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Biliary tract
Biliary tract
Biliary tract
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Biliary tract
Ducts of the biliary tract
Details
FunctionFacilitate movement of bile, which aids in fat absorption
Identifiers
MeSHD001659
FMA79646
Anatomical terminology

The biliary tract (also biliary tree or biliary system) refers to the liver, gallbladder and bile ducts, and how they work together to make, store and secrete bile.[1] Bile consists of water, electrolytes, bile acids, cholesterol, phospholipids and conjugated bilirubin.[2] Some components are synthesized by hepatocytes (liver cells); the rest are extracted from the blood by the liver.[3]

Bile is secreted by the liver into small ducts that join to form the common hepatic duct.[4] Between meals, secreted bile is stored in the gallbladder.[5] During a meal, the bile is secreted into the duodenum (part of the small intestine) to rid the body of waste stored in the bile as well as aid in the absorption of dietary fats and oils.[5]

Structure

[edit]
1. Bile ducts:
      2. Intrahepatic bile ducts
      3. Left and right hepatic ducts
      4. Common hepatic duct
      5. Cystic duct
      6. Common bile duct
      7. Ampulla of Vater
      8. Major duodenal papilla
9. Gallbladder
10–11. Right and left lobes of liver
12. Spleen
13. Esophagus
14. Stomach
15. Pancreas:
      16. Accessory pancreatic duct
      17. Pancreatic duct
18. Small intestine:
      19. Duodenum
      20. Jejunum
21–22. Right and left kidneys
The front border of the liver has been lifted up (brown arrow).[6]

The biliary tract refers to the path by which bile is secreted by the liver then transported to the duodenum, the first part of the small intestine. A structure common to most members of the mammal family, the biliary tract is often referred to as a tree because it begins with many small branches that end in the common bile duct, sometimes referred to as the trunk of the biliary tree. The duct, the branches of the hepatic artery, and the portal vein form the central axis of the portal triad.[7] Bile flows in the direction opposite to that of the blood present in the other two channels.[8]

The system is usually referred to as the biliary tract or system,[9] and can include the use of the term "hepatobiliary" when used to refer just to the liver and bile ducts.[1] The name biliary tract is used to refer to all of the ducts, structures and organs involved in the production, storage and secretion of bile.[10]

The tract is as follows:

Function

[edit]

Bile is secreted by the liver into small ducts that join to form the common hepatic duct.[2] Between meals, secreted bile is stored in the gall bladder, where 80–90% of the water and electrolytes can be absorbed, leaving the bile acids and cholesterol.[5] During a meal, the smooth muscles in the gallbladder wall contract, causing bile to be secreted into the duodenum to rid the body of waste stored in the bile as well as aid in the absorption of dietary fats and oils by solubilizing them using bile acids.[5]

Clinical significance

[edit]
Union of common bile duct and pancreatic duct terminating at duodenum (small intestine).

Gallstones can form within the gallbladder and get stuck within the biliary tract, leading to various diseases depending on the location of the stone.[11] Gallstone disease, or cholelithiasis, is very common in the United States, impacting over 20 million people.[11]

Gallstones frequently occur without causing symptoms– this is known as asymptomatic cholelithiasis.[11] Sometimes gallstones may get stuck in the cystic duct, which serves as a bridge between the gallbladder and the common bile duct, and can lead to inflammation in the wall of the gallbladder.[11] This inflammation of the gallbladder is known as cholecystitis and is a common indication for surgical removal of the gallbladder, or cholecystectomy.[12]

Occasionally gallstones may become lodged in the common bile duct and obstruct the flow of bile from the gallbladder to the small intestine– this condition is known as choledocholithiasis[11] and is another indication for cholecystectomy.[12] The common bile duct, commonly abbreviated CBD, is formed by the union of the cystic duct and common hepatic duct, and it later joins the pancreatic duct to terminate in the Ampulla of Vater at the small intestine. The function of the common bile duct is to allow bile to travel from the gallbladder to the small intestine, mixing with pancreatic digestive enzymes along the way.[4] One possible complication of choledocholithiasis is an infection of the bile ducts between the liver and the gallstone lodged in the common bile duct. This condition is known as acute cholangitis and is commonly associated with a triad of clinical symptoms known as Charcot's Triad, which includes fever, right upper quadrant abdominal pain, and jaundice.[11] This constellation of symptoms has a 96% specificity for cholangitis,[11] and can be expanded upon with the addition of hypotension and altered mental status to form Reynold's Pentad.[11]

The biliary tract can also serve as a reservoir for intestinal tract infections. Since the biliary tract is an internal organ, it has no somatic nerve supply, and biliary colic due to infection and inflammation of the biliary tract is not a somatic pain. Rather, pain may be caused by luminal distension, which causes stretching of the wall. This is the same mechanism that causes pain in bowel obstructions.[13]

Chronic inflammatory conditions of the biliary tract, including Primary Sclerosing Cholangitis (PSC) and Primary Biliary Cirrhosis (PBC), can lead to hardening of the ducts in the biliary tree.[14]

An obstruction of the biliary tract can result in jaundice, a yellowing of the skin and whites of the eyes.[15]

