Question 1: Pulmonary Nodule
Stem: A 68-year-old man with a 40-pack-year smoking history is found to have a 7 mm solid, non-calcified nodule in the right upper lobe on a CT scan. The margins are irregular and spiculated. No previous imaging is available.
Question: According to BTS (British Thoracic Society) guidelines, what is the most appropriate next step?
(A) Repeat CT in 12 months. (B) PET-CT scan. (C) Repeat CT in 3 months. (D) Discharge the patient. (E) CT-guided biopsy.
Correct Answer: (C) Repeat CT in 3 months.
Explanation:
- Why (C) is correct: According to BTS guidelines, for a solid nodule between 5-8 mm (volume 80-300 mm³) with a high risk of malignancy (spiculated, smoker, upper lobe), a 3-month follow-up CT is the recommended step. The purpose is to assess the volume doubling time.
- Why (A) is wrong: A 12-month repeat CT is for low-risk nodules in this size range, which this is not.
- Why (B) is wrong: PET-CT is generally recommended for high-risk nodules that are >8 mm (or >300 mm³), as its spatial resolution is not reliable for smaller nodules.
- Why (D) is wrong: Discharging a patient with a new, high-risk nodule is incorrect.
- Why (E) is wrong: Biopsy is typically reserved for larger nodules (>8-10 mm) or for nodules that have shown interval growth on follow-up, as the diagnostic yield and risk of biopsy for a 7 mm nodule are not favorable as a first-line step.
Key Points: Solid Pulmonary Nodule (BTS Guidelines)
- Risk Factors: Increased age, smoking, prior malignancy, larger size, upper lobe location, spiculated margin.
- Size < 5 mm (low risk): No follow-up needed.
- Size < 5 mm (high risk): Optional CT at 12 months.
- Size 5-8 mm (low risk): Repeat CT at 12 months.
- Size 5-8 mm (high risk): Repeat CT at 3 months.
- Size > 8 mm (high risk): Offer PET-CT and/or biopsy.
Question 2: Interstitial Lung Disease (UIP)
Stem: A 67-year-old man, a former smoker, presents with a 3-year history of progressive shortness of breath and a dry, persistent cough. A HRCT of the chest is performed. The scan demonstrates bilateral, basal-predominant, and subpleural reticulation with multiple layers of honeycomb cysts.
Question: This HRCT pattern is diagnostic of which of the following?
(A) Non-Specific Interstitial Pneumonitis (NSIP) (B) Hypersensitivity Pneumonitis (HP) (C) Usual Interstitial Pneumonitis (UIP) (D) Sarcoidosis (E) Asbestosis
Correct Answer: (C) Usual Interstitial Pneumonitis (UIP).
Explanation:
- Why (C) is correct: The combination of basal predominance, subpleural distribution, and honeycombing is the classic, diagnostic pattern of UIP. In the absence of other causes (like asbestosis or connective tissue disease), this is diagnostic of Idiopathic Pulmonary Fibrosis (IPF).
- Why (A) is wrong: NSIP is characterized by ground-glass opacification, often with subpleural sparing. Honeycombing is rare or absent.
- Why (B) is wrong: Chronic HP typically shows mid-to-upper zone predominant fibrosis, mosaic attenuation (air trapping), and “headcheese sign” (mix of GGO, normal lung, and air trapping).
- Why (D) is wrong: Sarcoidosis is characterized by a perilymphatic nodular distribution, typically in the mid-to-upper zones, with bilateral hilar lymphadenopathy.
- Why (E) is wrong: Asbestosis can cause a UIP pattern, but it is almost invariably accompanied by pleural plaques, which were not described. Without plaques, UIP is the correct radiological pattern.
Key Points: Usual Interstitial Pneumonitis (UIP)
- Hallmark: Fibrosis and lung destruction, often idiopathic (IPF).
- HRCT Pattern (Classic):
- Distribution: Basal and subpleural.
- Key Finding: Honeycombing (clustered cystic airspaces).
- Other findings: Reticulation, traction bronchiectasis.
- Absence of: Ground-glass opacification (if extensive, suggests another diagnosis).
