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1. Difference Between Pulmonary Agenesis and Aplasia

• Pulmonary agenesis = complete absence of lung parenchyma, bronchus, and pulmonary vasculature.
• Pulmonary aplasia = characterised by a blind-ending rudimentary bronchus, but no lung parenchyma or pulmonary vasculature.

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2. What Is Lung Agenesis?

• Type 1 – Agenesis: Complete absence of lung, bronchus, and vascular supply
• Type 2 – Aplasia: Rudimentary bronchus with complete absence of the lung itself
• Type 3 – Hypoplasia: Variable bronchial tree with reduced parenchyma and vasculature

• Unilateral agenesis is more compatible with life than bilateral
• The trachea extends directly into the main bronchus of the functioning lung
• Respiratory distress from inflammation and secretion retention
• Recurrent respiratory infections are common
• Associated congenital anomalies in ~75% of unilateral cases (Goldenhar syndrome, VACTERL, DiGeorge syndrome, trisomy 21)

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3. What Is Lung Sequestration?

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4. Symptoms and Diagnosis of Pulmonary Emphysema

Symptoms

• Dyspnoea (initially on exertion, later at rest) — the cardinal symptom
• Chronic productive cough (when co-existing with chronic bronchitis — COPD)
• Barrel chest (increased AP diameter), use of accessory muscles
• Pursed-lip breathing
• Hyperresonance to percussion, diminished breath sounds
• Prolonged expiratory phase
• Weight loss in advanced disease
• Cor pulmonale signs (right heart failure) in late disease

Diagnosis

• Spirometry (PFTs): Reduced FEV₁/FVC ratio (<0.7), reduced FEV₁, increased TLC and RV (air trapping), reduced DLCO (carbon monoxide diffusing capacity)
• Chest X-ray: Hyperinflated lungs, flattened diaphragm, increased retrosternal airspace, hyperlucency, narrow heart shadow
• CT scan (HRCT): Gold standard for detecting and quantifying emphysema — shows areas of low attenuation without walls; identifies distribution (centriacinar vs. panacinar); detects bullae
• ABGs: May show hypoxaemia; hypercapnia in severe disease
• Alpha-1-antitrypsin levels: If panacinar emphysema or atypical presentation (young non-smoker)

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5. What Is a Diaphragmatic Hernia? Classifications?

Major Classifications:

1. Bochdalek hernia (~70–90% of CDH): posterolateral defect, usually left-sided
2. Morgagni hernia (~2–5% of CDH): anterior retrosternal defect, usually right-sided

1. Hiatal hernia: Herniation through the esophageal hiatus (most common overall)
   • Type I: Sliding (GEJ slides above diaphragm) — 90–95%
   • Type II: Rolling/paraesophageal (fundus herniates, GEJ stays)
   • Type III: Mixed (both components)
   • Type IV: Complex (other organs, e.g., colon, in the hernia sac)
2. Traumatic hernia: Due to blunt or penetrating trauma creating a diaphragmatic tear
3. Iatrogenic hernia: Following surgical injury to the diaphragm

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6. Types of Diaphragmatic Hernia

Bochdalek Hernia

• Defect in the posterolateral diaphragm (pleuroperitoneal fold fails to fuse)
• ~80–85% left-sided (liver protects the right)
• Most common CDH — detected on antenatal ultrasound at 20-week screening
• Contents: stomach, small/large bowel, spleen, kidney
• Associated with pulmonary hypoplasia and pulmonary hypertension — the key life-threatening sequela

Morgagni Hernia

• Defect at the anterior retrosternal region (foramen of Morgagni, near xiphoid)
• ~90% right-sided (liver protects the left, as above)
• Rare (~2% of CDH)
• Typically presents later in life (childhood or adulthood)
• Contents: omentum, colon (transverse), rarely small bowel
• Usually asymptomatic or mildly symptomatic

Hiatal Hernia

• Herniation through the esophageal hiatus
• Extremely common, especially in the elderly
• Type I (sliding): GEJ + stomach slide above diaphragm — most common, associated with GERD
• Type II (rolling/paraesophageal): Fundus herniates alongside esophagus; GEJ stays sub-diaphragmatic; higher risk of strangulation
• Type III (mixed): Features of both I and II
• Type IV: Large hernia with additional organs (colon, pancreas)

Traumatic/Iatrogenic Hernia

• Diaphragmatic rupture from blunt trauma (RTA), penetrating wounds, or surgical injury
• May present acutely or with delayed herniation

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7. Symptoms and Diagnosis of Diaphragmatic Hernia

Symptoms

• Severe respiratory distress at birth
• Cyanosis
• Scaphoid abdomen (bowel in chest)
• Barrel chest on affected side
• Mediastinal shift to opposite side

• Dyspnoea, chest pain
• Gastrointestinal symptoms: epigastric/substernal pain, postprandial fullness, nausea, vomiting, constipation
• Heartburn, regurgitation (hiatal)
• Recurrent chest infections
• Symptoms may be intermittent if contents reduce spontaneously

Diagnosis

• Chest X-ray: Bowel loops in hemithorax, mediastinal shift; Morgagni hernia = smooth opacity at right cardiophrenic angle; Hiatal hernia = retrocardiac mass ± fluid level
• CT scan: Gold standard — shows extent of defect, contents, vascular supply; fine linear opacities in fat hernias (omental vessels) help distinguish from lipoma
• MRI: Excellent for soft tissue detail, especially in equivocal cases
• Barium swallow: Demonstrates GI contents in hernial sac
• Antenatal ultrasound: Primary modality for CDH diagnosis at 20-week scan
• Fetal MRI: Quantifies lung volume when USG inconclusive

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8. Main Etiology and Main Symptoms of Diaphragmatic Hernia

Etiology

Main Symptoms

• Respiratory: Dyspnoea, tachypnoea, cyanosis, recurrent chest infections
• Gastrointestinal: Postprandial fullness, nausea, vomiting, abdominal/chest pain, heartburn
• In neonates: Severe respiratory distress immediately after birth is the hallmark of large Bochdalek hernias

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9. Main Symptoms of Pulmonary Emphysema

