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Diseases of the Gallbladder and Bile Ducts¶

Chapter 357 | Part 10: Disorders of the Gastrointestinal System · Part 10 – Gastrointestinal Disorders · Chapter 357

Key Clinical Points¶

Cholesterol stones account for >90% of gallstones in Western industrialized countries; pigment stones are primarily composed of calcium bilirubinate.
Ultrasound is the procedure of choice for detecting gallstones (>95% accuracy) and is not limited by jaundice or pregnancy.
Biliary colic is the most specific and characteristic symptom of gallstone disease, typically lasting 30 min to 5 h and radiating to the interscapular area, right scapula, or shoulder.
Laparoscopic cholecystectomy is the gold standard for symptomatic cholelithiasis (death rate <0.1%, bile duct injury rate 0.2–0.6%).
Medical dissolution with UDCA is effective only for radiolucent stones ≤ 10 mm.
Acalculous cholecystitis occurs in 5–14% of acute cholecystitis cases and is associated with prolonged fasting, trauma, burns, or total parenteral nutrition (TPN).
Pregnancy increases cholesterol saturation of bile and causes sluggish gallbladder contraction; sludge develops in 20–30% of women but often resolves postpartum.
The bile acid pool size is ≈ 2–4 g and circulates ≈ 5–10 times daily; intestinal reabsorption is ≈ 95% efficient.
Genetic defects in transporters (BSEP/ABCB11, MRP2, MDR3/ABCB4, ABCG5/8) cause specific forms of cholestasis (PFIC1-3, Dubin-Johnson syndrome).
Plain abdominal X-ray is useful for detecting calcified stones, emphysematous cholecystitis, porcelain gallbladder, limey bile, and gallstone ileus.

DEFINITION & OVERVIEW¶

• Scope: Includes cholelithiasis (gallstones), cholecystitis (inflammation), choledocholithiasis (common duct stones), and cholangitis. • Pathophysiology of Stone Formation: Gallstones form due to abnormal bile composition involving: ◦ Supersaturation ◦ Nucleation ◦ Hypomotility

Physiology of Bile Production and Flow¶

• Anatomical Pathway: ◦ Hepatocytes → Canaliculi (lined by hepatocytes) → Canals of Hering (mixed lining) → Small bile ductules → Large bile ducts (lined by cholangiocytes). ◦ Biliary Tree: Interlobular bile ducts → Septal bile ducts → Right and Left hepatic ducts → Common hepatic duct. ◦ Final Junction: Common hepatic duct + Cystic duct → Common bile duct (CBD) → Ampulla of Vater (joins the main pancreatic duct). • Bile Composition & Concentration: ◦ Physical Properties: Isotonic fluid; electrolyte composition resembles blood plasma. ◦ Gallbladder Concentration: Water reabsorption increases solute concentration from 3–4 g/dL in hepatic bile to 10–15 g/dL in gallbladder bile. ◦ Major Solutes (by mole %): ◦ Bile acids: 80% ◦ Phospholipids (lecithins, cephalins, sphingomyelin): 16% ◦ Unesterified cholesterol: 4.0% (can reach 8–10% in lithogenic states). ◦ Other Components: Conjuged bilirubin; proteins (immunoglobulins, albumin); electrolytes; mucus; heavy metals; and drugs/metabolites.

The Bile Acids¶

• Types of Bile Acids: ◦ Primary: Cholic acid and chenodeoxycholic acid (CDCA) (synthesized from cholesterol, conjugated with glycine or taurine). ◦ Secondary: Deoxycholate and lithocholate (formed in colon as bacterial metabolites); note: lithocholic acid is less efficiently absorbed than deoxycholic acid. ◦ Rare: Ursodeoxycholic acid (UDCA), a stereoisomer of CDCA. • Chemistry & Physiology: ◦ Conjugation Ratio: Glycine to taurine ratio is ≈ 3:1 in healthy subjects. ◦ Micelle Formation: Occurs in aqueous solutions at concentrations ≥ 2 mM. Solubility depends on total lipid concentration and the relative molar percentages of bile acids and lecithin. ◦ Functions: ◦ Detergent-like molecules facilitating excretion of cholesterol. ◦ Facilitate intestinal absorption of dietary fats (mainly cholesterol) and fat-soluble vitamins via micellar transport. ◦ Primary driving force for hepatic bile flow. ◦ Hormonal activity: Bind to nuclear (farnesoid X receptor [FXR]) and G protein–coupled (TGR5) receptors to regulate metabolism and enterohepatic circulation.

Enterohepatic Circulation¶

• Mechanism of Recycling: ◦ Absorption: Unconjugated (passive diffusion) and conjugated (active transport in distal ileum) bile acids are absorbed. ◦ Efficiency: ≈ 95% efficient; daily fecal loss is 0.2–0.4 g. ◦ Dynamics: Pool size ≈ 2–4 g; circulates ≈ 5–10 times daily. • Regulatory Pathways: ◦ FGF19: Released by intestinal bile acids; suppresses hepatic synthesis of bile acids (inhibits CYP7A1) and promotes gallbladder relaxation. ◦ FXR: Upregulates BSEP (ABCB11); represses bile acid synthesis. ◦ LXR: Upregulates ABCG5/8 (oxysterol sensor). • Synthesis Limits: Maximum hepatic synthesis is ≈ 5 g/d; may be insufficient to replenish the pool if intestinal reabsorption is impaired.