References

[edit]
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Biliary tract

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from Grokipedia
The biliary tract, also known as the biliary system, is the integrated network of ducts and associated organs that facilitates the production, storage, transportation, and secretion of —a vital digestive synthesized by the liver. Comprising within the liver, extrahepatic ducts leading to the , the for storage, and regulatory structures like the , the biliary tract plays a central role in digestion and waste elimination. Anatomically, the system begins with microscopic canaliculi formed by hepatocytes, which coalesce into progressively larger intralobular and interlobular ducts within the liver's portal triads. These drain into the right and left hepatic ducts, which unite to form the common hepatic duct; this then joins the cystic duct from the gallbladder to create the common bile duct (CBD), measuring approximately 6-8 cm in length and less than 6 mm in diameter in adults. The CBD typically converges with the main pancreatic duct at the hepatopancreatic ampulla (ampulla of Vater) in the duodenum, where bile enters the gastrointestinal tract under control of the sphincter of Oddi to prevent reflux. The gallbladder, a pear-shaped sac attached to the liver's underside, has a capacity of about 50 mL and features mucosal folds that concentrate bile up to tenfold by absorbing water and electrolytes. Physiologically, hepatocytes produce 600-1000 mL of daily, an alkaline fluid ( 7.5-8.1) rich in bile salts, phospholipids, , , and electrolytes, which is further modified by cholangiocytes lining the ducts. 's primary functions include emulsifying dietary fats into micelles for enzymatic breakdown by lipases, enhancing absorption of fat-soluble vitamins (A, D, E, K), and excreting metabolic byproducts like excess and conjugated to prevent . Between meals, is stored and acidified in the ( 5.2-6.0); postprandial release is triggered by hormones such as cholecystokinin, with up to 95% of bile salts recycled via in the terminal for efficient reuse. This dynamic system ensures optimal nutrient assimilation while maintaining hepatic homeostasis.

Anatomy

Components of the biliary tract

The biliary tract, also known as the biliary tree, serves as the conduit for bile transport from hepatocytes in the liver to the , comprising both intrahepatic and extrahepatic components that form a branching network of ducts. This system ensures the delivery of for digestive processes, with the intrahepatic portions embedded within the liver and the extrahepatic portions extending outside the liver. Intrahepatic bile ducts originate from bile canaliculi, which are narrow tubular channels (approximately 1 μm in diameter) lined with microvilli that collect directly from hepatocytes. These canaliculi merge into cholangioles or ductules at the periphery of hepatic lobules, which then form interlobular ducts located in the portal triads alongside branches of the and hepatic artery. The interlobular ducts progressively converge into larger segmental ducts within the liver, draining into the right hepatic duct (draining segments V, VI, VII, and VIII; average length 0.9 cm, diameter 2.6 mm) and the left hepatic duct (draining segments II, III, and IV; average length 1.7 cm, diameter 3.0 mm), with the caudate lobe (segment I) contributing small ducts to both. The right and left hepatic ducts unite at the to form the . The extrahepatic bile ducts begin with the , which measures 1.0–7.5 cm in length and approximately 4 mm in diameter, traveling within the hepatoduodenal ligament of the , positioned anterior to the and to the right of the . The , 3–4 cm long and about 4 mm in diameter, connects the to the at an acute angle on its right side and contains spiral mucosal folds known as the valves of Heister, which regulate flow and prevent collapse. The union of the common hepatic and s forms the , which spans 6.0–8.0 cm in length with a normal diameter of less than 6 mm, divided into segments: supraduodenal (mean external diameter 9 mm, internal 8 mm, running in the hepatoduodenal ligament), retroduodenal (posterior to the first part of the ), retropancreatic (behind the pancreatic head), and intrapancreatic (within the pancreatic ). The is a pear-shaped reservoir attached to the undersurface of the liver in the cystic fossa between segments IV and V, measuring 7–10 cm in length and up to 4 cm in width, with a capacity of 30–50 mL. It consists of three main parts: the fundus (the widest, rounded distal portion projecting beyond the liver edge), the body (the central portion that contacts the liver and ), and the neck (tapering proximally into the infundibulum before connecting to the ). The organ lies in the right upper quadrant, with its inferior surface covered by and superior surface adherent to the liver without a distinct capsule. At its termination, the common bile duct joins the main pancreatic duct to form the hepatopancreatic ampulla (ampulla of Vater), which opens into the second part of the duodenum at the major duodenal papilla. The sphincter of Oddi, a complex of circular smooth muscle fibers surrounding the ampulla and distal portions of both ducts, measures about 4 mm in internal diameter at the ampulla and regulates the flow of bile and pancreatic secretions into the duodenum while preventing reflux. The common bile duct runs posteriorly to the first part of the duodenum and the head of the pancreas before penetrating the duodenal wall obliquely.

