Biliary Tract Disease

Stone composition — mechanism defines the risk profile

• Cholesterol stones (majority in the US): bile supersaturated with cholesterol relative to bile salts and phospholipids, plus gallbladder hypomotility. Usually radiolucent on plain film.
• Black pigment stones: chronic hemolysis (sickle cell disease, hereditary spherocytosis, thalassemia, mechanical valves), cirrhosis, and ileal disease increase unconjugated bilirubin delivered to bile → calcium bilirubinate precipitation. Typically radiopaque.
• Brown pigment stones: form within ducts from bacterial/parasitic deconjugation of bilirubin by β-glucuronidase — associated with biliary stasis, strictures, and Clonorchis sinensis or Ascaris infection in endemic regions.

Non-modifiable risk factors

• Female sex and age: estrogen increases hepatic cholesterol secretion; progesterone impairs gallbladder emptying. Prevalence rises steadily with age.
• Ethnicity/genetics: Native American (Pima) populations have the highest rates; family history and hepatobiliary cholesterol transporter (ABCG5/G8) variants contribute.
• Chronic hemolytic disease and cirrhosis: pigment stone mechanism above.

Modifiable/iatrogenic risk factors — the ones planted in stems

• Obesity and rapid weight loss: both raise biliary cholesterol saturation; very-low-calorie diets and bariatric surgery are classic triggers.
• Pregnancy and multiparity, estrogen therapy/OCPs: hormonal lithogenesis.
• Prolonged fasting and total parenteral nutrition: absent CCK stimulation → gallbladder stasis and sludge.
• Drugs: ceftriaxone (biliary pseudolithiasis, reversible), octreotide, fibrates, and ileal bile-salt sequestration.
• Terminal ileal disease or resection (Crohn disease), cystic fibrosis: bile salt malabsorption depletes the bile acid pool.

Acalculous cholecystitis and cholangitis substrates

• Critical illness: sepsis, burns, major trauma, mechanical ventilation, and TPN produce ischemia plus stasis; the Tokyo Guidelines (TG18) framework applies the same diagnostic criteria regardless of stones.
• Cholangitis causes beyond stones: postoperative or ischemic strictures, occluded biliary stents, pancreatic head or ampullary malignancy, cholangiocarcinoma, and primary sclerosing cholangitis.

• Bile stasis and supersaturation: Cholesterol precipitation occurs when bile becomes supersaturated with cholesterol relative to bile acids and phospholipids; this occurs with prolonged fasting, rapid weight loss, or alterations in enterohepatic circulation. Pigmented stones form from bilirubin polymers, particularly in hemolytic conditions and with bacterial overgrowth in the biliary tree.

• Gallstone formation (lithogenesis): The classic triad includes increased cholesterol secretion, decreased bile acid synthesis, and gallbladder hypomotility. Nucleation is accelerated by mucin-producing cells in the gallbladder epithelium; crystals aggregate into macroscopic stones over weeks to months.

• Inflammation in acute cholecystitis: Obstruction of the cystic duct by a stone causes bile accumulation, triggering mechanical inflammation initially; secondary bacterial infection (E. coli, Klebsiella, Bacteroides) occurs in 50-80% of cases. Acalculous cholecystitis (10-15% of cases) results from bile stasis, ischemia, or chemical inflammation without stone obstruction.

• Cholangitis pathogenesis: Obstruction of the common bile duct raises intraductal pressure above portal blood pressure (typically >25 mmHg), forcing bacteria and endotoxins into the bloodstream, causing the classic Charcot's triad (fever, jaundice, right upper quadrant pain). Ascending cholangitis is a medical emergency with mortality rates of 5-10% if untreated.

• Biliary pancreatitis mechanism: Passage of stones through the ampulla of Vater causes transient obstruction, raising pancreatic duct pressure and triggering pancreatic enzyme activation; this accounts for 40-50% of acute pancreatitis cases.

• Biliary colic: Sudden onset of constant, severe right upper quadrant or epigastric pain lasting 30 minutes to several hours, often after fatty meals; pain may radiate to the right shoulder (phrenic nerve irritation). Importantly, between episodes patients are completely asymptomatic—absence of pain does not indicate resolution of the underlying stone.

• Acute cholecystitis: Right upper quadrant pain (often more persistent than biliary colic), fever, and Murphy's sign positive on examination (inspiratory arrest when examiner palpates the RUQ during deep inspiration). Nausea, vomiting, and mild leukocytosis are common; signs of systemic toxicity suggest emphysematous cholecystitis (gas-forming organisms, often in diabetic patients).

