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📚 Liver Pathology — Important Point Notes (Easy Language)

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1. VIRAL HEPATITIS — Overview

• Definition: Viral infection of liver cells (hepatocytes) → causes cell death (necrosis) + inflammation
• Viruses: A, B, C, D, E — all are RNA viruses EXCEPT HBV (which is DNA)
• Two groups:
  • Hepatitis A & E → "Infectious hepatitis" → spread by fecal-oral route (dirty water/food)
  • Hepatitis B, C & D → "Serum hepatitis" → spread by blood/sexual/parenteral routes
• B, C, D can become chronic → lead to cirrhosis and liver cancer (HCC)

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2. HEPATITIS A VIRUS (HAV)

• Most common viral cause of jaundice
• Virus type: Nonenveloped, 27 nm, RNA virus; replicates in liver; has outer capsid protein (HAVAg)
• Source: Only infected person (excretes virus in feces ~2 weeks before symptoms)
• Most infectious: Just before jaundice appears
• Spread: Fecal-oral (contaminated water/food)
• Incubation: 3–6 weeks

Outcome:

• Mild, self-limiting — always resolves on its own
• Does NOT cause chronic hepatitis or carrier state
• Fulminant hepatitis is very rare

Lab findings:

• Serum bilirubin usually normal early
• AST/ALT rise before jaundice → peak within 1–2 days of jaundice; AST can go above 500 IU/L
• ALP usually < 300 IU/L
• Bilirubinuria + increased urobilinogen in urine

Diagnosis:

• IgM anti-HAV = appears at onset of illness → marker of acute/current infection
• IgG anti-HAV = appears later → marker of past infection / immunity

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3. HEPATITIS B VIRUS (HBV)

• Type: DNA virus, family Hepadnaviridae; spherical, double-layered

Antigens & Genes (the 4 genes):

Transmission:

• Vertical (mother to baby): In uterus, during birth, or soon after
• Horizontal: Most dominant mode
  • Percutaneous/mucous membrane exposure (blood, cuts)
  • IV drug use / blood transfusion
  • Unprotected sex (virus in semen and saliva)

Serological Markers (in order of appearance):

1. HBsAg — first to appear in blood (before symptoms); disappears in 3–6 months in acute infection
2. HBeAg + HBV-DNA — appear soon after HBsAg; indicate active infection and infectivity; if they persist >6 weeks → likely going chronic
3. IgM anti-HBc — appears ~2 weeks after HBsAg; present during the "window period" (when HBsAg has gone but anti-HBs hasn't appeared)
4. Anti-HBs — appears after HBsAg clears → marker of recovery and immunity
5. Anti-HBc (IgG) — stays lifelong; marker of past infection

Window Period:

• HBsAg gone, anti-HBs not yet appeared
• Only IgM anti-HBc is detectable — this is the key diagnostic marker in window period

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4. HEPATITIS C VIRUS (HCV)

• Type: RNA virus
• Spread: Mainly parenteral (needles, transfusion); less often sexual
• Incubation: 7–8 weeks
• Most dangerous — ~80% become chronic (highest chronicity of all hepatitis viruses)
• Chronic HCV → cirrhosis → HCC

Diagnosis:

• Anti-HCV antibody (detected by ELISA)
• HCV RNA (confirms active infection; appears early)

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5. HEPATITIS E VIRUS (HEV)

• Type: Unenveloped RNA virus (Hepevirus genus)
• Age group: Mainly young to middle-aged adults
• Source: Zoonotic — animal reservoirs (pigs, monkeys, cats, dogs); virus shed in stool
• Spread: Fecal-oral; water-borne
• Incubation: ~6 weeks

Outcome:

• Self-limiting acute hepatitis
• Does NOT cause chronic liver disease
• ⚠️ High mortality (~20%) in pregnant women — this is the most important clinical point

Diagnosis:

• Before illness: HEV RNA and virions in stool/serum
• After illness: AST/ALT rise + IgM anti-HEV rises
• After recovery: IgM replaced by IgG anti-HEV (persists)

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6. HEPATITIS D VIRUS (HDV)

• Type: Defective RNA virus — cannot replicate alone; needs HBV
• HDV infection = always accompanies HBV infection
• Two patterns:
  • Co-infection: HBV + HDV together at same time → usually self-limiting, 5% become chronic
  • Superinfection: HDV infects a person already chronically carrying HBV → ~70% become chronic → worse outcome

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7. QUICK COMPARISON TABLE (Hepatitis Viruses)

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8. ALCOHOLIC LIVER DISEASE (ALD)

• Cause: Chronic, excessive alcohol (ethanol) use
• Three overlapping stages:
  1. Hepatic steatosis (fatty liver) — earliest
  2. Alcoholic hepatitis — inflammatory
  3. Alcoholic cirrhosis — end-stage

Ethanol Metabolism (how alcohol damages liver):

1. Alcohol dehydrogenase (ADH) — main enzyme; in cytoplasm; works at low alcohol levels
2. Cytochrome P450 2E1 (CYP2E1) — in microsomes; works at high alcohol levels; generates free radicals (reactive oxygen species) → oxidative damage
3. Catalase — in peroxisomes; least important

How alcohol damages the liver (mechanisms):