1. Progressive exertional dyspnoea — the dominant symptom
2. Chronic cough — often with sputum production (when combined with chronic bronchitis)
3. Barrel chest — increased AP thoracic diameter
4. Pursed-lip breathing — patients instinctively use it to reduce air trapping
5. Use of accessory muscles of respiration (scalenes, sternocleidomastoids)
6. Prolonged expiratory phase
7. Hyperresonance on percussion
8. Diminished or absent breath sounds
9. Weight loss — increased work of breathing raises caloric demand
10. Cor pulmonale (right ventricular hypertrophy/failure) in advanced disease

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10. Describe Emphysema

Pathogenesis

Four Anatomical Types

Other Forms

• Compensatory emphysema: Alveolar dilation in response to surgical removal of lung tissue (not true destructive emphysema)
• Obstructive overinflation: Air trapping due to ball-valve airway obstruction (tumour, foreign body); congenital lobar emphysema in infants
• Bullous emphysema: Large subpleural blebs/bullae (>1 cm); prone to rupture → pneumothorax
• Interstitial (mediastinal) emphysema: Air enters connective tissue stroma; tracks to mediastinum/subcutaneous tissue

Morphology

Pathological Consequences

• Airflow obstruction (irreversible)
• Air trapping → increased RV, TLC
• Loss of alveolar surface area → impaired gas exchange, reduced DLCO
• Pulmonary hypertension → cor pulmonale

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11. Describe Diaphragmatic Hernia

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12. Symptoms of Pulmonary Sequestration

• Often presents in young adults
• Recurrent pulmonary infections (pneumonia, lung abscess) in the same location — most common presentation
• Cough, productive purulent sputum
• Haemoptysis
• Pleuritic chest pain
• Fever during infective episodes
• Dyspnoea (if extensive)

• Usually detected incidentally on antenatal ultrasound or neonatal imaging
• May present as respiratory distress in neonates if large
• Associated congenital anomalies may dominate the clinical picture
• Can occasionally cause recurrent infections

• Persistent opacity in lower lobe (especially left) that fails to resolve with antibiotics
• CT angiography demonstrates the anomalous systemic arterial supply from the aorta — pathognomonic

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13. What Is Lung Gangrene? What Are Its Symptoms?

Etiology / Pathogenesis

• Severe bacterial pneumonia (especially Klebsiella pneumoniae, Staphylococcus aureus, anaerobes, Streptococcus pneumoniae)
• Pulmonary embolism with secondary infection
• Bronchial obstruction (tumour, lymphadenopathy) → distal infection
• Opportunistic infections in immunocompromised patients

Symptoms

• High fever, rigors
• Severe chest pain (pleuritic in nature)
• Productive cough — copious purulent sputum
• Putrid (foul-smelling) sputum — suggests anaerobic infection
• Haemoptysis (may be massive)
• Dyspnoea

• Hypotension
• Tachycardia, tachypnoea
• Malaise, anorexia, weight loss
• Deterioration of consciousness / septic shock
• Signs of systemic sepsis

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14. How Is Lung Gangrene Diagnosed and Treated?

Diagnosis

• Chest X-ray: Large consolidation, often with cavitation and/or a freely mobile sloughed lung mass ("pulmonary sequestrum" within the cavity)
• CT with contrast (gold standard):
  • Obliteration/lack of pulmonary arterial supply to the necrotic lobe (no contrast uptake)
  • Central necrosis affecting >50% of the involved lobe suggests gangrene (vs. lung abscess ≤50%)
  • Large cavities containing devitalized tissue
  • Bronchial obstruction may be identified
• Blood cultures, sputum culture and sensitivity — identify causative organism
• Bronchoscopy — to identify obstructing lesions and obtain BAL samples
• Laboratory: Leucocytosis, elevated inflammatory markers (CRP, ESR, procalcitonin), possible anaemia

Treatment

1. Broad-spectrum IV antibiotics — covering gram-positives, gram-negatives, and anaerobes; adjusted per culture results; prolonged course (4–8 weeks)
2. Surgical debridement — the accepted definitive treatment; removal of sloughed/devitalised lung parenchyma
   • Pneumonectomy or lobectomy often required
   • Decortication if pleural empyema co-exists
3. Supportive care: Mechanical ventilation if respiratory failure; vasopressors for septic shock
4. Bronchoscopic drainage of associated abscess in selected cases

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15. Complications and Diagnostic Methods of Pleural (Interstitial) Emphysema

Causes

• Alveolar rupture from sudden increase in intra-alveolar pressure (violent coughing, vomiting, Valsalva, mechanical ventilation with high PEEP)
• Underlying bullous emphysema predisposes
• Chest wounds, fractured ribs puncturing the lung
• Iatrogenic (procedures, intubation)

Complications

• Pneumomediastinum — air in mediastinal tissues; may compress mediastinal structures
• Subcutaneous emphysema — air tracks to neck, chest wall; visible swelling and crepitus on palpation
• Tension pneumomediastinum (rare) — haemodynamic compromise
• Pneumothorax — if air ruptures through visceral pleura
• Pneumopericardium — air around heart, risk of cardiac tamponade

Diagnostic Methods

• Chest X-ray: Radiolucent streaks outlining mediastinal contours, "air outlining the heart" sign; subcutaneous air visible; Naclerio's "V" sign (air at left cardiophrenic angle)
• CT scan: Most sensitive — precisely delineates the distribution and extent of air in fascial planes, mediastinum, and soft tissues
• Air is resorbed spontaneously once the source seals in most uncomplicated cases

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16. What Is Lobar Emphysema?

1. Left upper lobe (42%)
2. Right middle lobe (35%)
3. Right upper lobe

• Neonatal or early infantile respiratory distress (tachypnoea, cyanosis, dyspnoea)
• Progressive respiratory compromise as the lobe overdistends and compresses adjacent normal lung and mediastinal structures

• Chest X-ray: In the early postnatal period, the affected lobe may appear radio-opaque (fluid-filled). Later, it becomes hyperlucent with overexpansion and variable mediastinal shift.
• CT: Confirms overinflation, reduced vascularity of the affected lobe, and excludes secondary causes (vascular anomalies, bronchial compression, mediastinal masses)

• Asymptomatic patients: Conservative management and follow-up (some spontaneously improve)
• Symptomatic patients: Surgical lobectomy of the affected lobe

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17. What Is Spontaneous Pneumothorax?