• Acute cholangitis: The classic Charcot's triad (fever, jaundice, right upper quadrant pain) occurs in only 50-70% of cases; the Reynolds' pentad adds hypotension and altered mental status, indicating septic shock and requiring emergent decompression. Pruritus may be prominent from bile salt deposition in skin.

• Chronic cholecystitis: Often asymptomatic; some patients develop postprandial epigastric discomfort. History of recurrent biliary colic is common. Risk of gallbladder malignancy increases with duration of disease, particularly with porcelain gallbladder (calcified gallbladder wall).

• Gallstone ileus: Rare but important; large stone erodes through gallbladder wall into duodenum, causing mechanical small bowel obstruction. Look for Rigler's triad: pneumobilia, bowel obstruction, and ectopic gallstone on imaging. More common in elderly patients.

• Mirizzi syndrome: External compression of the common hepatic duct by a stone impacted in the cystic duct, causing obstructive jaundice without choledocholithiasis; requires careful preoperative imaging to prevent bile duct injury.

• Right upper quadrant ultrasound: The gold standard initial imaging study; sensitivity and specificity >95% for detecting gallstones. Also assesses gallbladder wall thickness (>4 mm suggests cholecystitis), pericholecystic fluid, and bile duct dilatation. Sonographic Murphy's sign (maximal tenderness directly over the gallbladder) supports acute cholecystitis diagnosis.

• Laboratory findings: Elevated alkaline phosphatase and direct hyperbilirubinemia suggest biliary obstruction; elevated transaminases (particularly ALT >AST) may indicate stone-induced hepatitis. Elevated lipase/amylase suggests concurrent pancreatitis. Leukocytosis is common in acute inflammation but absent in uncomplicated cholelithiasis.

• HIDA scan (hepatobiliary scintigraphy): Most sensitive test for cystic duct obstruction; non-visualization of the gallbladder within 4 hours is diagnostic of acute cholecystitis. Less sensitive for common bile duct stones but useful when ultrasound is equivocal or acalculous cholecystitis is suspected.

• CT imaging: Useful for detecting complications including perforation, emphysematous cholecystitis, and assessing for malignancy. Multidetector CT also identifies stones in the common bile duct with reasonable sensitivity, though MRCP is superior.

• MRCP (magnetic resonance cholangiopancreatography): Excellent visualization of the biliary tree without contrast injection; sensitivity >95% for choledocholithiasis. Non-invasive alternative to ERCP when stone removal is not immediately planned. Also evaluates for strictures and masses.

• ERCP (endoscopic retrograde cholangiopancreatography): Both diagnostic and therapeutic; allows sphincterotomy and stone extraction. Indicated for symptomatic choledocholithiasis, acute cholangitis, or pancreatitis with persistent obstruction. Risk of pancreatitis (3-7%) limits its use to therapeutic indications.

• Acute cholecystitis — conservative initial management: NPO status, IV hydration, and broad-spectrum antibiotics covering gram-negatives and anaerobes (piperacillin-tazobactam 4.5 g IV q6-8h, or ceftriaxone 1-2 g IV daily plus metronidazole 500 mg IV q8h). Early laparoscopic cholecystectomy (ideally within 72 hours) is now preferred to delayed surgery, with lower morbidity and recurrence rates. High-risk patients (age >65, diabetes, immunocompromised) benefit from earlier intervention.

• Acute cholangitis — emergency decompression: Immediate ERCP with sphincterotomy is the definitive treatment; antibiotics must be started immediately before imaging (same regimens as above). Percutaneous transhepatic cholangiography (PTC) is reserved for ERCP failure, specifically when endoscopic anatomy prevents access (prior Billroth II, duodenal obstruction). Supportive care with IV fluids and vasopressors for septic shock.

• Asymptomatic cholelithiasis: No intervention is generally recommended; stones remain asymptomatic in 80-90% of patients over 10-15 years. Exceptions include: (1) solitary stone >3 cm (malignancy risk), (2) porcelain gallbladder (calcified wall, ~5% malignancy risk), (3) gallbladder polyps >10 mm, (4) primary sclerosing cholangitis (30% malignancy risk), and (5) Native American women <50 years (high malignancy risk). These patients warrant prophylactic cholecystectomy.

• Biliary pancreatitis: Urgent or early ERCP with sphincterotomy if common bile duct obstruction persists (elevated bilirubin, dilated ducts on imaging). For uncomplicated biliary pancreatitis with normal ducts, cholecystectomy during the same hospitalization prevents recurrent attacks. ERCP is not routinely performed for mild pancreatitis with spontaneous resolution.

