vs. nonpatent Rex: 12.7 ± 3.9 years, p = 0.001). Under-5-year children had a 12 times greater chance of having a patent Rex vein (odds ratio: 12.22, 95% confidence interval: 1.65-90.40, p = 0.004). Patency or pattern was unrelated to local factors like umbilical vein catheterization, systemic thrombophilia, or disease severity. CONCLUSION: Less than one-third of our pediatric EHPVO patients have a patent Rex vein. Younger age at evaluation is significantly associated with Rex vein patency.

Location and extent of cavernous transformation of the portal vein dictates different visceral side revascularization in Meso-Rex bypass.

BACKGROUND: As an emerging standard of care for portal vein cavernous transformation (PVCT), Meso-Rex bypass (MRB) has been complicated and variated. The study aim was to propose a new classification of PVCT to guide MRB operations. METHODS: Demographic data, the extent of extrahepatic PVCT, surgical methods for visceral side revascularization, intraoperative blood loss, operating time, changes in visceral venous pressure before and after MRB, postoperative complications and the condition of bypass vessels after MRB were extracted retrospectively from the medical records of 19 patients. RESULTS: The median age of the patients (13 males and 6 females) was 32.5 years, while two patients were underage. Causes of PVCT can be summarized as follows: thrombophilia such as dysfunction of antithrombin III or proteins C; secondary to abdominal surgeries; secondary to abdominal infection or traumatic intestinal obstruction, and unknown causes. Intraoperatively, the median operation time was 9.5 h (7-13 h), and the intraoperative blood loss was 300 mL (100-1,600 mL). Ten cases used autologous blood vessels while 10 used allogeneic blood vessels. The vascular anastomosis was divided into the following types according to the site and approach: Type (T) 1-PV pedicel type, T2-confluence type, T3-major visceral vascular type; and T4-collateral visceral vascular type. Furthermore, the visceral venous pressure before and after MRB dropped significantly from 36 cmH2O (28-44) to 24.5 cmH2O (15-31) (P < 0.01). Postoperatively, one patient had delayed wound healing, two developed biochemical pancreatic fistulae, one experienced lymphatic leakage, the former caused by heat damage of the pancreatic tissues, the latter by cutting lymphatic vessels in the mesentery or removing the local lymph nodes during the process of separating the superior mesenteric vein, and one was re-operated on for an intervening intestinal fistulae. Postoperative enhanced CT scans revealed a significant improvement in abdominal varix in the patients with patent bypass, and at the 1-year postoperative follow-up, enhanced CT scans of six patients showed that the long axis of the spleen was reduced by ≥ 2 cm. CONCLUSIONS: MRB can effectively reduce visceral venous pressure in patients with PVCT. It is feasible to determine the PVCT type according to the extent of involvement and to choose individualized visceral side revascularization performances.

Meso-Rex bypass shunt vs. transposition shunt for cavernous transformation of portal vein in children.

Background: Cavernous transformation of the portal vein (CTPV) causes portal hypertension in children. Among Meso-Rex treatments, it is unclear whether the Meso-Rex bypass shunt (MRB) or the Meso-Rex transposition shunt (MRT) offers lower postoperative morbidity. Our objective was to evaluate postoperative outcomes, comparing MRB and MRT for children with CTPV. Methods: A retrospective study was conducted on children undergoing Meso-Rex for CTPV from January 2010 to December 2020. The primary outcome was shunt complications, including shunt stenosis and thrombus. The secondary outcome was re-operation. Results: Of the 43 patients included, 21 underwent MRT and 22 underwent MRB. MRT was associated with a higher rate of shunt complications when compared to MRB (23.8 vs. 9.1%, p = 0.191). The patients exhibited a higher rate of re-operation under the MRT than under the MRB (19 vs. 4.5%, p = 0.138). The operative time in the MRT group was significantly shorter than in the MRB group. Compared to MRT, the reduction in the length and thickness of the spleen was significantly greater in the MRB group. The increases in platelets were significantly higher in the MRB group than in the MRT group. The postoperative shunt velocity of MRB was notably faster than MRT. There was no significant difference in postoperative portal pressure between the two groups (p > 0.05). Conclusion: Both MRB and MRT result in acceptable postoperative outcomes, but MRT is associated with higher post-shunt complications, which often increase the re-operation rate. This study suggests that MRB may offer advantages for children with CTPV.

Technical Aspects and Considerations of Meso-Rex Bypass Following Liver Transplantation With Left Lateral Segment Grafts: Case Report and Review of the Literature.