Question 3: Airways Disease (ABPA)
Stem: A 24-year-old man with a long-standing history of asthma presents with worsening wheeze and coughing up brownish mucous plugs. A CT chest shows central bronchiectasis, predominantly affecting the upper lobes. Several bronchi are impacted with high-attenuation mucus.
Question: What is the most likely diagnosis?
(A) Cystic Fibrosis (CF) (B) Allergic Bronchopulmonary Aspergillosis (ABPA) (C) Post-primary Tuberculosis (D) Kartagener Syndrome (E) Bronchial Carcinoid
Correct Answer: (B) Allergic Bronchopulmonary Aspergillosis (ABPA).
Explanation:
- Why (B) is correct: The combination of pre-existing asthma, central bronchiectasis (not peripheral), and high-attenuation mucus (from fungal hyphae) is classic for ABPA. The brownish mucus plugs are also a key clinical clue.
- Why (A) is wrong: CF also causes upper-lobe predominant bronchiectasis, but it is not specifically “central” and is not associated with high-attenuation mucus.
- Why (C) is wrong: TB causes upper-lobe cavitation and bronchiectasis from scarring, but not high-attenuation mucus.
- Why (D) is wrong: Kartagener Syndrome (primary ciliary dyskinesia) causes bronchiectasis, but it is typically in the lower lobes and associated with situs inversus.
- Why (E) is wrong: A bronchial carcinoid would cause a focal obstruction, leading to post-obstructive collapse or bronchiectasis in a single segment, not widespread central disease.
Key Points: Allergic Bronchopulmonary Aspergillosis (ABPA)
- Pathology: A hypersensitivity reaction to Aspergillus species in patients with asthma or CF.
- CT Findings:
- Central bronchiectasis (involves central 2/3 of lungs), upper-lobe predominant.
- High-attenuation mucus plugging (a key finding).
- “Finger-in-glove” opacities (mucoid impaction in dilated bronchi).
Question 4: Pulmonary Infection (Septic Emboli)
Stem: A 35-year-old intravenous drug user presents with a 3-day history of high fever, rigors, and pleuritic chest pain. A CT chest with contrast shows multiple, bilateral, ill-defined pulmonary nodules, which are most prominent at the lung periphery. Several of these nodules show central cavitation.
Question: These findings are most characteristic of what diagnosis?
(A) Miliary Tuberculosis (B) Wegener’s Granulomatosis (GPA) (C) Squamous cell carcinoma metastases (D) Septic emboli (E) Fungal pneumonia
Correct Answer: (D) Septic emboli.
Explanation:
- Why (D) is correct: The clinical history (IVDU, high fever) strongly suggests bacteremia. The CT pattern of multiple, bilateral, peripheral, cavitating nodules is the classic appearance of septic emboli, typically from tricuspid valve endocarditis.
- Why (A) is wrong: Miliary TB presents as innumerable, tiny (1-3 mm), randomly distributed micronodules.
- Why (B) is wrong: GPA also causes cavitating nodules, but it is a vasculitis, not an acute infection, and would not present with high fever and rigors in an IVDU.
- Why (C) is wrong: Squamous cell metastases can cavitate, but they are typically more well-defined and associated with a known primary, not an acute febrile illness.
- Why (E) is wrong: Fungal pneumonia (e.g., invasive aspergillosis) can cause nodules (often with a “halo sign”), but the classic septic emboli picture is the best fit for this specific clinical and radiological combination.
Key Points: Septic Emboli
- Source: Most commonly tricuspid valve endocarditis (especially in IVDUs) or infected central lines.
- CT Findings:
- Multiple nodules or wedge-shaped opacities.
- Peripheral (subpleural) distribution (as they travel via the pulmonary arteries).
- Frequent and often rapid cavitation.
- “Feeding vessel sign” (a distinct vessel leading to the nodule) can sometimes be seen.
Question 5: Pleural Disease (Mesothelioma)
Stem: A 74-year-old man with a documented history of significant asbestos exposure as a plumber presents with shortness of breath. A CT chest reveals circumferential, nodular thickening of the right pleura, which extends into and widens the interlobar fissures. There is an associated moderate right-sided pleural effusion.
Question: What is the most likely diagnosis?