Types:

• Occurs in young, tall, thin males without clinically apparent lung disease
• Pathological basis: rupture of small subpleural blebs/bullae at the lung apex, typically from distal acinar (paraseptal) emphysema
• Strong association with smoking

• Occurs as a complication of underlying lung disease
• Causes include: COPD/emphysema (ruptured bullae), cystic fibrosis, asthma, tuberculosis, Pneumocystis jirovecii pneumonia, lung cancer, Langerhans cell histiocytosis, lymphangioleiomyomatosis

Clinical Features:

• Sudden onset unilateral pleuritic chest pain
• Dyspnoea (severity depends on size of pneumothorax and underlying lung reserve)
• Reduced/absent breath sounds on the affected side
• Hyperresonance on percussion
• Tension pneumothorax (life-threatening): tracheal deviation away from the affected side, tachycardia, hypotension, hypoxia — requires immediate needle decompression

Diagnosis:

• Chest X-ray: Absence of lung markings peripherally; visceral pleural line visible
• CT scan: More sensitive; characterises size and identifies blebs/bullae

Treatment:

• Small, asymptomatic PSP: observation, supplemental O₂ (accelerates resorption)
• Symptomatic or large: needle aspiration, chest drain (intercostal tube)
• Recurrence: Video-assisted thoracoscopic surgery (VATS) with bullectomy + pleurodesis

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18. What Are Lung Cysts?

Congenital Lung Cysts:

• Lined with bronchial epithelium; contain mucinous or serous fluid (sometimes blood or air)
• Located in mediastinum or within lung parenchyma (lower lobes, proximal third)
• Often asymptomatic (mediastinal cysts); discovered incidentally
• Can cause mass effect → wheeze, stridor, dysphagia
• Can become infected → recurrent pneumonias
• CT: water-density smooth cyst (may be hyperdense if haemorrhage or high protein content)
• MRI: T2 hyperintense; variable T1 signal
• Surgical treatment only if symptomatic

• Mass of disorganised airway tissue, classified by Stocker (Types 0–4)
• Type 1 (large cysts >2 cm) and Type 2 (multiple small cysts <1 cm) are most common
• Can present with respiratory distress or as incidental finding
• Risk of infection and (rarely) malignant transformation (pleuropulmonary blastoma)

Acquired Cysts:

• Post-infectious cysts: Following necrotising pneumonia, TB, or abscess
• Bullae: Large (>1 cm) emphysematous spaces; prone to rupture → pneumothorax
• Blebs: Small subpleural collections (<1 cm); typical of PSP
• Cysts in systemic diseases: Lymphangioleiomyomatosis (LAM), Birt-Hogg-Dubé syndrome, Langerhans cell histiocytosis, Pneumocystis infection

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19. What Is a Bochdalek Hernia?

• ~80–85% left-sided (the liver closes the right-sided foramen earlier in development)
• Incidence: ~1 in 3000 live births
• Herniated contents (left side): stomach, small/large bowel, spleen; rarely kidney
• Herniated contents (right side): liver

• Antenatal ultrasound (20-week scan) — polyhydramnios may be present
• Fetal MRI for lung volume assessment
• Postnatal CXR: bowel gas in hemithorax, mediastinal shift, contralateral lung compression
• CT confirms anatomy

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20. What Is a Morgagni Hernia?

• ~90% right-sided (the pericardium protects the left)
• Bilateral in ~10%
• First described by Giovanni Battista Morgagni in 1761

• Usually presents later in life (childhood or adulthood) unlike Bochdalek hernia
• Up to 50% may be asymptomatic — incidental finding on imaging
• Symptomatic patients: dyspnoea, cough, chest/epigastric pain, nausea, recurrent chest infections, subileus
• Newborns: occasionally respiratory distress (rare)

• CXR: Smooth, well-defined opacity at the right cardiophrenic angle (anterior mediastinum); differentiated from pericardial cyst/fat pad by CT
• CT: Confirms anterior defect, identifies hernial contents (omental fat with fine linear vessels, or bowel)

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21. What Is a Hiatal Hernia?

Types (4-Type Classification):

Etiology:

• Weakening of diaphragmatic crura and phrenoesophageal ligament
• Increased intra-abdominal pressure (obesity, pregnancy, chronic cough, constipation)
• Ageing, congenital weakness
• Prior esophageal/gastric surgery

Symptoms:

• Sliding (Type I): Heartburn (worse on bending, lying down), regurgitation, belching — symptoms of GERD; often asymptomatic
• Paraesophageal (Types II–IV): Epigastric/substernal pain (especially postprandial), dysphagia, postprandial fullness, nausea
• Complications: Strangulation (sudden severe chest pain, inability to swallow), Cameron lesions (gastric ulceration → anaemia, GI bleed), incarceration

Diagnosis:

• Barium swallow / upper GI series
• Upper endoscopy (EGD)
• CT scan
• High-resolution manometry (for functional assessment)

Treatment:

• Small asymptomatic sliding hernias: lifestyle modification, PPIs
• Symptomatic or large hernias: laparoscopic surgical repair (cruroplasty + Nissen/partial fundoplication)
• Paraesophageal hernias: Surgery recommended due to strangulation risk

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22. What Is Pulmonary Sequestration and How Does It Present?

