Doppler sonography of hepatic arterial blood flow velocity after percutaneous transhepatic portal vein embolization

Interleaved x-ray imaging: A method for simultaneous acquisition of quantitative and diagnostic digital subtraction angiography

BACKGROUND

Flow altering angiographic procedures suffer from ill-defined, qualitative endpoints. Quantitative digital subtraction angiography (qDSA) is an emerging technology that aims to address this issue by providing intra-procedural blood velocity measurements from time-resolved, 2D angiograms. To date, qDSA has used 30 frame/s DSA imaging, which is associated with high radiation dose rate compared to clinical diagnostic DSA (up to 4 frame/s).

PURPOSE

The purpose of this study is to demonstrate an interleaved x-ray imaging method which decreases the radiation dose rate associated with high frame rate qDSA while simultaneously providing low frame rate diagnostic DSA images, enabling the acquisition of both datasets in a single image sequence with a single injection of contrast agent.

METHODS

Interleaved x-ray imaging combines low radiation dose image frames acquired at a high rate with high radiation dose image frames acquired at a low rate. The feasibility of this approach was evaluated on an x-ray system equipped with research prototype software for x-ray tube control. qDSA blood velocity quantification was evaluated in a flow phantom study for two lower dose interleaving protocols (LD1:3.7 ± 0.02 mGy / s $3.7 \pm 0.02\ {\mathrm{mGy}}/{\mathrm{s}}$ and LD2:1.7 ± 0.04 mGy / s $1.7 \pm 0.04{\mathrm{\ mGy}}/{\mathrm{s}}$ ) and one conventional (full dose) protocol (11.4 ± 0.04 mGy / s ) $11.4 \pm 0.04{\mathrm{\ mGy}}/{\mathrm{s}})$ . Dose was measured at the interventional reference point. Fluid velocities ranging from 24 to 45 cm/s were investigated. Gold standard velocities were measured using an ultrasound flow probe. Linear regression and Bland-Altman analysis were used to compare ultrasound and qDSA.

RESULTS

The LD1 and LD2 interleaved protocols resulted in dose rate reductions of -67.7% and -85.5%, compared to the full dose qDSA scan. For the full dose protocol, the Bland-Altman limits of agreement (LOA) between qDSA and ultrasound velocities were [0.7, 6.7] cm/s with a mean difference of 3.7 cm/s. The LD1 interleaved protocol results were similar (LOA: [0.3, 6.9] cm/s, bias: 3.6 cm/s). The LD2 interleaved protocol resulted in slightly larger LOA: [-2.5, 5.5] cm/s with a decrease in the bias: 1.5 cm/s. Linear regression analysis showed a strong correlation between ultrasound and qDSA derived velocities using the LD1 protocol, with aR 2 ${R}^2$ of0.96 $0.96$ , a slope of1.05 $1.05$ and an offset of1.9 $1.9$  cm/s. Similar values were also found for the LD2 protocol, with aR 2 ${R}^2$ of0.93 $0.93$ , a slope of0.98 $0.98$ and an offset of2.0 $2.0$  cm/s.

CONCLUSIONS

The interleaved method enables simultaneous acquisition of low-dose high-rate images for intra-procedural blood velocity quantification (qDSA) and high-dose low-rate images for vessel morphology evaluation (diagnostic DSA).

Hyperspectral Evaluation of the Human Liver During Major Resection

Objective

This study investigates the effects of PVE and vascular inflow control (VIC) on liver microperfusion and tissue oxygenation using hyperspectral imaging (HSI) technology.

Background

Mechanisms triggering future liver remnant (FLR) augmentation introduced by PVE have not been sufficiently studied in humans. Particularly, the arterial buffer response (ABR) of the liver might play a vital role.

Methods

Hyperspectral datacubes (TIVITA) acquired during 58 major liver resections were qualitatively and quantitatively analyzed for tissue oxygenation (StO2%), near-infrared (NIR) perfusion, organ-hemoglobin indices (OHI), and tissue-water indices (TWI). The primary study endpoint was measurement of hyperspectral differences in liver parenchyma subject to PVE and VIC before resection.

Results

HSI revealed parenchyma specific differences in StO2% with regard to the underlying disease (P < 0.001). Preoperative PVE (n = 23, 40%) lead to arterial hyperoxygenation and hyperperfusion of corresponding liver segments (StO2: 77.23% ± 11.93%, NIR: 0.46 ± 0.20[I]) when compared with the FLR (StO2: 66.13% ± 9.96%, NIR: 0.23 ± 0.12[I]; P < 0.001). In a case of insufficient PVE and the absence of FLR augmentation hyperspectral StO2 and NIR differences were absent. The hyperspectral assessment demonstrated increased liver tissue-oxygenation and perfusion in PVE-segments (n = 23 cases) and decreased total VIC in nonembolized FLR hemilivers (n = 35 cases; P < 0.001). Intraoperative HSI analysis of tumor tissue revealed marked tumor specific differences in StO2, NIR, OHI, and TWI (P < 0.001).

Conclusions

HSI allows intraoperative quantitative and qualitative assessment of microperfusion and StO2% of liver tissue. PVE lead to ABR-triggered tissue hyperoxygenation and cross-talk FLR augmentation. HSI furthermore facilitates intraoperative tumor tissue identification and enables image-guided liver surgery following VIC.

Hypertrophied Right Inferior Phrenic Artery in Cirrhotic Patients without Hepatocellular Carcinoma: An Interesting Observation on 256 Slice Multidetector Computed Tomography

Aim To evaluate whether right inferior phrenic artery (RIPA) is a source of extrahepatic arterial supply to the liver in cirrhotic patients without hepatocellular carcinoma (HCC) using 256 slice computed tomography (CT).

Materials and Methods Institutional review board approval was obtained for this retrospective study. A total of 262 consecutive cirrhotic patients (male:female–172:90; mean age 56.45 ± 12.96 years) without HCC and hepatic vascular invasion, and who underwent technically successful multiphase CT, were included in the study. Additionally, 280 noncirrhotic patients (male:female–169:111; mean age 54.56 ± 14.21 years) who underwent abdominal multiphase CT scans for indications other than liver disease and did not have focal liver lesions or hepatic vascular disease were included as a control group. The RIPA and left inferior phrenic artery (LIPA) diameters were measured at the level of the ascending segment of IPA located anterior to the diaphragmatic crus. The relationship between RIPA diameters and Child–Pugh score was assessed.