Complications of untreated inflammation (mechanism → signal)

• Gangrenous cholecystitis: progressive wall distention exceeds mural perfusion pressure → necrosis. Suspect with high fever, marked leukocytosis, and a paradoxically negative Murphy sign from denervation; ultrasound shows irregular or sloughed mucosa. Surgical emergency.
• Perforation and bile peritonitis: necrosis progresses transmurally, producing pericholecystic abscess (contained) or free perforation with diffuse peritonitis and shock. Emergency laparotomy/cholecystectomy.
• Emphysematous cholecystitis: gas-forming organisms (Clostridium perfringens, E. coli) in a poorly perfused, often diabetic gallbladder; air in the wall or lumen on CT. Very high perforation risk — emergency.
• Cholecystoenteric fistula → gallstone ileus: chronic pressure necrosis erodes into duodenum; a large stone lodges at the ileocecal valve (or the duodenum/pylorus in Bouveret syndrome). Pneumobilia plus obstruction is the tip-off.
• Ascending cholangitis with septic shock: raised intraductal pressure drives bacteremia. Reynolds pentad mandates emergent biliary decompression; the Tokyo Guidelines grade severity by organ dysfunction to set decompression urgency. Hepatic abscesses may follow.
• Secondary biliary cirrhosis and porcelain gallbladder/gallbladder adenocarcinoma: consequences of long-standing obstruction and chronic inflammation.

Complications of treatment

• Post-ERCP pancreatitis: the most common ERCP complication — papillary trauma and ductal hypertension. Signaled by post-procedure epigastric pain with rising lipase; ASGE supports rectal NSAID (indomethacin) prophylaxis and prophylactic pancreatic stenting in high-risk patients. Post-sphincterotomy bleeding, duodenal perforation, and stent-related cholangitis also occur.
• Bile duct injury at laparoscopic cholecystectomy: misidentification of the common duct as the cystic duct; presents days later with jaundice, pain, or biloma/bile leak. SAGES emphasizes the critical view of safety to prevent it.
• Retained CBD stone / post-cholecystectomy syndrome: persistent pain with cholestatic labs — evaluate with MRCP, treat with ERCP.
• Percutaneous cholecystostomy: temporizing drainage in non-operative candidates; tube dislodgement and recurrent cholecystitis after removal are the pitfalls.

• First test is always right upper quadrant ultrasound: for RUQ pain, ACR Appropriateness Criteria place ultrasound first; HIDA scan is the answer only when ultrasound is equivocal and cholecystitis is still suspected (non-visualization of the gallbladder = cystic duct obstruction).
• Charcot triad → antibiotics plus decompression, not surgery: the single best next step in acute cholangitis is broad-spectrum IV antibiotics followed by ERCP with sphincterotomy; cholecystectomy is deferred. Reynolds pentad means emergent decompression regardless of hemodynamics (Tokyo Guidelines 2018).
• Cholecystitis is a surgical disease, cholangitis is an endoscopic one: choosing ERCP for uncomplicated acute cholecystitis is the classic distractor. Early laparoscopic cholecystectomy is preferred.
• Pneumobilia + small bowel obstruction + ectopic stone = Rigler triad of gallstone ileus in an elderly woman; the answer is enterolithotomy, not urgent cholecystectomy.
• Courvoisier sign (palpable, non-tender gallbladder with painless jaundice) points to malignant distal obstruction — pancreatic head cancer or cholangiocarcinoma — not stones, because a chronically scarred stone-bearing gallbladder cannot distend.
• The mimic to keep on the list: a young, sexually active woman with RUQ pain and normal gallbladder imaging may have Fitz-Hugh–Curtis perihepatitis (violin-string adhesions) from chlamydial/gonococcal PID; acute hepatitis and right lower lobe pneumonia are the other stem traps.
• Pregnancy: symptomatic cholelithiasis in pregnancy is managed with laparoscopic cholecystectomy rather than deferral; SAGES supports operating in any trimester when indicated, and ERCP can be performed with abdominal shielding when a duct stone is present.
• Ceftriaxone causes biliary sludge/pseudolithiasis that resolves after stopping the drug — recognize it and avoid recommending cholecystectomy.
• Radiopacity clue: cholesterol stones are usually radiolucent; pigment stones (hemolysis, cirrhosis) are more often visible on plain film.