Presentation:

• Typically presents in adolescents and young adults
• Recurrent pneumonia in the same location (lower lobe, especially left) — the classic and most common presentation
• Cough, purulent sputum, haemoptysis, fever, chest pain
• The same area repeatedly consolidates on CXR, fails to clear completely with antibiotics, and re-infects

• Often detected on antenatal ultrasound as a well-defined echogenic mass
• May regress in utero
• Neonates: can cause respiratory distress if large; otherwise often asymptomatic
• Associated with congenital anomalies (ipsilateral diaphragmatic hernia in up to 60%, cardiac defects, vertebral anomalies)

Key Diagnostic Findings:

• CT angiography: Anomalous systemic artery arising from the aorta — the pathognomonic finding; also defines venous drainage
• CXR/CT: Opacity in lower lobe; no communication with bronchial tree
• MRI angiography: Alternative to CT, especially in children (no radiation)
• Doppler ultrasound: May identify feeding vessel

Treatment:

• Surgical resection (lobectomy for ILS, simple excision for ELS) — curative and prevents recurrent infection
• Pre-operative embolisation of the feeding artery in selected cases

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🫁 PULMONARY & THORACIC PATHOLOGY — COMPLETE TOPIC GUIDE

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TOPIC 1: CONGENITAL LUNG MALFORMATIONS

(Agenesis, Aplasia, Hypoplasia, Lung Cysts, Sequestration, Lobar Emphysema)

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📌 SECTION A: THE LUNG AGENESIS–HYPOPLASIA COMPLEX

Questions 1, 2

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🔑 KEY CONCEPT: The Three Degrees of Pulmonary Underdevelopment

MOST SEVERE ◄──────────────────────────────► LEAST SEVERE

   AGENESIS          APLASIA           HYPOPLASIA
 (complete           (blind-end        (small but
  absence)           bronchus only)     present lung)

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🫁 PULMONARY AGENESIS

• ❌ No bronchus
• ❌ No lung parenchyma (no alveoli, no airways)
• ❌ No pulmonary vasculature (no blood vessels)

• Goldenhar syndrome
• VACTERL association
• DiGeorge syndrome (22q11.2 deletion)
• Trisomy 21
• Cardiovascular, GI, skeletal, genitourinary defects

• In unilateral agenesis: the trachea extends directly into the main bronchus of the one functioning lung
• The functioning lung undergoes compensatory hyperinflation to fill the chest
• Recurrent respiratory infections occur because secretions stagnate
• Mediastinum shifts toward the affected side

• CXR: Completely opaque hemithorax on the affected side
• Mediastinal shift TOWARD the affected side
• Contralateral lung hyperinflated
• CT/MRI: Confirms complete structural absence — distinguishes it from aplasia and hypoplasia

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🫁 PULMONARY APLASIA

• ❌ No lung parenchyma develops from it
• ❌ No pulmonary vasculature
• ✅ Bronchial stump present (ends in a dead-end pouch)

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🫁 PULMONARY HYPOPLASIA

• ✅ Bronchi present (but reduced number)
• ✅ Alveoli present (but reduced number and size)
• ✅ Blood vessels present (but reduced)

• Primary: Direct developmental failure (rare)
• Secondary (more common): Compression of the developing lung by another structure:
  • Congenital diaphragmatic hernia — most common intrathoracic cause
  • Large CPAM or pulmonary sequestration
  • Potter sequence (severe oligohydramnios from renal agenesis — fetus can't "breathe" amniotic fluid)
  • Skeletal dysplasias (Jeune syndrome, thanatophoric dysplasia) — small thoracic cage

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✅ EASY MEMORY TABLE: Agenesis vs Aplasia vs Hypoplasia

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📌 SECTION B: PULMONARY SEQUESTRATION

Questions 3, 12, 22

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🔑 THE BIG PICTURE

"A piece of lung tissue that receives the wrong blood supply, connects to the wrong (or no) airway, and can't do its job — so it just sits there getting infected."

1. Separated from normal tracheobronchial tree (no normal airway connection)
2. Supplied by an anomalous systemic artery from the aorta (NOT the pulmonary artery)
3. Unable to participate in gas exchange (non-functioning)

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🫁 TWO TYPES: INTRALOBAR vs EXTRALOBAR

• Intralobar = the sequestered piece is inside the normal lung's pleural covering (like a room inside your house)
• Extralobar = the sequestered piece has its own pleural covering (like a separate shed in your yard)

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🏥 SYMPTOMS

• Young adult with recurrent pneumonia always in the same spot (left lower lobe)
• Cough with purulent sputum during infections
• Haemoptysis
• Pleuritic chest pain
• Fever during infective episodes
• The pneumonia never fully resolves and keeps coming back — this is the KEY CLUE

• Found on antenatal ultrasound as an echogenic mass
• Often completely asymptomatic at birth
• Neonatal respiratory distress only if very large
• Associated anomalies may dominate the picture

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🔬 DIAGNOSIS

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💊 TREATMENT

• Surgical resection — lobectomy (ILS) or simple excision (ELS)
• Curative; prevents further infections
• Pre-operative embolisation of the feeding artery is sometimes done first

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📌 SECTION C: LUNG CYSTS

Question 18

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🔑 WHAT ARE LUNG CYSTS?

CONGENITAL LUNG CYSTS

• Arise from abnormal budding of the primitive foregut
• Lined with bronchial epithelium
• Contain mucinous/serous fluid (sometimes blood or air)
• Location: Mediastinum (most common) or within lung (lower lobes, proximal 1/3)
• Symptoms:
  • Often ASYMPTOMATIC (found incidentally)
  • If large: wheeze, stridor, dysphagia from mass effect
  • If infected: recurrent pneumonias
• CT: Water-density smooth round cyst (may appear dense if haemorrhage/protein-rich)
• MRI: T2 hyperintense; variable T1
• Treatment: Surgery only if symptomatic

• Mass of disorganised airway tissue replacing normal lung
• Stocker Classification:
  • Type 0: Tracheal/bronchial origin; rare; fatal
  • Type 1: Large cysts >2 cm; most common; best prognosis
  • Type 2: Multiple small cysts <1 cm; associated with other anomalies
  • Type 3: Solid/micro-cystic; poor prognosis
  • Type 4: Large peripheral cysts; associated with pleuropulmonary blastoma (PPB)
• ⚠️ Must distinguish CPAM from Pleuropulmonary Blastoma (malignant!) — PPB has nodular/thick septa, not seen antenatally, associated with DICER1 mutation

ACQUIRED CYSTS

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📌 SECTION D: LOBAR EMPHYSEMA (CONGENITAL LOBAR OVERINFLATION)

Question 16

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🔑 WHAT IS IT?