Results The cirrhotic patient group and control group were matched for age (p = 0.11) and gender (p = 0.20). The mean diameter of RIPA in the cirrhotic group (1.93 ± 0.4 mm) was significantly higher than in the control group (1.50 ± 0.5 mm), p < 0.001. The mean diameter of LIPA in the cirrhotic group (1.34 ± 0.5 mm) was not significantly higher than in the control group (1.30 ± 0.5 mm), p = 0.32. We found a statistically linear and moderate degree relationship between RIPA diameter values and Child–Pugh scores (p = 0.002, r = 0.593).

Conclusion RIPA is hypertrophied in patients with cirrhosis without HCC. It may be an important contributor to the blood flow to the liver in cirrhotic patients even without HCC, especially with portal hypertension.

90Y-Radioembolization After Failed Portal Vein Embolization for Colorectal Liver Metastases: A Case Report

The main limiting factor for liver resection is insufficient future liver remnant (FLR). Portal vein embolization (PVE) is a standard of care treatment to induce FLR hypertrophy, but it is not always efficient. Radioembolization (RE) has a potential to induce liver hypertrophy for PVE-refractory patients. However, this was reported only for the patients with hepatocellular carcinoma. We described two cases of lobar RE after PVE failure for the patients with colorectal liver metastases. This enabled to reach sufficient FLR, provide good local disease control and bridge the patients to extended hepatectomy.

Hepatic adenoma rupture following portal vein embolization

Hepatic adenomas are benign liver tumors typically found in females of reproductive age. Though benign, hepatic adenomas are highly vascularized tumors, thus rupture and consequent hemorrhage present a feared complication. We report a case of a 31-year-old woman with hepatic adenoma who underwent preoperative portal vein embolization and subsequently suffered a rupture of her tumor. We postulate that the change in blood flow after portal vein embolization, a phenomenon known as the hepatic artery buffer response, may have contributed to the tumor rupture, though the possibility that the rupture was purely incidental remains. There is currently no prior report of such rupture occurring following portal vein embolization, and this case brings to light a potentially fatal complication of a generally safely regarded procedure in patients with hepatic adenoma.

Correlation of Hepatic Artery Resistive Index with Portal Pressure and Serum Nitric Oxide Levels in Patients with Extrahepatic Portal Vein Obstruction

Aim:

The aim was to study the correlation of hepatic artery resistive index (HARI) with the portal pressure (PP) and its surrogate marker serum nitric oxide (NO) levels and to determine the validity of HARI as noninvasive indirect marker of PP in extrahepatic portal venous obstruction (EHPVO) pre- and postoperatively.

Methods:

A prospective study was conducted on 19 patients with EHPVO undergoing proximal lienorenal (LR) shunt or devascularization from February 2016 to January 2018. HARI, calculated from Doppler sonography, and NO were measured preoperatively and 14, 30 and 90 days postoperatively. Intraoperatively, PP was measured before splenectomy, and both PP and NO were measured postshunt.

Results:

Mean age was 10.58 ± 2.85 years, and male:female ratio was 15:4. LR shunt was done in 16 while three patients required devascularization. There was a significant fall in the HARI (0.06 ± 0.02, P = 0.02), NO (14.31 ± 2.66 μmol/l, P < 0.001), and PP (11.81 ± 1.03 mmHg, P < 0.001) following shunt surgery. However, fall in HARI did not correlate with fall in PP. Preoperative HARI also did not correlate with preshunt/devascularization PP nor with preoperative NO. Postoperatively, HARI did not correlate with NO at 14-, 30-, and 90-day follow-up.

Conclusion:

HARI bears no correlation with PP or NO. Hence, it cannot be used as an indirect marker of PP.

In situ splitting after selective partial portal vein ligation or simultaneous hepatic artery ligation promotes liver regeneration

This study seeks to compare the impact of selective partial portal vein ligation (PPVL) or the combination of simultaneous hepatic artery ligation (PPVAL) with in situ splitting (ISS) on liver regeneration and injury. Rats were randomized into three groups; namely: selective PVL, PPVL + ISS and PPVAL + ISS. The changes in hepatic hemodynamics, liver regeneration and hepatocytic injury were examined. Blood flow to the left portal branch and the microcirculation of the left median lobe after PPVL or PPVAL was significantly reduced. Liver regeneration of PPVAL + ISS group was more pronounced than that in the PPVL + ISS and PVL groups at 48 and 72 hours as well as 7 d postoperatively. The serum biochemical markers and histopathological examination demonstrated reduced levels of liver injury in the PPVL + ISS group. Injury to hepatocytes was more pronounced with PPVAL + ISS than PVL. HGF, TNF-α and IL-6 expression in the regenerated lobes in both PPVAL + ISS and PPVL + ISS groups increased significantly when compared to the PVL group. We demonstrated that both PPVL + ISS and PPVAL + ISS were effective and feasible means of inducing remnant liver hypertrophy and could serve as a rapid clinical application for qualified patients.

Vascular input function correction of inflow enhancement for improved pharmacokinetic modeling of liver DCE-MRI

PURPOSE

To propose a simple method to correct vascular input function (VIF) due to inflow effects and to test whether the proposed method can provide more accurate VIFs for improved pharmacokinetic modeling.

METHODS

A spoiled gradient echo sequence-based inflow quantification and contrast agent concentration correction method was proposed. Simulations were conducted to illustrate improvement in the accuracy of VIF estimation and pharmacokinetic fitting. Animal studies with dynamic contrast-enhanced MR scans were conducted before, 1 week after, and 2 weeks after portal vein embolization (PVE) was performed in the left portal circulation of pigs. The proposed method was applied to correct the VIFs for model fitting. Pharmacokinetic parameters fitted using corrected and uncorrected VIFs were compared between different lobes and visits.

RESULTS

Simulation results demonstrated that the proposed method can improve accuracy of VIF estimation and pharmacokinetic fitting. In animal study results, pharmacokinetic fitting using corrected VIFs demonstrated changes in perfusion consistent with changes expected after PVE, whereas the perfusion estimates derived by uncorrected VIFs showed no significant changes.

