A bile duct is any of a number of long tube-like structures that carry
bile
Bile (from Latin ''bilis''), or gall, is a dark-green-to-yellowish-brown fluid produced by the liver of most vertebrates that aids the digestion of lipids in the small intestine. In humans, bile is produced continuously by the liver (liver bile ...
, and is present in most
vertebrate
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, ...
s.
Bile is required for the
digestion
Digestion is the breakdown of large insoluble food molecules into small water-soluble food molecules so that they can be absorbed into the watery blood plasma. In certain organisms, these smaller substances are absorbed through the small intest ...
of food and is secreted by the
liver
The liver is a major Organ (anatomy), organ only found in vertebrates which performs many essential biological functions such as detoxification of the organism, and the Protein biosynthesis, synthesis of proteins and biochemicals necessary for ...
into passages that carry bile toward the
hepatic duct
The common hepatic duct is the first part of the biliary tract. It joins the cystic duct coming from the gallbladder to form the common bile duct.
Structure
The common hepatic duct is the first part of the biliary tract. It is formed by the c ...
. It joins the
cystic duct
The cystic duct is the short duct that joins the gallbladder to the common hepatic duct. It usually lies next to the cystic artery. It is of variable length. It contains 'spiral valves of Heister', which do not provide much resistance to the ...
(carrying bile to and from the
gallbladder
In vertebrates, the gallbladder, also known as the cholecyst, is a small hollow organ where bile is stored and concentrated before it is released into the small intestine. In humans, the pear-shaped gallbladder lies beneath the liver, although ...
) to form the
common bile duct
The common bile duct, sometimes abbreviated as CBD, is a duct in the gastrointestinal tract of organisms that have a gallbladder. It is formed by the confluence of the common hepatic duct and cystic duct and terminates by uniting with pancreati ...
which then opens into the
intestine
The gastrointestinal tract (GI tract, digestive tract, alimentary canal) is the tract or passageway of the digestive system that leads from the mouth to the anus. The GI tract contains all the major organs of the digestive system, in humans ...
.
Structure
The top half of the common bile duct is associated with the liver, while the bottom half of the common bile duct is associated with the
pancreas
The pancreas is an organ of the digestive system and endocrine system of vertebrates. In humans, it is located in the abdomen behind the stomach and functions as a gland. The pancreas is a mixed or heterocrine gland, i.e. it has both an end ...
, through which it passes on its way to the intestine. It opens into the part of the intestine called the duodenum via the
ampulla of Vater
The ampulla of Vater, also known as the or the hepatopancreatic duct, is formed by the union of the pancreatic duct and the common bile duct. The ampulla is specifically located at the major duodenal papilla.
The ampulla of Vater is an import ...
.
Segments
The biliary tree (see below) is the whole network of various sized ducts branching through the liver.
The path is as follows:
Bile canaliculi
Bile canaliculus (plural:bile canaliculi; also called bile capillaries) is a thin tube that collects bile secreted by hepatocytes. The bile canaliculi empty into a series of progressively larger bile ductules and ducts, which eventually become comm ...
→
Canals of Hering
The canals of Hering, or intrahepatic bile ductules, are part of the outflow system of exocrine bile product from the liver. Liver stem cells are located in the canals of Hering.
Structure
They are found between the bile canaliculi and interlobu ...
→
interlobular bile ducts
The interlobular bile ducts (or interlobular ductules) carry bile in the liver between the Canals of Hering and the interlobar bile ducts. They are part of the interlobular portal triad and can be easily localized by looking for the much larger ...
→
intrahepatic bile ducts
Intrahepatic bile ducts compose the outflow system of exocrine bile product from the liver.
They can be divided into:
* Lobar ducts (right and left hepatic ducts) - stratified columnar epithelium.
* Interlobar ducts (between the main hepatic ...
→ left and right
hepatic ducts
The common hepatic duct is the first part of the biliary tract. It joins the cystic duct coming from the gallbladder to form the common bile duct.