(A) Malignant Mesothelioma (B) Empyema (C) Metastatic Adenocarcinoma (D) Tuberculous Pleurisy (E) Pleural Lymphoma
Correct Answer: (A) Malignant Mesothelioma.
Explanation:
- Why (A) is correct: The combination of significant asbestos exposure history and nodular, circumferential pleural thickening that encases the lung and invades the fissures is pathognomonic for malignant mesothelioma.
- Why (B) is wrong: An empyema is an infected collection. On CT, it typically has smooth, enhancing walls (the “split pleura sign”) rather than nodular thickening.
- Why (C) is wrong: Pleural metastases (e.g., from lung adenocarcinoma) are common, but they tend to cause multiple discrete pleural nodules and effusions, rather than a contiguous, circumferential “rind” of tumour.
- Why (D) is wrong: TB pleurisy typically causes a simple effusion with smooth pleural enhancement, not nodular thickening.
- Why (E) is wrong: Lymphoma can involve the pleura but, like metastases, usually presents as discrete nodules or plaques, not a full rind-like encasement.
Key Points: Malignant Mesothelioma
- Risk Factor: Strong association with asbestos exposure (can be latent for 20-40 years).
- CT Findings:
- Unilateral, nodular, or rind-like pleural thickening.
- Circumferential encasement of the lung.
- Extension into the interlobar fissures.
- Often associated with a large pleural effusion.
- Note: Associated calcified pleural plaques (from asbestos) support the diagnosis, but their absence does not exclude it.
Question 6: Airways Disease (Bronchiectasis)
Stem: A 58-year-old female non-smoker presents with a chronic, productive cough. A HRCT is performed. In the lower lobes, multiple bronchi are seen to be dilated, with an internal diameter greater than that of the adjacent pulmonary artery.
Question: This specific imaging finding is known as what?
(A) The “Signet Ring Sign” (B) The “Comb Sign” (C) The “Reversed Halo Sign” (D) The “Tree-in-Bud Sign” (E) The “Halo Sign”
Correct Answer: (A) The “Signet Ring Sign”.
Explanation:
- Why (A) is correct: This is the definition of the “signet ring sign,” the cardinal feature of bronchiectasis on HRCT. The dilated bronchus (seen in cross-section) forms the “ring,” and the adjacent, smaller pulmonary artery forms the “signet.”
- Why (B) is wrong: The “comb sign” refers to prominent vasa recta in the mesentery, seen in active Crohn’s disease.
- Why (C) is wrong: The “reversed halo sign” (central ground-glass with a peripheral ring of consolidation) is associated with Cryptogenic Organising Pneumonia (COP).
- Why (D) is wrong: The “tree-in-bud sign” represents mucus-filled, impacted centrilobular bronchioles and is a sign of infective bronchiolitis (e.g., TB).
- Why (E) is wrong: The “halo sign” (a halo of ground-glass opacification around a nodule) is a sign of hemorrhage, most often seen with invasive aspergillosis.
Key Points: Bronchiectasis
- Definition: Irreversible, abnormal dilatation of the bronchi.
- HRCT Findings:
- “Signet Ring Sign”: Broncho-arterial ratio > 1 (the key sign).
- Lack of bronchial tapering: Bronchi remain wide as they extend to the periphery.
- Visualization of bronchi: Ability to see bronchi within 1 cm of the costal pleura.
Question 7: Pulmonary Infection (Tuberculosis)
Stem: A 34-year-old man from an endemic region presents with a 2-month history of cough, night sweats, and weight loss. A CT chest demonstrates consolidation, cavitation, and multiple small nodules in the apical and posterior segments of the right upper lobe. Some of the small nodules have a branching, linear appearance.
Question: This pattern of findings is most typical for which diagnosis?
(A) Primary Tuberculosis (B) Post-primary (Re-activation) Tuberculosis (C) Atypical Mycobacterial (MAC) Infection (D) Staphylococcal Pneumonia (E) Silicosis
Correct Answer: (B) Post-primary (Re-activation) Tuberculosis.
Explanation:
- Why (B) is correct: This is the classic presentation of re-activation TB. The key features are upper lobe predominance (apical/posterior segments), cavitation, and “tree-in-bud” opacities (the branching nodules), which represent endobronchial spread of the infection.