In pediatric patients with extrahepatic portal vein obstruction and complications of portal hypertension, but with normal liver function, a meso-Rex bypass (MRB) connecting the superior mesenteric vein to the intrahepatic left portal is the favored surgical management. Pediatric patients with a history of a partial liver transplant (LT), especially living donors, are at greater risk for portal vein complications. Hence, an adequate knowledge of this technique and its additional challenges in the post-LT patient setting is crucial. We provide an overview of the available literature on technical aspects for an MRB post-LT. Preoperative considerations are highlighted, along with intraoperative considerations and postoperative management. Special attention is given to the even-more-demanding aspect of performing an MRB post-liver transplantation with a left lateral segment. Surgical alternatives are also discussed. In addition, we report here a unique case in which this surgical technique was performed on a complex pediatric patient with a history of a living-donor LT with a left lateral segment graft over a decade ago.

The rex shunt for left portal vein reconstruction during hepatectomy for malignancy using of rex-shunt in adults for oncoliver surgery.

BACKGROUND: Immediate portal reperfusion is mandatory following hepatectomy combined with portal vein (PV) resection. This retrospective study analyzes the feasibility and the outcomes of the Rex shunt (RS) for reconstruction of the left portal vein (LPV) and reperfusion of the remnant left liver or lobe following hepatectomy for cancer combined with resection of the PV in adult patients. METHODS: From 2018 to 2021, an RS was used in the above setting to achieve R0 resection or when the standard LPV reconstruction failed or was deemed technically impossible. RESULTS: There were 6 male and 5 female patients (median age, 58 years) with perihilar cancer (5 cases) or miscellaneous cancers invading the PV (6 cases). A major hepatectomy was performed in 10/11 patients. The RS was indicated to achieve R0 resection or for technical reasons in 8 and 3 cases, respectively, and was feasible in all consecutive attempts with (10 cases) or without an interposed synthetic graft (1 case). Two fatal complications (PV thrombosis and pulmonary embolism) and three non-severe complications occurred in four patients within 90 days of surgery. Two patients died of tumor recurrence with a patent RS at 13 and 29 months, and 7 were recurrence free with a patent shunt with a follow-up of 1 to 37 months (median, 15 months). CONCLUSION: In case of remnant left liver or lobe following hepatectomy combined with resection of the PV, the RS may help to achieve R0 resection and is a valuable option to perform technically satisfying portal reperfusion of the remnant left liver or lobe.

Optimal Treatment for Patients With Cavernous Transformation of the Portal Vein.

Cavernous transformation of the portal vein (CTPV) is a sequela of extrahepatic and/or intrahepatic portal vein obstruction caused by a combination of local and risk factors. It was ever taken as a relatively rare disease due to its scant literature, which was mainly based on clinical series and case reports. CTPV often manifests as gastroesophageal variceal bleeding, splenomegaly, and portal biliopathy after the long-term insidious presentation. It is unable for CTPV to be recanalized with anticoagulation because it is a complete obstruction of the mesentericoportal axis. Endoscopic therapy is mainly used for temporary hemostasis in acute variceal bleeding. Meso-Rex shunting characterized by portal-flow-preserving shunts has been widely performed in children with CTPV. The multitude of complications associated with CTPV in adults can be effectively addressed by various interventional vascular therapies. With the ubiquity of radiological examinations, optimal treatment for patients with CTPV becomes important. Multivisceral transplantation, such as liver-small intestinal transplantation, may be lifesaving and should be considered for patients with diffuse mesenteric venous thrombosis.

Meso-Rex bypass for the management of extrahepatic portal vein obstruction in adults (with video).

BACKGROUND: Extrahepatic portal vein obstruction (EHPVO) results in severe portal hypertension (PHT) leading to severely compromised quality of life. Often, pharmacological and endoscopic management is unable to solve this problem. Restoring hepatic portal flow using meso-Rex bypass (MRB) may solve it. This procedure, uncommon in adult patients, is considered the treatment of choice for EHPVO in children. METHODS: From 1997 to 2018, 8 male and 6 female adults, with a median age of 51 years (range 22-66) underwent MRB procedure for EHPVO at the University Hospitals Saint-Luc in Brussels, Belgium. Symptoms of PHT were life altering in all but one patient and consisted of repetitive gastro-intestinal bleedings, sepsis due to portal biliopathy, and/or severe abdominal discomfort. The surgical technique consisted in interposition of a free venous graft or of a prosthetic graft between the superior mesenteric vein and the Rex recess of the left portal vein. RESULTS: Median operative time was 500 min (range 300-730). Median follow-up duration was 22 months (range 2-169). One patient died due to hemorrhagic shock following percutaneous transluminal intervention for early graft thrombosis. Major morbidity, defined as Clavien-Dindo score ≥ III, was 35.7% (5/14). Shunt patency at last follow-up was 64.3% (9/14): 85.7% (6/7) of pure venous grafts and only 42.9% (3/7) of prosthetic graft. Symptom relief was achieved in 85.7% (12/14) who became asymptomatic after MRB. CONCLUSIONS: Adult EHPVO represents a difficult clinical condition that leads to severely compromised quality of life and possible life-threatening complications. In such patients, MRB represents the only and last resort to restore physiological portal vein flow. Although successful in a majority of patients, this procedure is associated with major morbidity and mortality and should be done in tertiary centers experienced with vascular liver surgery to get the best results.

