Have you seen the new hit movie The Sphincter of Oddi? Probably not, as it is the name of a part of your BILIARY TRACT and not a movie. But it would make a good movie title! Indiana Jones And the Sphincter of Oddi?
What is the biliary tract?
The extrahepatic (originating outside the liver) biliary tract, also known as the biliary tree, includes the gallbladder, bile ducts, and the sphincter of Oddi. The biliary tract collects, stores, concentrates, and delivers bile secreted by the liver to aid digestion.
We will discuss each of these components of the biliary tract in some detail and the functional changes and clinical symptoms of inflammatory and cancer disorders.
The Liver
Located in the upper right quadrant of the abdomen and weighing about 1.5 kilograms, the liver has 500 vital functions. Incredibly it can maintain normal function with only 30% of its cells in working condition. The liver has a vital role in filtering blood. At any given moment, the liver contains about 13% of your blood volume. The liver also has a significant role in digestion by synthesizing bile to digest fats and absorb vitamins.
Bile
Bile is a dark-green or yellowish-brown aqueous mixture produced inside the liver and helps emulsify and break down fat that we ingest into our bodies. Fat does not dissolve in water. Instead, bile contains bile salts, which are conjugated bile acids produced in the liver from cholesterol.
When the fat you consume reaches the small intestine, it is in the form of large fat droplets. Bile is released into the small intestine, and the bile salts mix with the large fat droplets emulsifying a breaking them down into smaller droplets.
The enzyme lipase from the pancreas can then break the fat into free fatty acids and monoglycerides to be absorbed through the small intestine wall. Bile also helps clear the liver of waste products.
The Gallbladder
The gallbladder is a small, slightly elongated pear-shaped organ where bile from the liver is stored and concentrated before releasing it into the small intestine. The gallbladder is an accessory organ of the digestive tract that sits underneath the liver slightly higher and adjacent to the duodenum (the first part of the small intestine) and pancreas. The gallbladder allows the gradual entry of bile by passive and active mechanisms.
It can store about 30 to 60 milliliters of bile. When fasting, the gallbladder can handle more. Covered by a thin layer of peritoneum, it’s connected to the common hepatic duct via the cystic duct. (See bile ducts next.) The gallbladder itself be divided into four parts, the fundus, the body, the infundibulum, and the neck.
Bile Ducts
Bile ducts are thin tubes that allow bile to go from the liver and gallbladder into the small intestine, helping digest the fats in your food.
There are a series of bile ducts that deliver this essential digestive enzyme to your small intestine. The two bile ducts in the liver are called the intrahepatic and extrahepatic ducts.
Intrahepatic ducts are a system of smaller tubes that collect and transport bile to the extrahepatic ducts. The extrahepatic ducts start on the right of the liver and the left. As they come down from the liver, they form the common hepatic duct that runs directly toward the small intestine.
The biliary duct from the gallbladder opens into the common hepatic duct. The bile duct from this point forward is known as the common bile duct or ductus choledochus. Before emptying into the small intestine, the common bile duct passes through the pancreas.
The Sphincter of Oddi
The sphincter of Oddi (SO) is a smooth muscle approximately 10mm (4 inches) in length that surrounds the end portion of the common bile duct and pancreatic duct. This muscle relaxes during a meal to allow bile and pancreatic juice to flow into the intestine.
During fasting, most of the hepatic bile is diverted toward the gallbladder by the resistance of The Sphincter of Oddi. During the digestive phase, the gallbladder contracts, and the SO relaxes, allowing bile to be released into the duodenum to digest and absorb fats.
Diseases Of the Biliary Tract
The biliary tract is a complex system of biliary ducts with the ultimate aim of storing and draining bile. Bile serves essential functions in the body by facilitating digestion, removal of toxic and metabolic waste products. Apart from the fact that it serves crucial physiological functions, the biliary system is home to various diseases ranging from infectious, metabolic, inflammatory to benign and malignant conditions.
Symptoms of biliary tract diseases include:
- Pain – Patients with disorders of the biliary tract may have abdominal pain after a meal. The pain can be caused by obstruction to the outflow of bile due to gallstones, which is the most common cause. Other causes may be bile duct inflammation, enlarged lymph nodes, hepatitis, or cancerous tumors.
With any obstruction, the visceral pain fibers supplying the Gall Bladder are activated due to its swelling resulting in pain in the left or right abdominal regions. If the obstruction is not relieved, bile can back up in the gall bladder, causing infection and inflammation. A condition termed acute cholecystitis.
- Fever – may be seen in patients with acute cholecystitis.
- Jaundice – Jaundice, a yellow discoloration of the eyes, skin, and urine, may be seen in a subset of patients with obstruction to the outflow of the biliary tract. It may be present in patients with cholangitis (inflammation of the common bile duct), choledocholithiasis (gallstones), and malignant biliary tract obstruction.
- Murphy’s sign – The voluntary cessation of respiration when an examiner exerts pressure under the right edge of the eighth through tenth ribs in the middle of the chest. This reaction is seen in patients with acute cholecystitis, inflammation of the gallbladder.
Bile Duct Cancer
Cancer of the bile duct is a rare cancer. Known as cholangiocarcinoma, it starts in the epithelial cells that line the bile ducts. Cholangiocarcinoma is classified depending on its location in the biliary tract, intrahepatic (in the liver,) and extrahepatic (outside the liver.) Intrahepatic tumors occur less frequently and behave like primary liver tumors.
Gallbladder Cancer
Gallbladder cancer (GBC) is an uncommon but highly fatal malignancy. Fewer than 5,000 new cases are diagnosed each year in the United States. However, GBC incidents steadily increase with age, and women are affected two to six times more often than men.
Sphincter of Oddi Dysfunction and Cancer
Nearly 400 hundred years ago, Frances Gliesson first described a sphincter structure at the far end of the common bile duct where it enters the duodenum. Still, it was not until 1889, when Rugero Oddi described its anatomy and physiology in detail, that the function of this structure and its role in the control of the flow of bile and pancreatic juices were appreciated.
So now you know where this classic name of this part of the biliary tract or biliary tree as some call it comes from. But is there cancer of The Sphincter of Oddi?
The Sphincter of Oddi has painful dysfunctions usually caused by spasms or fibrosis. These dysfunctions and cancer symptoms are the usual pain, fever, and jaundice experienced with other biliary tract diseases and dysfunctions. A malignancy diagnosis should be considered in the event of a patient experiencing these symptoms.