- Why (A) is wrong: Primary TB typically presents with a peripheral lung nodule (Ghon focus) and ipsilateral hilar lymphadenopathy. It does not typically cavitate (unless it’s progressive primary disease).
- Why (C) is wrong: Mycobacterium avium complex (MAC) can look identical but is most common in elderly patients with COPD or as the “Lady Windermere” syndrome (bronchiectasis in the middle lobe/lingula). Re-activation TB is more likely given the patient’s age and history.
- Why (D) is wrong: Staph pneumonia can cavitate rapidly, but it does not have the strong upper-lobe predilection.
- Why (E) is wrong: Silicosis presents as multiple small nodules, also in the upper zones, which can coalesce (progressive massive fibrosis), but cavitation is not a primary feature (unless it’s complicated by TB).
Key Points: Post-primary (Re-activation) Tuberculosis
- Pathology: Reactivation of a dormant primary infection, typically in a state of relative immunosuppression.
- CT Findings:
- Predilection: Upper lobes (apical and posterior segments) and superior segments of the lower lobes.
- Key Finding: Cavitation.
- “Tree-in-bud” opacities from endobronchial spread.
- Often associated with scarring, volume loss, and traction bronchiectasis.
Question 8: Mediastinal Mass
Stem: A 45-year-old woman is diagnosed with myasthenia gravis. A contrast-enhanced CT of the chest is requested. The scan reveals a well-defined, homogeneous, soft-tissue mass in the anterior mediastinum, located just anterior to the aortic root. It does not contain fat or calcification.
Question: What is the most likely diagnosis?
(A) Teratoma (B) Thymoma (C) Retrosternal Goitre (D) Lymphoma (E) Morgagni Hernia
Correct Answer: (B) Thymoma.
Explanation:
- Why (B) is correct: The diagnosis is made by combining the location (anterior mediastinum) with the strong clinical association. Myasthenia gravis has a very strong association with thymoma (15% of thymoma patients have MG, and 30-40% of MG patients have a thymoma). It is the most common anterior mediastinal mass in adults.
- Why (A) is wrong: A teratoma (a germ cell tumour) is also in the anterior mediastinum but is classically “multicomponent,” often containing fat, calcification (teeth), and cystic areas.
- Why (C) is wrong: A retrosternal goitre would be seen in continuity with the thyroid gland in the neck and is often high-attenuation (iodine-containing).
- Why (D) is wrong: Lymphoma is also a “terrible” anterior mediastinal mass, but it typically presents as a more bulky, lobulated mass and often involves multiple nodal stations, rather than a single well-defined mass.
- Why (E) is wrong: A Morgagni hernia is a defect in the anterior diaphragm, and it would typically contain fat (omentum) or bowel loops.
Key Points: Anterior Mediastinal Masses (The “4 T’s”)
- Thymoma: Most common primary tumour. Smooth, soft-tissue mass. Strong link to Myasthenia Gravis.
- Teratoma (and Germ Cell Tumours): Classically contains fat, calcification, and cystic components.
- Thyroid (Retrosternal Goitre): Continuous with the cervical thyroid; often high-density.
- “Terrible” Lymphoma: Typically a bulky, lobulated mass involving multiple nodes.
Question 9: Pulmonary Vascular Disease (PE)
Stem: A 55-year-old woman presents with acute-onset pleuritic chest pain 4 days after undergoing a total knee replacement. A CT Pulmonary Angiogram (CTPA) is performed. In the right lower lobe pulmonary artery, a central filling defect is seen in cross-section, surrounded by a thin rim of contrast.
Question: This specific CT sign is commonly referred to as what?
(A) The “Polo Mint Sign” (B) The “Feeding Vessel Sign” (C) The “Reversed Halo Sign” (D) The “Hampton’s Hump” (E) The “Westermark Sign”
Correct Answer: (A) The “Polo Mint Sign”.
Explanation:
- Why (A) is correct: This describes the “polo mint” sign (or “lifesaver” sign), a direct sign of an acute PE. It represents a central, dark thrombus seen en face (in cross-section), surrounded by a rim of bright contrast within the pulmonary artery.
