Gallstones for the ABIM Exam
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Gallstones (Cholelithiasis)
Overview
- Gallstones, also known as cholelithiasis, are crystalline concretions formed within the gallbladder due to imbalances in the composition of bile.
- Gallstones are classified into three main types:
- Cholesterol stones: The most common, constituting 80% of all gallstones, formed primarily from cholesterol.
- Pigment stones: Composed of bilirubin, often seen in patients with chronic hemolytic disorders.
- Mixed stones: Contain both cholesterol and pigment components.
Pathophysiology
- Cholesterol stones: Result from supersaturation of cholesterol in bile, decreased bile acid secretion, or impaired gallbladder motility.
- Risk factors include obesity, rapid weight loss, hyperlipidemia, and estrogen therapy.
- Four Fs mnemonic: Fat, Female, Fertile, and Forty are common risk characteristics for cholesterol stones.
- Pigment stones: Caused by increased production of unconjugated bilirubin, which precipitates in bile.
- Associated with chronic hemolytic diseases (e.g., sickle cell disease, spherocytosis), cirrhosis, and biliary infections.
- Mixed stones: A combination of cholesterol and bilirubin, often seen in a wide range of patients.
Risk Factors
- Age: Incidence increases with age, especially in those >40 years.
- Gender: Females are at higher risk due to estrogen, which increases cholesterol saturation in bile.
- Ethnicity: Higher prevalence in Native Americans and Hispanics; lower in African Americans.
- Obesity: Linked to increased cholesterol synthesis and secretion.
- Pregnancy: Estrogen and progesterone contribute to biliary stasis and cholesterol supersaturation.
- Rapid weight loss: Causes mobilization of cholesterol from adipose tissue, leading to cholesterol stone formation.
- Diabetes mellitus: Increased triglyceride levels in diabetics promote cholesterol stone formation.
Clinical Presentation
- Asymptomatic: Most patients (70-80%) with gallstones remain asymptomatic, discovered incidentally during imaging for other conditions.
- Biliary colic: The hallmark symptom of symptomatic cholelithiasis, characterized by:
- Sudden onset of severe, steady pain in the right upper quadrant (RUQ) or epigastrium, lasting 30 minutes to a few hours.
- Pain may radiate to the right shoulder or back and is often triggered by fatty meals.
- Associated symptoms include nausea and vomiting.
- The pain resolves as the gallbladder relaxes and the stone moves away from the cystic duct.
Complications
Acute Cholecystitis
- Occurs when a gallstone obstructs the cystic duct, leading to gallbladder inflammation.
- Clinical features:
- Persistent RUQ pain, often lasting >6 hours.
- Fever, leukocytosis, and Murphy’s sign (pain and inspiratory arrest on palpation of the RUQ).
- Ultrasound is the imaging modality of choice, showing gallbladder wall thickening, pericholecystic fluid, and stones.
Choledocholithiasis
- Gallstones in the common bile duct (CBD), which can obstruct bile flow and lead to complications such as:
- Obstructive jaundice (elevated bilirubin, dark urine, pale stools).
- Cholangitis: Inflammation of the bile ducts due to bacterial infection secondary to obstruction.
- The classic Charcot’s triad includes RUQ pain, fever, and jaundice.
- Reynold’s pentad: Charcot’s triad plus hypotension and altered mental status, indicating sepsis.
- Pancreatitis: Occurs when stones obstruct the pancreatic duct, leading to inflammation.
- Symptoms include epigastric pain radiating to the back, nausea, and vomiting.
- Diagnosis: Endoscopic retrograde cholangiopancreatography (ERCP) is both diagnostic and therapeutic.
Gallstone Ileus
- A rare complication where a large gallstone erodes through the gallbladder into the small bowel, causing mechanical obstruction.
- Presents with symptoms of small bowel obstruction: abdominal pain, vomiting, and absence of bowel movements.