"One lobe of a baby's lung progressively balloons up because air can get IN but can't get OUT."

• Inspiration: airway opens → air enters the lobe
• Expiration: weakened cartilage collapses the airway → air CANNOT escape
• Result: Progressive overdistension of that lobe

1. Left upper lobe (42%)
2. Right middle lobe (35%)
3. Right upper lobe

• Neonate or early infant in progressive respiratory distress
• Tachypnoea, cyanosis, dyspnoea — worsening over time
• As the lobe expands, it compresses the other lobes and shifts the mediastinum

• Early (fluid phase): Affected lobe appears radio-opaque (still full of fluid)
• Later: Hyperlucent, expanded lobe with mediastinal shift away from affected side
• CT: Confirms overinflation, reduced vascularity; excludes secondary causes (compression from vessel, mass)

• Asymptomatic: Watch and wait — can spontaneously improve
• Symptomatic: Surgical lobectomy of the offending lobe

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TOPIC 2: EMPHYSEMA — COMPLETE GUIDE

(Questions 4, 9, 10, 15, 17)

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📌 SECTION A: WHAT IS EMPHYSEMA?

Questions 4, 9, 10

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🔑 THE CORE DEFINITION

Emphysema = Permanent, irreversible enlargement of air spaces DISTAL to terminal bronchioles, WITH destruction of alveolar walls, WITHOUT significant fibrosis.

• Permanent/irreversible — not reversible with treatment (unlike asthma)
• Distal to terminal bronchioles — affects the acinus (the gas-exchange unit)
• Destruction of walls — the alveoli merge into big, floppy sacs
• No fibrosis — distinguishes it from fibrotic lung diseases

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🔬 PATHOGENESIS — HOW DOES EMPHYSEMA DEVELOP?

SMOKING / POLLUTANTS
        ↓
Recruits NEUTROPHILS & MACROPHAGES into lung
        ↓
They release ELASTASE (breaks down elastin in alveolar walls)
        ↓
Normally: α₁-ANTITRYPSIN neutralises elastase
        ↓
In smokers: Smoke INACTIVATES α₁-antitrypsin + overwhelms it
        ↓
UNCHECKED ELASTASE destroys alveolar walls
        ↓
Air spaces enlarge → EMPHYSEMA

• Genetic condition where patients have very little α₁-AT
• Elastase runs unchecked even WITHOUT smoking
• Results in panacinar emphysema in NON-smokers (though smoking dramatically worsens it)

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🗺️ THE FOUR ANATOMICAL TYPES OF EMPHYSEMA

Terminal bronchiole
      ↓
Respiratory bronchioles (proximal)
      ↓
Alveolar ducts
      ↓
Alveolar sacs / Alveoli (distal)

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TYPE 1: CENTRIACINAR (Centrilobular) Emphysema ⭐ MOST COMMON

[NORMAL ACINUS]          [CENTRIACINAR EMPHYSEMA]
Respiratory bronchiole   Respiratory bronchiole → DESTROYED, ENLARGED
Alveolar duct            Alveolar duct → normal
Alveoli                  Alveoli → normal (spared!)

• Affects the CENTRAL/PROXIMAL part of the acinus (respiratory bronchioles)
• Distal alveoli are SPARED → Both emphysematous and normal spaces in the SAME acinus
• Upper lobe predominance (especially apical segments)
• Cause: Heavy cigarette smoking; most common form in COPD
• >95% of clinically significant emphysema is this type

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TYPE 2: PANACINAR (Panlobular) Emphysema

[PANACINAR EMPHYSEMA]
Respiratory bronchiole → enlarged
Alveolar duct → enlarged
Alveoli → ALL enlarged uniformly

• Affects the ENTIRE acinus uniformly — everything from respiratory bronchiole to terminal alveolus
• Lower lobe predominance (bases and anterior margins)
• Cause: α₁-Antitrypsin deficiency (can occur in NON-smokers); smoking worsens it
• Less common than centriacinar

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TYPE 3: DISTAL ACINAR (Paraseptal) Emphysema ⭐ CLINICALLY IMPORTANT

[DISTAL ACINAR EMPHYSEMA]
Respiratory bronchiole → normal (spared!)
Alveolar duct → enlarged
Alveoli → DESTROYED (most affected at periphery)

• Affects the DISTAL part of acinus — near pleura and lobular septa
• Upper half of lungs predominance
• Enlarged spaces (0.5 mm to >2 cm) can form bullae (>1 cm cysts)
• Most cases of spontaneous pneumothorax in young adults — bullae rupture into pleural space
• Often young, non-smoking adults
• May be asymptomatic between pneumothorax episodes

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TYPE 4: IRREGULAR Emphysema

• Acinus irregularly involved
• Almost always associated with SCARRING (e.g., post-TB, old infarct)
• No distinct anatomical distribution

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✅ MASTER COMPARISON TABLE — 4 Types

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🩺 SYMPTOMS OF EMPHYSEMA

• Dyspnoea — starts on exertion, eventually at rest (insidious onset over years)
• Chronic cough — usually with sputum (especially with co-existing chronic bronchitis)
• Prolonged expiratory phase — characteristic wheeze on expiration
• Pursed-lip breathing — patients instinctively do this to create "auto-PEEP" and keep airways open

• Barrel chest — increased AP diameter (increased RV/TLC from air trapping)
• Use of accessory muscles — scalenes, sternocleidomastoids, intercostals visibly working
• Hyperresonance on percussion (increased air in chest)
• Diminished or absent breath sounds (destroyed alveoli, no turbulence)
• Tripod position — patients lean forward on arms to fix shoulders for accessory muscles

• Weight loss — increased work of breathing raises metabolic demand
• Cor pulmonale — pulmonary hypertension → right ventricular hypertrophy → right heart failure
  • Signs: elevated JVP, pedal oedema, hepatomegaly
• "Pink puffer" (in pure emphysema) vs "Blue bloater" (chronic bronchitis) — teaching concept

