Morphological and biomechanical remodelling of the hepatic artery in a swine model of portal hypertension

Hemodynamic analysis of hepatic arteries for the early evaluation of hepatic fibrosis in biliary atresia

BACKGROUND AND OBJECTIVE

Hepatic fibrosis is the prominent characteristic of biliary atresia (BA), may even progress continually after Kasai procedure (KP). BA, as a devastating pediatric hepatic disease, mainly leads to newborn cholestasis, even liver cirrhosis, eventually hepatic failure. Earlier diagnosis of hepatic fibrosis, which used to be detected by liver biopsy commonly, is consistent with better outcomes of KP. Due to potential risks and uncertainty of liver biopsy, it is an urge to seek a safer and more precise evaluation method as alternative. The purpose of this study is to investigate the hemodynamics of hepatic artery (HA) in hepatic fibrosis of early BA based on computational fluid dynamics (CFD) for evaluating the value of CFD for hepatic fibrosis diagnosis.

METHODS

40 patients were divided into three groups, including the control group, the abnormal liver function group and the mild to moderate hepatic fibrosis group. CFD was applied to quantify primary hemodynamic parameters of HA and related arteries, including blood flow distribution ratio (FDR), pressure, wall shear stress (WSS) and energy loss (EL). Statistical analyses were also performed to compare the differences amongst these above groups.

RESULTS

With the progression of hepatic fibrosis, the increasing tendency of hemodynamic parameters values of HA and related arteries were observed. Values of FDR, pressure, WSS and EL of the mild to moderate group was higher than those of the control group and the abnormal liver function group. There were significant differences on FDR_AA, FDR_HA and EL between the control group and the mild to moderate hepatic fibrosis group (t = 0.037, 0.030 and <0.001, P < 0.05).

CONCLUSION

Significant variations of HA hemodynamics acquired by CFD between the control group and the mild to moderate hepatic fibrosis group demonstrated the relationship between the progression of hepatic fibrosis and the hemodynamic disorder, and suggested that CFD had the potential to assist the diagnosis of hepatic fibrosis in early BA.

Hybrid Additive Fabrication of a Transparent Liver with Biosimilar Haptic Response for Preoperative Planning

Due to the complexity of liver surgery, the interest in 3D printing is constantly increasing among hepatobiliary surgeons. The aim of this study was to produce a patient-specific transparent life-sized liver model with tissue-like haptic properties by combining additive manufacturing and 3D moulding. A multistep pipeline was adopted to obtain accurate 3D printable models. Semiautomatic segmentation and registration of routine medical imaging using 3D Slicer software allowed to obtain digital objects representing the structures of interest (liver parenchyma, vasculo-biliary branching, and intrahepatic lesion). The virtual models were used as the source data for a hybrid fabrication process based on additive manufacturing using soft resins and casting of tissue-mimicking silicone-based blend into 3D moulds. The model of the haptic liver reproduced with high fidelity the vasculo-biliary branching and the relationship with the intrahepatic lesion embedded into the transparent parenchyma. It offered high-quality haptic perception and a remarkable degree of surgical and anatomical information. Our 3D transparent model with haptic properties can help surgeons understand the spatial changes of intrahepatic structures during surgical manoeuvres, optimising preoperative surgical planning.

The portal hypertension syndrome: etiology, classification, relevance, and animal models

BACKGROUND

Portal hypertension is a key complication of portal hypertension, which is responsible for the development of varices, ascites, bleeding, and hepatic encephalopathy, which, in turn, cause a high mortality and requirement for liver transplantation.

AIM

This review deals with the present day state-of-the-art preventative treatments of portal hypertension in cirrhosis according to disease stage. Two main disease stages are considered, compensated and decompensated cirrhosis, the first having good prognosis and being mostly asymptomatic, and the second being heralded by the appearance of bleeding or non-bleeding complications of portal hypertension.

RESULTS

The aim of treatment in compensated cirrhosis is preventing clinical decompensation, the more frequent event being ascites, followed by variceal bleeding and hepatic encephalopathy. Complications are mainly driven by an increase of hepatic vein pressure gradient (HVPG) to values ≥10 mmHg (defining the presence of Clinically Significant Portal Hypertension, CSPH). Before CSPH, the treatment is limited to etiologic treatment of cirrhosis and healthy life style (abstain from alcohol, avoid/correct obesity…). When CSPH is present, association of a non-selective beta-blocker (NSBB), including carvedilol should be considered. NSBBs are mandatory if moderate/large varices are present. Patients should also enter a screening program for hepatocellular carcinoma. In decompensated patients, the goal is to prevent further bleeding if the only manifestation of decompensation was a bleeding episode, but to prevent liver transplantation and death in the common scenario where patients have manifested first non-bleeding complications. Treatment is based on the same principles (healthy life style..) associated with administration of NSBBs in combination if possible with endoscopic band ligation if there has been variceal bleeding, and complemented with simvastatin administration (20-40 mg per day in Child-Pugh A/B, 10-20 mg in Child C). Recurrence shall be treated with TIPS. TIPS might be indicated earlier in patients with: 1) Difficult/refractory ascites, who are not the best candidates for NSBBs, 2) patients having bleed under NSBBs or showing no HVPG response (decrease in HVPG of at least 20% of baseline or to values equal or below 12 mmHg). Decompensated patients shall all be considered as potential candidates for liver transplantation.

CONCLUSION

Treatment of portal hypertension has markedly improved in recent years. The present day therapy is based on accurate risk stratification according to disease stage.

Impact of fluid-structure interaction on direct tumor-targeting in a representative hepatic artery system

Direct targeting of solid tumors with chemotherapeutic drugs and/or radioactive microspheres can be a treatment option which minimizes side-effects and reduces cost. Briefly, computational analysis generates particle release maps (PRMs) which visually link upstream particle injection regions in the main artery with associated exit branches, some connected to tumors. The overall goal is to compute patient-specific PRMs realistically, accurately, and cost-effectively, which determines the suitable radial placement of a micro-catheter for optimal particle injection. Focusing in this paper on new steps towards realism and accuracy, the impact of fluid-structure interaction on direct drug-targeting is evaluated, using a representative hepatic artery system with liver tumor as a test bed. Specifically, the effect of arterial wall motion was demonstrated by modeling a two-way fluid-structure interaction analysis with Lagrangian particle tracking in the bifurcating arterial system. Clearly, rapid computational evaluation of optimal catheter location for tumor-targeting in a clinical application is very important. Hence, rigid-wall cases were also compared to the flexible scenario to establish whether PRMs generated when based on simplifying assumptions could provide adequate guidance towards ideal catheter placement. It was found that the best rigid (i.e., time-averaged) geometry is the physiological one that occurs during the diastolic targeting interval.