Structure
The common hepatic duct is the first part of the biliary tract. It is formed by the ...
''merge to form'' →
common hepatic duct
The common hepatic duct is the first part of the biliary tract. It joins the cystic duct coming from the gallbladder to form the common bile duct.
Structure
The common hepatic duct is the first part of the biliary tract. It is formed by the ...
''exits liver and joins'' →
cystic duct
The cystic duct is the short duct that joins the gallbladder to the common hepatic duct. It usually lies next to the cystic artery. It is of variable length. It contains 'spiral valves of Heister', which do not provide much resistance to the ...
(from
gall bladder
In vertebrates, the gallbladder, also known as the cholecyst, is a small hollow organ where bile is stored and concentrated before it is released into the small intestine. In humans, the pear-shaped gallbladder lies beneath the liver, althoug ...
) ''forming'' →
common bile duct
The common bile duct, sometimes abbreviated as CBD, is a duct in the gastrointestinal tract of organisms that have a gallbladder. It is formed by the confluence of the common hepatic duct and cystic duct and terminates by uniting with pancreati ...
→ ''joins with''
pancreatic duct
The pancreatic duct, or duct of Wirsung (also, the major pancreatic duct due to the existence of an accessory pancreatic duct), is a duct joining the pancreas to the common bile duct. This supplies it with pancreatic juice from the exocrine pancre ...
→ ''forming''
ampulla of Vater
The ampulla of Vater, also known as the or the hepatopancreatic duct, is formed by the union of the pancreatic duct and the common bile duct. The ampulla is specifically located at the major duodenal papilla.
The ampulla of Vater is an import ...
→ ''enters''
duodenum
The duodenum is the first section of the small intestine in most higher vertebrates, including mammals, reptiles, and birds. In fish, the divisions of the small intestine are not as clear, and the terms anterior intestine or proximal intestine m ...
.
Nerve supply
Inflation of a balloon in the bile duct causes, through the
vagus nerve
The vagus nerve, also known as the tenth cranial nerve, cranial nerve X, or simply CN X, is a cranial nerve that interfaces with the parasympathetic control of the heart, lungs, and digestive tract. It comprises two nerves—the left and right ...
, activation of the
brain stem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...
and the
insular cortex
The insular cortex (also insula and insular lobe) is a portion of the cerebral cortex folded deep within the lateral sulcus (the fissure separating the temporal lobe from the parietal and frontal lobes) within each hemisphere of the mammalian bra ...
,
prefrontal cortex
In mammalian brain anatomy, the prefrontal cortex (PFC) covers the front part of the frontal lobe of the cerebral cortex. The PFC contains the Brodmann areas BA8, BA9, BA10, BA11, BA12, BA13, BA14, BA24, BA25, BA32, BA44, BA45, BA46, ...
, and
somatosensory cortex
In physiology, the somatosensory system is the network of neural structures in the brain and body that produce the perception of touch (haptic perception), as well as temperature (thermoception), body position (proprioception), and pain. It is ...
.
Clinical significance
Blockage
Blockage or obstruction of the bile duct by
gallstone
A gallstone is a calculus (medicine), stone formed within the gallbladder from precipitated bile components. The term cholelithiasis may refer to the presence of gallstones or to any disease caused by gallstones, and choledocholithiasis refers to ...
s,
scar
A scar (or scar tissue) is an area of fibrous tissue that replaces normal skin after an injury. Scars result from the biological process of wound repair in the skin, as well as in other organs, and tissues of the body. Thus, scarring is a na ...
ring from injury, or
cancer
Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
prevents the bile from being transported to the intestine and the active ingredient in the bile (
bilirubin
Bilirubin (BR) (Latin for "red bile") is a red-orange compound that occurs in the normal catabolic pathway that breaks down heme in vertebrates. This catabolism is a necessary process in the body's clearance of waste products that arise from the ...
