Liver
Anatomy, liver failure/portal hypertension, abscesses, benign vs malignant tumors, and transplant scoring for the Surgery Shelf.
Sources: extracted/STEP2CK-Surgery.md (Liver); First Aid 2026 (first-aid-usmle-bible).
High-Yield Points
- Blood supply: portal vein = 75% of flow (forms behind the pancreatic neck from splenic + SMV; no valves); hepatic artery = 25% but supplies most tumors. Pringle maneuver (clamp porta hepatis) controls arterial/portal — but not hepatic vein bleeding.
- Cantlie's line (gallbladder fossa → IVC) divides right/left lobes; caudate (segment I) drains directly to the IVC. Up to 75% of a normal liver can be resected. Factor VIII and vWF are NOT made in the liver.
- Cirrhosis/liver failure: best synthetic-function marker = PT/INR (factor VII shortest half-life). Acute (fulminant) failure → death from cerebral edema/intracranial hypertension (ammonia → astrocyte glutamine → swelling). Encephalopathy: lactulose (titrate to 2–3 stools/day) ± rifaximin/neomycin, limit protein.
- Ascites: water/salt restriction → diuretics (spironolactone + furosemide) → large-volume paracentesis (replace albumin 1 g/100 mL removed) → TIPS (only if good liver function; worsens encephalopathy). Hepatorenal syndrome = normal kidneys, poorly perfused; volume challenge fails → midodrine + octreotide, definitive = transplant.
- SBP: ascitic PMN >250, #1 E. coli, mono-microbial → cefotaxime + IV albumin.
- Variceal bleeding: ABCs → octreotide/vasopressin + prophylactic antibiotics + endoscopic band ligation; refractory → balloon tamponade → TIPS (best bridge to transplant). β-blockers + banding prevent, don't treat acutely.
- HCC: hepatitis B = #1 cause worldwide; AFP correlates with tumor size; screen cirrhotics with ultrasound q6 months. Assess reserve before resection with indocyanine green clearance + Child-Pugh (>15% retention at 15 min = abnormal); portal vein embolization hypertrophies the future remnant. Fibrolamellar variant: young, no cirrhosis, normal AFP, central scar that does NOT enhance (vs FNH scar which does).
- Metastases: liver:primary = 20:1; isolated colorectal liver mets → resect (best survival); intraoperative US = gold standard for localization. Mets are hypovascular; primaries are hypervascular. Known colorectal primary + typical lesion → diagnose by CT, no biopsy needed.
- Benign tumors: adenoma (OCP, "cold" on sulfur colloid, bleeds/malignant → resect if >5 cm, symptomatic, or male); FNH (central stellate scar enhances, "hot," observe); hemangioma (most common benign, do NOT biopsy → bleeding; observe, enucleate if symptomatic).
- Child-Pugh (Bilirubin, Albumin, INR, Ascites, Encephalopathy): A ~10% / B ~30% / C ~80% perioperative mortality (C = absolute contraindication to elective surgery). MELD (INR, creatinine, total bilirubin ± Na⁺) = objective; >15 to list for transplant.
Key Tables / Differentials
Benign liver lesions
| Adenoma | FNH | Hemangioma | |
|---|---|---|---|
| Association | OCPs, anabolic steroids | Idiopathic vascular | Most common benign; women 30–50 |
| Sulfur colloid | Cold (no Kupffer cells) | Hot (Kupffer cells) | — |
| Central scar | No | Yes, enhances | No (peripheral nodular → centripetal fill) |
| Risk | Rupture + malignancy | None | Rupture rare; no biopsy |
| Treatment | Resect if >5 cm/symptomatic/male | Observe | Observe; enucleate if symptomatic |
Liver abscess
| Amebic | Pyogenic | Hydatid (Echinococcus) | |
|---|---|---|---|
| Cause | Entamoeba histolytica (travel) | #1 E. coli/Klebsiella (post-cholangitis) | E. granulosus (sheep/dogs) |
| Number | Usually single | Often multiple | Cyst + daughter cysts |
| Clue | "Anchovy paste," + serology | Abnormal LFTs, diabetic | + serology, Casoni; calcified wall |
| Treatment | Metronidazole (aspirate only if fails) | IV antibiotics + drainage | Pericystectomy + albendazole, no spillage (anaphylaxis) |
Board Pearls
- Isolated gastric varices without esophageal varices = splenic vein thrombosis (MCC chronic pancreatitis) → splenectomy if symptomatic.
- Esophageal varices + splenomegaly, normal liver function = portal vein thrombosis.
- Postsinusoidal obstruction (hepatic vein thrombosis) + caudate hypertrophy = Budd–Chiari (myeloproliferative/hypercoagulable).
- Most common primary liver malignancy in children = hepatoblastoma (↑AFP, ± precocious puberty).
- Cirrhotic + umbilical hernia → treat the ascites first, then repair.
Classic Vignette Triggers
- "Chronic HBV/cirrhosis, RUQ mass, high AFP" → hepatocellular carcinoma.
- "24-year-old, no cirrhosis, normal AFP, liver mass with central scar" → fibrolamellar carcinoma.
- "Traveler, single right-lobe cyst, 'anchovy paste'" → amebic abscess → metronidazole.
- "Sheep farmer, cyst with daughter cysts" → hydatid → pericystectomy + albendazole, avoid spillage.
- "Young woman on OCPs, liver mass, bleeds" → hepatic adenoma → stop OCPs, resect.
- "Cirrhotic, hematemesis, bleeding despite banding + octreotide" → TIPS as bridge to transplant.