- Why (B) is wrong: The “feeding vessel sign” is a vessel seen leading directly into a nodule, most commonly a septic embolus or metastasis.
- Why (C) is wrong: The “reversed halo sign” (central GGO, peripheral consolidation) is seen in Cryptogenic Organising Pneumonia (COP).
- Why (D) is wrong: Hampton’s hump is a CXR sign (and indirect CT sign) of a wedge-shaped, peripherally-based infarct in the lung parenchyma resulting from a PE. It is not a sign of the clot itself.
- Why (E) is wrong: The Westermark sign is a CXR sign (and indirect CT sign) of regional oligemia (decreased blood flow) distal to a large PE.
Key Points: Acute Pulmonary Embolism (CTPA)
- Direct Signs (Signs of the clot):
- Partial filling defect: Clot partially filling the artery.
- “Polo Mint Sign”: Central defect seen in cross-section.
- “Railway Track Sign”: Clot seen along the wall of a vessel longitudinally.
- Complete occlusion: Artery is fully blocked with no contrast.
- Indirect Signs (Signs of the effect):
- Right heart strain: RV/LV diameter ratio > 1.
- Hampton’s Hump: Wedge-shaped pulmonary infarct.
- Mosaic Perfusion: Patchy areas of high and low lung density.
Question 10: Interstitial Lung Disease (NSIP)
Stem: A 52-year-old woman with a known diagnosis of systemic sclerosis (scleroderma) presents with worsening exertional dyspnoea. Her HRCT shows bilateral, symmetric ground-glass opacification and fine reticulations, which are most prominent in the lower lobes. There is relative sparing of the immediate subpleural lung.
Question: This HRCT pattern, especially in this clinical context, is most characteristic of:
(A) Usual Interstitial Pneumonitis (UIP) (B) Non-Specific Interstitial Pneumonitis (NSIP) (C) Cryptogenic Organising Pneumonia (COP) (D) Lymphangioleiomyomatosis (LAM) (E) Sarcoidosis
Correct Answer: (B) Non-Specific Interstitial Pneumonitis (NSIP).
Explanation:
- Why (B) is correct: NSIP is the most common ILD pattern found in patients with connective tissue diseases, particularly systemic sclerosis. The key radiological feature is bilateral, basal-predominant ground-glass opacification with subpleural sparing. This is the opposite of UIP.
- Why (A) is wrong: UIP (the second most common pattern in scleroderma) is defined by subpleural predominance and honeycombing, which is absent here.
- Why (C) is wrong: COP presents with peripheral consolidation, not basal ground-glass.
- Why (D) is wrong: LAM is characterized by diffuse, thin-walled, round cysts, not ground-glass opacities, and is not associated with scleroderma.
- Why (E) is wrong: Sarcoidosis is an upper-zone, perilymphatic nodular disease.
Key Points: Non-Specific Interstitial Pneumonitis (NSIP)
- Pathology: A common pattern of lung injury, strongly associated with connective tissue diseases (e.g., scleroderma, polymyositis).
- HRCT Pattern (Classic Cellular NSIP):
- Predominant finding: Bilateral, symmetric ground-glass opacification.
- Distribution: Basal-predominant.
- Key Feature: Relative subpleural sparing.
Question 11: Pulmonary Infection (PCP)
Stem: A 40-year-old man with untreated HIV (CD4 count of 50 cells/µL) presents with a 2-week history of severe dyspnoea and a dry cough. HRCT of the chest reveals extensive, bilateral, perihilar (“bat-wing”) ground-glass opacification. The peripheral lung fields are relatively spared.
Question: What is the most likely causative organism?
(A) Pneumocystis jirovecii (B) Mycobacterium tuberculosis (C) Streptococcus pneumoniae (D) Aspergillus fumigatus (E) Staphylococcus aureus
Correct Answer: (A) Pneumocystis jirovecii.
Explanation:
- Why (A) is correct: The clinical context of severe immunosuppression (CD4 count < 200) combined with the classic CT pattern of bilateral, central/perihilar ground-glass opacification is pathognomonic for Pneumocystis jirovecii pneumonia (PCP).
