ESGAR consensus statement on liver MR imaging and clinical use of liver-specific contrast agents

Objectives

To develop a consensus and provide updated recommendations on liver MR imaging and the clinical use of liver-specific contrast agents.

Methods

The European Society of Gastrointestinal and Abdominal Radiology (ESGAR) formed a multinational European panel of experts, selected on the basis of a literature review and their leadership in the field of liver MR imaging. A modified Delphi process was adopted to draft a list of statements. Descriptive and Cronbach’s statistics were used to rate levels of agreement and internal reliability of the consensus.

Results

Three Delphi rounds were conducted and 76 statements composed on MR technique (n = 17), clinical application of liver-specific contrast agents in benign, focal liver lesions (n = 7), malignant liver lesions in non-cirrhotic (n = 9) and in cirrhotic patients (n = 18), diffuse and vascular liver diseases (n = 12), and bile ducts (n = 13). The overall mean score of agreement was 4.84 (SD ±0.17). Full consensus was reached in 22 % of all statements in all working groups, with no full consensus reached on diffuse and vascular diseases.

Conclusions

The consensus provided updated recommendations on the methodology, and clinical indications, of MRI with liver specific contrast agents in the study of liver diseases.

Key points

• Liver-specific contrast agents are recommended in MRI of the liver.

• The hepatobiliary phase improves the detection and characterization of hepatocellular lesions.

• Liver-specific contrast agents can improve the detection of HCC.

Pathologic classification of cholangiocarcinoma: New concepts

Herein, we propose a new pathologic classification of cholangiocarcinoma (CCA) based on recent progress in studies of preinvasive CCA lesions and the relationship of CCA to hepatic progenitor cells, as well as a new concept with respect to the pathologic similarities between biliary and pancreatic neoplasms. Depending on anatomical location, CCA is classifiable as intrahepatic (iCCA), perihilar (pCCA), and distal CCA (dCCA). iCCA is classifiable as the conventional type and the bile ductular type, whereas pCCA and dCCA mainly present as conventional adenocarcinoma. In addition, these three CCAs may present as the intraductal neoplasm type or rare variants. Bile ductular CCA resembles proliferating bile ductules and expressing hepatic progenitor cell phenotypes. Four types of preinvasive lesions are proposed: flat, papillary, tubular lesion, and cystic lesion. These lesions are eventually followed by invasive CCA. Interestingly, these preinvasive lesions have pancreatic counterparts. This CCA classification may introduce a new field of CCA research.

Cholangiocarcinoma

Biliary tract cancer accounts for <1% of all cancers and affects chiefly an elderly population, with predominance in men. We distinguish cholangiocarcinoma (intrahepatic, hilar and distal) and gallbladder cancer, with different pathogenesis and prognosis. The treatment is based on surgery (whenever possible), radiotherapy in selected cases, and chemotherapy. The standard cytotoxic treatment for advanced/metastatic disease is represented by the combination of gemcitabine and cisplatin, whereas fluoropyrimidines are generally administered in second line setting. At the present time, no biologic drug demonstrated a clear efficacy in this cancer, although the molecular characterisation could provide a promising basis for experimental treatments. A good supportive care and an early palliative care are warranted in most patients and should be delivered as a part of a global approach.

Transcription factors SOX4 and SOX9 cooperatively control development of bile ducts

In developing liver, cholangiocytes derive from the hepatoblasts and organize to form the bile ducts. Earlier work has shown that the SRY-related High Mobility Group box transcription factor 9 (SOX9) is transiently required for bile duct development, raising the question of the potential involvement of other SOX family members in biliary morphogenesis. Here we identify SOX4 as a new regulator of cholangiocyte development. Liver-specific inactivation of SOX4, combined or not with inactivation of SOX9, affects cholangiocyte differentiation, apico-basal polarity and bile duct formation. Both factors cooperate to control the expression of mediators of the Transforming Growth Factor-β, Notch, and Hippo-Yap signaling pathways, which are required for normal development of the bile ducts. In addition, SOX4 and SOX9 control formation of primary cilia, which are known signaling regulators. The two factors also stimulate secretion of laminin α5, an extracellular matrix component promoting bile duct maturation. We conclude that SOX4 is a new regulator of liver development and that it exerts a pleiotropic control on bile duct development in cooperation with SOX9.