CONCLUSION

The proposed correction method improves accuracy of VIFs and therefore provides more precise pharmacokinetic fitting. This method may be promising in improving the reliability of perfusion quantification. Magn Reson Med 79:3093-3102, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Limits of and Complications after Embolization of the Hepatic Artery and Portal Vein to Induce Segmental Hypertrophy of the Liver: A Large Mini-Pig Study

Background: The aim of this study was to compare arterial embolization (AE) with portal vein embolization (PVE) for the induction of segmental hypertrophy regarding procedural efficacy, safety and outcome. Methods: A total of 29 mini pigs were subjected to PVE, AE or assigned to the sham (SO) group. Correspondingly, 75% of the hepatic artery or portal vein branches were embolized. Growth and atrophy of the liver lobes, calculating the liver-to-body weight index (LBWI), laboratory data, arteriography, portography, Doppler ultrasound (US) and histopathology were analyzed. Results: After PVE, 2 animals had to be excluded due to technical problems. After AE, 4 animals had to be excluded because of technical problems and early sacrifice. Postprocedural US demonstrated effective AE and PVE of the respective lobes. Four weeks after PVE, portography showed a slow refilling of the embolized lobe by collateral portal venous vessels. Four weeks after AE, arteriography revealed a slight revascularization of the embolized lobes by arterial neovascularization. Segmental AE led to extensive necrotic and inflammatory alterations in the liver and bile duct parenchyma. Significant hypertrophy of the non-embolized lobe was only noted in the PVE group (LBWI: 0.91 ± 0.28%; p = 0.001). There was no increase in the non-embolized lobe in the AE (LBWI: 0.45 ± 0.087%) and SO group (LBWI: 0.45 ± 0.13%). Conclusion: PVE is safe and effective to induce segmental hypertrophy. Portal reperfusion by collateral vessels may limit hypertrophy. AE did not increase the segmental hepatic volume but carries the risk of extensive necrotic inflammatory damage.

Preoperative Sequential Portal and Hepatic Vein Embolization in Patients with Hepatobiliary Malignancy

BACKGROUND

Preoperative portal vein embolization (PVE) induces shrinkage of the embolized lobe and compensatory regeneration in the non-embolized lobe, but does not always induce sufficient regeneration of the future remnant liver (FRL). We previously developed preoperative sequential PVE-hepatic vein embolization (HVE), and here we present our experience of treating 42 patients with sequential PVE-HVE.

METHODS

During 8-year study period, preoperative PVE-HVE was performed on 42 patients with hepatobiliary malignancies.

RESULTS

Primary diseases were bile duct cancers [perihilar cholangiocarcinoma (n = 33) and diffuse bile duct cancer (n = 1)], hepatocellular carcinomas (n = 4), and intrahepatic tumors [intrahepatic cholangiocarcinoma (n = 3) and gallbladder cancer liver invasion (n = 1)]. These patients demonstrated insufficient FRL regeneration following PVE, thus HVE was performed to induce further regeneration. No PVE-HVE procedure-associated complications occurred. In the bile duct cancer group, FRL volume was 33.9 ± 2.2 % before PVE, 38.4 ± 1.5 % before HVE, 43.7 ± 2.1 % at surgery, and 73.6 ± 8.3 % at 2 weeks after right hepatectomy. The degree of FRL hypertrophy was 13.3 % after PVE, 28.9 % after PHV-HVE, and 117.1 % at 2 weeks after right hepatectomy. All patients except one recovered uneventfully after surgery, and the 3-year patient survival rate was 45.1 %. In the HCC group, transarterial chemoembolization was initially performed and FRL regeneration following PVE-HVE occurred very slowly. Active FRL regeneration occurred in the liver tumor group, but rapid tumor growth was observed in 1 of 4 patients.

CONCLUSION

The sequential application of HVE following PVE safely and effectively induces further FRL regeneration in non-cirrhotic livers. Further validation using larger patient population and multicenter studies is needed to reliably widen the indications.

Duplex Doppler Ultrasound of the Hepatic Artery: A Window to Diagnosis of Diffuse Liver Pathology

The use of Doppler sonography for evaluation of the liver is well established, and evaluation of the portal and hepatic veins in native livers, as well as the hepatic artery in transplant livers, is a standard part of the examination. Less well known, however, is that assessment hepatic of artery blood flow velocities and waveforms can permit inferences to be made about liver and system pathophysiology even in native livers. This review will illustrate that hepatic parenchymal abnormalities, as well as primary vascular abnormalities both upstream and downstream of the proper hepatic artery, can be inferred from careful interrogation of its Doppler signature during routine abdominal sonography.

Preoperative portal vein embolization in liver cancer: indications, techniques and outcomes

Postoperative liver failure is a severe complication of major hepatectomies, in particular in patients with a chronic underlying liver disease. Portal vein embolization (PVE) is an approach that is gaining increasing acceptance in the preoperative treatment of selected patients prior to major hepatic resection. Induction of selective hypertrophy of the non-diseased portion of the liver with PVE in patients with either primary or secondary hepatobiliary, malignancy with small estimated future liver remnants (FLR) may result in fewer complications and shorter hospital stays following resection. Additionally, PVE performed in patients initially considered unsuitable for resection due to lack of sufficient remaining normal parenchyma may add to the pool of candidates for surgical treatment. A thorough knowledge of hepatic segmentation and portal venous anatomy is essential before performing PVE. In addition, the indications and contraindications for PVE, the methods for assessing hepatic lobar hypertrophy, the means of determining optimal timing of resection, and the possible complications of PVE need to be fully understood before undertaking the procedure. Technique may vary among operators, but cyanoacrylate glue seems to be the best embolic agent with the highest expected rate of liver regeneration for PVE. The procedure is usually indicated when the remnant liver accounts for less than 25-40% of the total liver volume. Compensatory hypertrophy of the non-embolized segments is maximal during the first 2 weeks and persists, although to a lesser extent during approximately 6 weeks. Liver resection is performed 2 to 6 weeks after embolization. The goal of this article is to discuss the rationale, indications, techniques and outcomes of PVE before major hepatectomy.