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🔬 DIAGNOSIS OF EMPHYSEMA

Reduced DLCO is the PFT hallmark of emphysema (distinguishes it from asthma where DLCO is normal)

• Hyperinflated lungs (lung fields extend below the level of right hemidiaphragm)
• Flattened diaphragm (classic — the diaphragm becomes flat instead of domed)
• Increased retrosternal air space (PA and lateral)
• Hyperlucency of lung fields
• Narrow vertical heart (Maypole heart)
• Bullae may be visible (radiolucent areas without lung markings)

• Areas of low attenuation without visible walls (destroyed alveoli)
• Identifies the distribution (centriacinar upper lobe vs. panacinar lower lobe)
• Quantifies the extent of emphysema
• Detects bullae
• Most sensitive and specific test

• Hypoxaemia (PaO₂ reduced)
• Hypercapnia (PaCO₂ elevated) in severe disease
• Respiratory acidosis in advanced cases

• Order if: panacinar pattern, young patient, non-smoker, lower lobe predominance
• Low levels confirm α₁-AT deficiency

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📚 OTHER FORMS OF EMPHYSEMA (Important for exams!)

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📌 SECTION B: INTERSTITIAL (PLEURAL) EMPHYSEMA

Question 15

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🔑 WHAT IS IT?

"Air escapes out of alveoli INTO the connective tissue of the lung, then spreads to the mediastinum, neck, and subcutaneous tissue."

• Pneumomediastinum — air in mediastinum
• Subcutaneous emphysema — air under the skin
• Pneumopericardium — air around the heart (rare, dangerous)

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CAUSES

• Violent coughing, vomiting, Valsalva → sudden rise in intra-alveolar pressure → alveolar wall tears
• Mechanical ventilation with high PEEP (barotrauma)
• Underlying bullous emphysema (weakened walls tear easily)
• Penetrating chest wounds, fractured ribs puncturing the lung

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COMPLICATIONS

1. Pneumomediastinum — air outlines mediastinal structures; usually benign but can cause pain
2. Subcutaneous emphysema — air tracks into neck and chest wall → characteristic crunching/crackling sensation on palpation (crepitus); visible swelling of face, neck, chest
3. Tension pneumomediastinum (rare) — compresses mediastinal structures → haemodynamic compromise
4. Pneumothorax — air ruptures through visceral pleura into pleural space
5. Pneumopericardium — air in pericardial sac → risk of cardiac tamponade

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DIAGNOSIS

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📌 SECTION C: SPONTANEOUS PNEUMOTHORAX

Question 17

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🔑 WHAT IS IT?

Spontaneous pneumothorax = Air in the pleural space occurring WITHOUT trauma or iatrogenic cause.

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TWO TYPES

• Occurs in apparently healthy young adults with NO known lung disease
• Classic patient: Tall, thin, young male, smoker
• Pathology: Rupture of small subpleural blebs/bullae — typically from distal acinar (paraseptal) emphysema at the lung apex
• These blebs may not be visible on CXR but are seen on CT
• Smoking is the main modifiable risk factor

• Complicates known lung disease — much more serious because the patient has less reserve
• Common causes:
  • COPD/Emphysema (most common) — ruptured bullae
  • Cystic fibrosis
  • Asthma (status asthmaticus)
  • Tuberculosis
  • Pneumocystis jirovecii pneumonia (AIDS)
  • Lung cancer
  • Langerhans cell histiocytosis
  • Lymphangioleiomyomatosis (LAM)

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CLINICAL FEATURES

• Sudden onset unilateral pleuritic chest pain — sharp, worsened by breathing
• Dyspnoea — severity depends on size + underlying lung reserve
• Patient may be breathless or relatively comfortable (PSP in a fit young person)

• Reduced/absent breath sounds on affected side
• Hyperresonance on percussion
• Tracheal deviation AWAY from affected side (if large)

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⚠️ TENSION PNEUMOTHORAX — LIFE-THREATENING EMERGENCY

• Progressive air accumulates → lung completely collapses → mediastinum shifts
• Signs: Trachea deviates AWAY from affected side, tachycardia, hypotension, hypoxia, elevated JVP, absent breath sounds
• Treatment: IMMEDIATE needle decompression (2nd intercostal space, midclavicular line) — do NOT wait for CXR

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DIAGNOSIS

• Small: <2 cm rim of air at apex
• Large: ≥2 cm rim of air

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TREATMENT

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TOPIC 3: DIAPHRAGMATIC HERNIAS — COMPLETE GUIDE

(Questions 5, 6, 7, 8, 11, 19, 20, 21)

═══════════════════════════════════

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📌 SECTION A: OVERVIEW — WHAT IS A DIAPHRAGMATIC HERNIA?

Questions 5, 11

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🔑 THE BIG PICTURE

A diaphragmatic hernia = Protrusion of abdominal contents through a defect in the diaphragm into the thoracic cavity.

• Thin, dome-shaped musculotendinous sheet
• Separates thorax (above) from abdomen (below)
• Has natural openings: esophageal hiatus, aortic hiatus, IVC foramen
• Has natural weak points where hernias form:
  • Posterolateral = Bochdalek triangle (most common site)
  • Anterior = Foramina of Morgagni
  • Esophageal hiatus = site of hiatal hernias

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CLASSIFICATION OF DIAPHRAGMATIC HERNIAS

DIAPHRAGMATIC HERNIAS
│
├── CONGENITAL
│   ├── Bochdalek Hernia (posterolateral, ~80-90% of CDH)
│   └── Morgagni Hernia (anterior, ~2-5% of CDH)
│
└── ACQUIRED
    ├── Hiatal Hernia (through esophageal hiatus — MOST COMMON overall)
    │   ├── Type I: Sliding
    │   ├── Type II: Rolling/Paraesophageal
    │   ├── Type III: Mixed
    │   └── Type IV: Complex
    ├── Traumatic (blunt/penetrating injury)
    └── Iatrogenic (surgical complication)

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GENERAL ETIOLOGY

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📌 SECTION B: BOCHDALEK HERNIA

Question 19

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🔑 ANATOMY AND BASICS

• Type: Most common congenital diaphragmatic hernia
• Location of defect: Posterolateral diaphragm (the Bochdalek foramen, pleuroperitoneal fold fails to fuse)
• Side: ~80–85% LEFT-sided (the liver on the right side naturally closes the right-sided defect earlier in development)
• Incidence: ~1 in 3000 live births
• Accounts for: ~70–90% of all CDH cases

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WHAT HERNIATES?