Mechanisms of Biliary Plastic Stent Occlusion and Efforts at Prevention

Biliary stenting via endoscopic retrograde cholangiopancreatography has greatly improved the quality of patient care over the last 30 years. Plastic stent occlusion limits the life span of such stents. Attempts to improve plastic stent patency duration have mostly failed. Metal stents (self-expandable metal stents [SEMSs]) have therefore replaced plastic stents, especially for malignant biliary strictures. SEMS are at least 10 times more expensive than plastic stents. In this focused review, we will discuss basic mechanisms of plastic stent occlusion, along with a systematic summary of previous efforts and related studies to improve stent patency and potential new techniques to overcome existing limitations.

Biliary tract intraductal papillary mucinous neoplasm: Report of 19 cases

AIM: To gain a better understanding of biliary tract intraductal papillary mucinous neoplasm (BT-IPMN).

METHODS: From January 2000 to December 2013, 19 cases of BT-IPMN were retrospectively identified from a total of 343 biliary tract tumors resected in our single institution. Demographic characteristics, clinical data, pathology, surgical strategies, and long-term follow-up were analyzed.

RESULTS: The mean age of the 19 BT-IPMN cases was 53.8 years (range: 25-74 years). The most common symptom was abdominal pain (15/19; 78.9%), followed by jaundice (7/19; 36.8%). Cholangitis was associated with most (16/19; 84.2%) of the BT-IPMN cases. Macroscopically visible mucin was detected in all 19 patients, based on original surgical reports. The most common abnormal preoperative imaging findings for BT-IPMN were bile duct dilation (19/19; 100%) and intraluminal masses (10/19; 52.6%). Thirteen (68.4%) cases involved the intrahepatic bile duct and hilum. We performed left hepatectomy in 11/19 (57.9%), right hepatectomy in 2/19 (10.5%), bile duct resection in 4/19 (21.1%), and pancreatoduodenectomy in 1/19 (5.3%) patients. One (5.3%) patient was biopsied and received a choledochojejunostomy because of multiple tumors involving the right extrahepatic and left intrahepatic bile ducts. Histology showed malignancy in 10/19 (52.6%) patients. The overall median survival was 68 mo. The benign cases showed a non-significant trend towards improved survival compared to malignant cases (68 mo vs 48 mo, P = 0.347). The patient without tumor resection died of liver failure 22 mo after palliative surgery.

CONCLUSION: BT-IPMN is a rare biliary entity. Complete resection of the tumor is associated with good survival, even in patients with malignant disease.

Functional self-expandable metal stents in biliary obstruction

Biliary stents are widely used not only for palliative treatment of malignant biliary obstruction but also for benign biliary diseases. Each plastic stent or self-expandable metal stent (SEMS) has its own advantages, and a proper stent should be selected carefully for individual condition. To compensate and overcome several drawbacks of SEMS, functional self-expandable metal stent (FSEMS) has been developed with much progress so far. This article looks into the outcomes and defects of each stent type for benign biliary stricture and describes newly introduced FSEMSs according to their functional categories.

