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Hepatitis - A Comprehensive Overview

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1. Etiology and Classification

Viral Hepatitis (most common)

Non-viral Causes

• Toxic/Drug-induced: acetaminophen overdose (treat with N-acetylcysteine immediately), isoniazid, alternative supplements
• Alcoholic hepatitis: direct toxicity plus metabolic damage
• Autoimmune hepatitis: immune-mediated hepatocyte destruction
• Metabolic: non-alcoholic fatty liver disease (NAFLD/MASH), Wilson's disease, hemochromatosis

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2. Clinical Presentation (General)

• Low-grade fever, fatigue, lethargy
• Anorexia, nausea, vomiting, diarrhea
• Right upper quadrant (RUQ) pain
• Arthralgias and myalgias
• Dark urine and jaundice (in more severe cases)

• Mental status changes (hepatic encephalopathy)
• Asterixis (liver flap)
• Ascites
• Prolonged prothrombin time (PT)

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3. Hepatitis A (HAV)

• Acute: IgM anti-HAV antibody (positive in acute infection)
• Past infection/immunity: IgG anti-HAV antibody

• Formalin-inactivated HAV vaccine (licensed in the US in 1995) - recommended for all children over 1 year, international travelers, men who have sex with men, and drug users
• Post-exposure: immune globulin (IG) within 1-2 weeks of exposure provides ~90% passive protection
• Hygiene: handwashing, 0.5% sodium hypochlorite disinfectant
• HAV vaccine produces more enduring immunity and should replace IG use. - Jawetz Medical Microbiology, 28e

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4. Hepatitis B (HBV)

• HBV vertical transmission accounts for approximately 50% of chronic infections worldwide
• Risk of chronic infection after neonatal exposure (without prophylaxis): 85-95%
• Women seropositive for both HBsAg AND HBeAg have ~90% vertical transmission rate without neonatal prophylaxis
• In the US, universal vaccination programs have significantly reduced transmission

• Most adults clear the infection spontaneously (~90% of immunocompetent adults)
• Risk of chronicity is inversely related to age at infection: neonates 85-95%, children 25-50%, adults ~5%
• Chronic infection can progress to cirrhosis, hepatocellular carcinoma (HCC)

• Nucleos(t)ide analogues (NAs): entecavir, tenofovir disoproxil fumarate (TDF), tenofovir alafenamide (TAF) - first-line
• Pegylated interferon-alfa (PEG-IFN-α): finite 48-week course; limited by side effects
• The 2025 AGA guideline also provides updated protocols for prevention of HBV reactivation in at-risk individuals (PMID: 39863345)
• A 2025 systematic review (PMID: 40528088) shows new antiviral regimens are achieving functional cure (HBsAg loss) in a subset of patients

• Recombinant HBV vaccine is universally recommended for all infants; part of routine immunization schedule
• Post-exposure prophylaxis: Hepatitis B immunoglobulin (HBIG) + vaccine series (for unvaccinated individuals)
• Screen all pregnant women for HBsAg at the start of prenatal care

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5. Hepatitis C (HCV)

• Most acute infections (~80%) are asymptomatic
• ~55-85% progress to chronic infection (compared to ~5% for HBV in adults)
• Chronic infection can lead to cirrhosis over 20-30 years, and HCC

• Screening: Anti-HCV antibody (ELISA)
• Confirmation: HCV RNA by PCR (most sensitive, detectable soon after infection; also used in chronic disease)
• Due to delayed antibody appearance, early diagnosis depends on history and excluding other causes

• Direct-acting antivirals (DAAs): highly effective (>95% sustained virologic response / SVR)
  • Sofosbuvir-based regimens, glecaprevir/pibrentasvir, ledipasvir/sofosbuvir
  • Treatment duration: 8-12 weeks typically
• No vaccine currently available for HCV
• Immunoglobulin and post-exposure prophylaxis are not effective; occupational health follow-up for baseline and follow-up testing is recommended

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6. Hepatitis D (HDV) - Delta Hepatitis

• HDV is only found in HBV-infected persons
• Uses host cell RNA polymerase (not its own) to replicate in the nucleus - unique for an RNA virus
• Transmission: same routes as HBV (parenteral, sexual)
• Greatest risk: injection drug users who are HBV-positive

1. Co-infection: HDV + HBV acute infection simultaneously - usually self-limiting but can cause fulminant hepatitis
2. Superinfection: HDV infects a chronic HBV carrier - higher risk of severe/fulminant hepatitis and worse prognosis

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7. Hepatitis E (HEV)

• Generally self-limiting
• Exception: pregnant women - HEV carries a disproportionately high mortality rate (up to 25%) in pregnant women, especially in the third trimester. This makes HEV uniquely dangerous in pregnancy.
• No progression to chronic hepatitis in immunocompetent patients (except HEV genotype 3/4 in immunosuppressed individuals)

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8. Comparative Summary Table

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9. Laboratory Findings

• Serum transaminases (AST, ALT) - greatly elevated (ALT typically > AST in viral hepatitis)
• Serum bilirubin - elevated
• Alkaline phosphatase (ALP) - elevated
• PT/INR - prolonged in severe disease (marker of synthetic function loss)

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10. Hepatitis in Pregnancy

• Hepatitis B vertical transmission responsible for ~50% of chronic infections worldwide
• Risk of chronic HBV if acquired perinatally: 85-95% with 25-30% lifetime risk of serious liver disease
• HBsAg is measured at the start of every prenatal visit
• Indications for antiviral therapy in pregnancy are the same as in non-pregnant patients
• Women with high viral load (HBV DNA >200,000 IU/mL) in the third trimester should receive antiviral prophylaxis (tenofovir) to reduce vertical transmission

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11. Imaging

• Acute hepatitis: liver enlargement, diffuse decrease in parenchymal echogenicity, echogenic portal triads ("starry sky" pattern - though nonspecific)
• Chronic hepatitis: may show coarsened echotexture, increased parenchymal echogenicity, periportal lymphadenopathy
• Gallbladder wall thickening can be present in acute hepatitis
• Yamada's Textbook of Gastroenterology notes that chronic hepatitis can appear completely normal on ultrasound in many cases

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12. Recent Evidence Updates (2025)

• A 2025 systematic review and meta-analysis (PMID: 40528088) found that new antiviral regimens including combined NA + PEG-IFN, or novel capsid assembly modulators, are achieving functional cure (HBsAg clearance) in a meaningful subset of chronic HBV patients - a development not possible with older standard-of-care monotherapy.
• A 2025 AGA clinical practice guideline (PMID: 39863345) provides updated recommendations on preventing HBV reactivation in at-risk individuals (those on immunosuppressive therapy, biologics, chemotherapy).
• A 2025 systematic review (PMID: 39874480) on corticosteroids in alcohol-associated hepatitis found that the evidence for steroid benefit remains uncertain - cautioning against routine use in severe alcoholic hepatitis.