Meso-Rex bypass versus portosystemic shunt for the management of extrahepatic portal vein obstruction in children: systematic review and meta-analysis.

PURPOSE: Extrahepatic portal vein obstruction (EHPVO) is a major cause of non-cirrhotic portal hypertension in children. Surgical procedures for EHPVO include portosystemic shunts (PSS) and meso-Rex bypass (MRB). We conducted a systematic review and meta-analysis to compare the effectiveness of MRB versus PSS in EHPVO patients. METHODS: A systematic literature search was performed using four databases. Articles reporting EHPVO and comparing patients who received MRB and PSS were included in the analysis. RESULTS: We retrieved 851 papers, of which five observational studies met the inclusion criteria. There was no difference in shunt complications, mortality, or gastrointestinal bleeding after surgery between MRB and PSS in the meta-analysis. MRB had increased shunt complications compared with PSS in the non-comparative studies. MRB had a potential advantage over PSS in long-term prognosis in one comparative study. Overall, the quality of the evidence was low. CONCLUSIONS: Based on available data, our meta-analysis indicates that MRB does not increase shunt complications, mortality, or gastrointestinal bleeding after surgery. The present study did not reveal superiority for either MRB or PSS. The paucity of well conducted trials in this area justifies future multicenter studies and studies that examine long-term outcomes.

Modified Meso-Rex bypass with umbilical vein recanalization and intra-operative stenting.

PURPOSE: The aim of the study was to evaluate the usefulness of a novel modified Meso-Rex bypass surgical technique with umbilical vein recanalization and intra-operative stenting to treat portal vein cavernous transformation. METHODS: In total, 13 portal vein cavernous transformation patients underwent Meso-Rex bypass surgery, consisting of bypass grafts between the superior mesenteric vein (SMV) and the recess of Rex as well as through the ligamentum teres hepatis without stent implantation (Group A, n = 9) and umbilical vein recanalization with intra-operative stent implantation (Group B, n = 4). RESULTS: In Group A, the bypass diameter was 0-6 mm (median 3 mm) and blood flow velocity 25-115 cm/s (median 72 cm/s) 1 month after Meso-Rex bypass surgery, with open bypass times of 0-67 months (median 6 months); 6 patients in this group developed postoperative Meso-Rex bypass occlusions. A patient in Group A treated with ligamentum teres hepatis recanalization needed a thrombectomy and stent implantation during a second surgery 2 days after the Meso-Rex bypass, because of bypass thrombosis and umbilical vein stenosis. In Group B, the average modified Meso-Rex bypass diameter was 5.5-6.5 mm (median 6 mm), and the bypass vessels remained open in all patients, with blood flow rates of 45-100 cm/s (median 76.5 cm/s) 1 month after the modified Meso-Rex bypass, up to the endpoint (15-33 months, median 24 months). The rate of bypass occlusions in Group A and Group B were 22.2% and 0%, 30.0% and 0%, and 55.6% and 0% at 1 month, 3 months, and 1 year, respectively, after bypass surgery. CONCLUSIONS: Our novel modified Meso-Rex bypass approach for portal vein cavernous transformation treatment was effective with excellent long-term bypass patency.

