14.3 Liver, Biliary Tree & Pancreas
Key Takeaways
- Unconjugated hyperbilirubinemia reflects hemolysis or impaired conjugation (Gilbert, Crigler–Najjar); conjugated hyperbilirubinemia reflects hepatocellular excretion defects or obstruction (Dubin–Johnson, Rotor, cholestasis, stones, stricture).
- Hepatitis serologies: HAV IgM = acute; HBV—HBsAg marks infection, anti-HBc IgM acute, anti-HBs immunity; HBeAg/HBV DNA track replication; HCV Ab + RNA confirm; HEV fecal–oral, severe in pregnancy.
- Alcoholic hepatitis classically AST:ALT ≥2:1; NAFLD/NASH is metabolic; cirrhosis yields portal hypertension sequelae (varices, ascites, splenomegaly, encephalopathy, hepatorenal patterns).
- Hemochromatosis (Fe, HFE), Wilson (Cu, ATP7B, low ceruloplasmin), α1-antitrypsin (PAS+ globules, PiZZ) are high-yield metabolic liver diseases; PBC (anti-mitochondrial, middle-aged women) vs PSC (p-ANCA, IBD/UC, onion-skin bile ducts, beading).
- Gallstones: cholesterol (most common) vs pigment; ascending cholangitis = Charcot triad/Reynolds pentad with choledocholithiasis/obstruction; acute pancreatitis from gallstones, alcohol, hyperTG; pancreatic adenocarcinoma associates with smoking, chronic pancreatitis, and painless jaundice when head lesions obstruct bile duct.
14.3 Liver, Biliary Tree & Pancreas
Quick Answer: Split bilirubin into unconjugated vs conjugated pathways. Read hepatitis panels as timelines of antigens/antibodies. Alcohol vs metabolic steatohepatitis both can progress to cirrhosis and portal hypertension. Memorize hemochromatosis, Wilson, α1-AT, PBC vs PSC. Stones + obstruction → cholangitis/pancreatitis; pancreatic head cancers present with painless jaundice.
This section is dense with classic Step-style tables. Anchor every lab pattern to a cellular step: uptake, conjugation, excretion, canalicular flow, or duct patency.
Bilirubin Metabolism
Senescent RBC hemoglobin → heme oxygenase → biliverdin → biliverdin reductase → unconjugated bilirubin (insoluble, albumin-bound). Hepatocyte uptake → UGT1A1 conjugation with glucuronic acid → conjugated (direct) bilirubin excreted into bile canaliculi (MRP2 and related transporters). Gut bacteria convert bilirubin to urobilinogens; some reabsorbed (enterohepatic); stercobilin colors stool; urobilin colors urine.
Unconjugated hyperbilirubinemia: hemolysis/hematoma resorption (↑ production), impaired uptake, or decreased conjugation—Gilbert (mild UGT1A1 ↓, fasting/stress unmasks), Crigler–Najjar (severe UGT deficiency; type I near-absent, kernicterus risk). No bilirubinuria (unconjugated not water-soluble).
Conjugated hyperbilirubinemia: hepatocellular disease impairing excretion, Dubin–Johnson (MRP2 defect; black liver), Rotor (storage/uptake related; no black liver), extrahepatic obstruction (stone, stricture, pancreatic head mass), intrahepatic cholestasis. Dark urine (conjugated bilirubinuria), clay-colored stools if complete biliary obstruction (no stercobilin).
| Pattern | Mechanism examples | Urine bilirubin | Stool color notes |
|---|---|---|---|
| ↑ Unconjugated | Hemolysis, Gilbert, Crigler–Najjar | Negative | Normal unless severe illness |
| ↑ Conjugated (hepatic) | Viral hepatitis, Dubin–Johnson | Positive | Variable |
| ↑ Conjugated (obstructive) | CBD stone, PSC stricture, pancreatic head ca | Positive | Pale if complete block |
Viral Hepatitis A–E Serologies
HAV: fecal–oral; acute only (no chronic); IgM anti-HAV = acute; IgG = past/vaccination immunity.
HBV: DNA virus; parenteral/sexual/perinatal. Key markers:
- HBsAg: current infection (acute or chronic)
- Anti-HBs: recovery or vaccination immunity
- Anti-HBc IgM: acute/window; total anti-HBc: exposed (not from vaccine alone)
- HBeAg / HBV DNA: high replication and infectivity; anti-HBe often lower replication
- Window period: HBsAg gone, anti-HBs not yet up → anti-HBc IgM diagnoses acute infection Chronic HBV: HBsAg >6 months; risk cirrhosis/HCC (integration/inflammation).
HCV: RNA virus; blood-borne; high chronicity; anti-HCV indicates exposure; HCV RNA confirms active infection; major cirrhosis/HCC risk; no classic vaccine.
HDV: defective RNA virus needing HBsAg coat; coinfection or superinfection worsens course.
HEV: fecal–oral; epidemic waterborne; usually acute; high mortality in pregnancy (third trimester classic).
| Virus | Route | Chronic? | Signature test pearl |
|---|---|---|---|
| HAV | Fecal–oral | No | IgM anti-HAV acute |
| HBV | Blood/sex/perinatal | Yes | HBsAg; anti-HBc IgM window |
| HCV | Blood | Yes (common) | RNA confirms activity |
| HDV | With HBV | Yes | Needs HBsAg |
| HEV | Fecal–oral | Rare (immunocomp.) | Severe in pregnancy |
Steatohepatitis, Cirrhosis, Portal Hypertension
Alcoholic liver disease spectrum: steatosis → alcoholic hepatitis → cirrhosis. Alcoholic hepatitis: neutrophil infiltrates, Mallory–Denk bodies, ballooning; AST:ALT ratio often ≥2:1 (mitochondrial AST, ALT synthesis limit). NAFLD/NASH: metabolic syndrome (obesity, insulin resistance, T2DM, dyslipidemia); histology can mirror alcohol (steatosis, ballooning, Mallory bodies, fibrosis) without significant alcohol—clinical history separates.