Diffusion-weighted imaging of biliopancreatic disorders: Correlation with conventional magnetic resonance imaging

Diffusion-weighted magnetic resonance imaging (DWI) is a well established method for the evaluation of intracranial diseases, such as acute stroke. DWI for extracranial application is more difficult due to physiological motion artifacts and the heterogeneous composition of the organs. However, thanks to the newer technical development of DWI, DWI has become increasingly used over the past few years in extracranial organs including the abdomen and pelvis. Most previous studies of DWI have been limited to the evaluation of diffuse parenchymal abnormalities and focal lesions in abdominal organs, whereas there are few studies about DWI for the evaluation of the biliopancreatic tract. Although further studies are needed to determine its performance in evaluating bile duct, gallbladder and pancreas diseases, DWI has potential in the assessment of the functional information on the biliopancreatic tract concerning the status of tissue cellularity, because increased cellularity is associated with impeded diffusion, as indicated by a reduction in the apparent diffusion coefficient. The detection of malignant lesions and their differentiation from benign tumor-like lesions in the biliopancreatic tract could be improved using DWI in conjunction with findings obtained with conventional magnetic resonance cholagiopancreatography. Additionally, DWI can be useful for the assessment of the biliopancreatic tract in patients with renal impairment because contrast-enhanced computed tomography or magnetic resonance scans should be avoided in these patients.

Role of β-catenin in development of bile ducts

Beta-catenin is known to play stage- and cell-specific functions during liver development. However, its role in development of bile ducts has not yet been addressed. Here we used stage-specific in vivo gain- and loss-of-function approaches, as well as lineage tracing experiments in the mouse, to first demonstrate that β-catenin is dispensable for differentiation of liver precursor cells (hepatoblasts) to cholangiocyte precursors. Second, when β-catenin was depleted in the latter, maturation of cholangiocytes, bile duct morphogenesis and differentiation of periportal hepatocytes from cholangiocyte precursors was normal. In contrast, stabilization of β-catenin in cholangiocyte precursors perturbed duct development and cholangiocyte differentiation. We conclude that β-catenin is dispensable for biliary development but that its activity must be kept within tight limits. Our work is expected to significantly impact on in vitro differentiation of stem cells to cholangiocytes for toxicology studies and disease modeling.

Biliary tumors with pancreatic counterparts

Some biliary diseases mimic pancreatic diseases pathologically as well as pathogenetically. Such diseases can be called "biliary diseases with pancreatic counterparts". Biliary intraepithelial neoplasm (BilIN), intraductal papillary neoplasm of bile ducts (IPNB), hepatobiliary mucinous cystic neoplasm (hMCN), and IgG4-inflammatory pseudotumor represent the biliary counterparts of pancreatic intraepithelial neoplasm (PanIN), intraductal papillary mucinous neoplasm of pancreas (IPMN), pancreatic MCN, and mass forming type 1 autoimmune pancreatitis (AIP), respectively. BilIN and PanIN represent pre-invasive intraepithelial stages of nodular sclerosing cholangiocarcinoma and pancreatic ductal adenocarcinoma, respectively. IPNB and IPMN are grossly visible, predominant papillary, intraductal neoplasms that may progress to invasive carcinoma. Morphologically similar MCNs with subepithelial ovarian-like stroma occur in both the hepatobiliary system as well as the pancreas. IgG4-inflammatory pseudotumor, usually of the lymphoplasmacytic type, and mass forming type 1 AIP represent IgG4-related disease in the biliary tree and pancreas respectively. The biliary tract, which is associated with the peribiliary glands, including the pancreatic acini, can be regarded as an incomplete pancreas, so several diseases mimicking pancreatic diseases may be expected to occur in the biliary tract (biliary diseases with pancreatic counterparts).

Cystic malformation of cystic duct: 10 cases and review of literature

AIM: To evaluate cystic malformations of the cystic duct.

METHODS: Over a 2-year period, we came across 10 cases of cystic malformation of the cystic duct among patients who were investigated in our radiology department with ultrasonography, multidetector computed tomography, or magnetic resonance imaging for abdominal complaints. Radiological diagnosis of cystic malformation of the cystic duct was made on the basis of a dilated, nonvascular cystic structure near the porta hepatis, and visualization of a clear communication with either the gallbladder, normal caliber cystic duct and/or common bile duct (CBD) on at least one imaging modality.

