Cholelithiasis

Overview
  • Cholelithiasis refers to disease associated with the development of stones within the biliary tree or gallbladder.
Stone Subtypes
  • Two basic subtypes of gallstones exist which are generated by different pathogenic mechanisms and are composed of distinct chemical species. Cholesterol stones are composed of crystaline cholesterol and are the predominant stone type in Western developed countries. Pigment Stones are composed of bilirubin salts together with calcium and occur due to specific derangements in handling of unconjugated bilirubin.
Pathogenesis
  • Cholesterol Stones
    • The genesis of cholesterol stones appears to require the existence of three pathological factors. Excess levels of cholesterol are eliminated through biliary secretion, resulting in increased biliary cholesterol concentrations which may exceed the capacity of other bile constituents to solubilize the cholesterol. In this context, precipitation of hyper-saturated cholesterol is enhanced when there is a nidus for nucleation of the crystal. Finally, cholesterol stones take time to develop and so require hypomotility of the gallbladder to grow to sufficiently large sizes.
  • Pigment Stones
    • Pigment Stones generally develop due to excessive biliary excretion of unconjugated bilirubin which is fairly water insoluble and thus can precipitate out of the bile at high concentrations.
Risk Factors
  • Cholesterol Stones
    • Any factor that increases body cholesterol levels or renders the gallbladder hypomotile can increase the risk of cholesterol stones.
    • Obesity and High-fat/Western diets: Associated with high intakes of cholesterol and thus increased biliary cholesterol excretion.
    • Pregnancy: Appears to increase cholesterol excretion and may render the gallbladder hypomotile
    • Fad Dieters: Undergo rapid weight loss due to an extremely low-caloric diet are at risk possibly due to gallbladder hypomotility.
    • Clofibrate: Increases biliary cholesterol excretion and thus naturally poses a risk factor for cholesterol stones
    • Genetic factors: Play a role as those with a family-history of gallstones are at greater risk and select populations such as certain Native American tribes like the Pima Indians are prone
    • Age: The risk of developing cholesterol stones increases with age and is greatest in the elderly
  • Pigment Stones
Morphology
  • Cholesterol stones always arise in the gallbladder, are typically yellow, and tend to be radiolucent due to their low calcium content. Pigment stones can arise anywhere in biliary tree, are black or brown, and are generally radioopaque due to their high calcium content.
Clinical Consequences
  • Overview
    • The clinical consequences of gallstones largely depends on where they are located and if they are obstructing outflow of bile. Large gallstones within the gallbladder that are not obstructive are often asymptomatic.
  • Biliary Colic
    • Severe and acute obstruction of the gallbladder neck, cystic duct, or common bile duct often results in a characteristic pain termed "Biliary Colic" often after ingestion of fatty meals which promote contraction of the gallbladder. "Biliary Colic" is characterized by episodes of sustained and excruciating right upper quadrant or epigastric abdominal pain associated with obstruction of the common bile duct or cystic duct.
  • Cholecystitis
    • Obstruction or mere physical presence of gallstones can cause inflammation of the gallbladder which is covered in cholecystitis.
  • Choledocholithiasis
    • Choledocholithiasis refers to obstruction of the biliary tree with gallstones. In most cases, this occurs when a cholesterol stone passes into and obstructs the common bile duct or Ampulla of Vater. This can result in acute or chronic stasis of bile all the way into the liver, resulting in an array of possible complications.
    • Cholestasis may arise along with its traditional clinical and laboratory anomalies such as elevated serum alkaline phosphatase, conjugated hyperbilirubinemia, jaundice, pruritis, and malabsorptive steatorrhea. If obstruction is low-grade but prolonged, secondary biliary cirrhosis can result.
    • Cholangitis may develop due to secondary bacterial infection of the upstream obstructed bile
    • Acute Pancreatitis may occur if gallstone obstructs the Ampulla of Vater and thus the outlet of the main pancreatic duct