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HEPATITIS - Complete Clinical Reference

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1. DEFINITION

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2. TYPES

A. By Duration

B. By Etiology

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3. CAUSES (Detailed)

Infectious

• HAV: RNA enteroviral picornavirus. Spread by fecal-oral route through contaminated food/water. Sporadic or epidemic (restaurants, shellfish). Incubation 15-45 days.
• HBV: Small partially double-stranded DNA virus (Hepadnaviridae). Transmitted parenterally (blood, needlestick), sexually, and vertically (mother-to-child). Incubation 45-180 days.
• HCV: Single-stranded (+) RNA virus (Flaviviridae), 6 genotypes. Primarily parenteral (IVDU, pre-1992 transfusions). Incubation 14-180 days. ~80% asymptomatic acutely.
• HDV (Delta hepatitis): Small icosahedral (-) ssRNA circular virus (Deltaviridae). Requires HBsAg for its lipid envelope - only infects HBV carriers. Parenteral/sexual. Greatest risk in IV drug users.
• HEV: Non-enveloped (+) ssRNA (Hepeviridae). Fecal-oral, contaminated water, endemic in developing countries. Uniquely severe in pregnancy (up to 25% mortality in third trimester).
• Other viruses: EBV (mononucleosis), CMV, HSV, adenovirus, coxsackievirus, COVID-19

Toxic/Drug-Induced

• Acetaminophen overdose - dose-dependent direct hepatotoxin (most common cause of acute liver failure in the West)
• Alcohol - direct hepatotoxicity + metabolic disruption
• Isoniazid, rifampicin, pyrazinamide (anti-TB)
• Statins, valproate, amiodarone, methotrexate
• Herbal supplements (e.g., kava, comfrey)
• Amanita phalloides mushroom poisoning
• Carbon tetrachloride (occupational exposure)

Autoimmune

• Type 1: ANA + anti-smooth muscle antibody (SMA) - predominantly young women
• Type 2: Anti-LKM1 (liver-kidney microsome) antibody - children, Mediterranean populations

Metabolic

• NAFLD/NASH: Fatty change progressing to steatohepatitis
• Wilson's disease: Copper accumulation - "the great imitator"
• Alpha-1 antitrypsin deficiency
• Hemochromatosis

Ischemic / Vascular

• Shock liver (ischemic hepatitis): Massive AST/ALT elevation (>20x ULN) with rapid normalization after hemodynamic restoration; bilirubin paradoxically only mildly elevated

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4. CLINICAL FEATURES, SIGNS AND SYMPTOMS

Prodromal Phase (1-2 weeks before jaundice)

• Fatigue, malaise, lethargy
• Anorexia, nausea, vomiting
• Low-grade fever
• Arthralgias and myalgias
• Right upper quadrant (RUQ) discomfort
• Headache, photophobia (rare)

Icteric Phase (jaundice appears)

• Jaundice (scleral icterus first, then skin) - lasts 2-12 weeks
• Dark urine (bilirubinuria - conjugated bilirubin spills into urine)
• Pale/clay-coloured stools (reduced bilirubin reaching gut)
• Pruritus (bile salt deposition in skin)
• Hepatomegaly, liver tenderness on palpation
• Splenomegaly (~25% of cases)
• Resolution phase: Symptoms improve before liver enzymes normalize

Signs of Severe/Chronic Disease

• Hepatic encephalopathy: confusion, asterixis (liver flap), somnolence
• Ascites (portal hypertension, hypoalbuminaemia)
• Spider angiomata, palmar erythema (oestrogen excess in chronic disease)
• Caput medusae (dilated periumbilical veins)
• Splenomegaly with thrombocytopenia (hypersplenism)
• Coagulopathy (prolonged PT/INR)
• Gynecomastia (chronic liver disease)
• Dupuytren's contracture (alcoholic liver disease)

Extrahepatic Manifestations (especially HCV)

• Cryoglobulinemia: purpura, arthralgias, Raynaud phenomenon, peripheral neuropathy
• Membranoproliferative glomerulonephritis / cryoglobulinemic nephropathy
• Sicca syndrome, vasculitis
• HBV: polyarteritis nodosa, membranous nephropathy, serum sickness-like prodrome

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5. INVESTIGATIONS - WITH EXPECTED FINDINGS AND RATIONALE

A. Liver Function Tests (LFTs)

Key Pattern in Acute Hepatitis: ALT and AST markedly elevated (8-50×), ALP mildly elevated (<3×), bilirubin variable. Enzyme elevations peak before peak bilirubin. ALT typically remains elevated longer than AST due to its longer half-life. - Tietz Textbook of Laboratory Medicine, 7e

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B. Serological Markers (to identify the specific cause)

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C. Additional Investigations

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6. PATHOPHYSIOLOGY

Viral Hepatitis (Immune-Mediated Mechanism - HBV Model)

1. Viral entry: HBV enters hepatocytes via sodium-taurocholate cotransporting polypeptide (NTCP) receptor using HBsAg
2. Viral replication: HBV DNA replicates in the nucleus; viral proteins (HBsAg, HBcAg, HBeAg) are expressed on the hepatocyte surface
3. Immune recognition: CD8+ cytotoxic T lymphocytes (CTLs) recognize viral antigens on MHC class I molecules on hepatocyte surface
4. Hepatocyte destruction: CTLs attack infected hepatocytes causing necrosis and apoptosis (the primary mechanism of liver damage)
5. Innate immune response: NK cells, interferon release also contribute
6. Wound-healing response: Repeated hepatocyte injury triggers activation of hepatic stellate cells (Ito cells) → collagen deposition → fibrosis
7. Chronic inflammation → progressive fibrosis → cirrhosis → portal hypertension + risk of hepatocellular carcinoma (HCC)

Phases of Chronic HBV (Immune Staging):

HAV / HEV Pathophysiology (Direct Injury)

• These enteric viruses have some degree of direct cytopathic effect in addition to immune-mediated damage
• Inflammation is generally self-limiting as virus is cleared; no chronic state

Alcoholic Hepatitis

• Alcohol metabolism produces acetaldehyde and ROS (reactive oxygen species) → direct hepatocyte membrane damage
• Lipid peroxidation → steatosis
• Gut dysbiosis + increased gut permeability → endotoxin (LPS) enters portal circulation → activates Kupffer cells → pro-inflammatory cytokine release (TNF-α, IL-1β, IL-6, IL-8)
• Mallory-Denk bodies (abnormal intermediate filament aggregates) form in hepatocytes
• Histology: steatosis, lobular neutrophilic infiltration, hepatocyte ballooning, Mallory-Denk bodies, pericellular fibrosis
• AST predominates over ALT (>2:1 ratio) because: alcohol depletes pyridoxal phosphate (ALT requires more of it than AST), and alcohol-damaged mitochondria release mitochondrial AST

Drug-Induced Hepatitis

• Type 1 - Direct/dose-dependent (e.g. acetaminophen): overdose depletes glutathione stores → N-acetyl-p-benzoquinone imine (NAPQI) accumulates → oxidative hepatocyte destruction → Zone 3 centrilobular necrosis (highest CYP2E1 activity)
• Type 2 - Idiosyncratic: unpredictable, immune-mediated, dose-independent (e.g. isoniazid, halothane); mimics viral hepatitis

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7. DIAGNOSTIC CRITERIA

A. Acute Viral Hepatitis (General)

• ALT/AST >8-50× ULN (sensitivity >90% if ALT >300 or AST >200)
• ALP <3× ULN (distinguishes from cholestatic disease)
• Positive specific serology (see above)

B. Chronic Hepatitis

• Duration of inflammation ≥6 months (clinical or biochemical)
• Confirmed etiology by serology/autoantibodies/histology
• Biopsy: graded (inflammatory activity) and staged (fibrosis)

C. Autoimmune Hepatitis (AIH) - Simplified Scoring System

• ≥6 points = probable AIH
• ≥7 points = definite AIH
• Max autoantibody points = 2. - Symptom to Diagnosis: An Evidence-Based Guide, 4e

D. Alcoholic Hepatitis Severity - Maddrey Discriminant Function (MDF)

MDF = 4.6 × (PT_patient - PT_control) + serum bilirubin (mg/dL)