RESULTS: Four of 10 patients had saccular dilatation of the cystic duct. Six patients had fusiform dilatation of the cystic duct, and two of these had only mild fusiform dilatation. Two patients had associated CBD dilatation and one had associated cystic duct calculi and malignancy.

CONCLUSION: Cystic malformations of the cystic duct should be recognized as a distinct type of choledochal cyst and should be added as type VI cyst in Todani’s classification.

Biliary issues in the bariatric population

Biliary disease is common in the obese population and increases after bariatric surgery. This article reviews management of the gallbladder at the time of bariatric surgery, as well as imaging modalities in the bariatric surgery population and prevention of lithogenesis in the rapid weight loss phase. In addition, diagnosis and treatment options for biliary diseases are discussed, including laparoscopic-assisted percutaneous transgastric endoscopic retrograde cholangiopancreatography in the patient having bariatric surgery.

Common bile duct schwannoma: A case report and review of literature

Schwannoma is a myelin sheath tumor complicated with neurofibroma, neurofibromatosis and neurogenic sarcoma. Peripheral nerve sheath tumors represent 2%-6% of gastrointestinal tract stromal tumors (GIST), but there are deficient data about location of neurogenic tumors in the biliary system and only nine cases of schwannoma of the extrahepatic biliary tract have been reported. These tumors are clinically non-specific. They are usually symptomatic by compressing the close or adjacent structures when being retroperitoneal, and their preoperative diagnosis is extremely difficult. This paper reviews the literature data and describes a case of schwannoma of the common bile duct associated with cholestasis in a healthy young woman, diagnosed and treated in our department. This case is of interest on account of the complexity of its diagnosis and the atypical macroscopic growth pattern of the tumor.

Interventional radiology in the management of malignant biliary obstruction

Malignant biliary obstruction is commonly due to pancreatic carcinoma, cholangiocarcinoma and metastatic disease which are often inoperable at presentation and carry a poor prognosis. Percutaneous biliary drainage and stenting provides a safe and effective method of palliation in such patients, thereby improving their quality of life. It may also be an adjunct to surgical management by improving hepatic and, indirectly, renal function before resection of the tumor.

A deep learning-based system for bile duct annotation and station recognition in linear endoscopic ultrasound

BACKGROUND

Detailed evaluation of bile duct (BD) is main focus during endoscopic ultrasound (EUS). The aim of this study was to develop a system for EUS BD scanning augmentation.

METHODS

The scanning was divided into 4 stations. We developed a station classification model and a BD segmentation model with 10681 images and 2529 images, respectively. 1704 images and 667 images were applied to classification and segmentation internal validation. For classification and segmentation video validation, 264 and 517 videos clips were used. For man-machine contest, an independent data set contained 120 images was applied. 799 images from other two hospitals were used for external validation. A crossover study was conducted to evaluate the system effect on reducing difficulty in ultrasound images interpretation.

FINDINGS

For classification, the model achieved an accuracy of 93.3% in image set and 90.1% in video set. For segmentation, the model had a dice of 0.77 in image set, sensitivity of 89.48% and specificity of 82.3% in video set. For external validation, the model achieved 82.6% accuracy in classification. In man-machine contest, the models achieved 88.3% accuracy in classification and 0.72 dice in BD segmentation, which is comparable to that of expert. In the crossover study, trainees' accuracy improved from 60.8% to 76.3% (P < 0.01, 95% C.I. 20.9-27.2).

INTERPRETATION

We developed a deep learning-based augmentation system for EUS BD scanning augmentation.

FUNDING

Hubei Provincial Clinical Research Center for Digestive Disease Minimally Invasive Incision, Hubei Province Major Science and Technology Innovation Project, National Natural Science Foundation of China.