Gallstone Pathogenesis¶

• Mechanism of Cholesterol Stone Formation (Flowchart 1): 1. Unstable Cholesterol Vesicles → (Triggered by high cholesterol/phospholipid ratio) → Nucleation (Formation of crystals). 2. Nucleation → Microstone (Aggregation of crystals into clusters). 3. Microstone → Gallstone (Growth into a large, solid mass). • Contributing Factors: ◦ High Cholesterol/Phospholipid Ratio: Driven by obesity, metabolic syndrome, high-calorie/high-fat diet, and clofibrate. ◦ Genetic Defects: ◦ CYP7A1: Reduced bile acid synthesis. ◦ MDR3 (ABCB4): Reduced phospholipid secretion. ◦ Other Factors: Pregnancy (progesterone causes sluggish emptying), aging (reduced bile acid pool size), and medications like octreotide.

Predisposing Factors for Stone Formation¶

• Cholesterol Stones: ◦ Demographics/Genetics: Higher in North American/Chilean Indians; higher in Northern Europe/North America than Asia. ◦ Metabolic: Obesity, metabolic syndrome, rapid weight loss (mobilizes tissue cholesterol). ◦ Hormonal: Estrogens (increase uptake of dietary cholesterol); Pregnancy (progesterone-induced impaired emptying). ◦ Age: Increasing age → increased cholesterol secretion; decreased bile acid pool size. ◦ Hypomotility: TPN, fasting, pregnancy, drugs (octreotide). ◦ Genetics: CYP7A1 mutation; MDR3 mutation. • Pigment Stones: ◦ Demographics: Asia, rural settings (parasitic infections). ◦ Hematologic: Chronic hemolysis (sickle cell), Ineffective erythropoiesis (pernicious anemia). ◦ Liver/Biliary: Alcohol-related cirrhosis, Cystic fibrosis, chronic biliary tract infection. ◦ Other: Increasing age; Ileal disease, resection, or bypass.

DIAGNOSTIC APPROACH¶

Ultrasound (Primary Choice): • Advantages: Rapid; accurate identification of gallstones (>95%); simultaneous scanning of GB, liver, bile ducts, and pancreas; real-time assessment of GB volume/contractility; not limited by jaundice or pregnancy. • Capabilities: Can detect very small stones.
Plain Abdominal X-Ray: • Utility: Lower yield but specific for: calcified gallstones, limey bile, porcelain gallbladder, emphysematous cholecystitis, and gallstone ileus.
Cholecystigraphy (HIDA, DISIDA): • Indications: Confirmation of suspected acute cholecystitis; assessment of GB emptying (when given with CCK). • Limitations: Less sensitive/specific in chronic cholecystitis; contraindicated in pregnancy.
Bile Duct Evaluation: • MRCP: Non-invasive; first choice to assess for choledocholithiasis (high sensitivity for dilation, stricture, and intraductal abnormalities). • ERCP: Used for therapeutic intervention; risk of pancreatitis, cholangitis, and sepsis. • PTC: Best when bile ducts are dilated or ERCP is contraindicated/failed; used for proximal biliary tract drainage and obtaining cytology/culture.

MANAGEMENT & TREATMENT¶

Symptomatic Cholelithiasis: • Gold Standard: Laparoscopic cholecystectomy. • Safety Profile: Death rate <0.1%; bile duct injury rate 0.2–0.6%.
Medical Dissolution: • Indication: Radiolucent stones ≤ 10 mm. • Agent: UDCA.

KEY PEARLS & HIGH-YIELD POINTS¶

• Diagnostic Rule: Ultrasound is the primary modality for gallstones; X-ray is reserved for specific calcifications or complications like gallstone ileus. • Pathophysiology: Cholesterol stone formation is a progression from unstable vesicles → nucleation → microstones → stones. • Bile Chemistry: Gallbladder bile is more concentrated than hepatic bile due to water reabsorption; cholesterol content increases in lithogenic states. • Genetic Markers: BSEP (ABCB11), MDR3 (ABCB4), and ABCG5/8 are critical transporters in the management of cholestatic conditions.