• MDF > 32 = severe disease → consider corticosteroids
• MELD score >20 also indicates severe disease

E. Chronic HBV - Indications for Treatment

• HBV DNA >2,000 IU/mL (HBeAg-negative) or >20,000 IU/mL (HBeAg-positive)
• ALT >2× ULN
• Liver biopsy showing moderate/severe inflammation or significant fibrosis
• Decompensated cirrhosis (any HBV DNA level) - Goldman-Cecil Medicine

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8. COMPLICATIONS

A. Acute Complications

B. Chronic Complications

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9. PREVENTION

A. Vaccination

B. Post-Exposure Prophylaxis (PEP)

C. Harm Reduction Strategies

• Safe sex education, condom use (HBV, HCV)
• Needle exchange programs and opioid substitution therapy (HBV, HCV)
• Safe blood supply screening (blood banks screen for HBsAg, anti-HCV)
• Universal precautions in healthcare settings (gloves, masks, no needle recapping)
• Antenatal screening for HBsAg in all pregnant women
• Neonatal HBIG + HBV vaccine for infants of HBsAg-positive mothers (within 12 hours of birth)
• Food hygiene, clean water supply, handwashing (HAV, HEV)

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10. MANAGEMENT

A. Non-Pharmacological

B. Pharmacological

Hepatitis B

• HBeAg-positive: Continue until HBeAg seroconversion + undetectable HBV DNA, then ≥6 more months
• HBeAg-negative: At least 1 year; often lifelong
• Decompensated cirrhosis: Lifelong

Hepatitis C - Direct-Acting Antivirals (DAAs)

Hepatitis A and E

• Supportive care only - no antiviral therapy available or required
• HAV: self-limiting; complete recovery expected
• HEV immunocompromised patients: Ribavirin (off-label, 12-24 weeks) for chronic HEV

Autoimmune Hepatitis

• Induction: Prednisone 40-60 mg/day alone, OR Prednisone 30 mg/day + Azathioprine 50 mg/day
• Maintenance: Azathioprine 1-2 mg/kg/day (most patients need lifelong therapy)
• Remission achieved in ~85% of patients
• Alternative agents (MMF, tacrolimus, cyclosporine) for non-responders/intolerant

Alcoholic Hepatitis (MDF >32 / MELD >20)

• Prednisone 40 mg/day PO or methylprednisolone 32 mg IV daily for 28 days (if no contraindication)
• Contraindications to steroids: active GI bleeding, sepsis, renal failure
• Pentoxifylline 400 mg TID (alternative if steroids contraindicated - inhibits TNF-α)
• Note: A 2025 systematic review (PMID: 39874480) challenges routine steroid use, finding uncertain benefit across RCTs

Fulminant Hepatic Failure

• N-acetylcysteine (NAC): Treatment of choice for acetaminophen-induced ALF; also benefits non-acetaminophen ALF
• Acute HBV (severe): Entecavir 0.5 mg/day or TDF 300 mg/day
• Lactulose for encephalopathy (15-30 mL TID/QID to produce 2-3 soft stools/day)
• Liver transplantation for acute liver failure unresponsive to medical therapy

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11. DIFFERENTIAL DIAGNOSIS (DDx) WITH POINTS FOR AND AGAINST

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• Rosen's Emergency Medicine, 10e
• Tietz Textbook of Laboratory Medicine, 7e
• Sleisenger and Fordtran's Gastrointestinal and Liver Disease
• Goldman-Cecil Medicine
• Symptom to Diagnosis: An Evidence-Based Guide, 4e
• Morgan and Mikhail's Clinical Anesthesiology, 7e
• Yamada's Textbook of Gastroenterology, 7e
• Jawetz Medical Microbiology, 28e
• Sherris Medical Microbiology, 8e
• Textbook of Family Medicine, 9e

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HEPATITIS - Everything Explained in Full Detail

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SECTION 1: TYPES

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By Duration

Acute Hepatitis (< 6 months)

Chronic Hepatitis (≥ 6 months)

Fulminant Hepatic Failure

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By Cause

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SECTION 2: DEFINITION

• It processes everything you eat, drink, and absorb
• It makes proteins (albumin, clotting factors)
• It detoxifies drugs, alcohol, and waste products
• It makes bile to digest fat
• It converts ammonia (from protein breakdown) into urea (excreted by kidneys)
• It stores glycogen (energy reserve)

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SECTION 3: CAUSES (Deep Explanation)

Why Does HAV Cause Hepatitis?

Why Does HBV Cause Both Acute and Chronic Hepatitis?

• Neonates: Their immune system is immature and "tolerant." They cannot mount an effective T-cell response. The virus hides. Result: 85-95% become chronic.
• Adults with healthy immune systems: Strong CD8+ T-cell response clears the virus. Result: 95% clear it.
• Immunosuppressed adults: Poor response → higher chronicity rate.

Why Does HCV Almost Always Become Chronic?

Why Does HDV Require HBV?

Why Is HEV Lethal in Pregnancy?

1. Hormonal immunosuppression: Pregnancy naturally dampens the immune system to protect the fetus. This allows HEV to replicate more aggressively.
2. Altered liver metabolism: The liver is working harder in pregnancy due to increased metabolic demands.

Why Does Alcohol Damage the Liver?

• Ethanol → (Alcohol dehydrogenase) → Acetaldehyde → very toxic, binds to proteins and DNA, causes direct hepatocyte membrane damage and triggers immune response
• Acetaldehyde → (Acetaldehyde dehydrogenase) → Acetate (harmless)
• Excess NADH is produced in this process → blocks normal fat oxidation → fat accumulates in liver = steatosis (fatty liver)

• The CYP2E1 pathway (another alcohol metabolism route) generates reactive oxygen species (ROS) → lipid peroxidation → cell membrane destruction

• Alcohol damages the gut lining → bacteria and their products (especially lipopolysaccharide, LPS) leak from gut into portal blood → reach the liver → activate Kupffer cells (the liver's resident macrophages)
• Activated Kupffer cells release inflammatory cytokines: TNF-α, IL-1β, IL-6, IL-8
• These cytokines cause further hepatocyte death and activate stellate cells

• Hepatic stellate cells (Ito cells) normally store vitamin A in a quiescent state
• When activated by inflammation signals, they transform into myofibroblasts
• Myofibroblasts produce massive amounts of Type I collagen → laid down as scar tissue = fibrosis
• Continued injury → fibrosis → cirrhosis

• Alcohol depletes pyridoxal phosphate (Vitamin B6) - a cofactor that ALT needs more than AST
• So ALT production is disproportionately reduced
• Alcohol-damaged mitochondria release mitochondrial AST, raising total AST further
• Classical finding: AST:ALT ratio >2:1 (rarely exceeds 300 U/L total)

Why Does Acetaminophen (Paracetamol) Cause Hepatitis?