Endoscopic diagnosis of cholangiocarcinoma: From endoscopic retrograde cholangiography to bile proteomics

Cholangiocarcinoma (CCA) is the second most common primary liver cancer. In clinical practice, the diagnosis remains challenging and often requires endoscopic approaches. Endoscopic retrograde and percutaneous transhepatic cholangiography are the first-line endoscopic procedures for the evaluation of indeterminate bile duct strictures. Tissue acquisition via brush cytology and forceps biopsies allows the cytological and/or histological confirmation of the disease. Due to the low sensitivity of these techniques, repetitive examinations and/or alternative approaches are required. Cholangioscopy, endoscopic and intraductal ultrasound and confocal laser endomicroscopy are additional methods which can be applied for the diagnosis of CCA. Particularly, new experimental approaches like bile and urine proteomic analyses show promising results which have to be evaluated prospectively for further integration in diagnostic algorithms.

Choledochal malformations: global research, scientific advances and key controversies

Choledochal malformations (CMs) represent a spectrum of relatively rare and complex congenital anomalies, characterized by abnormal dilatation of the biliary tract in the absence of any acute obstruction. Today, almost 20% of CMs can be detected in-utero using maternal ultrasonography. Formal scientometric analysis was used to identify where modern CM research is taking place and perhaps where our attention should be directed in the future. Thus, this article offers a comprehensive review of recent scientific advances relating to CMs including the current understanding of etiology and classification, whilst also discussing key controversies such as risk of malignant transformation and the role of newer modalities of surgical treatment. Although laparoscopic excision of CMs and biliary reconstruction is nowadays feasible and safe, care should be taken before dispensing with standard open techniques, which have minimal complication rates and proven long-term benefit.

New endoscopic ultrasonography techniques for pancreaticobiliary diseases

Endoscopic ultrasonography (EUS) is widely used to evaluate pancreaticobiliary diseases, especially pancreatic masses. EUS has a good ability to detect pancreatic masses, but it is not sufficient for the differential diagnosis of various types of lesions. In order to address the limitations of EUS, new techniques have been developed to improve the characterization of the lesions detected by EUS. EUS-guided fine needle aspiration (EUS-FNA) has been used for diagnosing pancreatic tumors. In order to improve the histological diagnostic yield, a EUS-FNA needle with a core trap has recently been developed. Contrast-enhanced harmonic EUS is a new imaging modality that uses an ultrasonographic contrast agent to visualize blood flow in fine vessels. This technique is useful in the diagnosis of pancreatic solid lesions and in confirming the presence of vascularity in mural nodules for cystic lesions. EUS elastography analyzes several different variables to measure tissue elasticity, color patterns, and strain ratio, using analytical techniques such as hue-histogram analysis, and artificial neural networks, which are useful for the diagnosis of chronic pancreatitis and pancreatic cancer.

Biliary tract injuries after lap cholecystectomy-types, surgical intervention and timing

Bile duct lesions, including leaks and strictures, are immanent complications of open or laparoscopic cholecystectomy (LC). Endoscopic procedures have gained increasing potential as the treatment of choice in the management of postoperative bile duct injuries. Bile duct injury (BDI) is a severe and potentially life-threatening complication of LC. Several series have described a 0.5% to 0.6% incidence of BDI during LC. Early recognition and an adequate multidisciplinary approach are the cornerstones for the optimal final outcome. Suboptimal management of injuries often leads to more extensive damage to the biliary tree and its vasculature. Early referral to a tertiary care center with experienced hepatobiliary surgeons and skilled interventional radiologists would appear to be necessary to assure optimal results.

Endoscopic management of benign biliary strictures

Endoscopic management of biliary obstruction has evolved tremendously since the introduction of flexible fiberoptic endoscopes over 50 years ago. For the last several decades, endoscopic retrograde cholangiopancreatography (ERCP) has become established as the mainstay for definitively diagnosing and relieving biliary obstruction. In addition, and more recently, endoscopic ultrasonography (EUS) has gained increasing favor as an auxiliary diagnostic and therapeutic modality in facilitating decompression of the biliary tree. Here, we provide a review of the current and continually evolving role of gastrointestinal endoscopy, including both ERCP and EUS, in the management of biliary obstruction with a focus on benign biliary strictures.