Vascular supply and innervation

The arterial supply to the biliary tract primarily derives from branches of the , which originates from the celiac trunk. The and receive blood from the , a branch of the right hepatic artery, while the is supplied by the posterior superior pancreaticoduodenal artery inferiorly and retroduodenal branches superiorly; the supraduodenal portion of the has a relatively sparse arterial network, rendering it vulnerable to ischemia. The is primarily supplied by the , a branch of the right hepatic artery; anatomical variations may include accessory cystic arteries arising from other branches such as the . Venous drainage parallels the arterial supply through epicholedochal and paracholedochal plexuses. The cystic vein drains the directly into the or its right branch, while hepatic ducts empty via tributaries of the ; the paracholedochal plexus connects to the and gastrocolic trunk, facilitating efficient return of nutrient-rich blood from the digestive tract. Lymphatic drainage begins at initial nodes along the , known as cystic nodes, and proceeds to hepatic nodes at the , then to celiac and peripancreatic nodes, ultimately converging at the ; this pathway is clinically significant in the spread of metastases from biliary malignancies. The gallbladder lymphatics follow superior and inferior routes, with the superior path along the and hepatic artery to celiac nodes, and the inferior to nodes near the and . Innervation of the biliary tract involves both autonomic divisions and an intrinsic . Sympathetic fibers arise from the celiac and superior mesenteric plexuses via (originating from spinal segments T7-T9), providing inhibitory control over the and ductal . Parasympathetic innervation comes from the vagus nerve's hepatic branch, promoting secretory activity and gallbladder contraction, often modulated by hormones like cholecystokinin. The within duct walls coordinates local reflexes for and .

Histological features

The biliary tract's histological structure is adapted for bile transport, storage, and modification, featuring specialized epithelia and supporting tissues. , forming part of the portal triads alongside hepatic arteries and portal veins, are lined by cholangiocytes that vary by duct size: cuboidal in smaller interlobular and septal ducts (15–300 μm diameter), transitioning to low columnar in larger area, segmental, and hepatic ducts (>300 μm). These cholangiocytes possess microvilli, tight junctions, and primary cilia for sensory functions, enabling selective permeability and fluid regulation. Peribiliary glands, present in larger intrahepatic and all extrahepatic ducts, consist of mucous and serous acini that secrete bicarbonate-rich fluid to neutralize acidic duodenal contents. Extrahepatic ducts, including the common hepatic, cystic, and common bile ducts, exhibit a pseudostratified or simple columnar epithelium with interspersed goblet cells for mucin production, supported by a lamina propria of loose connective tissue containing blood vessels, lymphatics, and occasional inflammatory cells. Subepithelial layers include a thin muscularis mucosae of longitudinal smooth muscle fibers, a submucosa with tubuloacinar mucous glands (more prominent in the common bile duct), and an outer muscularis of intermingled circular and longitudinal smooth muscle bundles facilitating peristalsis. These ducts lack a serosa, being enveloped by adventitia except at the intraduodenal portion where partial serosal covering occurs; the peribiliary vascular plexus, derived from hepatic artery branches, nourishes the epithelium. The mucosa comprises tall, with prominent microvilli for absorption and concentration of , forming rugose folds that increase surface area without goblet cells in the normal state. Beneath lies a of rich in capillaries, lymphatics, and leukocytes, with deep invaginations known as Rokitansky-Aschoff sinuses extending into the to facilitate . Absent a , the wall features a thin, disorganized muscularis of fibers oriented longitudinally, circularly, and obliquely for powerful contractions, covered externally by serosa (except the hepatic attachment) or . At the distal end, the consists of circularly arranged fibers encircling the intramural portions of the common and main pancreatic ducts, providing a high-pressure zone (15–35 mmHg) to regulate and pancreatic juice flow into the . The smallest biliary elements, bile canaliculi (1–2 μm), form intercellular channels between glycogen-rich hepatocytes, sealed by tight junctions to direct toward cholangiocytes without paracellular leakage. These features collectively support efficient handling, with cholangiocytes modifying composition through ion transport linked to production processes.

Physiology

Bile production and composition

Bile is primarily produced by hepatocytes in the liver, which synthesize the majority of its organic components, including 80-90% of acids, , and . Cholangiocytes lining the bile ducts contribute up to 40% of bile volume through the of and water, modifying the initial hepatic bile. In adults, the liver produces approximately 600-1200 mL of bile daily, with about 95% of bile acids recycled via to maintain efficient . The composition of hepatic bile is approximately 97% water, with the remaining solids consisting mainly of bile salts (about 50% of solids, such as cholic acid and ), phospholipids (primarily ), solubilized by bile salts, conjugated bilirubin derived from breakdown, electrolytes (including Na⁺, K⁺, Cl⁻, and HCO₃⁻), , and immunoglobulins. This watery, alkaline fluid (pH 7.5-8.0) is achieved through cholangiocyte secretion of , which neutralizes acidity and facilitates fat emulsification in the intestine. Primary bile acids are synthesized from in hepatocytes via the classic pathway, initiated by the rate-limiting cholesterol 7α-hydroxylase (CYP7A1), a , leading to the formation of cholic acid and . These primary acids are then conjugated with or in the to enhance solubility and reduce toxicity, forming salts that are actively transported into bile canaliculi. , a byproduct of , undergoes in hepatocytes by (UGT1A1) to produce water-soluble conjugated for safe excretion. Hepatic bile composition varies between fasting and postprandial states; during , bile flow is lower and more dilute, while postprandial stimulation increases secretion rates, resulting in bile with higher concentrations of bile acids and electrolytes to support .