) instead accumulates in the
blood
Blood is a body fluid in the circulatory system of humans and other vertebrates that delivers necessary substances such as nutrients and oxygen to the cells, and transports metabolic waste products away from those same cells. Blood in the c ...
. This condition results in
jaundice
Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme meta ...
, where the
skin
Skin is the layer of usually soft, flexible outer tissue covering the body of a vertebrate animal, with three main functions: protection, regulation, and sensation.
Other cuticle, animal coverings, such as the arthropod exoskeleton, have diffe ...
and
eyes
Eyes are organs of the visual system. They provide living organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes detect light and conve ...
become yellow from the bilirubin in the blood. This condition also causes severe itchiness from the bilirubin deposited in the tissues. In certain types of jaundice, the urine will be noticeably darker, and the stools will be much paler than usual. This is caused by the bilirubin all going to the bloodstream and being filtered into the urine by the kidneys, instead of some being lost in the stools through the
ampulla of Vater
The ampulla of Vater, also known as the or the hepatopancreatic duct, is formed by the union of the pancreatic duct and the common bile duct. The ampulla is specifically located at the major duodenal papilla.
The ampulla of Vater is an import ...
.
Jaundice
Jaundice
Jaundice, also known as icterus, is a yellowish or greenish pigmentation of the skin and sclera due to high bilirubin levels. Jaundice in adults is typically a sign indicating the presence of underlying diseases involving abnormal heme meta ...
is commonly caused by conditions such as
pancreatic cancer
Pancreatic cancer arises when cell (biology), cells in the pancreas, a glandular organ behind the stomach, begin to multiply out of control and form a Neoplasm, mass. These cancerous cells have the malignant, ability to invade other parts of t ...
, which causes blockage of the bile duct passing through the cancerous portion of the pancreas;
cholangiocarcinoma
Cholangiocarcinoma, also known as bile duct cancer, is a type of cancer that forms in the bile ducts. Symptoms of cholangiocarcinoma may include abdominal pain, yellowish skin, weight loss, generalized itching, and fever. Light colored stool ...
, cancer of the bile ducts; blockage by a stone in patients with
gallstone
A gallstone is a calculus (medicine), stone formed within the gallbladder from precipitated bile components. The term cholelithiasis may refer to the presence of gallstones or to any disease caused by gallstones, and choledocholithiasis refers to ...
s; and from scarring after injury to the bile duct during gallbladder removal.
Drainage
Biliary drainage is performed with a tube or catheter (called a ''biliary drain'', ''biliary
stent
In medicine, a stent is a metal or plastic tube inserted into the lumen of an anatomic vessel or duct to keep the passageway open, and stenting is the placement of a stent. A wide variety of stents are used for different purposes, from expandab ...
'' or ''biliary catheter'') by a
surgeon
In modern medicine, a surgeon is a medical professional who performs surgery. Although there are different traditions in different times and places, a modern surgeon usually is also a licensed physician or received the same medical training as ...
or, commonly, an
interventional radiologist
Interventional radiology (IR) is a medical specialty that performs various minimally-invasive procedures using medical imaging guidance, such as x-ray fluoroscopy, computed tomography, magnetic resonance imaging, or ultrasound. IR performs bo ...
. It can be used to relieve a blockage in the bile duct, either permanently or as a temporary solution before definite treatment such as surgery. The drain can be placed
percutaneous {{More citations needed, date=January 2021
In surgery, a percutaneous procedurei.e. Granger et al., 2012 is any medical procedure or method where access to inner organs or other tissue is done via needle-puncture of the skin, rather than by using ...
ly through the liver, with the procedure then being called ''percutaneous transhepatic biliary drainage'' (PTBD).
This can additionally be performed as part of a
percutaneous transhepatic cholangiography
Percutaneous transhepatic cholangiography, percutaneous hepatic cholangiogram (PTHC) is a radiological technique used to visualize the anatomy of the biliary tract. A contrast medium is injected into a bile duct in the liver, after which X-rays are ...