Common bile duct diameter in an asymptomatic population: A magnetic resonance imaging study

AIM: To measure the common bile duct (CBD) diameter by magnetic resonance cholangiopancreatography (MRCP) in a large asymptomatic population and analyze its some affecting factors.

METHODS: This study included 862 asymptomatic subjects who underwent MRCP. The CBD diameter was measured at its widest visible portion on regular end-expiration MRCP for all subjects. Among these 862 subjects, 221 volunteers also underwent end-inspiration MRCP to study the effect of respiration on the CBD diameter. The age, sex, respiration, body length, body weight, body mass index (BMI), portal vein diameter (PVD), length of the extrahepatic duct and CBD, cystic junction radial orientation and location were recorded. The subjects were divided into 7 groups according to age. All of the above factors were compared with the CBD diameter on end-expiration MRCP.

RESULTS: Among the 862 subjects, the CBD diameter was 4.13 ± 1.11 mm (range, 1.76-9.45 mm) and was correlated with age (r = 0.484; P < 0.05), with a dilation of 0.033 mm per year. The upper limit of the 95% reference range was 5.95 mm, resulting in a reasonable upper limit of 6 mm for the asymptomatic population. Respiration and other factors, including sex, body length, body weight, BMI, PVD, length of the extrahepatic duct and CBD, cystic junction radial orientation and location, were not related to the CBD diameter.

CONCLUSION: We established a reference range for the CBD diameter on MRCP for an asymptomatic population. The CBD diameter is correlated with age. Respiration did not affect the non-dilated CBD diameter.

Endoderm specification and liver development

The endoderm is the innermost embryonic germ layer, and in zebrafish, it gives rise to the lining of the gut, the gills, liver, pancreas, gallbladder, and derivatives of the pharyngeal pouch. These organs form the gastrointestinal tract and are involved with the absorption, delivery, and metabolism of nutrients. The liver has a central role in regulating these processes because it controls carbohydrate and lipid metabolism, protein synthesis, and breakdown of endogenous and xenobiotic products. Liver dysfunction frequently leads to significant morbidity and mortality; however, in most settings of organ injury, the liver exhibits remarkable regenerative capacity. In this chapter, we review the principal mechanisms of endoderm and liver formation and provide protocols to assess liver formation and liver regeneration.

The Expanding Role of Contrast-Enhanced Endoscopic Ultrasound in Pancreatobiliary Disease

Since its introduction into clinical practice in the 1980s, endoscopic ultrasound (EUS) has been described as a good imaging modality for the diagnosis of pancreatobiliary diseases. However, differential diagnosis of certain lesions based only on B-mode ultrasound images can be challenging. Clinical use of ultrasound contrast agents has expanded the utility of EUS from that of detection to characterization of pancreatobiliary lesions based on the enhancement features of contrast-enhanced EUS (CE-EUS). Current low mechanical index techniques for CE-EUS using second-generation contrast agents have a number of distinct advantages over conventional diagnostic modalities in evaluating pancreatobiliary lesions, including real-time assessment of perfusion pattern, availability, and the absence of exposure to radiation. This article describes the technical aspects of CE-EUS and reviews the expanding indications in pancreatobiliary diseases and further development of this technique.

Basic Knowledge about Metal Stent Development

Biliary self-expandable metal stents (SEMS), a group of non-vascular stents, have been used in the palliative management of biliary obstruction around the world. However, there are still unmet needs in the clinical application of biliary SEMS. Comprehensive understanding of the SEMS is required to resolve the drawbacks and difficulties of metal stent development. The basic structure of SEMS, including the materials and knitting methods of metal wires, covering materials, and radiopaque markers, are discussed in this review. What we know about the physical and mechanical properties of the SEMS is very important. With an understanding of the basic knowledge of metal stents, hurdles such as stent occlusion, migration, and kinking can be overcome to develop more ideal SEMS.