- Why (B) is wrong: TB in an AIDS patient can be atypical but classically presents as upper lobe cavitation (if CD4 is high) or miliary disease/adenopathy (if CD4 is low). It does not typically cause a bat-wing GGO pattern.
- Why (C) is wrong: Streptococcus causes lobar consolidation.
- Why (D) is wrong: Aspergillus causes invasive disease (halo sign) or fungal balls (mycetoma) in immunocompromised patients.
- Why (E) is wrong: Staphylococcus causes cavitating nodules/abscesses (septic emboli).
Key Points: Pneumocystis jirovecii Pneumonia (PCP)
- Risk Factor: Severe immunosuppression, classically CD4 count < 200.
- CT Findings:
- Bilateral, symmetric ground-glass opacification.
- Distribution: Perihilar or “bat-wing” distribution is classic.
- Can also have a “crazy-paving” pattern (GGO + septal thickening).
- Pneumatoceles (thin-walled cysts) can develop.
Question 12: Airways Disease (Emphysema)
Stem: A 35-year-old non-smoker is investigated for dyspnoea. A CT chest demonstrates diffuse, bilateral panlobular emphysema, which is most severe in the lower lobes. The liver appears nodular and shrunken.
Question: What is the most likely underlying diagnosis?
(A) Smoking-related COPD (B) Alpha-1-Antitrypsin Deficiency (C) Lymphangioleiomyomatosis (LAM) (D) Hypersensitivity Pneumonitis (E) Cystic Fibrosis
Correct Answer: (B) Alpha-1-Antitrypsin Deficiency.
Explanation:
- Why (B) is correct: The combination of panlobular emphysema (affecting the entire acinus) with a lower-lobe predominance in a young non-smoker is the classic presentation of Alpha-1-Antitrypsin Deficiency. The finding of cirrhosis (nodular, shrunken liver) is also a well-known comorbidity, as the abnormal protein accumulates in the liver.
- Why (A) is wrong: Smoking-related emphysema is centrilobular and has an upper-lobe predominance.
- Why (C) is wrong: LAM causes diffuse cysts, not emphysema (which is parenchymal destruction with no visible walls).
- Why (D) is wrong: HP causes fibrosis and air-trapping, not panlobular emphysema.
- Why (E) is wrong: CF causes upper-lobe bronchiectasis and cysts, not lower-lobe emphysema.
Key Points: Emphysema Types
- Centrilobular: Upper lobes. Strongest link to smoking. Destroys the center of the lobule.
- Panlobular (Panacinar): Lower lobes. Classic for Alpha-1-Antitrypsin Deficiency. Destroys the entire acinus.
- Paraseptal: Subpleural. Associated with spontaneous pneumothorax in young adults.
Question 13: Interstitial Lung Disease (Sarcoidosis)
Stem: A 42-year-old woman presents with a persistent cough and erythema nodosum. A CT chest is performed. It reveals bilateral, symmetric hilar and right paratracheal lymphadenopathy. Additionally, there are numerous small, well-defined nodules within the lung parenchyma, which are most prominent along the bronchovascular bundles, interlobular septa, and subpleural surfaces.
Question: This specific distribution of pulmonary nodules is best described as:
(A) Centrilobular (B) Random (Miliary) (C) Perilymphatic (D) Panlobular (E) Consolidative
Correct Answer: (C) Perilymphatic.
Explanation:
- Why (C) is correct: The case describes classic sarcoidosis (hilar adenopathy, erythema nodosum). The pulmonary nodules in sarcoidosis follow the path of the lymphatics, which are located in the bronchovascular bundles, interlobular septa, and subpleural regions. This is the definition of a perilymphatic distribution.
- Why (A) is wrong: Centrilobular nodules are clustered in the center of the secondary pulmonary lobule, seen in infectious bronchiolitis (“tree-in-bud”) or HP.
- Why (B) is wrong: A random or miliary distribution implies haematogenous (bloodstream) spread, with nodules scattered randomly, like in miliary TB or metastases.
- Why (D) & (E) are wrong: These are not nodular patterns.
Key Points: Sarcoidosis
- Pathology: A multisystem granulomatous disease of unknown origin.