Storage, concentration, and release

The gallbladder functions as a for produced by the liver, storing 30 to 50 mL of concentrated during states, with filling occurring at low pressure through the from the hepatic bile ducts. This storage capacity allows for the accumulation of between meals, preventing continuous low-volume drainage into the intestine and enabling efficient deployment during . The low-pressure inflow is facilitated by the relaxed during interdigestive phases, ensuring gradual accumulation without undue strain on the biliary system. Bile concentration within the gallbladder is achieved primarily through active transport of sodium ions (Na+) and ions across the , driven by Na+/+- pumps, which creates an osmotic gradient for passive . This process reduces the bile volume by 5- to 10-fold, from the initial hepatic secretion of approximately 500-1000 mL per day to a more viscous, lipid-rich form, while organic components like , salts, and phospholipids remain solubilized in micelles and vesicles. The absorptive , featuring microvilli and tight junctions, enhances this efficiency, resulting in that is hypertonic relative to plasma and optimized for emulsification. The release of stored bile is triggered postprandially by the cholecystokinin (CCK), secreted from duodenal I-cells in response to ingested fats and proteins, which binds to receptors on gallbladder to induce contraction; this is augmented by vagal parasympathetic neural stimulation. Gallbladder emptying typically expels 50-80% of its contents within 30-60 minutes, propelling through the cystic and common bile ducts toward the at a rate of 1-2 mL/min. Concurrently, CCK and mediate relaxation of the , a valve at the , allowing unimpeded flow into the intestinal lumen. Between meals, interdigestive refilling occurs via continuous basal hepatic secretion, often termed the hepatic pump, maintaining reservoir function. Impaired or absorption in these mechanisms can promote stasis, elevating the risk of formation through and of solutes.

Enterohepatic circulation

The represents a highly efficient mechanism for bile acids, enabling their repeated utilization in while minimizing hepatic synthesis demands. Following release into the , bile acids facilitate the emulsification and of dietary fats by forming micelles that enhance lipid solubility and absorption in the . Approximately 95% of these bile acids are reabsorbed primarily in the terminal through mediated by the apical sodium-dependent bile acid transporter (ASBT, also known as SLC10A2), which is expressed on the apical membrane of ileal enterocytes. This reabsorption prevents excessive loss and supports the conservation of the pool. Reabsorbed bile acids enter the portal bloodstream and are transported back to the liver, where they are efficiently taken up by hepatocytes via the basolateral sodium-taurocholate cotransporting polypeptide (NTCP, SLC10A1). Once inside hepatocytes, bile acids are resecreted into the bile canaliculi through the bile salt export pump (BSEP), re-entering the biliary tract to complete the cycle. This portal vein-mediated return ensures rapid recirculation, with the process occurring 4 to 12 times per day in humans, handling approximately 20 grams of bile acids daily despite a relatively small total pool size of 2 to 4 grams. Fecal accounts for only 0.2 to 0.6 grams per day, which is compensated by de novo hepatic synthesis to maintain pool . The efficiency of this circulation is tightly regulated by feedback mechanisms to prevent overaccumulation or depletion of bile acids. In the ileum, bile acids activate the farnesoid X receptor (FXR), which induces expression of fibroblast growth factor 19 (FGF19); this is secreted into the portal circulation and signals the liver to inhibit the rate-limiting cholesterol 7α-hydroxylase (CYP7A1), thereby suppressing bile acid synthesis. Hepatic FXR also contributes to this by directly repressing CYP7A1 transcription in response to recirculating bile acids. These regulatory pathways ensure that the bile acid pool remains stable, with the entire circulatory process supporting multiple daily cycles over a typical turnover period of 1 to 2 days per before potential loss. Disruption of , such as through ileal resection, impairs ASBT-mediated reabsorption, leading to increased delivery to the colon and subsequent due to secretory effects on colonic mucosa. In severe cases, excessive fecal loss depletes the pool, promoting supersaturation in and elevating the risk of (lithogenesis) formation, as hepatic synthesis often fails to fully compensate. Such interruptions highlight the circulation's role in maintaining digestive and metabolic balance.

Embryology

Embryonic development

The biliary tract originates from the endodermal , which buds from the ventral wall of the during the third to fourth week of . This gives rise to the liver parenchyma, intrahepatic and extrahepatic bile ducts, , and ventral , establishing the shared embryological lineage of the hepatobiliary and pancreatic systems. Duct formation begins with the proliferation of hepatic cords from the cranial portion of the , which canalize to form the between weeks 6 and 8. The extrahepatic ducts develop through elongation of the ventral bud, with the initially solidifying and then recanalizing by week 12. The arises as a caudal outgrowth from the hepatic around week 5, becoming recognizable as a distinct shortly thereafter. Key developmental milestones include the formation of the ductal plate around week 8, induced by interactions with the branching , which drives remodeling through duplication and tubulogenesis between weeks 8 and 12. By week 10, the right and left hepatic ducts separate, contributing to the intrahepatic arborization that continues until birth. The emerges from the duodenal around week 10, with muscular differentiation progressing through week 16 and nearing completion by week 28. The extrahepatic biliary system achieves maturity by week 12, while full intrahepatic duct arborization occurs by birth. Molecular regulators orchestrate hepatobiliary specification and ductal , with transcription factors such as Hhex, , and Foxa2 playing pivotal roles. Hhex is essential for hepatoblast differentiation and bile duct , Sox9 controls the timing of asymmetric tubule maturation in intrahepatic ducts, and Foxa2, often in concert with Foxa1, regulates biliary . Notch signaling, involving receptors like Notch2 and ligands such as Jagged1, promotes biliary epithelial cell fate and ductal branching, ensuring proper tubulogenesis.