Trombosis venosa portal extrahepática, manejo quirúrgico con derivación meso-Rex. Serie de 3 casos / Extrahepatic portal vein thrombosis, surgical management with meso-Rex shunt. Series of 3 cases

La vena porta es un conducto que drena el flujo esplácnico al hígado y se puede ocluir por diferentes patologías, variando su presentación clínica de acuerdo con la causa de la obstrucción. Es muy importante diferenciar la trombosis portal asociada o no a la cirrosis, ya que su tratamiento y pronóstico es diferente. La trombosis venosa portal extrahepática es una condición netamente de origen vascular, y es la principal causa de trombosis portal en niños y adultos. Presentamos tres casos tratados con derivación meso-Rex, con seguimiento a 6 meses

The portal vein is a conduit that drains splanchnic flow to the liver, it can be occluded by different pathologies and its clinical presentation varies according to the cause of the obstruction. It is very important to differentiate portal thrombosis associated or not with cirrhosis, since its treatment and prognosis is different. Extrahepatic portal vein thrombosis (PEVT) is a condition of purely vascular origin, being the main cause of portal thrombosis in children and adults. We present three cases with meso-Rex shunt, with a 6-month follow-up

[Clinical Value of Ultrasound in Evaluating Stent Placement for Managing Graft Stenosis after Meso-rex Bypass].

Objective To explore the feasibility of using ultrasound to evaluate stent placement for managing graft stenosis after Meso-rex bypass for cavernous transformation of the portal vein in adults. Methods This study enrolled the patients who underwent Meso-rex bypass due to cavernous transformation of the portal vein,were diagnosed graft stenosis by postoperative ultrasound,and then underwent percutaneous portal vein puncture portography and stent placement.We then compared the ultrasonic measurement indicators and sonographic manifestations before and after stent placement,and evaluated the alleviation of portal hypertension symptoms after stent placement and related clinical indexes. Results Finally,8 patients were enrolled in this study,including 5 males and 3 females,with an average age of(32.4±14.7)years.The median duration of follow-up was 26 months after stent placement.The mean diameter of graft stenosis was(2.74±0.23)mm after Meso-rex bypass and became wider[(7.23±0.68)mm]after stent placement(P=0.000).The mean maximum velocity at graft stenosis was(195.88±30.83)cm/s after Meso-rex bypass and became lower[(72.75±29.94)cm/s]after stent placement(P=0.000).The color Doppler flow imaging at graft stenosis presented colorful blood flow,and presented regular near laminar flow within the stent and characteristic reverse flow within the left portal vein after stent placement.No gastrointestinal bleeding or ascites occurred after interventional therapy,and the mean thickness of spleen decreased from 6.0 cm before stent placement to 5.4 cm(P=0.018).After stent placement,the platelet count increased from(51.57±18.83)×109/L to(149.00±58.96)×109/L(P=0.002),and the serum ammonia level decreased from(66.25±21.78)µmol/L to(44.88±10.60)µmol/L(P=0.012). Conclusions Ultrasound can accurately assess graft patency before and after stent placement in patients with stenosis after Meso-rex bypass,and effectively monitor the hemodynamic changes in the portal venous system.The clinical symptoms can be relieved after interventional therapy.

Clinical Value of Ultrasound in Evaluating Stent Placement for Managing Graft Stenosis after Meso-rex Bypass / 中国医学科学院学报

Objective To explore the feasibility of using ultrasound to evaluate stent placement for managing graft stenosis after Meso-rex bypass for cavernous transformation of the portal vein in adults. Methods This study enrolled the patients who underwent Meso-rex bypass due to cavernous transformation of the portal vein,were diagnosed graft stenosis by postoperative ultrasound,and then underwent percutaneous portal vein puncture portography and stent placement.We then compared the ultrasonic measurement indicators and sonographic manifestations before and after stent placement,and evaluated the alleviation of portal hypertension symptoms after stent placement and related clinical indexes. Results Finally,8 patients were enrolled in this study,including 5 males and 3 females,with an average age of(32.4±14.7)years.The median duration of follow-up was 26 months after stent placement.The mean diameter of graft stenosis was(2.74±0.23)mm after Meso-rex bypass and became wider[(7.23±0.68)mm]after stent placement(

Standard or Variant Meso-Rex Shunts for Children with Variceal Bleeding due to Extrahepatic Portal Vein Obstruction: A Report of Two Cases.

Extrahepatic portal vein obstruction (EHPVO) is the most common cause of pediatric portal hypertension and can cause life-threatening variceal bleeding. Meso- Rex shunt (MRS) is a surgical procedure that restores physiological portal venous blood flow to the liver by using a graft to connect the superior mesenteric vein and the left portal vein within the Rex recess, and can relieve variceal bleeding and other complications associated with EHPVO. Although the MRS is regarded as an optimal and potentially curative treatment with good long-term patency, graft thrombosis or failure due to unknown causes is not rare, prompting the need for further research on the risk factors of graft failure or poor patency. Herein, we report two cases of EHPVO in patients with recurrent or uncontrolled variceal bleeding, one treated with the classic Rex shunt and the other with the modified Rex shunt, which resulted in a failure and success, respectively.