Physiological outflow boundary conditions methodology for small arteries with multiple outlets: A patient-specific hepatic artery haemodynamics case study

Physiological outflow boundary conditions are necessary to carry out computational fluid dynamics simulations that reliably represent the blood flow through arteries. When dealing with complex three-dimensional trees of small arteries, and therefore with multiple outlets, the robustness and speed of convergence are also important. This study derives physiological outflow boundary conditions for cases in which the physiological values at those outlets are not known (neither in vivo measurements nor literature-based values are available) and in which the tree exhibits symmetry to some extent. The inputs of the methodology are the three-dimensional domain and the flow rate waveform and the systolic and diastolic pressures at the inlet. The derived physiological outflow boundary conditions, which are a physiological pressure waveform for each outlet, are based on the results of a zero-dimensional model simulation. The methodology assumes symmetrical branching and is able to tackle the flow distribution problem when the domain outlets are at branches with a different number of upstream bifurcations. The methodology is applied to a group of patient-specific arteries in the liver. The methodology is considered to be valid because the pulsatile computational fluid dynamics simulation with the inflow flow rate waveform (input of the methodology) and the derived outflow boundary conditions lead to physiological results, that is, the resulting systolic and diastolic pressures at the inlet match the inputs of the methodology, and the flow split is also physiological.

Triggered liver regeneration: from experimental model to clinical implications

BACKGROUND

Major liver resection is the only therapeutic option for patients with malignant liver tumors. However, extended hepatectomy often leads to postoperative liver failure, mainly due to insufficient amounts of the remnant liver. Recently, selective portal vein occlusion (PVO) has been introduced to increase the remnant liver volume. This novel surgical technique initiated a progressive development in liver surgery, resulting in a significant increment in potential candidates for curative liver resection.

SUMMARY

The theoretical basis for this great advancement is formed by an understanding of the mechanisms of PVO-induced liver regeneration, mainly obtained from animal studies. The aim of this review is to give a comprehensive overview of the relevant animal models of PVO and to discuss the main characteristics of triggered liver regeneration, including the induced hemodynamic, morphological and functional alterations as well as the underlying molecular mechanisms, which might be of interest in both the laboratory and the clinic. Key Messages: Although basic research revealed the main characteristics of PVO-triggered liver regeneration within the last decades, several important issues regarding the regenerative process remain uncertain. To answer these open questions, additional well-designed animal experiments are needed in the future, which allow further refinement of this surgical technique.

Portal vein embolization using absolute ethanol: evaluation of its safety and efficacy

BACKGROUND

Previously, we reported on the clinical efficacy and safety of portal vein embolization (PVE) with fibrin glue. Our embolic materials for PVE changed from fibrin glue to absolute ethanol (EOH) after 2001 due to prohibition of using fibrin glue for PVE. With introducing our technique of PVE with EOH, we evaluated its safety and efficacy with attention to the amount of EOH.

METHODS

The medical records of 154 patients who underwent PVE using EOH were retrospectively reviewed.

RESULTS

Changes with time in both the serum levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) after PVE returned to the initial condition within 7 days after PVE. In the 96 patients who underwent CT volumerty 14 to 21 days after PVE, the volume of the embolized lobe decreased from 701 ± 165 cm(3) to 549 ± 148 cm(3) (P < 0.0001). Meanwhile, the volume of the non-embolized lobe increased from 388 ± 105 cm(3) to 481 ± 113 cm(3) (P < 0.0001). On simple linear regression, the amount of EOH was positively correlated with both the maximum of AST and that of ALT after PVE; however, it never correlated with changes in liver volume after PVE.

CONCLUSIONS

Portal vein embolization with EOH has a substantial effect on both hypertrophy of the non-embolized lobe and atrophy of the embolized lobe. Quick recoveries of changes with time in AST and ALT after PVE proved that PVE with EOH is a safe procedure. The amount of EOH affected the extent of liver damage but had no clinical effects on changes in liver volume after PVE.

Does preoperative portal vein embolization have any impact on the outcome of right-side hepatectomy for Klatskin tumor?

BACKGROUND AND AIM

The clinical usefulness of portal vein embolization (PVE) for Klatskin tumor is not well established. The authors explored the change in liver volume and function before and after major hepatectomy and evaluated the effect of PVE.

METHODS

Thirty-three consecutive patients who underwent right hepatectomy with an initial future liver remnant (FLR) ≤ 30% for Klatskin tumors at Seoul National University Hospital were included.

RESULTS

Eleven patients underwent PVE, and eight patients received right trisectionectomy. PVE induced a mean FLR increase of 19.3% after a mean of 15.8 days. At postoperative month 1, liver volume and liver hypertrophy ratio was comparable between PVE and no-PVE group. For patients with an initial FLR ≤ 20%, postoperative liver hypertrophy rate of PVE group was comparable to no-PVE group. Liver function tests were not affected by PVE or the initial FLR. Postoperative liver hypertrophy ratio was negatively correlated with the initial FLR (hypertrophy ratio (%) = 326.7-0.4×initial FLR (ml), P = 0.001). There was no severe PVE-related morbidity, and postoperative morbidity rate was comparable in PVE and no-PVE group.

CONCLUSION

The postoperative liver hypertrophy ratio, final liver volume, or liver function tests were not affected by PVE. Postoperative liver hypertrophy was related to the initial FLR.

Hepatic artery Doppler indices in children with extra hepatic portal vein obstruction

Doppler measurement provides information on the hemodynamics in the hepatic artery and the portal venous system.

AIM

To study the hepatic artery hemodynamics in children with extra hepatic portal vein obstruction.

MATERIALS AND METHODS

Hepatic artery indices were studied using Doppler indices in 15 children (<12 years) with extra hepatic portal hypertension (EHPVO) and obliterated esophageal varices. The hepatic artery resistive index, the arterial acceleration time and the acceleration index were used to determine the flow pattern within the hepatic artery. Controls were 15 healthy age-sex matched children, belonging to the same socioeconomic strata in absence of liver disease.

