The biliary tree is a network of organs and ducts that moves a digestive fluid called bile. This system supports digestion by delivering bile when and where it is needed. The network also aids in the breakdown of food and the removal of certain waste products from the body.
Anatomy and Function of the Biliary System
Bile’s journey begins in the liver, where it is produced by liver cells. This fluid is secreted into small canals that merge into progressively larger ducts. These channels culminate in the right and left hepatic ducts, which drain bile from their respective sides of the liver. These two ducts then unite to form the common hepatic duct.
From the common hepatic duct, some bile flows directly to the intestine, while about half is diverted for storage through the cystic duct into the gallbladder. The gallbladder, a small organ beneath the liver, holds and concentrates this bile, increasing its potency. This storage allows for the release of a larger amount of bile in response to a meal.
When fatty foods enter the small intestine, a hormone signals the gallbladder to contract, pushing stored bile out through the cystic duct. The cystic duct then merges with the common hepatic duct to form the common bile duct. This channel connects to the first part of the small intestine (the duodenum), delivering bile to mix with food. The primary purpose of this bile is to emulsify fats by breaking large fat globules into smaller droplets, allowing digestive enzymes to work more efficiently.
Common Disorders of the Biliary Tree
The most prevalent issue is the formation of gallstones (cholelithiasis). These are hard deposits that develop in the gallbladder when substances in the bile, like cholesterol or bilirubin, become overly concentrated and solidify. While many gallstones are asymptomatic, they can cause problems if they move and create a blockage in a bile duct. This obstruction can lead to sudden, intense pain in the upper right abdomen, known as biliary colic.
A blockage from a gallstone can trigger inflammation. If an obstruction in the cystic duct causes the gallbladder to become inflamed, the condition is called cholecystitis. This leads to persistent pain, fever, and nausea. Similarly, if a stone blocks the common bile duct, it can cause a bacterial infection and inflammation within the ducts, a condition called cholangitis.
Biliary ducts can also be affected by other problems, such as biliary strictures, which involve an abnormal narrowing of a duct. This narrowing can impede or block bile flow and may arise from injury during surgery, pancreatitis, or chronic inflammation. Over time, the backup of bile can lead to significant liver damage.
Diagnosis and Treatment Options
Symptoms of a biliary tree problem include a steady, severe pain in the upper right abdomen. Other signs are jaundice (a yellowing of the skin and eyes), light-colored stools, and dark urine. Fever, chills, nausea, and vomiting often accompany these symptoms, prompting a visit to a healthcare provider.
Diagnosis begins with non-invasive methods like blood tests, which check for inflammation and measure liver function and bilirubin levels. An abdominal ultrasound uses sound waves to create pictures of the gallbladder and bile ducts to detect gallstones or inflammation. For a more detailed view, a physician may order a Magnetic Resonance Cholangiopancreatography (MRCP), a specialized MRI scan of the biliary system.
Symptomatic gallstones are often treated with the surgical removal of the gallbladder (cholecystectomy), which is frequently performed laparoscopically for a quicker recovery. If a stone is lodged in a bile duct, a procedure called Endoscopic Retrograde Cholangiopancreatography (ERCP) may be used. During an ERCP, a flexible scope is passed to the small intestine, allowing a doctor to view the bile duct opening, remove stones, or place a stent.