• Small intestine
• Large intestine
• Stomach
• Spleen
• (Rarely) left kidney, pancreas

• Liver (liver fills the defect — this is actually protective on the right side, which is why fewer right-sided hernias occur, and why right-sided ones often have better prognosis)

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THE KEY CONSEQUENCE: PULMONARY HYPOPLASIA

Herniation of abdominal organs into thorax
              ↓
Compression of developing lung (critical period: weeks 6-16 gestation)
              ↓
Both lungs underdeveloped (BILATERAL hypoplasia)
              ↓
After birth: lungs too small and stiff to ventilate adequately
              ↓
RESPIRATORY FAILURE + PULMONARY HYPERTENSION
              ↓
Right-to-left shunting through PDA/PFO
              ↓
Cyanosis, hypoxia, acidosis
              ↓
DEATH if untreated

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SYMPTOMS — NEONATAL PRESENTATION

• Severe respiratory distress immediately after birth
• Cyanosis (blue discolouration from hypoxia)
• Scaphoid abdomen — looks sunken (because bowel is in the chest, not abdomen!)
• Decreased/absent breath sounds on affected side (left)
• Bowel sounds heard in chest
• Barrel chest on affected side
• Mediastinum shifted to the right

• CNS malformations
• Cardiac: Tetralogy of Fallot, hypoplastic left heart syndrome (worst prognostic factor)
• Chromosomal abnormalities

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DIAGNOSIS

• Liver-up (liver herniated) = worse prognosis
• Low lung-head ratio (LHR) on ultrasound = more severe
• Early herniation = more severe hypoplasia
• Associated cardiac anomalies = significantly worse

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TREATMENT

1. Immediate stabilisation — gentle ventilation (avoid bag-mask ventilation → distends bowel in chest)
2. Nasogastric tube — decompress bowel
3. ECMO (Extracorporeal Membrane Oxygenation) — if too sick for surgery
4. Surgical repair — once stabilised:
   • Reduce herniated contents back into abdomen
   • Close diaphragmatic defect (primary closure or patch)
   • Open or minimally invasive (thoracoscopic/laparoscopic)
5. Post-op: Management of pulmonary hypertension (iNO, sildenafil)

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📌 SECTION C: MORGAGNI HERNIA

Question 20

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🔑 ANATOMY AND BASICS

• Type: Rarest congenital diaphragmatic hernia (~2–5% of CDH)
• Location: Anterior diaphragm — through the foramina of Morgagni (parasternal, adjacent to xiphoid process)
• Side: ~90% RIGHT-sided (the pericardium partially protects the left)
• First described: Giovanni Battista Morgagni, 1761

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WHAT HERNIATES?

• Omentum (most common)
• Transverse colon
• Rarely: small bowel, liver, stomach

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SYMPTOMS

• Up to 50% completely ASYMPTOMATIC — found incidentally
• When symptomatic:
  • Dyspnoea, cough
  • Epigastric/abdominal pain (especially after eating)
  • Nausea, vomiting
  • Recurrent chest infections
  • Subileus, constipation (bowel obstruction symptoms)
  • In neonates (rare): respiratory distress similar to Bochdalek

• Bowel obstruction and incarceration (bowel gets stuck)
• Strangulation (blood supply cut off → necrosis)

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DIAGNOSIS

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TREATMENT

• Surgical repair recommended even in asymptomatic patients (due to strangulation risk)
• Laparoscopic approach is the standard
• Good prognosis; low recurrence rate

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📌 SECTION D: HIATAL HERNIA

Question 21

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🔑 WHAT IS IT?

Hiatal hernia = Protrusion of abdominal contents (primarily stomach) through the ESOPHAGEAL HIATUS of the diaphragm into the thoracic cavity.

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THE FOUR TYPES

🔵 TYPE I — SLIDING HIATAL HERNIA (90–95%)

Normal:                    Type I (Sliding):
  Esophagus                  Esophagus
     ↓                          ↓
  GEJ [at diaphragm]         GEJ ← ABOVE diaphragm (slides up)
     ↓                          ↓ (slides back down)
  Stomach                    Fundus stays below

• The gastroesophageal junction (GEJ) AND cardia slide UP through the hiatus
• "Sliding" because it moves up and down
• Loss of angle of His → incompetent lower esophageal sphincter → GERD
• The most common cause of heartburn
• Often asymptomatic if small

🟡 TYPE II — ROLLING / PARAESOPHAGEAL HERNIA (Rare)

Type II (Rolling):
  Esophagus
     ↓
  GEJ ← STAYS BELOW diaphragm (fixed)
     ↓
  Fundus → ROLLS up alongside esophagus ABOVE diaphragm

• GEJ stays fixed below the diaphragm
• Fundus herniates through the hiatus, rolling up beside the esophagus
• Angle of His is maintained → LESS reflux
• BUT: Higher risk of strangulation and volvulus (stomach can rotate)

🟠 TYPE III — MIXED HERNIA (~5%)

• Features of both Type I and Type II
• Both the GEJ AND the fundus are above the diaphragm
• Large hernias that progressed from Type II

🔴 TYPE IV — COMPLEX / LARGE HERNIA (Rare)

• Large defect with other organs entering the hernia sac
• May contain: colon, spleen, pancreas, small bowel
• Mechanical complications common

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✅ TYPE COMPARISON TABLE

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ETIOLOGY

• Weakening of diaphragmatic crura and phrenoesophageal ligament
• Risk factors:
  • Obesity (↑ intra-abdominal pressure)
  • Pregnancy
  • Advanced age (ligaments weaken)
  • Chronic constipation/straining
  • Heavy lifting
  • Prior esophageal/gastric surgery

