Embryology, Anatomy, and Imaging of the Biliary Tree

Imaging of Benign Biliary Tract Disease

This review article discusses the most common benign biliary disorders and the various radiological findings on multiple modalities. A broad spectrum of diseases including various congenital disorders, infective and parasitic etiologies, immunological pathologies such as primary sclerosing cholangitis, and immunoglobulin G4-related sclerosing cholangitis are discussed along with obstructive diseases and ischemic cholangitis. The article emphasized the imaging differential diagnosis of the above lesions as well as clinical correlates those that are most relevant to radiologists. The article briefly touched upon management and intervention where relevant.

Surgical Management of the Horrible Gallbladder

Laparoscopic cholecystectomy is one of the most frequently performed operations by general surgeons, with up to 1 million cholecystectomies performed annually in the United States alone. Despite familiarity, common bile duct injury occurs in no less than 0.2% of cholecystectomies, with significant associated morbidity. Understanding biliary anatomy, surgical techniques, pitfalls, and bailout maneuvers is critical to optimizing outcomes when encountering the horrible gallbladder. This article describes normal and aberrant biliary anatomy, complicated cholelithiasis, ways to recognize cholecystitis, and considerations of surgical approach.

Biliary Disorders, Anomalies, and Malignancies in Children

Biliary abnormalities in children are uncommon, and the spectrum of biliary disorders is broader than in adult patients. Unlike in adults, biliary disorders in children are rarely neoplastic and are more commonly rhabdomyosarcoma rather than cholangiocarcinoma. Pediatric biliary disorders may be embryologic or congenital, such as anatomic gallbladder anomalies, anomalous pancreaticobiliary tracts, various cholestatic processes, congenital cystic lesions, or genetic conditions. They may also be benign, such as biliary filling anomalies, biliary motility disorders, and biliary inflammatory and infectious disorders. Distinguishing these entities with a single imaging modality is challenging. US is the primary imaging modality for initial evaluation of biliary abnormalities in children, due to its wide availability, lack of ionizing radiation, and low cost and because it requires no sedation. Other examinations such as MRI, CT, and nuclear medicine examinations may provide anatomic and functional information to narrow the diagnosis further. Hepatobiliary-specific contrast material with MRI can provide better assessment of biliary anatomy on delayed images than can traditional MRI contrast material. MR cholangiopancreatography (MRCP) allows visualization of the intra- and extrahepatic biliary ducts, which may not be possible with endoscopic retrograde cholangiopancreatography (ERCP). Suspected biliary atresia requires multiple modalities for diagnosis and timely treatment. Determining the type of choledochal cyst calls for a combination of initial US and MRCP. Many benign and malignant biliary masses require biopsy for definitive diagnosis. Knowledge of the imaging appearances of different pediatric biliary abnormalities is necessary for appropriate imaging workup, providing a diagnosis or differential diagnosis, and guiding appropriate management. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

An uncommon case of right hepatic duct entering cystic duct associated to multiple complications of biliary tract disease: acute pancreatitis, hepatolithiasis, acute cholecystitis and hepatic abscess

Anatomical variations of the biliary tree pose diagnostic and treatment challenges. While most are harmless and often discovered incidentally during procedures, some can lead to clinical issues and biliary complications, making knowledge of these variants crucial to prevent surgical mishaps. Here, we present an unusual and clinically significant case. A 61-year-old man is admitted to the hospital with epigastric pain and diagnosis of pancreatitis of biliary origin and intermediate risk of choledocholithiasis. Magnetic resonance cholangiopancreatography (MRCP) reported hepatolithiasis and choledocholithiasis, whereas endoscopic retrograde cholangiopancreatography showed cystic drain of the right hepatic duct. One month later the patient presented again to the emergency room with increasing abdominal pain and a computed tomography that demonstrated the presence of hepatic abscess and acute cholecystitis. The patient underwent percutaneous drain abscess and a subtotal laparoscopic cholecystectomy. Biliary anatomical variants present challenges on the diagnostic investigations, interventional and surgical procedures, understanding the possible complications is essential.