Congenital anomalies

Congenital anomalies of the biliary tract encompass a range of structural birth defects arising from disruptions in embryonic development, particularly during the recanalization of bile ducts around the 8th to 12th week of . These anomalies often manifest as obstructions, dilations, or absences in the intrahepatic or extrahepatic biliary structures, leading to early-onset , , and potential liver damage if untreated. While most are sporadic, some have genetic underpinnings, and their collective incidence varies by region, with higher rates reported in Asian populations compared to Western ones. Biliary atresia represents the most common and severe congenital anomaly of the biliary tract, characterized by the failure of recanalization of the extrahepatic bile ducts, resulting in progressive and obliteration. It occurs in approximately 1 in 10,000 to 15,000 live births worldwide, with higher incidence in (up to 1 in 5,000). Two main types are recognized: the fetal or embryonic form (about 10-20% of cases), which presents at birth with and associated malformations like polysplenia; and the perinatal form (80-90%), which develops postnatally and leads to between 2 and 8 weeks of age. Without intervention, such as the Kasai portoenterostomy performed ideally before 60 days of life—achieving bile drainage success in about 50% of early cases—infants face rapid progression to biliary cirrhosis and the need for . Choledochal cysts are congenital dilations of the ducts, often linked to an anomalous pancreaticobiliary that allows reflux of pancreatic enzymes into the biliary tree, causing weakening and cystic expansion. Their incidence is estimated at 1 in 100,000 to 150,000 live births in Western populations and approximately 1 in 1,000 in Asian populations. The Todani classification delineates five types: Type I ( dilation of the extrahepatic duct, 80-90% of cases), Type II (), Type III (choledochocele), Type IV (multiple intra- and extrahepatic cysts), and Type V (intrahepatic dilation, akin to ). These cysts predispose to recurrent cholangitis and carry a lifetime risk of of 20-30% if not excised, emphasizing the need for early surgical management to mitigate infectious and malignant complications. Alagille syndrome is a multisystem featuring paucity of , resulting from mutations in the JAG1 gene (94% of cases) or NOTCH2 gene (1-2%), which disrupt Notch signaling critical for biliary development. It affects about 1 in 30,000 to 70,000 live births and manifests with alongside cardiac defects (e.g., pulmonary artery stenosis in 90%), characteristic facial features (broad forehead, pointed chin), and skeletal abnormalities (butterfly vertebrae). The intrahepatic biliary leads to chronic , pruritus, and xanthomas, with variable severity influenced by the specific mutation type. Other notable congenital anomalies include biliary hypoplasia, often seen in syndromic contexts like , where there is underdevelopment of intrahepatic ducts leading to impaired flow. Caroli disease involves saccular ectasia of intrahepatic ducts due to abnormal remodeling, with an estimated incidence of 1 in 1,000,000; it predisposes to cholangitis and stone formation from recurrent infections. , a rare absence of the gallbladder, occurs in 0.01-0.06% of the population and may be isolated or associated with other biliary malformations, typically presenting asymptomatically but occasionally with or .