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SYMPTOMS

• Often asymptomatic (especially small hernias)
• Heartburn — worse when bending forward, lying down, straining
• Regurgitation of stomach contents
• Chronic belching
• Dysphagia (if large)

• Epigastric or substernal pain (especially after eating)
• Postprandial fullness
• Nausea, retching
• Dysphagia
• Shortness of breath (large hernia compressing lung)
• Cameron lesions — gastric ulcers at the hernial neck → anaemia, GI bleeding

• Sudden severe chest pain
• Inability to swallow
• Vomiting (obstruction)
• Requires IMMEDIATE surgery

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DIAGNOSIS

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TREATMENT

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MAIN SYMPTOMS SUMMARY (for all diaphragmatic hernias)

• Dyspnoea, tachypnoea
• Cyanosis (neonates with Bochdalek)
• Recurrent chest infections

• Heartburn, regurgitation (hiatal)
• Postprandial pain/fullness
• Nausea, vomiting
• Constipation/obstruction symptoms

• Respiratory distress immediately at birth
• Scaphoid abdomen
• Cyanosis
• Bowel sounds in chest

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═══════════════════════════════════

TOPIC 4: LUNG GANGRENE

(Questions 13, 14)

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📌 UNDERSTANDING THE SPECTRUM OF NECROTISING LUNG INFECTION

PNEUMONIA → NECROTISING PNEUMONIA → LUNG ABSCESS → LUNG GANGRENE
  (simple)     (multiple small         (single cavity,   (massive necrosis,
               cavities forming)        ≤50% of lobe)     >50% of lobe,
                                                          vascular thrombosis,
                                                          sloughed tissue)

• Lung abscess — necrosis ≤50% of affected lobe; cavitation
• Lung gangrene — necrosis >50% of affected lobe; LARGE VESSEL PULMONARY ARTERY THROMBOSIS; devitalized, sloughed tissue (like a pulmonary sequestrum/gangrenous slough within the cavity)

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🔑 DEFINITION

Lung (Pulmonary) Gangrene = Massive, full-thickness necrosis of lung parenchyma caused by vascular thrombosis (obliteration of pulmonary arterial supply), resulting in devitalized, sloughed lung tissue, often involving an entire lobe or segment.

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🦠 ETIOLOGY / CAUSES

• Klebsiella pneumoniae (classic in diabetics/alcoholics)
• Staphylococcus aureus (including MRSA)
• Anaerobic bacteria (Bacteroides, Peptostreptococcus) → putrid sputum
• Streptococcus pneumoniae (rare)
• Pseudomonas aeruginosa (immunocompromised)
• Polymicrobial infections

• Severe bacterial pneumonia (primary cause)
• Pulmonary embolism with secondary infection
• Bronchial obstruction (tumour, lymphadenopathy) → distal stagnant infection
• Diabetes mellitus, alcoholism, immunosuppression
• Aspiration

Severe infection → vascular invasion and thrombosis
                 → obliteration of pulmonary arterial supply
                 → infarction of entire lobe/segment
                 → total necrosis and sloughing of lung tissue
                 → gangrenous cavity containing dead tissue

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🩺 SYMPTOMS

LOCAL SYMPTOMS:

SYSTEMIC SYMPTOMS (severe/advanced):

REMEMBER: Foul-smelling/putrid sputum = anaerobic infection = think lung gangrene or lung abscess

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🔬 DIAGNOSIS

Imaging:

• Large consolidation, often with cavitation
• May show a freely mobile mass within the cavity (sloughed lung tissue = "pneumatocele" or gangrenous sequestrum)
• Pleural effusion/empyema may accompany

• Gangrene: Lack of perfusion + central necrosis >50% of lobe
• Abscess: Cavitary lesion ≤50% of affected lobe, with ring enhancement

Microbiological Tests:

• Blood cultures (often positive in bacteraemia/sepsis)
• Sputum culture and sensitivity — guides antibiotic therapy
• Bronchoscopy + BAL — identifies obstructing lesions, collects samples

Laboratory:

• Leucocytosis (very high WBC)
• Elevated CRP, ESR, procalcitonin
• Anaemia (from chronic infection)
• Hypoalbuminaemia

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💊 TREATMENT

1. Antibiotics (cornerstone of initial management)

• Broad-spectrum IV antibiotics targeting:
  • Gram-positive bacteria
  • Gram-negative bacteria
  • Anaerobes (crucial — metronidazole, clindamycin, or beta-lactam/beta-lactamase inhibitors)
• Duration: 4–8 weeks (long course required for cavitating/necrotic infections)
• Adjusted based on culture sensitivity

2. Surgical Treatment (definitive)

• The accepted definitive treatment
• Pneumonectomy or lobectomy — removal of the gangrenous lobe
• Decortication — if pleural empyema co-exists
• Timing: as soon as patient is stable enough

3. Supportive Care

• Mechanical ventilation if respiratory failure
• Vasopressors for septic shock
• Nutritional support (patients are catabolic and malnourished)
• Chest physiotherapy/postural drainage

4. Bronchoscopic drainage (selected cases)

• For associated abscesses
• To identify/remove obstructing bronchial lesions

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QUICK REVISION TABLES

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📋 MASTER TABLE: CONGENITAL LUNG MALFORMATIONS

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📋 MASTER TABLE: TYPES OF EMPHYSEMA

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📋 MASTER TABLE: DIAPHRAGMATIC HERNIAS

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📋 PNEUMOTHORAX — QUICK SUMMARY

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🧠 MEMORY AIDS

• Smokers → CentriACINAR (centriacinar)
• Panacinar → α₁-AT deficiency (Panacinar)
• Distal → spontaneous pneumothorax (Distal acinar)
• Irregular → scarring (Irregular)

• Bochdalek = Back (posterior) + Left
• Morgagni = Midsternal (anterior) + Right

• Extralobar = Extra-pleural wrapping (own pleura)
• Intralobar = Intra-pleural (inside normal lung's pleura)

• Abscess = cavity ≤50% of lobe (localised death)
• Gangrene = cavity >50% + vascular obliteration (massive death)

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