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SECTION 4: PATHOPHYSIOLOGY (Step-by-Step)

The Universal Final Common Pathway

Trigger (virus/toxin/immune attack)
        ↓
Hepatocyte damage (necrosis/apoptosis)
        ↓
Intracellular enzymes (ALT, AST) leak into blood → elevated LFTs
        ↓
Kupffer cell activation → cytokine storm → inflammation
        ↓
Bilirubin processing disrupted → jaundice
        ↓
Synthetic function impaired → low albumin, prolonged PT
        ↓
Ammonia accumulation → encephalopathy (if severe)
        ↓
Stellate cell activation → collagen deposition → fibrosis
        ↓
(If chronic/repeated injury) → Cirrhosis → Portal hypertension → Complications

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Pathophysiology of HBV in Detail

Phase 1 - Viral Entry

• HBV circulates in blood
• HBV uses its surface proteins (Pre-S1) to bind to the NTCP receptor (sodium-taurocholate cotransporting polypeptide) on the hepatocyte surface
• This is the "lock-and-key" entry point; bile acid transporter hijacked by the virus
• Virus enters and releases its DNA into the nucleus

Phase 2 - Establishment of cccDNA (The Master Template)

• The partially double-stranded HBV DNA is repaired inside the nucleus to form cccDNA
• cccDNA is like a permanent hard drive inside the cell - it cannot be eradicated by current antivirals
• This is why HBV cannot be fully cured (only suppressed) - cccDNA persists even when blood viral load is undetectable

Phase 3 - Viral Gene Expression

• cccDNA transcribes several RNA products:
  • Pregenomic RNA (pgRNA) → packaged and reverse-transcribed into new HBV DNA
  • mRNAs → translated into HBsAg, HBcAg, HBeAg, and X protein
• HBeAg is secreted into blood as a "decoy" - it may suppress immune response by inducing T-cell tolerance

Phase 4 - Immune Recognition (Key Step)

• The immune system is NOT fighting the virus directly - it is fighting the infected hepatocytes
• CD8+ cytotoxic T lymphocytes (CTLs) circulate and scan cells
• Infected hepatocytes display viral peptides on their MHC class I molecules
• CTLs recognize these peptides → activate → kill the infected hepatocytes (via perforin-granzyme and Fas-FasL pathways)
• This killing = liver cell necrosis = the rise in ALT/AST
• The more vigorous the CTL response, the worse the hepatitis BUT the better the chance of clearing the virus

Phase 5 - Fibrosis Development (Chronic HBV)

• In chronic infection, repeated rounds of hepatocyte death → healing → scar
• Dead hepatocytes release TGF-β, PDGF
• These cytokines activate hepatic stellate cells (HSCs)
• HSCs transform from fat-storing cells into collagen-producing myofibroblasts
• Type I and III collagen is deposited in the Space of Disse (between hepatocytes and sinusoids)
• This disrupts normal liver architecture → bands of scar tissue form between portal tracts = fibrosis
• Eventually the entire architecture is replaced by regenerative nodules surrounded by fibrosis = cirrhosis

Phase 6 - HCC (Hepatocellular Carcinoma) Risk

• Two mechanisms:
  1. Indirect: Repeated hepatocyte death → regeneration → proliferating cells accumulate mutations → cancer
  2. Direct: HBV's X protein (HBx) is a transcriptional transactivator - it activates proto-oncogenes, inhibits p53 tumour suppressor, and promotes cell survival signalling → can directly drive malignant transformation even without cirrhosis

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Pathophysiology of HCV in Detail

Why HCV Is Harder to Clear Than HAV

• HCV's RNA-dependent RNA polymerase has no proofreading ability → generates ~10^12 viral particles per day with very high mutation rate
• This creates a swarm of slightly different variants (quasispecies) → immune system cannot keep up
• HCV also specifically blocks innate immune signalling:
  • NS3/4A protease cleaves TRIF and MAVS (key adaptor proteins in interferon signalling pathways) → prevents interferon production
  • Less interferon = less antiviral defence = virus survives

Liver Damage Mechanism in HCV

• HCV is partially directly cytopathic (more so than HBV) AND causes immune-mediated damage
• The steatosis seen in HCV (especially genotype 3) is caused by HCV core protein disrupting lipid metabolism in hepatocytes
• CD4+ and CD8+ T-cells attack infected hepatocytes → necro-inflammation → fibrosis
• Fibrosis in HCV typically progresses through 5 stages (METAVIR: F0-F4):
  • F0: No fibrosis
  • F1: Portal fibrosis without septa
  • F2: Portal fibrosis with rare septa
  • F3: Numerous septa without cirrhosis
  • F4: Cirrhosis
• Average time from infection to cirrhosis: 20-30 years (faster with alcohol, HIV co-infection, older age at infection)

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Pathophysiology of Autoimmune Hepatitis

• The immune system incorrectly recognizes liver self-antigens as foreign
• Molecular mimicry: Viral or environmental triggers cause the immune system to produce antibodies and T-cells that cross-react with hepatocyte proteins
• Type 1 AIH: Antibodies against smooth muscle (anti-SMA) and nuclear antigens (ANA) - attack hepatocyte cytoskeleton and nuclear proteins
• Type 2 AIH: Anti-LKM1 antibodies - target CYP2D6 enzyme inside hepatocytes
• CD4+ T-helper cells and CD8+ CTLs infiltrate portal tracts → interface hepatitis (inflammation at the junction of portal tract and liver parenchyma) = the histological hallmark
• Because the attack is immune-mediated, it responds to immunosuppression (steroids, azathioprine)

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The Final Common Pathway: How Cirrhosis Causes All Its Complications

Portal Hypertension

• Normal portal vein pressure: 5-10 mmHg
• Fibrosis and nodule formation distort the intrahepatic vasculature → increased resistance to blood flow
• Portal vein pressure rises to >12 mmHg = portal hypertension
• Blood seeks alternative routes (collaterals) to drain into systemic circulation

Oesophageal Varices

• Portal blood diverts through the left gastric vein → oesophageal submucosal veins → azygos vein → systemic
• These thin-walled veins become dilated and tortuous = varices
• They are superficial and fragile → rupture → massive haematemesis → 10-15% mortality per episode

Ascites

• Portal hypertension → increased hydrostatic pressure in splanchnic capillaries → fluid leaks into peritoneal cavity
• Low albumin (synthetic failure) → reduced oncotic pressure → fluid stays out
• Portal hypertension triggers splanchnic vasodilation → renin-angiotensin-aldosterone system activates → sodium and water retention → fluid accumulates

Hepatic Encephalopathy

• Normal liver converts toxic ammonia (from gut bacterial metabolism of amino acids + nitrogenous waste) → urea → excreted in urine
• In cirrhosis: liver cells fail + blood shunts bypass the liver through portosystemic collaterals
• Ammonia accumulates in blood → crosses blood-brain barrier → converted to glutamine in astrocytes → astrocyte swelling → cerebral oedema
• Ammonia also disrupts neuronal inhibitory/excitatory balance (increases GABAergic tone) → altered consciousness
• Precipitants: GI bleeding (large protein load from blood in gut), infection, dehydration, hypokalemia (raises renal ammonia production), constipation

Hepatorenal Syndrome (HRS)

• Splanchnic vasodilation (from portal hypertension) → blood pools in gut vessels → effective circulating volume falls
• Kidneys sense reduced perfusion → vasoconstriction of renal arterioles (via angiotensin II, vasopressin, sympathetic activation)
• Renal blood flow drops → acute kidney injury without intrinsic kidney disease
• The kidneys are structurally normal (proven by the fact that if transplanted into a healthy person, they work fine)
• Type 1 HRS: Rapid (creatinine doubles to >226 μmol/L in <2 weeks) - very high mortality
• Type 2 HRS: Slower, associated with refractory ascites

Hepatocellular Carcinoma (HCC)

• Repeated cell death → regeneration → replicating cells accumulate DNA mutations
• Hepatocytes in cirrhosis are in a constant cycle of death and proliferation
• Mutations in tumour suppressor genes (p53, Rb) and proto-oncogenes (CTNNB1, TERT) accumulate
• HBV additionally has HBx protein that directly promotes oncogenesis
• HCC can arise even without cirrhosis in HBV (unique among liver diseases)

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SECTION 5: CLINICAL FEATURES - WHY EACH SYMPTOM OCCURS

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SECTION 6: INVESTIGATIONS - FULLY EXPLAINED

Why We Do Each Test and What Each Result Tells Us

ALT (Alanine Aminotransferase)

• Location: Found in high concentrations in hepatocyte cytoplasm
• Why it rises: When hepatocytes die (necrosis or apoptosis), this enzyme leaks out into the blood. Think of it like breaking open a bag of flour - the contents spill everywhere.
• Why ALT > AST in viral hepatitis: ALT has a longer half-life than AST (47 hours vs 17 hours). Also, in viral hepatitis, cytoplasmic release of ALT predominates. ALT is more specific to the liver (AST also exists in heart, muscle, red blood cells).
• Expected level: 8-50× upper limit of normal (ULN) in acute viral hepatitis. An ALT >300 U/L has >90% sensitivity for acute hepatitis.
• Why it matters: Best real-time marker of hepatocyte injury. Used to monitor treatment response - as hepatocytes recover, ALT falls back to normal.