Clinical significance

Biliary tract disorders

The biliary tract is susceptible to several acquired disorders, primarily stemming from imbalances in bile composition, obstruction, , or autoimmune processes. These conditions often manifest with symptoms related to biliary obstruction or , such as , , and fever, and can lead to significant morbidity if complications arise. Gallstones, or cholelithiasis, represent the most common biliary disorder, affecting a substantial portion of the adult population worldwide. Cholelithiasis involves the formation of crystallized deposits in the or biliary tree, predominantly composed of (accounting for approximately 80% of cases in Western populations) or in pigment stones. The arises from supersaturation of with , impaired gallbladder motility, and nucleation factors, leading to stone precipitation. Risk factors include the classic "4F's": female sex, age over forty, (fat), and (multiple pregnancies), alongside rapid , , and hemolytic disorders. Epidemiologically, gallstones affect 10-15% of adults in developed countries, with a of about 20 million individuals in the United States alone, predominantly women. Most cases remain , but complications such as —characterized by episodic right upper quadrant pain radiating to the back—and acute , involving and potential perforation, occur in 10-20% of affected individuals. Biliary atresia is a rare but critical congenital disorder characterized by progressive obliteration of the extrahepatic bile ducts, leading to , cholangitis, and if untreated. It affects approximately 1 in 10,000 to 15,000 live births, with higher incidence in Asian populations, and manifests in infancy with and acholic stools. Early and intervention are essential to restore bile flow and prevent end-stage . Choledocholithiasis refers to gallstones migrating into the common bile duct, often precipitating secondary conditions like acute cholangitis. The etiology typically involves stones obstructing bile flow, allowing bacterial ascension from the duodenum, with Escherichia coli as the most common pathogen (isolated in up to 50% of cases). Pathophysiologically, this obstruction leads to bile stasis, increased intraductal pressure, and bacterial proliferation, resulting in suppurative infection and potential sepsis. Symptoms include the Charcot's triad of fever, jaundice, and right upper quadrant pain, present in 50-70% of patients; severe cases may progress to Reynolds pentad with hypotension and altered mental status. Epidemiologically, choledocholithiasis complicates 1-15% of cholelithiasis cases, with rates up to 10-20% in symptomatic gallstone patients, with acute cholangitis occurring in 6-9% of hospitalized individuals with gallstone disease. Untreated cholangitis carries a mortality rate of up to 50%, driven by septic shock and multi-organ failure. Cholangiocarcinoma, a highly aggressive arising from cholangiocytes lining the bile ducts, accounts for 10-25% of all hepatobiliary malignancies. Its etiology involves chronic inflammation and cellular injury leading to dysplasia, with key risk factors including (PSC), chronic , and parasitic infections such as liver flukes ( or ) in endemic areas. Pathophysiologically, oncogenic mutations (e.g., in , TP53) accumulate amid persistent biliary irritation, resulting in desmoplastic tumors that obstruct ducts and invade locally. Intrahepatic, perihilar (Klatskin tumors at the hepatic duct bifurcation, comprising 50-60% of extrahepatic cases), and distal subtypes differ in presentation, but common symptoms include painless , weight loss, pruritus, and due to biliary obstruction. The global incidence is 1-2 per 100,000, with higher rates in (up to 90 per 100,000 from fluke-related cases) and a rising trend in Western countries linked to . is poor, with 5-year survival under 10% for advanced disease. Primary sclerosing cholangitis (PSC) is a chronic, progressive cholangiopathy characterized by autoimmune-mediated inflammation and of intra- and extrahepatic ducts. The etiology remains idiopathic but involves immune dysregulation, with 70-80% of cases associated with (IBD), particularly , suggesting a gut-liver axis role. Pathophysiologically, periductal leads to multifocal strictures, stasis, and recurrent cholangitis, culminating in biliary cirrhosis, , and end-stage in 50% of patients over 10-15 years. Symptoms often include fatigue, pruritus, and right upper quadrant pain; and emerge in advanced stages. Epidemiologically, PSC has an incidence of approximately 1 per 100,000 in Northern European populations, predominantly affecting males (2:1 ratio) aged 30-40, with a cumulative risk of of 10-20%. In contrast, (PBC) targets small through autoimmune destruction, primarily affecting women. It is characterized by lymphocytic infiltration and progressive nonsuppurative cholangitis, with antimitochondrial antibodies (AMA) present in 90-95% of cases, indicating an autoimmune etiology possibly triggered by environmental factors in genetically susceptible individuals (e.g., HLA associations). Pathophysiologically, ductopenia leads to , copper accumulation, and , advancing to in untreated patients. Early symptoms are (affecting 65%) and pruritus (55%), followed by and in later stages. The incidence is 2-4 per 100,000, with a strong female predominance (9:1 ratio) and peak onset at 40-60 years, more common in Northern European descent populations.

Diagnostic approaches

Diagnosis of biliary tract disorders begins with a thorough clinical , focusing on patient history and . Common presenting symptoms include , right upper quadrant , and fever, which may suggest conditions such as choledocholithiasis or acute cholangitis. tests are essential for initial assessment, including (LFTs) that typically reveal elevated total , (ALP), and gamma-glutamyl transferase (GGT), indicating . Additional tests may include serum amylase or lipase to evaluate for associated and blood cultures if is suspected. Imaging modalities form the cornerstone of biliary tract diagnostics, with abdominal ultrasound serving as the first-line investigation due to its non-invasive nature and high sensitivity for detecting gallstones, approximately 90%. can identify (CBD) dilatation, defined as greater than 6 mm in diameter, as well as gallbladder wall thickening exceeding 3 mm, which may indicate or obstruction. For more complex cases, advanced imaging techniques are employed. Computed tomography (CT) and (MRI) are useful for identifying masses, stones, or vascular involvement in the biliary tract. (MRCP) provides non-invasive visualization of the biliary ducts with high accuracy, around 95%, making it particularly valuable for delineating strictures or stones without procedural risks. (ERCP) offers both diagnostic and therapeutic capabilities, allowing direct visualization of the and biopsy sampling, though it carries a 5% risk of post-procedure and is thus reserved when intervention is anticipated. MRCP is generally preferred over ERCP for purely diagnostic purposes to minimize complications. Additional specialized tests enhance diagnostic precision in select scenarios. Hepatobiliary iminodiacetic acid (HIDA) assesses gallbladder function by measuring ; values below 35% suggest . (EUS) excels at detecting small lesions or early malignancies in the biliary tract and periampullary region, with sensitivity up to 90% for such abnormalities. Liver biopsy may be required for confirming (PBC) or (PSC), often in conjunction with serologic testing for antimitochondrial antibodies (AMA), which are positive in over 90% of PBC cases. Specific diagnostic criteria guide evaluation of acute cholangitis, as outlined in the Tokyo Guidelines, which require evidence of (e.g., fever or elevated white blood cell count), (e.g., or elevated /ALP), and imaging findings of biliary dilatation or . This triad achieves high diagnostic accuracy, with sensitivity around 88% and specificity 78%.