, then a form of
interventional radiology
Interventional radiology (IR) is a medical specialty that performs various minimally-invasive procedures using medical imaging guidance, such as x-ray fluoroscopy, computed tomography, magnetic resonance imaging, or ultrasound. IR performs bo ...
. A biliary drain can also be used to take bile samples for diagnostic workup or disease monitoring, as well as providing a
route of administration
A route of administration in pharmacology and toxicology is the way by which a medication, drug, fluid, poison, or other substance is taken into the body.
Routes of administration are generally classified by the location at which the substance i ...
for medical substances.
![Choledochojejunstomy diagram](https://upload.wikimedia.org/wikipedia/commons/4/4c/Choledochojejunstomy_diagram.svg)
A surgically created passage between the common bile duct and the
jejunum
The jejunum is the second part of the small intestine in humans and most higher vertebrates, including mammals, reptiles, and birds. Its lining is specialised for the absorption by enterocytes of small nutrient molecules which have been previous ...
in a procedure called a choledochojejunostomy, can be carried out to relieve the symptoms of biliary obstruction.
In infants with
biliary atresia
Biliary atresia, also known as extrahepatic ductopenia and progressive obliterative cholangiopathy, is a childhood disease of the liver in which one or more bile ducts are abnormally narrow, blocked, or absent. It can be congenital or acquired. I ...
,
hepatoportoenterostomy
A hepatoportoenterostomy or Kasai portoenterostomy is a surgical treatment performed on infants with Type IVb choledochal cyst and biliary atresia to allow for bile drainage. In these infants, the bile is not able to drain normally from the small ...
is an alternative method of providing bile drainage.
Cholangiocarcinoma
Cholangiocarcinoma
Cholangiocarcinoma, also known as bile duct cancer, is a type of cancer that forms in the bile ducts. Symptoms of cholangiocarcinoma may include abdominal pain, yellowish skin, weight loss, generalized itching, and fever. Light colored stool ...
or bile duct cancer is a form of cancer that is composed of mutated
epithelial
Epithelium or epithelial tissue is one of the four basic types of animal tissue, along with connective tissue, muscle tissue and nervous tissue. It is a thin, continuous, protective layer of compactly packed cells with a little intercellula ...
cells (or cells showing characteristics of epithelial differentiation) that originate in the bile ducts. Cholangiocarcinoma is considered to be an incurable and rapidly lethal cancer unless both the primary tumor and any
metastases
Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, then, ...
can be fully removed by surgery. No potentially curative treatment exists except surgery, but most people have advanced stage disease at presentation and are inoperable at the time of diagnosis.
Injury
In
cholecystectomy
Cholecystectomy is the surgical removal of the gallbladder. Cholecystectomy is a common treatment of symptomatic gallstones and other gallbladder conditions. In 2011, cholecystectomy was the eighth most common operating room procedure performed i ...
there is a slight risk (0.3–0.5%) of injury of the bile ducts, most commonly of the
common bile duct
The common bile duct, sometimes abbreviated as CBD, is a duct in the gastrointestinal tract of organisms that have a gallbladder. It is formed by the confluence of the common hepatic duct and cystic duct and terminates by uniting with pancreati ...
.
This complication can range from mild forms, which are easy to address during the operation, to more severe forms.
If not addressed such injury can be debilitating and lead to considerable morbidity.
Such injury can be prevented by routinely using X-ray investigation of the bile ducts (intraoperative cholangiography (IOC)).
Additional images
File:3DPrinted biliary system 20151201.jpg, 3D Printed biliary system.
File:Gray1093.png, Section across portal canal of pig. ×250.
File:Laprascopy-Roentgen.jpg , An intraoperative cholangiogram, which is an X-Ray of the bile ducts during a laprascopic cholecystectomy
File:Slide54ior.JPG, Deep dissection of bile duct, anterior view
References
External links
*
The Cholangiocarcinoma Foundation*
The Johns Hopkins Gall Bladder & Bile Duct Cancer Web page*
{{Authority control
Digestive system
Hepatology