AST (Aspartate Aminotransferase)

• Location: Hepatocyte cytoplasm AND mitochondria; also in heart, skeletal muscle, red blood cells
• AST:ALT ratio > 2:1 = strongly suggests alcoholic hepatitis because:
  1. Mitochondrial AST is released specifically by alcohol-damaged mitochondria
  2. Alcohol depletes Vitamin B6, which ALT needs more than AST for its enzymatic function
• In shock liver (ischaemic hepatitis): Both AST and ALT can shoot up to 50-100× ULN but then fall rapidly within 48-72 hours as hypoperfusion resolves

ALP (Alkaline Phosphatase)

• Location: Canalicular surface of hepatocytes AND bile duct epithelium; also in bone, placenta, intestine
• Why it rises: ALP is embedded in the bile canaliculi. When bile flow is obstructed (inside or outside the liver), bile pressure rises → ALP is "washed back" into blood. Also, bile acids and bilirubin stimulate ALP synthesis.
• Why it is only mildly elevated in hepatitis (<3× ULN in 90%): The hepatocyte injury in hepatitis is primarily in the liver parenchyma, not the biliary system. Severe cholestatic obstruction (gallstone, tumour) causes ALP >3× ULN.
• Differentiating hepatic vs bone source of elevated ALP: Check GGT - if GGT is also high, the source is hepatic; if GGT is normal, suspect bone (e.g., Paget's disease)

GGT (Gamma-Glutamyl Transferase)

• Location: Liver, kidneys, pancreas - most sensitive in the liver
• Why it rises with alcohol: Alcohol is a potent inducer of CYP enzymes and also of GGT synthesis. GGT rises even with moderate, regular alcohol use.
• Why it's clinically important: Disproportionately high GGT relative to other LFTs strongly suggests alcohol as the cause even if the patient denies drinking

Serum Bilirubin (Total, Direct/Conjugated, Indirect/Unconjugated)

Red blood cells break down (reticuloendothelial system, especially spleen)
        ↓
Haemoglobin → Haem + Globin
        ↓ (Kupffer cells in liver; macrophages in spleen)
Haem → Biliverdin → Unconjugated bilirubin (lipid-soluble, bound to albumin in blood)
        ↓ (enters hepatocytes)
Conjugated to glucuronic acid by UGT1A1 enzyme → Conjugated bilirubin (water-soluble)
        ↓
Excreted into bile canaliculi → Bile ducts → Small intestine
        ↓
Intestinal bacteria convert to urobilinogen → Stercobilin (brown colour of stool)
        ↓ (small amount reabsorbed)
Urobilinogen → Blood → Kidneys → Urine (gives urine its pale yellow colour)

• In hepatitis: The conjugating machinery is intact BUT the excretion of conjugated bilirubin into bile is impaired (injured hepatocytes cannot pump bilirubin into canaliculi). Conjugated bilirubin refluxes back into the blood.
• Why dark urine: Conjugated bilirubin is water-soluble → kidneys filter it → dark urine
• Why pale stools: Less bilirubin reaching the gut → less stercobilin → pale stools
• Why jaundice appears at bilirubin >35-50 μmol/L: This is the threshold at which tissues (especially sclera, which has high elastin that binds bilirubin well) become visibly yellow

Albumin

• Produced exclusively by the liver (the main protein synthesiser in the body)
• Half-life ~21 days - very long. Albumin is like a long-running project; it takes time to fall.
• Why it is NORMAL in acute hepatitis: Even with significant acute hepatitis, the liver still has enough residual function to maintain albumin levels for weeks. Albumin falls only when >80% of functional liver tissue is destroyed.
• Why it falls in chronic hepatitis/cirrhosis: Prolonged loss of hepatocytes → sustained reduction in albumin synthesis
• Clinical consequence of low albumin: Oncotic pressure drops → fluid leaks out of vessels → oedema and ascites

PT/INR (Prothrombin Time)

• The liver makes almost all clotting factors: I (fibrinogen), II (prothrombin), V, VII, IX, X, XI, XIII
• Factor VII has the shortest half-life (~6 hours) → PT/INR is the EARLIEST and MOST SENSITIVE marker of acute liver synthetic failure
• In acute liver failure, PT/INR is the single best prognostic marker - if it continues to rise despite treatment, it indicates the liver is losing the battle
• PT prolongation means the time it takes for blood to clot is longer → bleeding risk

Serum Ammonia

• Ammonia is produced in the gut (bacterial protein metabolism) and enters the portal blood
• Normal liver: Converts ammonia → urea via Ornithine Cycle (urea cycle) → excreted in urine
• Cirrhotic liver: Reduced urea cycle activity + portosystemic shunting (blood bypasses liver) → ammonia accumulates
• In encephalopathy: Ammonia enters the brain → astrocytes (the brain's housekeeping cells) take it up and use it to convert glutamate → glutamine (a detoxification mechanism) → but glutamine accumulation causes astrocyte swelling → cerebral oedema → encephalopathy

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Serological Tests - What They Mean and WHY

Hepatitis A Serology

• IgM is the FIRST antibody the immune system makes against any new infection (appears within 1-2 weeks of infection)
• Positive IgM = the body just encountered HAV = ACUTE infection
• IgM disappears after 3-6 months

• IgG comes later (weeks after IgM) and persists for life
• Positive IgG = past infection OR successful vaccination = IMMUNITY
• You cannot tell the difference between natural immunity and vaccine immunity from IgG alone

Hepatitis B Serology - The Full Map

• This is a protein on the surface of HBV. When the virus is replicating, it makes massive excess amounts of HBsAg particles (even more than actual virus).
• Positive HBsAg = virus is present = active infection (acute or chronic)
• Persistent >6 months = chronic HBV infection
• HBsAg alone cannot distinguish acute from chronic - you need IgM anti-HBc for that

• HBcAg (core antigen) is NEVER found free in blood (it is inside the viral particle). But the immune response to it is detectable.
• IgM anti-HBc appears early in acute infection and persists for ~6 months
• This is the definitive marker of ACUTE HBV infection
• It also becomes positive in reactivation of chronic HBV (important to know)

• Persists for life after any HBV infection, whether resolved or chronic
• If this is positive but HBsAg is negative and anti-HBsAg is positive → past resolved infection with immunity
• If this is positive and HBsAg is positive → chronic infection ongoing

• Appears after HBsAg clears (recovery) or after vaccination
• This is the protective antibody - it neutralises the virus
• Level >10 mIU/mL = protected
• Only anti-HBsAg is positive (with negative anti-HBc) = vaccinated person (not natural infection, as vaccination only generates surface antigen antibodies)