Treatment and management

The treatment and management of biliary tract disorders encompass a range of medical, endoscopic, and surgical interventions tailored to the underlying condition, such as gallstones, cholangitis, (PBC), (PSC), and malignancies. Medical management forms the cornerstone for chronic cholestatic conditions like PBC and PSC. (UDCA), administered at 13-15 mg/kg/day, is the first-line therapy for PBC and improves (LFTs) in approximately 60% of patients, enhancing transplant-free survival. In PSC, UDCA may modestly improve LFTs but lacks strong evidence for altering disease progression. For acute cholangitis, intravenous antibiotics such as piperacillin-tazobactam are recommended to cover enteric pathogens, with prompt biliary decompression to resolve infection. due to gallstones is managed with analgesics, prioritizing nonsteroidal anti-inflammatory drugs (NSAIDs) like for pain relief, while avoiding opioids to minimize spasm. Endoscopic interventions are pivotal for obstructive pathologies. Endoscopic retrograde cholangiopancreatography (ERCP) achieves successful stone extraction and sphincterotomy in 85-95% of cases for choledocholithiasis, with complications including post-ERCP occurring in 3-5% of procedures. Biliary stenting via ERCP provides palliation for strictures and malignancies, improving in over 80% of patients with unresectable . For cases where ERCP fails (5-10% of attempts), (EUS)-guided biliary drainage offers technical success rates of 90-95% and clinical success in 92%, serving as an alternative for distal obstructions. Percutaneous transhepatic cholangiography (PTC) is employed when endoscopic approaches fail, achieving drainage in 85-90% of malignant obstructions. Surgical options address definitive correction of structural issues. Laparoscopic remains the gold standard for symptomatic gallstones, with success rates exceeding 95% and approximately 90% of procedures performed outpatient; , approximately 750,000-1,000,000 such operations occur annually (as of 2024). For localized , offers the best chance of cure, with 5-year survival rates of 20-40% in resectable cases. In infants with , the Kasai portoenterostomy procedure restores bile flow in 50-60% of cases if performed before 60 days of age, delaying the need for transplantation. Advanced and recent therapies target refractory or end-stage disease. , a farnesoid X receptor agonist approved by the FDA in 2016, is used as second-line treatment for PBC patients unresponsive to UDCA, reducing levels by 10-20% in non-responders. Immunosuppressants like may be added for overlap syndromes, though evidence is limited. is curative for end-stage PBC and PSC, with 5-year survival rates of 80-85%; eligibility often requires a (MELD) score greater than 15 in decompensated cases.