Reference Tables¶

TABLE 357-2 Diagnostic Evaluation of the Gallbladder¶

Harrison's 22e, p.2730

Cholesterol Stones
1. Demographic/genetic factors: Prevalence highest in North American Indians,
  Chilean Indians, and Chilean Hispanics, greater in Northern Europe and North
  America than in Asia, lowest in Japan; familial disposition; hereditary aspects
  2. Obesity, metabolic syndrome: Normal bile acid pool and secretion but
  increased biliary secretion of cholesterol
  3. Rapid weight loss: Mobilization of tissue cholesterol leads to increased
  biliary cholesterol secretion while enterohepatic circulation of bile acids is
  decreased
  4. Female sex hormones
  a. Estrogens stimulate hepatic lipoprotein receptors, increase uptake of
  dietary cholesterol, and increase biliary cholesterol secretion
  b. Natural estrogens, other estrogens, and oral contraceptives lead to
  decreased bile salt secretion and decreased conversion of cholesterol to
  cholesteryl esters
  5. Pregnancy: Impaired gallbladder emptying caused by progesterone
  combined with the influence of estrogens, which increase biliary cholesterol
  secretion
  6. Increasing age: Increased biliary secretion of cholesterol, decreased size of
  bile acid pool, decreased secretion of bile salts
  7. Gallbladder hypomotility leading to stasis and formation of sludge
  a. Total parenteral nutrition
  b. Fasting
  c. Pregnancy
  d. Drugs such as octreotide
  8. Clofibrate therapy: Increased biliary secretion of cholesterol
  9. Decreased bile acid secretion
  a. Genetic defect of the CYP7A1 gene
  10. Decreased phospholipid secretion: Genetic defect of the MDR3 gene
  11. Miscellaneous
  a. High-calorie, high-fat diet
  b. Spinal cord injury
Pigment Stones
1. Demographic/genetic factors: Asia, rural setting (presumed due to increased
  prevalence of parasitic biliary infections; the incidence has been dropping
  with time)
  2. Chronic hemolysis (example: sickle cell disease)
  3. Alcohol related liver cirrhosis
  4. Ineffective erythropoiesis (example: pernicious anemia)
  5. Cystic fibrosis
  6. Chronic biliary tract infection, parasite infections
  7. Increasing age
  8. Ileal disease, ileal resection or bypass

TABLE 357-2 Diagnostic Evaluation of the Gallbladder

DIAGNOSTIC ADVANTAGES	DIAGNOSTIC LIMITATIONS	COMMENT
Ultrasound
Rapid Accurate identification of gallstones (>95%) Simultaneous scanning of GB, liver, bile ducts, pancreas “Real-time” scanning allows assessment of GB volume, contractility Not limited by jaundice, pregnancy May detect very small stones	Bowel gas Massive obesity Ascites	Procedure of choice for detection of stones
Plain Abdominal X-Ray
Cholescintigraphy (HIDA, DISIDA, etc.)
Accurate identification of cystic duct obstruction Simultaneous assessment of bile ducts	Contraindicated in pregnancy Serum bilirubin >103–205 μmol/L (6–12 mg/dL) Cholecystogram of low resolution	Indicated for confirmation of suspected acute cholecystitis; less sensitive and less specific in chronic cholecystitis; useful in the diagnosis of acalculous cholecystopathy, especially if given with CCK to assess GB emptying

TABLE 357-3 Diagnostic Evaluation of the Bile Ducts¶

Harrison's 22e, p.2736

DIAGNOSTIC ADVANTAGES	DIAGNOSTIC LIMITATIONS	CONTRAINDICATIONS	COMPLICATIONS	COMMENT
Ultrasound
Rapid Simultaneous scanning of GB, liver, bile ducts, pancreas Accurate identification of dilated bile ducts Not limited by jaundice, pregnancy Guidance for fine-needle biopsy	Bowel gas Massive obesity Ascites Barium Partial bile duct obstruction Poor visualization of distal CBD	None	None	Initial procedure of choice in investigating possible biliary tract obstruction
Computed Tomography
Extreme cachexia Movement artifact Ileus Partial bile duct obstruction	Pregnancy	Reaction to iodinated contrast, if used
Magnetic Resonance Cholangiopancreatography
Noninvasive modality for visualizing pancreatic and biliary ducts Has excellent sensitivity for bile duct dilatation, biliary stricture, and intraductal abnormalities Can identify pancreatic duct dilatation or stricture, pancreatic duct stenosis, and pancreas divisum	Cannot offer therapeutic intervention High cost	Claustrophobia Certain metals (iron)	None	First choice to assess for choledocholithiasis given comparable sensitivity and specificity to ERCP
Endoscopic Retrograde Cholangiopancreatography
Gastroduodenal obstruction Roux-en-Y biliary-enteric anastomosis	Pregnancy Acute pancreatitis Severe cardiopulmonary disease	Pancreatitis Cholangitis, sepsis Infected pancreatic pseudocyst Perforation (rare) Hypoxemia, aspiration
Percutaneous Transhepatic Cholangiogram
Best when bile ducts dilated Best visualization of proximal biliary tract May be used to obtain bile cytology/culture Allows for percutaneous transhepatic drainage	Nondilated or sclerosed ducts	Pregnancy Uncorrectable coagulopathy Massive ascites Hepatic abscess	Bleeding Hemobilia Bile peritonitis Bacteremia, sepsis	Indicated for the drainage of obstructed and infected ducts when ERCP is contraindicated or failed
Endoscopic Ultrasound