MBBS viva · Infectious Diseases / Respiratory
Community-acquired pneumonia — CXR interpretation and management viva
A final-prof viva on interpreting a consolidation CXR, framing the differential, grading severity with CURB-65 and justifying empirical therapy. Examiner expects mechanism and dose-level detail, not labels.
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Interpretation
The examiner presents a CXR showing right lower-lobe homogeneous opacity with air-bronchograms and loss of the right hemidiaphragm silhouette, and asks: "What do you see, what is the diagnosis, and how would you manage this patient?"
- Radiograph: right lower-lobe consolidation (alveolar filling) with air-bronchograms — the hallmark of lobar pneumonia. Volume loss is absent (distinguishes it from collapse).[1]
- Likely aetiology: typical bacterial — Streptococcus pneumoniae most commonly. Consider Klebsiella (upper-lobe, bulging fissure, alcoholic), S. aureus (post-influenza, cavitation), and atypicals (interstitial pattern, dry cough) depending on the radiographic and clinical pattern.
- Clinical correlation is mandatory — a radiograph alone never makes the diagnosis; combine with fever, cough, sputum and examination.
Key points
The examiner will probe each of these; be ready to defend them at viva depth:
- Definition and classification — CAP vs HAP (48 h threshold); typical vs atypical (pathology + CXR); severity by CURB-65/PSI.[1]
- CURB-65 reproduced verbatim — Confusion, Urea over 7 mmol/L, RR over 30, BP under 90/60, age over 65; 0–1 home, 2 hospital, 3–5 ICU; mortality rises from ~1.5% (score 0) to ~40% (score 5).[3]
- Empirical antibiotics — low severity: oral amoxicillin; ward: IV beta-lactam + macrolide; ICU: beta-lactam + macrolide (+ MRSA/Pseudomonas cover if risk). Antibiotics within 4 hours.[1]
- Pathophysiology — microaspiration → alveolar colonisation → cytokine-mediated neutrophil exudate → consolidation → V/Q mismatch and shunt → hypoxaemia.
- Atypical clues — Legionella (diarrhoea, hyponatraemia, confusion, urinary antigen); Mycoplasma (cold agglutinins, bullous myringitis); Coxiella (farm animals).
- Complications — parapneumonic effusion (drain if pH under 7.2), empyema, abscess, sepsis/ARDS.
- Prevention — pneumococcal, influenza and COVID-19 vaccination; smoking cessation.
References
- Metlay JP, et al. ATS/IDSA 2019 CAP guideline. Am J Respir Crit Care Med 2019.[1]
- Lim WS, et al. CURB-65 derivation. Thorax 2003.[3]
References2ShowHide
- [1]Metlay JP, et al. Diagnosis and Treatment of Adults with Community-Acquired Pneumonia. ATS/IDSA 2019. Am J Respir Crit Care Med, 2019.PMID 31573350
- [3]Lim WS, et al. Defining community acquired pneumonia severity on presentation to hospital: an international derivation and validation study. Thorax, 2003.PMID 12728155