Gallbladder and Biliary Tract Disease Flashcards
What does the biliary system refer to?
The liver, gallbladder, bile ducts, and how they work together to make, store, and secrete bile.
What does bile consist of?
Water, electrolytes, bile acids, cholesterol, phospholipids, and conjugated (bilirubin)
Liver produces 500 to 1500 mL of bile per day
Pathway of bile from the lvier
Tonic contraction of the sphincter of oddi during fasting diverts about half og the bile to the cystic duct –> gallbladder where it is stored and concentrated.
Hepatic vs concentrated bile in the GB
Hepatic is isotonic fluid while concentrated (made in the GB) has removed some water and electrolytes through active transport of sodium.
Cholecystokinin (CCK)
Hormone synthesized and secreted by enteroendocrine cells that is released after food is ingested and causes relaxation of sphincter of oddi to allow bile into duodenum.
Secretin
Hormone synthesize in duodenum that enhances the effects of CCK by signaling for release of digestive enzymes from the pancreas and bicarbonate from the liver.
Enterohepatic circulation
Bile acids are efficiently reabsorbed by the small intestinal mucosa in the terminal ileum (95%) and then recycled to the liver for re-excretion.
Diseases that damage the ileum can cause a loss of bile salts which can end up in the stool causing bile acid diarrhea.
Bilirubin
Yellow breakdown product of normal heme catabolism.
Reminder to go through the bilirubin break down process again slides 13-15.
Review** Indirect (unconjugated hyperbilirubinemia)
Increased bilirubin production via hemolysis (increased destruction of of RBCs) and dyserythropoiesis (ineffective erythropoiesis)
Still conjugating and excreting now an increased amount of conjugated bilirubin
↑ conjugated bilirubin enter the gut resulting in ↑ urobilinogen
Hyperbilirubinemia and jaundice
Hyperbilirubinemia causes increased levels of bilirubin in the extracellular fluid.
Causes a yellowish pigmentation of skin, the bulbar conjunctiva, and mucous membrane.
Concentration of total bilirubin greater than 2.5-3mg/dL leads to jaundice
Prehepatic jaundice lab findings
Serum: increased unconjugated (indirect) bilirubin
Urine
no bilirubin present
urobilinogen > 2 units
Stool: increased fecal urobilinogen
Review** Hepatocellular jaundice
Interference in all major steps of bilirubin metabolism:
Uptake, conjugation, excretion (usually to the greatest extent)
Indirect (unconjugated) bilirubin rises if →
Liver has difficulty taking up bilirubin from the circulation
Liver has difficulty conjugating indirect bilirubin
Direct (conjugated) bilirubin rises if → Excretion into the bile is obstructed. Conjugated bilirubin leaks back out and is returned to the blood.
Hepatocellular jaundice lab findings
Serum:
increased total bilirubin
increased direct (conjugated) bilirubin
increased indirect (unconjugated) bilirubin
Urine:
decreased urobilinogen
+ conjugated bilirubin
dark color
Stool:
pale color, decreased fecal urobilinogen
**Review posthepatic or obstructive jaundice
Caused by an interruption to the drainage of bile.
Most common causes
Gallstones in the common bile duct(CBD)
Pancreatic cancer in the head of the pancreas.
Posthepatic jaundice lab findings
Serum:
increased total bilirubin
increased conjugated(direct) bilirubin
normal unconjugated bilirubin
Urine:
decreased or no(in complete obstruction) urobilinogen
+conjugated bilirubin
dark color
Stool:
pale color
Obstructive disease and enzymes
Bile duct epithelial cells are damaged in result of the obstructive process –> leads to increased enzymes in circulation. Measuring these enzymes will indicate bile duct obstruction.
Examples of these enzymes: Alkaline Phosphatase (ALP),
Alkaline phosphatase (ALP)
Function to remove phosphate groups from proteins and other molecules.
Found in the epithelium of the biliary tract and liver as well as osteoblasts, intestinal epithelium, and placenta.
Gamma-glutamyltransferase (GGT)
An enzyme that correlates more with obstruction and cholestasis. Can be ordered with ALP in order to determine if damage is hepatic in origin.
Hepatocellular function enzymes
Those that are essential for the production of the correct amino acids needed to synthesize proteins in the liver –> associated with hepatocellular damage.
ex: Aminotransferases (ASL/ALT) Aspartate aminotransferase (AST) Alanine aminotransferase (ALT)
Protein metabolism
Most of the blood plasma proteins are made in the liver and are synthesize by amino acids.
Hepatocytes are also responsible for breaking down worn out protein into urea.
Most than 90% of overall liver function must be lost before urea and amino acid regulation are measurably affected.
Serum albumin
Measure of proteins in the blood. When severe hepatocellular disease lasts more than 3 weeks this will be decreased.
Decreased levels caused reduced plasma oncotic pressure which pulls fluid out causes ascites and edema.
Liver: Coagulation factors
Liver synthesizes most coagulation proteins. Some are also dependent on vitamin K (Factors II (prothrombin), VII, IX, and X).
If these levels are declined could be due to hepatocellular dysfunction or insufficient vitamin K.
Coagulation factors: PT and PTT
Prothrombin time (PT) and partial thromboplastin time (PT) represent the time it takes for a clot to form in a blood specimen.
Factors that affect PT
II, VII, and X
** Factor VII has the shortest half life so its levels will fall first –> PT will be prolonged earlier than PTT.
Factors that affect PTT
II, IX, and X
Cholelithiasis
Stone formation within within the gallbladder as a concentration of bile components. Typically are formed in the gallbladder by may pass to other parts of the biliary tract.
Choledocholithiasis
Presence of 1 or more gallstones in the common bile duct (CBD).
Gallstone ileus
In severe inflammation, gallstones may erode through the gallbladder into adherent bowel.
Process of stone formation in the gallbladder
When bile is concentrated in the GB it can be supersaturated with bile substances –> crystals are trapped in GB mucus which produces gallbladder sludge–> overtime sludge crystals fuse to form macroscopic stones
What are the 2 main substances that are involved in gallstone formation?
Cholesterol (~80%)
Calcium bilirubinate
Cholesterol stones
Main factors in determine stone formation:
- Amount of cholesterol secreted by hepatocytes relative to lecithin and bile salts.
- Degree of concentration and extent of stasis of bile in the gallbladder.
Estrogen and cholesterol stones
Increased estrogen levels may increase cholesterol in bile and decreased GB movement
Ex: Pregnancy, hormone therapy, use of estrogen containing OCP.
Black pigment stones (calcium bilirubinate)
Represents ~10-20% of gallstones in US.
Increased unconjugated bilirubin concentrations in the bile which eventually crystalized to form solution and stones that are a jet-black color.
Cholelithiasis- mixed stones
Cholesterol gallstones may become colonized with bacteria.
Over time, cholesterol stones may accumulate a substantial proportion of calcium bilirubinate and other calcium salts, producing mixed gallstones. These may develop a surface rim of calcium which may be visible of plain abdominal xray as eggshell appearance.
Cholesteroal gallstone formation risk factors (The five F’s)
Fair Fertile Female Forty Flatulent Fat (BMI>30)
Other risk factors: Metabolic syndrome (inc. cholesterol secretion), Prolonged fasting of TPN, rapid weight loss, hx of multiple pregnancies, dysfunction of the ileum (liver making more bile and overloading GB)