Cirrhosis is diffuse fibrosis + regenerative nodules destroying architecture. Portal hypertension (↑ resistance in sinusoids + splanchnic vasodilation/hyperdynamic circulation) yields:
- Esophageal/gastric varices, portal gastropathy
- Ascites (underfill + overflow + hypoalbuminemia + Na retention)
- Splenomegaly → sequestration thrombocytopenia
- Portosystemic shunting → hepatic encephalopathy (ammonia and other toxins; asterixis)
- Caput medusae, hemorrhoids (collaterals)
- Hepatorenal physiology conceptually (splanchnic vasodilation → renal vasoconstriction) Failure of synthetic function: ↓ albumin, ↑ PT/INR; detox failure; estrogen excess signs (palmar erythema, spider angiomas, gynecomastia) in chronic liver disease.
Metabolic and Cholestatic Liver Diseases
Hereditary hemochromatosis: HFE mutations (C282Y classic) → low hepcidin → uncontrolled Fe absorption → parenchymal iron overload (liver, pancreas “bronze diabetes,” heart, joints, pituitary). Prussian blue iron; risk HCC; treat with phlebotomy conceptually.
Wilson disease: ATP7B copper ATPase defect → failed copper incorporation into ceruloplasmin and biliary copper excretion → hepatic injury, neuropsychiatric disease, Kayser–Fleischer rings, low ceruloplasmin, high hepatic copper, low alkaline phosphatase relative in acute liver failure patterns sometimes tested.
α1-Antitrypsin deficiency: PiZZ misfolded AAT retained in ER → PAS-positive diastase-resistant globules in hepatocytes + lung emphysema (loss of antiprotease in serum). Liver disease from retention; lung from lack of circulating AAT.
Primary biliary cholangitis (PBC): middle-aged women; autoimmune destruction of intrahepatic interlobular bile ducts; anti-mitochondrial antibodies (AMA); fatigue, pruritus, cholestatic enzymes (↑ALP/GGT); florid duct lesions; can progress to cirrhosis; associated with other autoimmunity (Sicca, thyroid).
Primary sclerosing cholangitis (PSC): fibro-obliterative inflammation of intra- and extrahepatic bile ducts; “onion-skin” fibrosis; multifocal strictures/beading on cholangiography; strong UC/IBD link; p-ANCA often positive; ↑ risk cholangiocarcinoma; men more than PBC demographic.
| Feature | PBC | PSC |
|---|---|---|
| Demographic | Middle-aged women | Men, IBD (UC) |
| Antibody | AMA | p-ANCA (nonspecific) |
| Ducts | Intrahepatic small ducts | Intra- and extrahepatic |
| Imaging | Often normal large ducts | Beading/strictures |
| Cancer risk | HCC if cirrhotic | Cholangiocarcinoma |
Gallstones, Cholangitis, Pancreatitis, Pancreatic Cancer
Cholesterol stones (most common in US): supersaturated cholesterol bile, female, forty, fertile, fat, rapid weight loss, Native American ancestry pearls. Black pigment stones: unconjugated bilirubin (hemolysis, cirrhosis). Brown pigment stones: infection/parasites, bile duct stasis, Asian ascending cholangitis associations.
Complications of cholelithiasis: biliary colic, acute cholecystitis (cystic duct obstruction, often secondary infection), choledocholithiasis, gallstone pancreatitis, gallstone ileus (fistula, Rigler triad conceptually).
Ascending cholangitis: biliary obstruction + infection (E. coli, Klebsiella, Enterococcus); Charcot triad (RUQ pain, jaundice, fever); Reynolds pentad adds hypotension and mental status change (severe). Life-threatening; needs biliary decompression conceptually.
Acute pancreatitis: premature zymogen activation and autodigestion; gallstones (ampullary obstruction) and alcohol lead causes; also hypertriglyceridemia (often >1000 mg/dL), hypercalcemia, drugs, trauma (seatbelt/ERCP), mumps, scorpion in lore. Clinical: epigastric pain to back, ↑ amylase/lipase; complications necrosis, infection, pseudocyst, ARDS, hypocalcemia (soap formation). Chronic pancreatitis: recurrent injury, fibrosis, calcifications, malabsorption (fat), diabetes (islet loss); alcohol dominant in many regions; CF in children.
Pancreatic adenocarcinoma: ductal origin; head > body/tail; smoking strongest modifiable risk; chronic pancreatitis, diabetes, age. Head tumors → painless obstructive jaundice, pale stools, dark urine, Courvoisier gallbladder (painless palpable GB), migratory thrombophlebitis (Trousseau). Body/tail present later with pain/weight loss. Tumor markers (CA19-9) clinical adjunct, not primary CBSE mechanism.
Integrate: conjugated bilirubin + dilated ducts → obstruction until proven otherwise; unconjugated + anemia → hemolysis; AST:ALT 2:1 + history → alcohol; AMA woman → PBC; IBD + beading → PSC; epigastric pain through to back after heavy meal/alcohol → pancreatitis until labs say otherwise.
A patient’s labs show elevated conjugated bilirubin, bilirubinuria, and pale stools. Which mechanism best fits?
Which serologic pattern indicates acute HBV infection in the window period when HBsAg has cleared but anti-HBs is not yet detectable?
A middle-aged woman with pruritus, elevated ALP, and anti-mitochondrial antibodies most likely has which duct-centered disease?