Endoscopic Treatment of Malignant Hilar Biliary Obstruction

Stent implantation is an effective approach for palliative treatment of Bismuth-Corlette type III-IV malignant hilar biliary obstructions (MHBOs). In this article, we reviewed the currently used access methods for biliary stent placement (percutaneous transhepatic biliary drainage, endoscopic biliary drainage, endosonography guided biliary drainage), the available stent types (plastic stent, self-expanding metallic stent, full cover self-expanding metallic stent, radioactive self-expanding metallic stent), major approaches (unilateral, bilateral) and deployment methods (stent-in-stent, stent-by-stent). Finally, this review gives an outlook on perspectives of development in stenting and other palliative methods in MHBO.

Association between anatomic variations of extrahepatic and intrahepatic bile ducts: Do look up!

Biliary anatomic variations are usually asymptomatic, but they may cause problems in diagnostic investigations and interventional and surgical procedures, increasing both their technical difficulty and their postoperative complication rates. The aim of the present study was to evaluate the prevalence of anatomic variations in the intrahepatic biliary ducts (IHBD) in relation to demographical and clinical characteristics in a large study population requiring magnetic resonance cholangiopancreatography (MRCP) for various clinical conditions. The possible association between IHBD and extrahepatic biliary ducts (EHBD) variants was then explored. From January 2017 to May 2019, 1004 patients underwent MRCP. Demographical and clinical data were collected. IHBD and EHBD anatomy were recorded and the EHBD anatomy was classified using both qualitative and quantitative classifications. The presence of a type 3 EHBD variant (an abnormal proximal cystic duct [CD] insertion) in both qualitative and quantitative classifications and an intrapancreatic CD were associated with the presence of IHBD variants at univariate analysis (p = 0.008, p = 0.019, and p = 0.001, respectively). The presence of a posterior or medial insertion of the CD into the EHBD was a strong predictive factor of the presence of IHBD variants both at uni- and multivariate analysis (p = 0.002 and p = 0.003 for posterior insertion and p = 0.002 and p = 0.002 for medial insertion, respectively). The presence of gallstones on MRCP resulted in a strong predictor of the presence of an anatomical variant of the IHBD both at uni- and multivariate analysis (p = 0.027 and p = 0.046, respectively). In conclusion, the presence of a type 3 variant of the EHBD, an intrapancreatic CD and, especially, a posterior/medial CD insertion into the EHBD represent predictive factors of the concomitant presence of IHBD variants, thus radiologists must be vigilant when encountering these EHBD configurations and always remember to "look up" at the IHBD. Finally, the presence of an IHBD variant is a strong predictive factor of gallstones.

Biliary Anatomy

The hepatobiliary system is known to have high anatomic variability, as studies have shown variant rates of over 40% among individuals. This review will describe biliary anatomy and the most common anatomic variants, knowledge of which is critical to ensuring safe and effective biliary interventions.

Complete Absence of the Extrahepatic Biliary Tree in a Newborn With Pigmented Stools

"Yellow stools in neonatal cholestasis exclude biliary atresia." This conventional wisdom led to the development of the infant stool color card, which alerts parents to seek medical referral when pale stools are observed, a strategy that has been shown to improve survival in infants with biliary atresia (BA). Here, we present a case of a newborn with significant direct hyperbilirubinemia (direct bilirubin level of up to 9.2 mg/dL on day of life 10) who continued to produce colored stools. Whole-genome sequencing results were negative for genetic causes of cholestasis. Hepatobiliary scintigraphy findings were nonexcretory. A liver biopsy specimen revealed cholestasis, ductular hyperplasia, giant cell formation, minimal inflammation, minimal portal or periportal fibrosis, and no evidence of viral changes. On day of life 38, during the exploratory laparotomy, the patient was found to have complete absence of the extrahepatic biliary tree, or biliary aplasia, possibly a rare, severe form of BA. This report aims to increase our vigilance and help prevent diagnostic error in patients with signs and symptoms of BA who may produce pigmented stools. Primary care physicians should hence refer an infant (early and urgently) to a pediatric gastroenterologist for further workup for a direct bilirubin level >1.0 mg/dL with any total bilirubin level, irrespective of the color of the infant's stools.

Prevalence of Different Hepatobiliary Tree Variants on Magnetic Resonance Cholangiopancreatography in Patients Visiting a Tertiary Care Teaching Hospital in Karachi

Introduction

Hepatobiliary tree variant anatomy is crucial to understand the preoperative planning of hepatobiliary surgeries. Although the presence of variant anatomy is not an absolute contraindication for liver transplantation, inadvertent mapping can lead to postoperative biliary complications. These variants are also important to be recognized in various hepatobiliary surgeries and interventional procedures. Magnetic resonance cholangiopancreatography (MRCP) is an excellent non-invasive imaging tool that can identify biliary anatomy. The purpose of the current study is focused on determining anatomical variants of the biliary tree on MRCP in our population visiting a teaching hospital in Karachi.