• A secreted form of the core protein, released by highly replicating hepatocytes
• Presence = high viral replication = high infectivity
• It also acts as an immunological decoy - tricks the immune system into tolerating the virus

• Appears when HBeAg is cleared (seroconversion)
• Marks transition from active replication to lower replication
• However, HBeAg-negative chronic HBV still exists (precore mutant virus - does not make HBeAg but still replicates dangerously)

• Directly measures viral load in blood
• Gold standard for monitoring antiviral therapy
• Used to determine whether treatment is needed and whether it is working

Hepatitis C Serology

• Detects antibodies to HCV proteins
• Window period: Antibodies may not appear until 8-12 weeks after infection → early acute HCV can be missed
• Positive = EXPOSED to HCV at some point (does NOT mean currently infected - could be past cleared infection)
• Does NOT distinguish acute from chronic from past cleared infection

• Detects actual viral genetic material in blood
• Becomes detectable within 1-2 weeks of infection (much earlier than antibody)
• Used to: confirm active infection, determine viral load (predicts treatment success), and monitor treatment
• Undetectable HCV RNA at 12 weeks post-treatment = SVR (Sustained Virologic Response) = CURE

• Different strains of HCV (like different subspecies)
• Genotype determines which DAA regimen to use and how long to treat
• Genotype 3: More fibrosis, more steatosis, harder to treat historically (though modern pan-genotypic regimens work well)

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Liver Biopsy - Why It Remains Important

1. How inflamed is the liver right now? (Grade of necroinflammation: G0-G4)
2. How much scar tissue is there? (Stage of fibrosis: F0-F4 or Ishak 0-6)
3. What does the cause look like histologically? (AIH has interface hepatitis; alcoholic hepatitis has Mallory-Denk bodies; NASH has steatohepatitis)
4. Are there features of malignant transformation?

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Imaging

Ultrasound - The First-Line Tool

• Non-invasive, cheap, no radiation
• In acute hepatitis: Liver enlarges → decreased echogenicity (looks darker) compared to the kidney. Portal tracts become echogenic (look bright) against the dark background = "Starry sky" pattern (like stars in a dark sky). This is classic but not pathognomonic.
• In chronic hepatitis: Echogenicity increases (liver looks coarser and brighter) as fibrosis replaces normal tissue; the portal vein radicles become less visible as they are surrounded by fibrosis
• Detects cirrhosis (nodular surface, right lobe atrophy, caudate/left lobe hypertrophy), ascites, splenomegaly, dilated portal vein

MRI - Most Sensitive for Acute Hepatitis

• Gadolinium-enhanced MRI during the late arterial phase (18-22 seconds after injection) shows periportal enhancement in acute hepatitis
• T2-weighted images show periportal oedema as increased signal
• More expensive than ultrasound but more sensitive for subtle disease

Fibroscan (Transient Elastography)

• Sends a vibration wave into the liver; measures how stiff the liver is
• Stiff liver = more fibrosis
• Provides a liver stiffness measurement (kPa) that correlates with METAVIR fibrosis stage
• Has replaced liver biopsy for staging fibrosis in many chronic hepatitis patients

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SECTION 7: COMPLICATIONS - FULLY EXPLAINED

How Each Complication Develops

Variceal Bleeding

• When portal pressure exceeds 12 mmHg, varices form
• When portal pressure exceeds 20 mmHg, risk of rupture is very high
• The risk of bleeding from a varix is directly proportional to its size and the presence of red wale signs (red streaks on varix surface indicating wall thinning)
• When a varix ruptures: massive haemorrhage into the oesophageal or gastric lumen → haematemesis (vomiting blood) or melaena (black tarry stools from digested blood)
• Bleeding itself raises ammonia (blood in the gut is a protein load → bacteria metabolise it → ammonia rises) → can trigger encephalopathy

Spontaneous Bacterial Peritonitis (SBP)

• In cirrhosis, the immune defence of the peritoneal fluid is impaired (low complement, low opsonic activity)
• Gut bacteria translocate across the damaged intestinal wall into lymphatics → portal blood → ascitic fluid
• Without normal immune defences, bacteria multiply in ascitic fluid
• Diagnosis: Ascitic fluid neutrophil count >250 cells/mm³ (even before culture results)
• Treatment: Third-generation cephalosporin (ceftriaxone) + albumin infusion (prevents HRS)

Hepatocellular Carcinoma

• Once cirrhosis is established, HCC risk = 1-8% per year depending on aetiology (HBV highest)
• HBV can cause HCC even WITHOUT cirrhosis (unique - due to HBx protein)
• Surveillance: 6-monthly liver ultrasound + serum AFP (alpha-fetoprotein) in all cirrhotic patients and HBV carriers
• AFP elevation suggests HCC but is not diagnostic alone (can be elevated in regenerative nodules)
• Diagnosis confirmed by contrast CT/MRI showing arterial enhancement + washout of a liver lesion (no biopsy needed if imaging is typical)

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SECTION 8: PREVENTION - WHY EACH MEASURE WORKS

Hepatitis A Vaccine

• Formalin-inactivated HAV is injected → your immune system sees the dead virus → produces IgG anti-HAV antibodies and memory B cells
• If you later encounter live HAV, your memory B cells rapidly produce antibodies before the virus can establish infection → sterilising immunity
• Two doses give >95% seroprotection for at least 25 years (likely lifetime)

Hepatitis B Vaccine

• Contains recombinant HBsAg (produced by genetically modified yeast - no live virus)
• Immune system makes anti-HBsAg antibodies
• Anti-HBs >10 mIU/mL = protective threshold
• Three-dose schedule (0, 1, 6 months) builds robust, long-lasting immunity
• Universal infant vaccination is the single most impactful intervention against HBV worldwide - it reduces HBV transmission by 95% in immunised populations
• Immunosuppressed patients (dialysis, chemotherapy, HIV) respond poorly → may need higher doses or additional doses

Post-Exposure Prophylaxis for HBV

• This is pre-formed anti-HBsAg antibody from pooled human plasma of vaccinated donors
• It provides immediate passive immunity - neutralises circulating HBV before it can establish infection
• Must be given within 96 hours (ideally <24 hours) for maximum effect
• Given together with vaccine to bridge the gap until the vaccine-induced active immunity develops

Why There Is No HCV Vaccine

• HCV mutates rapidly (quasispecies) → no stable surface antigen to target
• Past infection does NOT confer immunity to re-infection (unlike HAV and HBV)
• Any vaccine-induced antibodies are quickly outpaced by new viral variants
• Research is ongoing but progress is very slow

Harm Reduction for HCV

• Needle exchange programs: Remove the contaminated needle as the transmission vector
• Opioid substitution therapy (methadone, buprenorphine): Reduces injecting frequency → reduces HCV transmission
• These are population-level interventions that have demonstrably reduced new HCV infections in multiple countries

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SECTION 9: MANAGEMENT - HOW EVERY TREATMENT WORKS

Non-Pharmacological Management

Rest

• During acute hepatitis, liver blood flow and metabolic demands matter
• Physical activity diverts blood to muscles away from the liver
• Rest maximises hepatic perfusion and provides optimal conditions for hepatocyte regeneration
• However, prolonged bed rest is not necessary - activity as tolerated is the modern approach