RESULTS

The mean age of the children was 8.43 ± 3.2 years and male female ratio was 4:1. All the children had obliterated esophageal varices. The hepatic artery resistive index in the children with EHPVO was normal and similar to controls. The hepatic arterial early systolic acceleration index was significantly higher in cases compared to controls (436 ± 290 vs 214 ± 100; P value <0.004). The hepatic arterial acceleration time though low in the cases (86 ± 35 cm/s) was not statistically different from the controls (128 ± 14 cm/s).

CONCLUSION

There was a significant increase in hepatic arterial early systolic acceleration in children with chronic EHPVO. The latter may be responsible for an increase in hepatic arterial in flow velocity in a slow flow system despite a normal resistive index.

Perihilar cholangiocarcinoma: a surgeon's viewpoint on current topics

Perihilar cholangiocarcinomas are defined anatomically as "tumors that are located in the extrahepatic biliary tree proximal to the origin of the cystic duct". However, as the boundary between the extrahepatic and intrahepatic bile ducts is not well defined, perihilar cholangiocarcinomas potentially include two types of tumors: one is the "extrahepatic" type, which arises from the large hilar bile duct, and the other is the "intrahepatic" type, which has an intrahepatic component with the invasion of the hepatic hilus. The new TNM staging system published by the International Union Against Cancer (UICC) has been well revised with regard to perihilar cholangiocarcinoma, but it still lacks stratification of patient prognosis and has little applicability for assessing the feasibility of surgical treatment; therefore, further refinement is essential. Most patients with perihilar cholangiocarcinomas present with jaundice, and preoperative biliary drainage is mandatory. Previously, percutaneous transhepatic biliary drainage was used in many centers; however, it is accepted that endoscopic naso-biliary drainage is the most suitable method of preoperative drainage. Portal vein embolization is now widely used as a presurgical treatment for patients undergoing an extended hepatectomy to minimize postoperative liver dysfunction. The surgical resection of a perihilar cholangiocarcinoma is technically demanding and continues to be the most difficult challenge for hepatobiliary surgeons. Because of advances in diagnostic and surgical techniques, surgical outcomes and survival rates after resection have steadily improved. However, survival, especially for patients with lymph node metastasis, is still unsatisfactory, and the establishment of adjuvant chemotherapy is necessary. Further synergy of endoscopists, radiologists, oncologists, and surgeons is required to conquer this intractable disease.

Role of portal vein embolization in hepatocellular carcinoma management and its effect on recurrence: a case-control study

Background

Liver regeneration that occurs after portal vein embolization (PVE) may have adverse effects on the microscopic tumor foci in the residual liver mass in patients with hepatocellular carcinoma (HCC).

Methods

Fifty-four HCC patients with inadequate functional residual liver volume were offered PVE during a seven-year period. Among them, 34 (63%) patients underwent curative resection. They were compared with a matched control group (n = 102) who underwent surgery without PVE. Postoperative complications, pattern of recurrence, and survival were compared between groups.

Results

In the PVE group, a pre-embolization functional residual liver volume of 23% (12–33.5%) improved to 34% (20–54%) (p = 0.005) at the time of surgery. When the two groups were compared, minor (PVE, 24%; control, 29%; p = 0.651) and major (PVE, 18%; control, 15%; p = 0.784) complications were similar. After a follow-up period of 35 months (standard deviation 25 months), extrahepatic recurrences were detected in 10 PVE patients (29%) and 41 control patients (40%) (p = 0.310). Intrahepatic recurrences were seen in 10 (29%) and 47 (46%) cases (p = 0.109) in the PVE and control groups, respectively. In the PVE group, 41% (n = 14) of the recurrences were detected before one year, compared with 42% (n = 43) in the control group (p = 1). Disease-free survival rates at 1, 3, and 5 years were 57, 29, and 26% in the control group and 60, 42, and 42% in the PVE group (log-rank, p = 0.335). On multivariate analysis, PVE was not a factor affecting survival (p = 0.821).

Conclusions

Portal vein embolization increases the resectability of initially unresectable HCC due to inadequate functional residual liver volume, and it has no deleterious oncological effect after major resection of HCC.

Nonocclusive hepatic artery hypoperfusion syndrome (splenic steal syndrome) in liver transplant recipients

There are numerous causes of reduced arterial inline flow to the liver transplant despite a patent hepatic artery. These include causes of increased peripheral resistance in the hepatic arterial bed, siphoning of the hepatic arterial flow by a dominant splenic artery (splenic steal syndrome), functional reduction of hepatic arterial flow in response to hyperdynamic portal inline flow, and small hepatic graft relative to normal portal inline flow (relative increase of portal flow). These causes are incompletely understood, and perhaps the most controversial of all is the splenic steal syndrome, which is possibly an underrecognized cause of graft ischemia in the United States. Splenic steal syndrome presents nonspecifically as graft dysfunction; if overlooked, it may lead to graft failure. Its incidence is reported to be 0.6 to 10.1% in liver transplant recipients, with some institutions performing prophylactic and/or posttransplant treatment procedures in up to a quarter of their transplant recipients. This wide disparity in the incidence of the diagnosis is probably because there are no objective diagnostic imaging criteria. This article presents a review of the literature that addresses the differential diagnostic considerations of hepatic artery hypoperfusion (splenic steal syndrome included) in the absence of an anatomical defect (hepatic artery stenosis, thrombosis, and/or kinks).

Impact of biomarkers expression before and after portal vein embolization on recurrence after two-stage hepatectomy for colorectal liver metastases

BACKGROUND

The adverse oncological effect of portal vein embolization (PVE) in patients with colorectal liver metastases (CLM) remains controversial. This study was designed to evaluate the effect of PVE on change of tumor characteristics using tumor specimens obtained from sequential hepatectomy before and after PVE.

METHODS

Between December 1996 and April 2009, among 55 patients who achieved two-stage hepatectomy (TSH) combined with PVE, 39 had available cancer tissue blocks from both the first- and second-stage hepatectomy and constituted the study population. The immunohistochemistry of Ki67 and Bcl-2 before and after PVE was performed. Biomarker expressions and clinicopathological variables were assessed and their impact on recurrence was analyzed.