Methods

This cross-sectional study was conducted on patients referred to Dr. Ziauddin Hospital for MRCP. MRCP was performed on MAGNETOM Avanto, SIEMENS, Belgium, Germany. Images were analyzed on a workstation by two radiologists and a postgraduate trainee. A senior radiologist reviewed equivocal cases. SPSS 22.0 (SPSS Inc., Chicago, IL) was used for statistical analysis. Chi-square test was used to see the link between anatomical variants of biliary tree and gender. P-value of ≤0.05 was considered as statistically significant.

Results

We recruited 369 patients undergoing MRCP consecutively for our study. Out of 369, 342 patients were eligible for analysis (139 males and 203 females). Standard anatomy was found to be prevalent in 65.8%. Type 3 was the leading variant. A statistically significant difference was recorded for the type 2 anatomic variant which was more frequent in males than females (p-value <0.001), while types 1, 3, and 4 anatomic variants were found to be more in females than males but this difference was not statistically significant. Few other variants were also recorded.

Conclusion

This study is robust evidence regarding biliary variants in Pakistan. It is important to consider these variants in our region, owing to an increased trend of liver transplants and other hepatobiliary procedures.

Wnt/β-catenin signalling controls bile duct regeneration by regulating differentiation of ductular reaction cells

Recently, the incidence of bile duct‐related diseases continues to increase, and there is no effective drug treatment except liver transplantation. However, due to the limited liver source and expensive donations, clinical application is often limited. Although current studies have shown that ductular reaction cells (DRCs) reside in the vicinity of peribiliary glands can differentiate into cholangiocytes and would be an effective alternative to liver transplantation, the role and mechanism of DRCs in cholangiole physiology and bile duct injury remain unclear. A 3,5‐diethoxycarbonyl‐1,4‐dihydrocollidine (DDC)‐enriched diet was used to stimulate DRCs proliferation. Our research suggests DRCs are a type of intermediate stem cells with proliferative potential that exist in the bile duct injury. Meanwhile, DRCs have bidirectional differentiation potential, which can differentiate into hepatocytes and cholangiocytes. Furthermore, we found DRCs highly express Lgr5, and Lgr5 is a molecular marker for neonatal DRCs (P < .05). Finally, we confirmed Wnt/β‐catenin signalling achieves bile duct regeneration by regulating the expression of Lgr5 genes in DRCs (P < .05). We described the regenerative potential of DRCs and reveal opportunities and source for the treatment of cholestatic liver diseases.

Risk of Gallstone Formation in Aberrant Extrahepatic Biliary Tract Anatomy: A Review of Literature

The age-long mnemonic of '5Fs' (fat, female, fertile, forty, and fair) has traditionally been used in medical school instructions to describe the risk factors for gallstone disease. However, evidence suggests that aberrant extrahepatic biliary tract (EHBT) anatomy may contribute significantly to the risk of gallstone disease. This review explores the anatomy and embryological bases of EHBT variations as well as the prevalence of these variations. Also, we discuss the risk factors for gallstone formation in the relationship between gallstone disease and aberrant EHBT anatomy.

Fascial Nomenclature: An Update

Throughout the development of anatomy as a scientific study, authors have been challenged to give a singular comprehensive definition of what should be considered as a fascial tissue. Instead, the multiplicity of synthesis and analysis is the true richness of scientific research: individual points of view and background look at the fascia from their own perspective, sometimes influenced by their own cultural assumptions. No person or organization in science ever have the absolute truth, because scientific truth is always evolving, driven by new observations and analysis of data. Only by observing the fascia from multiple perspectives (doctor, surgeon, osteopath, physiotherapist, bioengineer and more) can we define more fully what fascial tissue is. It becomes the synergistic result of several scientific disciplines (anatomy, cardiology, angiology, orthopaedics, osteopathy, cytology, and more). The fascia is not the exclusive domain of a few people or individual private associations, but of all researchers who journey through the study of knowledge and arrive at an understanding, improving the clinical aspects for the good of the patient, without profit. This article reviews the embryological evolution of muscle and connective tissue to affirm how the fascial system should be ideally conceptualized: an absolute anatomic functional continuum.