Diet

• High carbohydrate, moderate protein, low fat: The injured liver struggles with fat metabolism; carbohydrates provide easy energy. Protein is needed for cell repair but excess raises ammonia in encephalopathy.
• Avoid alcohol completely: Even small amounts cause further mitochondrial damage in an already inflamed liver
• No paracetamol: Depletes glutathione reserves in an already stressed liver
• Thiamine supplementation in alcoholic hepatitis (prevents Wernicke's encephalopathy - a brain complication of B1 deficiency)

Managing Ascites

• Salt restriction (<88 mmol sodium/day): Reduces osmotic drive for fluid retention
• Spironolactone (first-line diuretic): Blocks aldosterone → kidney stops retaining sodium/water → fluid excreted
• Furosemide (loop diuretic): Added if spironolactone alone insufficient
• Therapeutic paracentesis: For large-volume ascites (>5L): drain fluid with a needle. Must give albumin (8g per litre removed) to prevent circulatory dysfunction and hepatorenal syndrome

Managing Variceal Bleeding

• Terlipressin: A vasopressin analogue → causes splanchnic vasoconstriction → reduces portal pressure → slows variceal bleeding. First given in the ambulance/ER.
• Endoscopic variceal banding (EVL): A rubber band is placed around the varix → strangulates it → varix thromboses and falls off
• Propranolol / Carvedilol: Non-selective beta-blockers for PRIMARY prophylaxis → reduce cardiac output AND cause splanchnic vasoconstriction → lower portal pressure

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Pharmacological Management

How Antivirals Work - Step by Step

Tenofovir (TDF/TAF) - For Chronic HBV

• Class: Nucleotide analogue (mimics adenosine monophosphate)
• Mechanism: Tenofovir is taken up by hepatocytes → phosphorylated to its active triphosphate form → competes with the natural substrate (dATP) for binding to HBV's reverse transcriptase (the enzyme that copies viral RNA into DNA)
• Once incorporated into the growing HBV DNA chain, it acts as a chain terminator (lacks the 3'-OH group needed for the next nucleotide to attach) → viral DNA synthesis stops → no new virions can be made
• Why it doesn't cure HBV: Tenofovir does NOT affect the cccDNA already established in the nucleus - it only prevents production of NEW viral copies
• TAF vs TDF: TAF is a prodrug that delivers tenofovir more efficiently to liver cells (a "targeted delivery" form), so a much lower dose is needed, with less systemic exposure → less kidney toxicity, less bone density loss

Entecavir - For Chronic HBV

• Class: Guanosine nucleoside analogue
• Mechanism: Competitively inhibits three steps of HBV reverse transcriptase:
  1. Priming of pgRNA
  2. Reverse transcription (RNA → DNA)
  3. Synthesis of the positive strand DNA
• Very high barrier to resistance - requires three simultaneous mutations for HBV to escape → almost no resistance with long-term use (unlike older agents like lamivudine)

Pegylated Interferon-alfa-2a - For Chronic HBV/HCV

• Mechanism: Not directly antiviral - it works by boosting the immune system's natural defences
• Interferon-α binds to interferon receptors on liver cells → activates the JAK-STAT signalling pathway → nucleus produces interferon-stimulated genes (ISGs)
• ISGs create an antiviral state: degrade viral RNA, block protein synthesis, inhibit viral budding
• Also activates NK cells and enhances MHC class I expression (helps CTLs find and kill infected hepatocytes)
• "Pegylated" = attached to polyethylene glycol molecule → slows its removal from blood → allows once-weekly dosing instead of three times daily
• Advantages: Finite course (48 weeks); can achieve functional cure (HBsAg loss) in a subset; no resistance
• Disadvantages: Many side effects (flu symptoms, depression, hair loss, cytopenia, thyroid dysfunction) because you are essentially creating a prolonged artificial "infection-fighting" state

Sofosbuvir - For Chronic HCV

• Class: NS5B RNA-dependent RNA polymerase inhibitor (nucleotide analogue)
• Mechanism: HCV uses its own RNA polymerase (NS5B) to copy its genome. Sofosbuvir mimics uridine → gets incorporated into the growing HCV RNA chain → chain termination → no new HCV RNA copies
• HCV has NO proofreading on its RNA polymerase → theoretically lots of resistance. BUT sofosbuvir resistance requires very specific mutations in the polymerase that severely cripple viral fitness → very rare

NS5A Inhibitors (Ledipasvir, Velpatasvir, Pibrentasvir)

• Target: NS5A protein - a non-structural HCV protein with no known enzymatic function but essential for viral replication, assembly, and secretion
• NS5A inhibitors bind to this protein → disrupt the membranous web (the intracellular compartment where HCV replicates) → virus cannot assemble or be secreted
• Ultra-potent: Can reduce HCV viral load by 4-5 log₁₀ within days
• Combined with sofosbuvir (hit two different targets simultaneously) → synergistic effect + prevents resistance from emerging

Glecaprevir - NS3/4A Protease Inhibitor

• HCV uses a protease (NS3/4A) to cleave a large viral polyprotein into individual functional proteins
• Without cleavage, the proteins remain fused and non-functional
• Glecaprevir inhibits this protease → viral proteins cannot be processed → no functional virions

Why DAA Combinations Work So Well (>95% SVR)

• Each drug hits a different step in HCV's lifecycle
• For resistance to emerge, HCV would need to simultaneously develop resistant mutations to all three targets
• The probability of three simultaneous resistance mutations is essentially zero at any given replication cycle
• This is the same principle as combination HIV therapy (HAART)

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Steroids for Autoimmune Hepatitis - Mechanism

• Prednisolone suppresses immune activation by:
  1. Entering immune cells → binds glucocorticoid receptor → enters nucleus → suppresses NF-κB (the master switch for inflammatory gene transcription)
  2. Reduces production of IL-1, IL-2, IL-6, TNF-α, and interferon-γ
  3. Causes lymphocyte redistribution (lymphocytes exit blood → less immune attack on liver)
• Azathioprine (maintenance therapy):
  • Converted to 6-mercaptopurine → inhibits purine synthesis → lymphocytes CANNOT proliferate without purines (they rely on de novo synthesis unlike other cells)
  • Specifically reduces CD4+ T-helper cell activation → less immune attack
  • Used at lower doses for maintenance (fewer side effects than prolonged steroids)

N-Acetylcysteine (NAC) for Acetaminophen Toxicity

• Mechanism: NAC is a glutathione precursor. It donates cysteine for glutathione synthesis.
• Replenishes hepatic glutathione stores → newly produced glutathione neutralises NAPQI before it can bind to proteins
• Must be given early (within 8-10 hours ideally for maximum effect; still beneficial up to 24 hours)
• Also used in non-acetaminophen acute liver failure: appears to improve outcomes, possibly by reducing oxidative stress and improving mitochondrial function

Lactulose for Hepatic Encephalopathy

• Mechanism (dual):
  1. Osmotic laxative: Non-absorbable disaccharide → draws water into the colon → diarrhoea → rapid clearance of ammonia-producing bacteria and nitrogenous waste from the gut
  2. Acidification of colon: Gut bacteria convert lactulose to lactic and acetic acid → lowers colonic pH → ammonia (NH₃) is trapped as ammonium (NH₄⁺) which is charged and cannot be absorbed → excreted in stool
• Target: 2-3 soft stools per day

Rifaximin

• Non-absorbable antibiotic (stays in gut)
• Kills ammonia-producing gut bacteria (specifically targets bacterial RNA polymerase)
• Reduces gut ammonia production → reduces hepatic encephalopathy recurrence
• Used as add-on to lactulose for prevention of recurrent HE

