Biliary Tree and Gallstones Flashcards
Describe the biliary tree.
Biliary canaliculi to interlobular bile ducts to septal bile ducts to intrahepatic ducts to right and left hepatic ducts to common hepatic duct to common bile duct
Where does the bile duct pass?
Passes behind the duodenum, through the head of the pancreas to join the main pancreatic duct, becoming the bile duct.
This then enters the duodenum at the major/minor duodenal papilla
Where is the gallbladder located?
In the gallbladder fossa on the inferior surface of the right lobe of the liver
What is the epithelial lining and function of the gallbladder?
Columnar epithelium
- concentrates bile by absorbing water and electrolytes
What is bile composed of?
Water Bile acids Bile pigments Phospholipids Cholesterol Electrolytes
Describe the bile acid synthesis.
Derived from cholesterol in the hepatocyte. Cholic acid is the primary bile acid
Describe bile salt synthesis.
Cholic acid is conjugated to bile salts by the addition of an amino acid group (taurine or glycine) before active export. These are primary bile salts.
What forms secondary bile salts.
The action of intestinal bacteria (de-hydroxylation) of primary bile salts
What causes gallbladder contraction?
Vagal stimulation
CCK release into the duodenum
- causes by detection of luminal fat
- sphincter of Oddi relaxation
What causes gallbladder relaxation?
Sympathetic nerves
Gut hormones
- somatostatin
- VIP
What do the following and and prefixes mean? Chol Lith Docho Ang itis iasis
Chol = bile Lith = stone Docho = duct Ang = vessel itis = inflammation iasis = process
What is the function of bile salts?
Promote emulsification and formation of micelles to help fat absorption
- fat soluble vitamins are absorbed
- facilitates cholesterol excretion by solubilising it in bile
Influences the intestinal metabolic pathways
What is the entero-hepatic circulation?
95% of bile salts are reabsorbed from the gut (6-8 times a day)
- they are reabsorbed by the terminal ilium by active transport into the portal vein
How do bile salts travel in the blood?
Bound to albumin because it’s hydrophobic
What are the risk factors for gallstones?
The six F's - female - forty - fat - fertile - family history Caucasian Low fibre diet Inflammatory bowel disease
Name the three types of gallstones.
Cholesterol stones
Bile pigment stones
Mixed
Describe cholesterol stones.
Usually solitary
Oval and large (up to 3cm)
Describe bile pigment stones.
Usually multiple
Hard and irregular
Can be associated with chronic heamolysis (sick cell)
Describe mixed stones.
The most common (80%)
Multiple and multi-faceted
Has a laminated structure with layers of bile pigment, cholesterol and calcium salts
In gallstone pathogenesis there are three main events (that often occur toegther). What are they?
Cholesterol supersaturation
Biliary stasis
Increased bilirubin secretion
Describe the process of cholesterol supersaturation.
Cholesterol is normally solubilised in bile, but very high levels cause supersaturation.
This can be due to increased oestrogen or decreased bile salt levels.
When does biliary stasis occur?
Occurs during periods of fasting, starvation or prolonged enteral feeding
Describe what happens in increased bilirubin secretion.
Pigmented stones can develop in increased heamolysis or a failure in hepatic conjugation
What complications can gallstones in the gallbladder cause?
Acute cholecystitis - can cause jaundice and abnormal LFTs Empyema Mucocele Cancer Biliary colic - stone impacted in gallbladder - pain when eating
What complications can gallstones in the common bile duct cause?
Obstructive jaundice
Cholangitits
Pancreatitis
What complications can gallstones in the small intestine cause?
Gallstone ileus
What are some of the casues of obstructive jaundice?
Choldocholithiasis Pancreatic cancer Pancreatitis Cholangiocarcinoma Benign bile duct stricture
What are the signs and symptoms of obstructive jaundice?
Pale stools and dark urine Yellow sclera Hepatomegaly Itch S/S of chronic liver disease Palpable gallbladder
Where do gallstones commonly impact in the bile duct?
The ampulla of Vater
How do you diagnose a gallstone in the bile duct (choledocholithiasis)?
Ultrasound with or without EUS and MRCP to confirm
Treatment of gallstones in the bile duct?
- antibiotics if cholangitis
- ECRP to attempt stone removal (incision in the sphincter of Oddi to increase the diameter)
- cholecystectomy to prevent recurrence
What happens to the LFTs in obstructive jaundice?
- ALP increases early (with a GGP increase)
- bilirubin rises steadily (level suggests the duration of disease)
- coagulopathy is common in prolonged obstructive jaundice