RESULTS

Whereas tumor volume and carcinoembryonic serum level significantly increased after PVE, the expression of Ki67 and Bcl-2 remained similar before and after PVE. The Bcl-2 ratio (expressed as Bcl-2 after PVE over Bcl-2 before PVE) was an independent prognostic factor for recurrence-free survival (P=0.030). Patients with Bcl-2 ratio ≤ 1 had a significantly longer median recurrence-free survival compared with those with Bcl-2 ratio >1 receiving or not receiving adjuvant chemotherapy (24.8 months versus 8.9 or 5.8 months, respectively).

CONCLUSION

Bcl-2 ratio may predict early recurrence and identify patients who do not require postoperative chemotherapy in patients undergoing TSH with PVE for CLM.

Single-element ultrasound transducer for combined vessel localization and ablation

This report describes a system that utilizes a single high-intensity focused ultrasound (HIFU) transducer for both the localization and ablation of arteries with internal diameters of 0.5 and 1.3 mm. In vitro and in vivo tests were performed to demonstrate both the imaging and ablation functionalities of this system. For imaging mode, pulsed acoustic waves (3 cycles for in vitro and 10 cycles for in vivo tests, 2 MPa peak pressure) were emitted from the 2-MHz HIFU transducer, and the backscattered ultrasonic signal was collected by the same transducer to calculate Doppler shifts in the target region. The maximum signal amplitude of the Doppler shift was used to determine the location of the target vessel. The operation mode was then switched to the therapeutic mode and vessel occlusion was successfully produced by high-intensity continuous HIFU waves (12 MPa) for 60 s. The system was then switched back to imaging mode for residual flow to determine the need for a second ablation treatment. The new system might be used to target and occlude unwanted vessels such as vasculature around tumors, and to help with tumor destruction.

Computer modeling of controlled microsphere release and targeting in a representative hepatic artery system

Combating liver tumors via yttrium-90 ((90)Y) radioembolization is a viable treatment option of nonresectable liver tumors. Employing clinical (90)Y microparticles (i.e., SIR-Spheres and TheraSpheres) in a computational model of a representative hepatic artery system, laminar transient 3D particle-hemodynamics were simulated. Specifically, optimal particle release positions in the right hepatic (parent) artery as well as the best temporal release window were determined for the microspheres to exit specific outlet daughter vessels, potentially connected to liver tumors. The results illustrate the influence of a curved geometry on the velocity field and the particle trajectory dependence on the spatial and temporal particle injection conditions. The differing physical particle characteristics of the SIR-Spheres and the TheraSpheres had a subtle impact on particle trajectories in the decelerating portion of the arterial pulse, i.e., when the inertial forces on the particles are weaker. Conversely, particle characteristics and inelastic wall collisions had little effect on particles released during the accelerating phase of the arterial pulse, i.e., both types of microspheres followed organized paths to predetermined outlets. Such results begin paving the way towards directing 100% of the released microspheres to specific daughter vessels (e.g., those connected to tumors) under transient flow conditions in realistic geometries via a novel drug-particle targeting methodology.

Sequential preoperative ipsilateral hepatic vein embolization after portal vein embolization to induce further liver regeneration in patients with hepatobiliary malignancy

OBJECTIVE

To assess the effect of ipsilateral hepatic vein embolization (HVE) performed after portal vein embolization (PVE) on liver regeneration.

SUMMARY BACKGROUND DATA

PVE induces shrinkage of the embolized lobe and compensatory enlargement of the non-embolized lobe, but it does not always induce sufficient liver regeneration. There was no effective method to accelerate liver regeneration in addition to PVE yet.

METHODS

During a 1-year study period, preoperative HVE were performed on 12 patients who had shown limited liver regeneration after PVE awaiting right hepatectomy. The right hepatic vein was embolized with multiple coils after insertion of vena cava filters or vascular plugs.

RESULTS

No HVE procedure-related complications occurred, but embolization of the wrong hepatic vein trunk occurred in 1 patient. The increase in blood liver enzymes after HVE was comparable with that after PVE alone. In 9 patients who underwent hepatectomy, the proportions of future liver remnant volume to total liver volume were 34.8% +/- 1.5% before PVE, 39.7% +/- 0.6% 1 to 2 weeks after PVE, 44.2% +/- 1.1% 2 weeks after HVE, and 64.5% +/- 6.2% 1 week after right hepatectomy. Cirrhotic livers showed lower regeneration rates following HVE after PVE and 1 patient underwent hepatectomy 17 months after HVE. Immunohistochemistry showed that apoptosis occurred more in the liver area affected by both PVE and HVE than in that affected by PVE alone.

CONCLUSIONS

Preoperative sequential application of PVE and HVE seems to be safe and effective in facilitating contralateral liver regeneration by inducing more severe liver damage than PVE alone.

Induction of tumor growth after preoperative portal vein embolization: is it a real problem?

Although preoperative portal vein embolization (PVE) is an effective means to increase future remnant liver (FRL) volume, little has been published on possible adverse effects. This review discusses the clinical and experimental evidence regarding the effect of PVE on tumor growth in both embolized and nonembolized liver lobes, as well as potential strategies to control tumor progression after PVE. A literature review was performed using MEDLINE with keywords related to experimental and clinical studies concerning PVE, portal vein ligation (PVL), and tumor growth. Cross-references and references from reviews were also checked. Clinical and experimental data suggest that tumor progression can occur after preoperative PVE in embolized and nonembolized liver segments. Clinical evidence indicating possible tumor progression in patients with colorectal metastases or with primary liver tumors is based on studies with small sample size. Although multiple studies demonstrated tumor progression, evidence concerning a direct increase in tumor growth rate as a result of PVE is circumstantial. Three possible mechanisms influencing tumor growth after PVE can be recognized, namely changes in cytokines or growth factors, alteration in hepatic blood supply and an enhanced cellular host response promoting local tumor growth after PVE. Post-PVE chemotherapy and sequential transcatheter arterial chemoembolization (TACE) before PVE have been proposed to reduce tumor mass after PVE. We conclude that tumor progression can occur after PVE in patients with colorectal metastases as well as in patients with primary liver tumors. However, further research is needed in order to rate this risk of tumor progression after PVE.