Revision of meso-Rex bypass utilizing a collateral vein in a patient with portal steal phenomenon after liver transplant: A case report.

INTRODUCTION: In children with extrahepatic portal vein obstruction or those who develop portal vein thrombosis after liver transplant, the use of Meso-Rex Bypass (MRB) creates a more physiological state by redirecting mesenteric blood flow back into the intrahepatic portal system via a venous conduit. PRESENTATION OF CASE: A 3-year-old female with biliary atresia associated with polysplenia syndrome and a surgical history of Kasai portoenterostomy procedure, and an ABO incompatible whole liver transplant. Within a year after transplant she presented with prehepatic portal hypertension, that was treated with MRB using a deceased donor ABO compatible iliac vein as conduit. Six months later, she was taken to the operating room for bypass revision, during the procedure the MRB showed no flow and no thrombus, and a large splenorenal collateral vein that was causing a portal perfusion steal phenomenon was observed. After dissecting the collateral vein, an 8 cm x8 mm segment of this vessel was used as an autologous conduit to re-do the Rex. DISCUSSION: Failed of MRB can be attributed to portal steal phenomenon, hypercoagulable disorders, bypass contraction or kinking. In this case we believe the culprit to be the former. When there is a history of longstanding portal hypertension, large collaterals develop; thus, intraoperative portal vein flow measurement is critical and ligation of large collaterals during liver transplantation and MRB should be performed to avoid portal steal phenomenon postprocedure. CONCLUSION: Using a collateral vein as an alternative autologous venous conduit is a feasible option that can have durable success.

Multimodality imaging of the Meso-Rex bypass.

Extrahepatic portal vein obstruction (EHPVO) is the most common cause of upper gastrointestinal bleeding in children. It is defined as thrombosis of the extrahepatic portal vein with or without extension to the intrahepatic portal veins. The Meso-Rex shunt is the gold standard treatment in children with favorable anatomy since it restores physiological portal liver reperfusion. This is achieved by rerouting the splanchnic venous blood through an autologous graft from the superior mesenteric vein (SMV) into the Rex recess of the left portal vein, curing portal hypertension by doing so. General and hepatobiliary radiologists must be familiar with multimodality imaging appearances of EHPVO and with the role of imaging in identifying suitable candidates for Meso-Rex bypass surgery. Imaging might also detect complications of this procedure, some of which might be treated via interventional radiology.

MR angiography and 2-D phase-contrast imaging for evaluation of meso-rex bypass function.

BACKGROUND: The meso-Rex bypass restores blood flow to the liver in patients with extrahepatic portal vein thrombosis. Stenosis occurs in some cases, causing the reappearance of portal hypertension. Complications such as thrombocytopenia present on a spectrum and there are currently no guidelines regarding a threshold for endovascular intervention. While Doppler ultrasound (US) is common for routine evaluation, magnetic resonance (MR) angiography with two-dimensional phase-contrast MRI (2-D PC-MRI) may improve the assessment of meso-Rex bypass function. OBJECTIVES: To determine the feasibility and utility of MR angiography with 2-D PC-MRI in evaluating children with meso-Rex bypass and to correlate meso-Rex bypass blood flow to markers of portal hypertension. MATERIALS AND METHODS: MR angiography and 2-D PC-MRI in meso-Rex bypass patients were retrospectively analyzed. Minimum bypass diameter was measured on MR angiography and used to calculate cross-sectional area. Meso-Rex bypass blood flow was measured using 2-D PC-MRI and divided by ascending aortic flow to quantify bypass flow relative to systemic circulation. Platelet and white blood cell counts were recorded. Correlation was performed between minimum bypass area, blood flow and clinical data. RESULTS: Twenty-five children (median age: 9.5 years) with meso-Rex bypass underwent MR angiography and 2-D PC-MRI. The majority of patients were referred to imaging given clinical concern for complications. Eighteen of the 25 patients demonstrated >50% narrowing of the bypass cross-sectional area. The mean platelet count in 19 patients was 127 K/µL. There was a significant correlation between minimum cross-sectional bypass area and bypass flow (rho=0.469, P=0.018) and between bypass flow and platelet counts (r=0.525, P=0.021). CONCLUSION: Two-dimensional PC-MRI can quantify meso-Rex bypass blood flow relative to total systemic flow. In a cohort of 25 children, bypass flow correlated to minimum bypass area and platelet count. Two-dimensional PC-MRI may be valuable alongside MR angiography to assess bypass integrity.