1. Acetaldehyde toxicity — damages membranes and proteins; forms adducts (MAA) that trigger autoimmune response
2. Oxidative stress — CYP2E1 generates free radicals → membrane/protein damage
3. Inflammation — alcohol damages intestinal cells → endotoxins released → cytokines (TNF-α, IL-1, IL-6, TGF-β) → hepatocyte apoptosis/necrosis
4. Hypoxia — chronic alcohol increases liver oxygen demand → hypoxia in zone 3 (centrilobular) → cell death

Risk Factors for ALD:

1. Gender — females more susceptible (develop advanced disease with less alcohol); estrogen increases gut permeability → more endotoxins
2. Drinking pattern — 60–80 gm ethanol/day for 10+ years → likely cirrhosis
3. Malnutrition — protein/vitamin deficiency worsens liver damage
4. Infections — intercurrent bacterial infections common in cirrhosis

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9. MORPHOLOGY OF ALCOHOLIC LIVER DISEASE

A. Hepatic Steatosis (Fatty Liver)

• Gross: Enlarged, soft, yellow, greasy liver (can weigh 4–6 kg)
• Microscopy:
  • Microvesicular steatosis — small fat droplets in cytoplasm; initial change; affects centrilobular region
  • Macrovesicular steatosis — with continued drinking; large fat vacuole pushes nucleus to cell periphery
  • Usually no inflammation or fibrosis at this stage (reversible if alcohol stopped)

B. Alcoholic Hepatitis

• Hepatocyte necrosis — especially in centrilobular zone
• Mallory bodies (Mallory-Denk bodies) — clumps of damaged keratin filaments inside hepatocytes (hallmark of alcoholic hepatitis)
• Neutrophil infiltration around damaged cells
• Fatty change still present
• Steatofibrosis — fibrosis begins around central veins → spreads outward → "chicken wire fence" pattern

C. Alcoholic Cirrhosis (Laennec's Cirrhosis / Portal Cirrhosis)

• Chronic, irreversible, end-stage
• Early: Liver enlarged, yellow-tan, fatty, >2 kg
• Late: Liver brown, shrunken, firm, non-fatty — micronodular "hobnail" surface (nodules <3 mm)
• Over time nodules coalesce → mixed micro/macronodular pattern
• Microscopy:
  • Loss of normal architecture
  • Regenerating nodules
  • Diffuse fibrosis
  • Vascular reorganization

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10. LIVER CIRRHOSIS (General)

• One of the top 10 causes of death in the Western world
• Definition: Irreversible end-stage liver disease with 3 features:
  1. Involves entire liver
  2. Normal lobular architecture disorganized
  3. Nodules separated by irregular bands of fibrosis

Classification:

• Micronodular (nodules <3 mm)
• Macronodular (nodules >3 mm)
• Mixed

1. Alcoholic cirrhosis — most common (60–70%)
2. Post-necrotic cirrhosis (10%)
3. Biliary cirrhosis (5–10%)
4. Pigment cirrhosis — hemochromatosis (5%)
5. Wilson's disease
6. Alpha-1 antitrypsin deficiency
7. Cardiac cirrhosis
8. Indian childhood cirrhosis (ICC)
9. Autoimmune hepatitis
10. Non-alcoholic steatohepatitis (NASH)
11. Cryptogenic cirrhosis

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11. HEPATOCELLULAR CARCINOMA (HCC)

• Primary liver cancer arising from hepatocytes
• Hallmark: Bile production by tumor cells

Risk Factors / Genetic Alterations:

• Chronic HBV/HCV → cirrhosis → HCC
• HBV genome integrates into host DNA → inactivates tumor suppressor genes (e.g., TP53)
• KRAS mutations → oncogene activation
• c-MYC amplification (epigenetic)
• Telomerase activation → cells become immortal
• Alpha-1 antitrypsin deficiency

Gross Patterns (3 types):

1. Unifocal — single large mass in one part of liver
2. Multifocal — multiple nodules of varying sizes, widely scattered
3. Diffusely infiltrative — entire or large part of liver diffusely infiltrated

• Color: Light brown / yellowish-white / gray
• Bile production → greenish-brown discoloration

Microscopy (graded):

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12. PORTAL HYPERTENSION

• Increased pressure in the portal vein system
• Main cause: Cirrhosis

Consequences (4 major):

1. Ascites — fluid in peritoneal cavity
2. Portosystemic venous shunts — varices
3. Congestive splenomegaly
4. Hepatic encephalopathy

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13. ASCITES

• Abnormal accumulation of fluid in the peritoneal cavity
• 85% of cases caused by portal hypertension from cirrhosis

Pathogenesis (simplified):

• Cirrhosis → portal hypertension → splanchnic vasodilation (nitric oxide mediated)
• Low plasma albumin → low osmotic pressure → fluid leaks out
• Underfilling of circulation → activates renin-angiotensin-aldosterone system (RAAS)
• Kidneys retain Na⁺ and water → worsens fluid accumulation
• Lymph formation exceeds lymph return → fluid accumulates in peritoneum

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14. VARICES AND VARICEAL HEMORRHAGE

• Complication of portal hypertension
• Increased portal resistance → blood flow reversed → collateral vessels dilate → varices form
• Most dangerous: Esophageal varices (can rupture and cause massive, fatal bleeding)
• Mechanism: Portal vein → left gastric vein → esophageal veins → rupture

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15. SPLENOMEGALY AND HYPERSPLENISM

• Long-standing portal hypertension → congestion of spleen → congestive splenomegaly
• Enlarged spleen destroys blood cells → hypersplenism → anemia, low platelets, low WBCs

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🔑 Key Summary Points to Remember