Hepatic artery hemodynamics suggest operation of a buffer response in the human fetus

After birth, the hepatic artery buffer response helps to maintain liver perfusion. Here, the authors establish a Doppler technique to measure fetal hepatic artery flow velocity and test the hypothesis that the buffer response also operates prenatally. Women with low-risk pregnancies were recruited to a longitudinal study (N = 161). Measurement techniques and reference ranges for hepatic artery velocities and pulsatility index (PI) were established. Ductus venosus peak velocity (V(DVps)) represented the portocaval pressure gradient, and umbilical venous flow (Q(UV)) represented portal flow. Reference ranges were established for the more accessible left hepatic artery branch. Hepatic artery PI was lower in fetuses with V(DVps) <10th centile (P < .05) and in those with Q(UV) <10th centile ( P < .0001). Conversely, hepatic artery PI was higher in those with Q(UV) >90th centile (P < .0001). The authors establish a method for measuring fetal hepatic arterial blood velocity, provide reference ranges, and show that the hepatic artery buffer response operates prenatally.

Recent advances in the treatment of hilar cholangiocarcinoma: portal vein embolization

The clinical application of portal vein embolization (PVE) has contributed to improving the postoperative outcome of hilar cholangiocarcinoma. The enlarged nonembolized lobe after PVE protects the patient from postoperative hepatic failure, due to the increased functional reserve, and shortens the hospital stay. Although numerous reports have shown beneficial effects of PVE on postoperative outcome after extended hepatectomy, no randomized controlled study has been performed so far. It is urgent to establish a "gold standard" of PVE, because the indications, approach to the portal vein, types of embolic materials, and methods used to evaluate the function of the future liver remnant are variable among institutions. The indications and procedures of PVE for hilar cholangiocarcinoma may be different from those for hepatocellular carcinoma or colorectal metastasis, because, in many patients with hilar cholangiocarcinoma, biliary cancer is associated with biliary obstruction and cholangitis. This review article summarizes the contribution of PVE to the outcome of postoperative management in patients with hilar cholangiocarcinoma needing extended hepatectomy. We also describe our PVE procedure, which has been established from our experience of more than 240 cases of biliary cancer. Furthermore, the drawbacks of PVE, which may reduce the pool of candidates for surgery, are also discussed.

Mechanisms of hepatic regeneration following portal vein embolization and partial hepatectomy: a review

BACKGROUND

Portal vein embolization (PVE) improves outcome following major hepatectomy, and basic studies have presented evidence related to the mechanisms responsible for hepatic regeneration. Hemodynamic changes following PVE are similar to, but slightly different from, those of partial hepatectomy (PH) because arterial flow to the embolized lobe is preserved. However, the process of hepatic regeneration is essentially the same after both PVE and PH. A number of mediators are involved in PVE or PH-induced hepatic regeneration. These include inflammatory cytokines, vasoregulators, growth factors, eicosanoids, and various hormones. These mediators activate a complex network of signal transduction that promotes hepatic regeneration. A variety of conditions have been shown to modulate the function of these mediators and inhibit regeneration. These include biliary obstruction, diabetes, chronic ethanol consumption, malnutrition, gender, aging, and infection.

CONCLUSION

Optimizing these factors, where possible, before PVE or PH, is essential to maximize hypertrophy of the liver. A fuller understanding of hepatic physiology and pathophysiology following PVE or PH may lead to greater functional capacity of the remaining liver and extend the indications for hepatectomy in patients who require large liver volume resection.

A simple catheter-vessel model for MR assessment of drug distribution in arteries and optimization of catheter design for intraarterial infusion therapy

PURPOSE

To investigate the efficacy of a new catheter-vessel model for MRI to evaluate drug distribution and to optimize catheter design for intraarterial infusion therapy

MATERIALS AND METHODS

The model consisted of a hepatic artery simulant tube through which blood simulant water flowed continuously and a water cistern. Catheters were inserted into the tube and a gadolinium contrast medium was injected at rates suitable for angiographic or computed tomographic evaluation and commensurate with the clinical drug infusion rate. Axial images of the tube were obtained with a 0.2-T scanner and gradient echo technique. Preliminary studies and catheter tests were conducted. The points at which drug and water were completely mixed were defined as the site with uniform enhancement nearest the catheter tip.

RESULTS

Flip angle and gadolinium concentrations were optimized at 90 degrees, and at 62.5 and 500 mM for the high and low infusion rates, respectively. Drug distribution near the catheter tips was clearly visualized. The drug was mixed in shorter distances via the slit side-hole than the end- or side-hole catheters, and the smaller diametrical than the larger at either rate.

CONCLUSION

This model appeared to be effective for evaluation of drug distribution and optimization of catheter design.

Mechanism of impaired hepatic regeneration in cholestatic liver

The regenerative capacity of the liver is an important factor following liver surgery. The dramatic change in portal venous flow, due to either portal vein embolization or partial hepatectomy, induces a rapid change in liver volume. In response to these stresses, hepatocytes are primed, through the release of inflammatory cytokines, to increase the expression of immediate early genes and increase the activation of transcriptional factors. The primed hepatocytes then respond to growth factors, including hepatocyte growth factor, epidermal growth factor, and transforming growth factor-alpha. Several pathologic conditions have been shown to inhibit hepatic regeneration. These include diabetes mellitus, malnutrition, aging, infection, chronic ethanol consumption, and biliary obstruction. Impaired hepatic regeneration in the setting of biliary obstruction is an especially serious problem because it can be a major determinant in not considering surgical treatment. The mechanism responsible for impaired hepatic regeneration in patients with biliary obstruction includes decreased portal venous flow, attenuated production of liver proliferation-associated factors, an increased rate of apoptosis, and lack of enterohepatic circulation. Restoring these factors may lead to an improvement in regeneration in a cholestatic liver following portal vein embolization or partial hepatectomy. This review article summarizes the current understanding of the mechanism of hepatic regeneration, with particular emphasis on that in the cholestatic liver.

Two hundred forty consecutive portal vein embolizations before extended hepatectomy for biliary cancer: surgical outcome and long-term follow-up

OBJECTIVE

To assess clinical benefit of portal vein embolization (PVE) before extended, complex hepatectomy for biliary cancer.

SUMMARY BACKGROUND DATA

Many investigators have addressed clinical utility of PVE before simple hepatectomy for metastatic liver cancer or hepatocellular carcinoma, but few have reported PVE before hepatectomy for biliary cancer due to the limited number of surgical cases.