References

  1. https://www.ncbi.nlm.nih.gov/books/NBK537107/
  2. https://www.ncbi.nlm.nih.gov/books/NBK459246/
  3. https://pmc.ncbi.nlm.nih.gov/articles/PMC4244820/
  4. https://www.ncbi.nlm.nih.gov/books/NBK459288/
  5. https://teachmeanatomy.info/abdomen/viscera/gallbladder/
  6. https://pmc.ncbi.nlm.nih.gov/articles/PMC2504380/
  7. https://pmc.ncbi.nlm.nih.gov/articles/PMC3733049/
  8. https://pmc.ncbi.nlm.nih.gov/articles/PMC4319126/
  9. https://pmc.ncbi.nlm.nih.gov/articles/PMC3743051/
  10. https://pubmed.ncbi.nlm.nih.gov/31707436/
  11. https://histologyguide.com/slideview/MHS-261-common-bile-duct/15-slide-1.html
  12. https://www.pathologyoutlines.com/topic/gallbladderhistology.html
  13. https://www.ncbi.nlm.nih.gov/books/NBK551515/
  14. https://www.ncbi.nlm.nih.gov/books/NBK470209/
  15. https://pmc.ncbi.nlm.nih.gov/articles/PMC5003190/
  16. https://www.sciencedirect.com/topics/immunology-and-microbiology/bile-flow
  17. https://my.clevelandclinic.org/health/body/what-is-bile
  18. https://www.sciencedirect.com/topics/medicine-and-dentistry/bile
  19. https://www.ncbi.nlm.nih.gov/books/NBK549765/
  20. https://www.ncbi.nlm.nih.gov/books/NBK279386/
  21. https://www.ncbi.nlm.nih.gov/books/NBK482488/
  22. https://pmc.ncbi.nlm.nih.gov/articles/PMC3831216/
  23. https://www.sciencedirect.com/topics/medicine-and-dentistry/gallbladder-emptying
  24. https://pubmed.ncbi.nlm.nih.gov/10705178/
  25. https://pmc.ncbi.nlm.nih.gov/articles/PMC2796132/
  26. https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2017.00617/full
  27. https://www.jlr.org/article/S0022-2275%2820%2930658-1/fulltext
  28. https://pmc.ncbi.nlm.nih.gov/articles/PMC5954621/
  29. https://pmc.ncbi.nlm.nih.gov/articles/PMC8515273/
  30. https://www.sciencedirect.com/science/article/pii/S0022227520307033
  31. https://www.cell.com/cell-metabolism/fulltext/S1550-4131%2805%2900261-5
  32. https://pmc.ncbi.nlm.nih.gov/articles/PMC2614454/
  33. https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/580106
  34. https://pmc.ncbi.nlm.nih.gov/articles/PMC1412201/
  35. https://karger.com/dsu/article/27/2/87/116576/Embryology-of-the-Biliary-Tract
  36. https://pmc.ncbi.nlm.nih.gov/articles/PMC3328609/
  37. https://pmc.ncbi.nlm.nih.gov/articles/PMC2990791/
  38. https://pmc.ncbi.nlm.nih.gov/articles/PMC3766137/
  39. https://www.ncbi.nlm.nih.gov/books/NBK537262/
  40. https://pmc.ncbi.nlm.nih.gov/articles/PMC8658215/
  41. https://pmc.ncbi.nlm.nih.gov/articles/PMC4877133/
  42. https://www.ncbi.nlm.nih.gov/books/NBK557762/
  43. https://pmc.ncbi.nlm.nih.gov/articles/PMC2769090/
  44. https://pmc.ncbi.nlm.nih.gov/articles/PMC3632844/
  45. https://www.ncbi.nlm.nih.gov/books/NBK1273/
  46. https://pmc.ncbi.nlm.nih.gov/articles/PMC5736143/
  47. https://pmc.ncbi.nlm.nih.gov/articles/PMC5390567/
  48. https://pmc.ncbi.nlm.nih.gov/articles/PMC7158313/
  49. https://www.ncbi.nlm.nih.gov/books/NBK513307/
  50. https://pmc.ncbi.nlm.nih.gov/articles/PMC3604316/
  51. https://www.ncbi.nlm.nih.gov/books/NBK459370/
  52. https://pmc.ncbi.nlm.nih.gov/articles/PMC3343155/
  53. https://www.ncbi.nlm.nih.gov/books/NBK537181/
  54. https://www.ncbi.nlm.nih.gov/books/NBK441961/
  55. https://www.ncbi.nlm.nih.gov/books/NBK558946/
  56. https://pmc.ncbi.nlm.nih.gov/articles/PMC2784509/
  57. https://pmc.ncbi.nlm.nih.gov/articles/PMC5823698/
  58. https://www.ncbi.nlm.nih.gov/books/NBK560708/
  59. https://pmc.ncbi.nlm.nih.gov/articles/PMC5290446/
  60. https://www.mayoclinic.org/diseases-conditions/primary-sclerosing-cholangitis/symptoms-causes/syc-20355797
  61. https://pmc.ncbi.nlm.nih.gov/articles/PMC6378537/
  62. https://www.ncbi.nlm.nih.gov/books/NBK459209/
  63. https://pmc.ncbi.nlm.nih.gov/articles/PMC10241503/
  64. https://www.sciencedirect.com/science/article/pii/S1878788619300670
  65. https://emedicine.medscape.com/article/171386-workup
  66. https://www.merckmanuals.com/professional/hepatic-and-biliary-disorders/testing-for-hepatic-and-biliary-disorders/laboratory-tests-of-the-liver-and-gallbladder
  67. https://pubmed.ncbi.nlm.nih.gov/7979854/
  68. https://radiopaedia.org/articles/common-bile-duct-2?lang=us
  69. https://ajronline.org/doi/10.2214/AJR.10.4341
  70. https://pmc.ncbi.nlm.nih.gov/articles/PMC4404370/
  71. https://www.guysandstthomas.nhs.uk/health-information/ercp-endoscopic-retrograde-cholangio-pancreatography
  72. https://pmc.ncbi.nlm.nih.gov/articles/PMC7847953/
  73. https://ejim.springeropen.com/articles/10.1186/s43162-024-00275-y
  74. https://arupconsult.com/content/primary-biliary-cirrhosis
  75. https://onlinelibrary.wiley.com/doi/10.1002/jhbp.512
  76. https://link.springer.com/article/10.1007/s00534-012-0561-3
  77. https://www.aasld.org/practice-guidelines
  78. https://www.aafp.org/pubs/afp/issues/2014/0515/p795.html
  79. https://www.asge.org/docs/default-source/guidelines/asge-guideline-on-the-role-of-endoscopy-in-the-evaluation-and-management-of-choledocholithiasis-2019-june-gie.pdf?sfvrsn=6757df52_4
  80. https://pubmed.ncbi.nlm.nih.gov/39078360/
  81. https://pmc.ncbi.nlm.nih.gov/articles/PMC8716984/
  82. https://www.sages.org/publications/guidelines/guidelines-for-the-clinical-application-of-laparoscopic-biliary-tract-surgery/
  83. https://my.clevelandclinic.org/health/procedures/kasai-procedure
  84. https://www.nejm.org/doi/full/10.1056/NEJMoa1509840
  85. https://pubmed.ncbi.nlm.nih.gov/21837735/
  86. https://www.hepatologytextbook.com/book/chapter_19.php
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