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SECTION 10: DIAGNOSTIC CRITERIA - HOW TO APPLY THEM

Acute Hepatitis - No Formal Criteria; Clinical + Lab Diagnosis

1. Compatible symptoms (prodrome + jaundice)
2. ALT/AST elevated 8-50× (or >300 U/L)
3. ALP mildly elevated (<3× ULN)
4. Specific serology confirms the agent

Chronic Hepatitis - Definition-Based

• Same abnormalities persisting beyond 6 months
• Graded (inflammation) and staged (fibrosis) by biopsy or non-invasive tools

Autoimmune Hepatitis Simplified Scoring (IAIHG)

• Score 6 = Probable AIH; Score ≥7 = Definite AIH
• The scoring makes it systematic - you cannot diagnose AIH from just one positive antibody

Maddrey Discriminant Function (MDF) for Alcoholic Hepatitis

MDF = 4.6 × (PT_patient - PT_control in seconds) + Serum Bilirubin (mg/dL)

• MDF < 32: Mild-moderate disease; mortality ~15%; supportive care only
• MDF ≥ 32: Severe disease; 1-month mortality ~35%; treat with prednisolone 40 mg/day
• If no improvement after 7 days of steroids (Lille score calculation) → steroids are not working → stop them

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SECTION 11: DIFFERENTIAL DIAGNOSIS - DETAILED REASONING

Step 1: Is This Hepatocellular or Cholestatic?

Step 2: Work Through Each Differential

1. Viral Hepatitis A

• FOR: Ate raw shellfish/contaminated food recently; travelled to endemic area (Africa, South Asia); fecal-oral exposure; IgM anti-HAV positive; prodrome + jaundice
• AGAINST: IV drug use or sexual exposure as sole risk factor; HBsAg or anti-HCV positive; chronic course; jaundice recurring

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2. Viral Hepatitis B

• FOR: IV drug use; multiple sexual partners; tattoo/piercings; birth in endemic country; HBsAg positive; IgM anti-HBc positive (acute); serum-sickness like prodrome (urticaria + arthritis) before jaundice; can recur/become chronic
• AGAINST: Purely fecal-oral exposure; IgM anti-HAV positive; normal viral serology

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3. Viral Hepatitis C

• FOR: IV drug use; blood transfusion before 1992; haemodialysis; needle-stick injury; anti-HCV positive; HCV RNA detectable; typically asymptomatic acutely; persistent mild ALT elevation
• AGAINST: No parenteral risk factor; acute jaundice (HCV is usually subclinical acutely); positive HAV/HBV serology

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4. Alcoholic Hepatitis

• FOR: Heavy daily alcohol use (typically >80g/day for years); AST:ALT >2:1; neither AST nor ALT >300-500 U/L despite jaundice; fever + leucocytosis (neutrophilic); tender hepatomegaly; signs of chronic liver disease; hypoglycaemia; elevated GGT disproportionately; Mallory-Denk bodies on biopsy
• AGAINST: No alcohol history; ALT > AST; viral serology positive; ALT >1000 U/L (alcohol rarely causes this - think viral, ischaemic, or acetaminophen if >1000)

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5. Drug-Induced Liver Injury (DILI)

• FOR: Started a new drug or supplement within weeks to months before symptoms; improvement after stopping the drug; eosinophilia + rash (hypersensitivity-type DILI); all viral serology negative; acetaminophen history + dose >4g/day (or lower with alcohol)
• AGAINST: No new drug exposure; viral serology positive; clinical improvement despite continuing medication

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6. Autoimmune Hepatitis (AIH)

• FOR: Young woman; fluctuating transaminases over years; ANA positive, anti-SMA positive, anti-LKM1 positive; IgG elevated; other autoimmune conditions (thyroiditis, IBD); responds to steroids; interface hepatitis on biopsy; AIH score ≥6
• AGAINST: Male sex (less likely); positive viral serology explaining all abnormalities; normal immunoglobulins; no autoantibodies

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7. Biliary Obstruction (Choledocholithiasis/Cholangitis)

• FOR: Colicky RUQ pain (gallstone pattern) or constant pain; ALP disproportionately elevated (>3× ULN); dilated bile ducts on ultrasound/CT; prior history of gallstones; Charcot's triad for cholangitis (fever + RUQ pain + jaundice); elevated serum amylase if pancreatitis
• AGAINST: Predominantly ALT/AST pattern; prodromal viral illness; no biliary dilation on imaging; alcohol history

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8. Ischaemic Hepatitis (Shock Liver)

• FOR: Recent episode of hypotension/circulatory failure (MI, septic shock, cardiac arrest, massive bleed); extremely rapid AST/ALT rise to 50-100× ULN; rapid normalization within 48-72 hours as haemodynamics recover; bilirubin paradoxically mild given the severity of enzyme rise; LD also very high (ischaemic injury releases LD)
• AGAINST: No haemodynamic event; gradual enzyme rise; positive viral serology; persistent enzyme elevation

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9. Wilson's Disease

• FOR: Young patient (<40 years, usually <30); paradoxically LOW or normal ALP (Wilson's damages hepatocytes that make ALP AND it causes haemolysis which consumes ALP substrate); Kayser-Fleischer rings in eyes (copper deposits in Descemet's membrane of cornea - seen on slit-lamp); haemolytic anaemia; neurological/psychiatric symptoms; low ceruloplasmin; raised 24-hour urinary copper; liver copper elevated on biopsy
• AGAINST: Age >40; elevated ALP; positive viral serology; no haemolysis; normal copper studies
• Clinical pearl: In Wilson's presenting as acute liver failure, ceruloplasmin may paradoxically be normal (released from dying hepatocytes temporarily raises it) - look for the ALP:bilirubin ratio (<4 strongly suggests Wilson's in ALF)

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10. EBV/CMV Hepatitis

• FOR: Young adult; pharyngitis + cervical lymphadenopathy (mononucleosis features); splenomegaly; heterophile antibody (Monospot) positive; lymphocytosis with atypical lymphocytes on blood film; EBV/CMV IgM serology positive; hepatitis is mild and self-limiting; mild transaminase elevation (rarely exceeds 5× ULN)
• AGAINST: Positive HAV/HBV/HCV serology; no lymphadenopathy/pharyngitis; severe hepatitis; IV drug use

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11. Non-Alcoholic Steatohepatitis (NASH/MASH)

• FOR: Metabolic syndrome (obesity, Type 2 diabetes, hypertriglyceridaemia, hypertension); AST/ALT typically <3× ULN and persistent; all viral serology negative; no significant alcohol intake; steatosis on ultrasound (bright echogenic liver); AST:ALT <1 typically; gradual, asymptomatic course
• AGAINST: Acute jaundice; significant ALT elevation >10× ULN; positive viral serology; active alcohol use (alcohol causes a similar picture but is treated as ARLD); autoantibodies positive

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• Tietz Textbook of Laboratory Medicine, 7e - Investigations and pathogenesis
• Sleisenger and Fordtran's Gastrointestinal and Liver Disease - Chronic hepatitis, HBV/HCV mechanisms
• Rosen's Emergency Medicine, 10e - Clinical approach, alcoholic hepatitis
• Goldman-Cecil Medicine - Antiviral drug doses and indications
• Morgan and Mikhail's Clinical Anesthesiology, 7e - Drug-induced hepatitis, acute hepatitis
• Yamada's Textbook of Gastroenterology, 7e - DDx, imaging
• Symptom to Diagnosis: An Evidence-Based Guide, 4e - AIH criteria, DDx tables
• Sherris Medical Microbiology, 8e - HDV structure and mechanism
• Jawetz Medical Microbiology, 28e - Prevention and vaccination