METHODS

This study involved 240 consecutive patients with biliary cancer (150 cholangiocarcinomas and 90 gallbladder cancers) who underwent PVE before an extended hepatectomy (right or left trisectionectomy or right hepatectomy). All PVEs were performed by the "ipsilateral approach" 2 to 3 weeks before surgery. Hepatic volume and function changes after PVE were analyzed, and the outcome also was reviewed.

RESULTS

There were no procedure-related complications requiring blood transfusion or interventions. Of the 240 patients, 47 (19.6%) did not undergo subsequent hepatectomy. The incidence of unresectability was higher in gallbladder cancer than in cholangiocarcinoma (32.2% versus 12.0%, P < 0.005). The remaining 193 patients (132 cholangiocarcinomas and 61 gallbladder cancers) underwent hepatectomy with resection of the caudate lobe and extrahepatic bile duct (n = 187), pancreatoduodenectomy (n = 42), and/or portal vein resection (n = 63). Seventeen (8.8%) patients died of postoperative complications: mortality was higher in gallbladder cancer than in cholangiocarcinoma (18.0% versus 4.5%, P < 0.05); and it was also higher in patients whose indocyanine green clearance (KICG) of the future liver remnant after PVE was <0.05 than those whose index was >or=0.05 (28.6% versus 5.5%, P < 0.001). The 3- and 5-year survival after hepatectomy was 41.7% and 26.8% in cholangiocarcinoma and 25.3% and 17.1% in gallbladder cancer, respectively (P = 0.011). In 136 other patients with cholangiocarcinoma who underwent a less than 50% resection of the liver without PVE, a mortality of 3.7% and a 5-year survival of 27.6% were observed, which was similar to the 132 patients with cholangiocarcinoma who underwent extended hepatectomy after PVE.

CONCLUSIONS

PVE has the potential benefit for patients with advanced biliary cancer who are to undergo extended, complex hepatectomy. Along with the use of PVE, further improvements in surgical techniques and refinements in perioperative management are necessary to make difficult hepatobiliary resections safer.

Portal vein embolization before major hepatectomy

To discuss the rationale, techniques and the unsolved issues regarding preoperative portal vein embolization (PVE) before major hepatectomy. After a systematic search of Pubmed, we reviewed and retrieved literature related to PVE. Preoperative PVE is an approach that is gaining increasing acceptance in the preoperative treatment of selected patients prior to major hepatic resection. Induction of selective hypertrophy of the nondiseased portion of the liver with PVE in patients with either primary or secondary hepatobiliary, malignancy with small estimated future liver remnants (FLR) may result in fewer complications and shorter hospital stays following resection. Additionally, PVE performed in patients initially considered unsuitable for resection due to lack of sufficient remaining normal parenchyma may add to the pool of candidates for surgical treatment. The results suggest that PVE is recomm-endable in treating the cirrhotic patients before major liver resection.

Percutaneous transhepatic pancreatic islet cell transplantation in type 1 diabetes mellitus: radiologic aspects

PURPOSE

To report our experience with percutaneous transhepatic pancreatic islet cell transplantation in patients with type 1 diabetes mellitus.

MATERIALS AND METHODS

Between March 1999 and May 2002, 34 patients underwent 68 islet cell transplantation procedures. Patients with C-peptide-negative type 1 diabetes were selected on the basis of poor metabolic control (hypoglycemia or lability) despite compliance with optimal medical therapy. Islet cells were isolated from brain-dead donors. Access to the portal vein was gained from a right percutaneous transhepatic approach, and islet cells were infused with intermittent pressure monitoring. Twenty patients underwent two transplantations, seven patients underwent three transplantations, and seven patients underwent one transplantation. Complications during and after the procedure and postprocedural diabetic status were monitored.

RESULTS

Successful portal vein cannulation and islet cell infusion were achieved in all cases. Fluoroscopy was used as the primary guidance modality in 58 of 68 (85%) procedures, and ultrasonography was used in 10 of 68 (15%). Total recorded fluoroscopy time varied from 0.6 to 103 minutes, with a median of 6.9 minutes. Potentially serious complications occurred in six of 68 (9%) procedures. Two patients developed portal venous thrombosis, and with subsequent anticoagulation therapy, one of the two developed an expanding hepatic hematoma that required surgery. Clinically important hemorrhage occurred in four patients, three of whom required blood transfusions. Of 26 patients who received completed transplants, all became insulin independent, and 81% (21 of 26) remained insulin free at 1 year.

CONCLUSION

The percutaneous transhepatic approach for the implantation of islet cells into the portal vein is a safe procedure, and together with use of current cell separation techniques and an immunosuppressive regimen, offers a marked advance in the treatment of type 1 diabetes mellitus.

Mechanical stress-dependent secretion of interleukin 6 by endothelial cells after portal vein embolization: clinical and experimental studies

BACKGROUND/AIMS

Interleukin-6 (IL-6) is an essential early signal in liver regeneration, however, little is known about what triggers IL-6 release. Changes in portal hemodynamics after portal vein embolization (PVE) may contribute to IL-6 release, leading to regeneration of non-embolized lobe.

METHODS

In 22 patients who underwent right PVE, the diameters of the left portal branches, liver volumes, and serum concentrations of IL-6, tumor necrosis factor-alpha (TNF-alpha), and hepatocyte growth factor (HGF) were measured. We then studied endothelial cells cultured on an elastic silicone membrane and subjected to continuous uni-axial stretch. Supernatant cytokine concentrations were measured.

RESULTS

The diameters of the portal branches increased by 150% after PVE. Serum IL-6 concentrations increased within 3h after PVE. The concentrations of TNF-alpha and HGF remained unchanged. The left lobe volume increased 2 weeks after PVE. The IL-6 concentrations in the supernatant of endothelial cells with stretch stress were higher than that in the non-stretched control group.

CONCLUSIONS

These findings indicate that PVE dilates the portal branches in the non-embolized lobe, exposing hepatic vasculature to stretch stress. This hemodynamic change may act as a trigger for IL-6 release from endothelial cells and contribute to the activation of regenerative cascade in the non-embolized lobes.