Back
ditki Logo
medical & biological sciences

Gallstones for the USMLE Step 3

Start your One-Week Free Trial
Already subscribed? Log in »
Gallstones (Cholelithiasis) for the USMLE Step 3 Exam
Overview
  • Gallstones are solid formations within the gallbladder due to abnormal bile composition.
  • Types of gallstones:
    • Cholesterol stones: Most common (80%), formed due to cholesterol supersaturation.
    • Pigment stones: Composed of bilirubin, associated with hemolytic disorders or infections.
Pathophysiology
Cholesterol Stones
  • Develop due to cholesterol supersaturation, decreased bile salts, and gallbladder stasis.
  • Risk factors include:
    • Obesity: Increases cholesterol synthesis.
    • Rapid weight loss: Causes mobilization of cholesterol from adipose tissue.
    • Estrogen exposure: Pregnancy and hormone therapy increase bile cholesterol saturation.
    • Metabolic syndrome: Associated with insulin resistance and hyperlipidemia.
Pigment Stones
  • Form due to excess unconjugated bilirubin, which precipitates in bile.
  • Risk factors include:
    • Chronic hemolysis (e.g., sickle cell anemia, hereditary spherocytosis).
    • Cirrhosis and biliary infections.
Clinical Presentation
  • Asymptomatic: Most gallstones remain silent and are discovered incidentally.
  • Biliary colic: Occurs when a stone temporarily obstructs the cystic duct, causing:
    • RUQ or epigastric pain after fatty meals, radiating to the right shoulder or back.
    • Pain lasts 30 minutes to several hours, accompanied by nausea and vomiting.
  • Acute cholecystitis: Inflammation of the gallbladder caused by prolonged cystic duct obstruction.
    • Persistent RUQ pain (>6 hours), fever, and Murphy’s sign (pain during inspiration while palpating the RUQ).
    • Requires antibiotics and cholecystectomy.
Biliary colic
Complications
Acute Cholecystitis
  • Inflammation of the gallbladder due to cystic duct obstruction.
    • Symptoms: RUQ pain, fever, and leukocytosis.
    • Ultrasound: Reveals gallbladder wall thickening, pericholecystic fluid, and stones.
    • Treated with antibiotics and laparoscopic cholecystectomy.
Choledocholithiasis and Cholangitis
  • Choledocholithiasis: Gallstones in the common bile duct, leading to bile duct obstruction.
    • Symptoms: Jaundice, RUQ pain, and elevated bilirubin and alkaline phosphatase.
  • Cholangitis: Infection due to biliary obstruction, presenting with Charcot’s triad (RUQ pain, jaundice, fever).
    • Reynold’s pentad: Charcot’s triad plus hypotension and altered mental status, indicating sepsis.
    • Urgent ERCP is needed for stone removal and drainage.
Gallstone Pancreatitis
  • Obstruction of the pancreatic duct by a stone, leading to pancreatic inflammation.
    • Symptoms: Epigastric pain radiating to the back, nausea, and vomiting.
    • Diagnosed with elevated amylase and lipase.
    • Treated with supportive care, and ERCP if needed for stone removal.
Diagnosis
Imaging
  • Ultrasound: First-line imaging to detect gallstones, showing echogenic foci with posterior acoustic shadowing.
  • MRCP: Used to visualize bile duct stones non-invasively.
  • ERCP: Both diagnostic and therapeutic for choledocholithiasis and cholangitis.
Laboratory Tests
  • Liver function tests (LFTs): Elevated bilirubin, ALP, and GGT suggest biliary obstruction.
  • Leukocytosis: Indicates infection or inflammation, such as acute cholecystitis or cholangitis.
Management
Asymptomatic Gallstones
  • Observation: No treatment needed unless symptoms or complications develop.
Symptomatic Gallstones (Biliary Colic)
  • Laparoscopic cholecystectomy: The definitive treatment to prevent recurrence and complications.
Acute Cholecystitis
  • Antibiotics: Broad-spectrum antibiotics covering gram-negative and anaerobic bacteria (e.g., ceftriaxone and metronidazole).
  • Cholecystectomy: Performed within 72 hours of symptom onset.
Choledocholithiasis and Cholangitis
  • ERCP: The treatment of choice for removing common bile duct stones and resolving cholangitis.
Key Points
  • Cholesterol stones are the most common type, and risk factors include obesity, rapid weight loss, and estrogen exposure.
  • Biliary colic presents as episodic RUQ pain after meals, and laparoscopic cholecystectomy is the definitive treatment.
  • Complications include acute cholecystitis, choledocholithiasis, cholangitis, and gallstone pancreatitis.
  • ERCP is the diagnostic and therapeutic modality of choice for choledocholithiasis and cholangitis.
  • Ultrasound is the first-line imaging modality for detecting gallstones.

Related Tutorials