- Classic CXR/CT Findings:
- Bilateral, symmetric hilar lymphadenopathy (often with right paratracheal node – “1-2-3 sign”).
- Nodules: Small, well-defined, with a perilymphatic distribution.
- Fibrosis: Tends to be in the mid-to-upper zones in later stages.
Question 14: Congenital Lung Lesion
Stem: A 30-year-old asymptomatic man has a chest X-ray for an insurance medical, which shows a well-defined, triangular opacity in the right cardiophrenic angle. A subsequent CT angiogram confirms a segment of non-aerated lung tissue receiving a large systemic arterial supply directly from the thoracic aorta. Venous drainage is via the pulmonary veins.
Question: What is the most likely diagnosis?
(A) Bronchogenic Cyst (B) Pulmonary Arteriovenous Malformation (AVM) (C) Intralobar Pulmonary Sequestration (D) Extralobar Pulmonary Sequestration (E) Congenital Pulmonary Airway Malformation (CPAM)
Correct Answer: (C) Intralobar Pulmonary Sequestration.
Explanation:
- Why (C) is correct: A pulmonary sequestration is non-functioning lung tissue with no normal connection to the bronchial tree and a systemic arterial supply (the key feature). An intralobar sequestration (the more common type) is located within the normal lung pleura and typically drains via pulmonary veins.
- Why (A) is wrong: A bronchogenic cyst is a simple fluid-filled cyst and does not have a systemic arterial supply.
- Why (B) is wrong: A pulmonary AVM is a direct connection (fistula) between a pulmonary artery and a pulmonary vein. It does not have a systemic arterial supply.
- Why (D) is wrong: An extralobar sequestration also has a systemic arterial supply, but it has its own pleural covering (is “extra” to the lung) and drains via systemic veins (e.g., IVC, azygos).
- Why (E) is wrong: A CPAM (formerly CCAM) is a multicystic mass of abnormal lung tissue, not typically a solid, sequestered segment.
Key Points: Pulmonary Sequestration
- Definition: Non-functioning (sequestered) lung tissue with a systemic arterial supply.
- Intralobar (Common): Inside the lung’s pleura. Drains via Pulmonary Veins. Presents in adulthood, often with infection.
- Extralobar (Rare): Has its own pleura. Drains via Systemic Veins. Presents in infancy with respiratory distress.
Question 15: Pleural Disease (Pneumothorax)
Stem: A 22-year-old tall, thin man presents to the emergency department with a sudden onset of sharp, left-sided pleuritic chest pain and dyspnoea. A chest X-ray confirms a large left-sided pneumothorax.
Question: What is the most likely underlying cause for this patient’s condition?
(A) Rupture of an apical subpleural bleb (B) Diffuse centrilobular emphysema (C) Underlying Pneumocystis jirovecii pneumonia (D) Lymphangioleiomyomatosis (LAM) (E) Metastatic sarcoma
Correct Answer: (A) Rupture of an apical subpleural bleb.
Explanation:
- Why (A) is correct: This is the classic presentation of a primary spontaneous pneumothorax (PSP). The typical patient is a tall, thin, young male. The underlying cause is the rupture of a small, apical, subpleural bleb or bulla (often related to paraseptal emphysema).
- Why (B) is wrong: Centrilobular emphysema is related to smoking and is a cause of secondary spontaneous pneumothorax in older patients, not the classic cause for a PSP in this demographic.
- Why (C) is wrong: PCP can cause pneumothorax due to cyst formation, but the patient has no risk factors for immunosuppression.
- Why (D) is wrong: LAM causes cystic lung disease and pneumothorax, but it occurs almost exclusively in females of child-bearing age.
- Why (E) is wrong: Metastases (especially sarcoma) can cause pneumothorax, but this is rare and not the most likely cause in this classic demographic.
Key Points: Primary Spontaneous Pneumothorax (PSP)
- Definition: A pneumothorax occurring without a precipitating event in a patient with no known clinical lung disease.
- Classic Patient: Tall, thin, young males (20s-30s).
- Underlying Cause: Rupture of an apical subpleural bleb or bulla.
- Secondary Spontaneous Pneumothorax (SSP): Occurs in patients with known lung disease (e.g., COPD, CF, PCP, LAM).