- Diagnosis is confirmed with abdominal imaging, often showing pneumobilia (air in the biliary tree) and a calcified stone in the intestine.
Diagnosis
Imaging
- Ultrasound: The first-line imaging modality, highly sensitive for detecting gallstones within the gallbladder.
- Findings include echogenic foci with posterior acoustic shadowing.
- Also useful for diagnosing acute cholecystitis by showing gallbladder wall thickening or pericholecystic fluid.
- Endoscopic Ultrasound (EUS): Used for identifying stones in the common bile duct, especially when ERCP is contraindicated.
- CT scan: Less sensitive for gallstones but useful for detecting complications such as perforation, abscesses, or gallstone ileus.
- Magnetic resonance cholangiopancreatography (MRCP): A non-invasive imaging technique to visualize bile ducts and assess for choledocholithiasis.
Laboratory Tests
- Liver function tests (LFTs): Elevated in choledocholithiasis and cholangitis, particularly:
- Elevated bilirubin (direct), alkaline phosphatase (ALP), and gamma-glutamyl transferase (GGT).
- Mild elevation in AST/ALT may occur with early biliary obstruction.
- Leukocytosis: Seen in acute cholecystitis and cholangitis, indicating inflammation or infection.
Management
Asymptomatic Gallstones
- Observation: Asymptomatic patients generally do not require treatment, as the risk of complications is low (<1-2% per year).
Symptomatic Cholelithiasis (Biliary Colic)
- Cholecystectomy:
- Laparoscopic cholecystectomy is the standard treatment for symptomatic gallstones, offering definitive relief from biliary colic and preventing future complications.
- It is indicated in patients with recurrent biliary colic or gallstone complications (e.g., acute cholecystitis).
- Medications:
- Ursodeoxycholic acid: A bile acid that can dissolve cholesterol stones in patients unwilling or unable to undergo surgery, though it is less effective and requires long-term use.
- Analgesics (e.g., NSAIDs) for pain management.
Acute Cholecystitis
- Antibiotics: Broad-spectrum antibiotics targeting gram-negative and anaerobic organisms (e.g., ceftriaxone plus metronidazole) are administered.
- Cholecystectomy:
- Laparoscopic cholecystectomy is performed within 72 hours of symptom onset.
- In high-risk patients, a percutaneous cholecystostomy (drainage of the gallbladder) may be considered as a temporizing measure.
Choledocholithiasis
- Endoscopic retrograde cholangiopancreatography (ERCP): The treatment of choice for removing stones from the common bile duct. It is often followed by a laparoscopic cholecystectomy to prevent recurrence.
- Sphincterotomy during ERCP allows stone removal and improves bile flow.
Cholangitis
- Urgent ERCP: Performed for drainage and stone removal, particularly in severe or septic patients.
- IV antibiotics: Given for gram-negative and anaerobic coverage (e.g., piperacillin-tazobactam or ceftriaxone with metronidazole).
Prevention
- Ursodeoxycholic acid: Used in certain high-risk populations (e.g., rapid weight loss or bariatric surgery patients) to prevent gallstone formation by reducing bile cholesterol saturation.
- Dietary changes: Low-fat diets may reduce the recurrence of biliary colic.
Key Points
- Cholesterol stones are the most common type of gallstone, and risk factors include obesity, rapid weight loss, and estrogen exposure.
- Biliary colic is characterized by episodic RUQ pain, often after fatty meals, and resolves spontaneously within a few hours.
- Acute cholecystitis involves persistent RUQ pain, fever, and leukocytosis, often requiring laparoscopic cholecystectomy.
- Choledocholithiasis presents with jaundice and elevated liver enzymes and is treated with ERCP for stone removal.
- Cholangitis is a life-threatening complication of common bile duct obstruction, requiring urgent ERCP and antibiotics.
- Laparoscopic cholecystectomy is the definitive treatment for symptomatic gallstones and prevents future complications.