History 71-year-old ex-smoker with 6 weeks of progressive breathlessness, dry cough and 6 kg weight loss. SpO₂ 91% on room air.
Frontal chest radiograph · Click an image to enlarge.
Answer each question aloud before you reveal it. Marks and domains appear only in the revealed answers, as in the exam.
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Q1 What are your observations?
Reveal answer
A Annotated 3 marks Observation
- Near-complete homogeneous opacification of the left hemithorax (1)
- Mediastinum and trachea displaced to the right (1)
- Left heart border and left hemidiaphragm obscured; only a small aerated area at the left apex (0.5)
- Right lung clear; no rib destruction seen (0.5)
Examiner note Commit to the direction of mediastinal shift: it decides the differential.
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Q2 What is your preferred diagnosis? Give two differential diagnoses.
Reveal answer
3 marks Interpretation
- Preferred: massive left pleural effusion (1)
- Differentials (1 mark each, max 2): large intrathoracic or pleural mass (e.g. sarcoma, large lung tumour); haemothorax or empyema; congenital diaphragmatic hernia (paediatric) (2)
Examiner note Total lung collapse and pneumonectomy pull the mediastinum TOWARDS the opacity, so they do not fit this film.
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Q3 What is the next imaging test, and what procedure would you offer?
Reveal answer
2 marks Management/Safety
- Thoracic ultrasound: confirms fluid, shows septation, echogenicity and pleural nodularity, and marks or guides the procedure (LO 6.5.1) (1)
- US-guided diagnostic and therapeutic aspiration (biochemistry, cytology, microbiology); contrast-enhanced CT chest (pleural phase), ideally before complete drainage (1)
Examiner note BTS 2010 (Hooper): do the CT with fluid still present, as it helps show pleural nodularity. Avoid large-volume drainage in one sitting (re-expansion oedema).
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Q4 What determines the direction of mediastinal shift when one hemithorax is opaque?
Reveal answer
2 marks Applied sciences
- Shift away from the opacity = a space-occupying process (large fluid volume or mass) raising pressure in that hemithorax (1)
- Shift towards it = volume loss (total collapse, pneumonectomy). Central mediastinum = balanced forces, e.g. fluid plus underlying collapse from a central tumour, or a 'frozen' mediastinum (mesothelioma, malignant infiltration) (1)
Examiner note An opaque hemithorax with a midline mediastinum is a red flag for a central obstructing tumour.
End of the OSCER block (10 marks).
Beyond the exam: teaching extension
Q5–Q9: not part of the 10-mark OSCER block. Untimed, viva-style discussion: mimics and pitfalls, complications, guidelines and report wording.
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Q5 How do Light's criteria separate a transudate from an exudate?
Reveal answer
- Exudate if ANY one of: pleural/serum protein > 0.5; pleural/serum LDH > 0.6; pleural LDH > two-thirds of the upper limit of normal serum LDH (Light 1972)
- Transudates: cardiac failure, cirrhosis, nephrotic syndrome, hypoalbuminaemia
- Exudates: malignancy, parapneumonic effusion/empyema, TB, PE, inflammatory disease
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Q6 How does pleural fluid behave on erect, supine and decubitus films?
Reveal answer
- Erect: fluid gravitates to the costophrenic recesses; roughly 200 mL is needed to blunt the lateral angle on a PA film, less for the posterior angle on a lateral
- Supine: fluid layers posteriorly, giving a hazy veil with visible vessels and no meniscus; easy to under-call
- Lateral decubitus: free fluid layers along the dependent chest wall; ultrasound is more sensitive and has largely replaced it
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Q7 What are the complications of drainage?
Reveal answer
- Re-expansion pulmonary oedema; stop if chest tightness or cough develops and avoid large volumes in one sitting
- Pneumothorax; non-expandable ('trapped') lung, seen as a hydropneumothorax after drainage
- Bleeding (intercostal artery), infection or empyema, drain malposition
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Q8 How is a suspected malignant effusion worked up and managed?
Reveal answer
- Cytology first; sensitivity is limited (about 60%) and repeat samples add less each time
- If non-diagnostic: image-guided (US/CT) pleural biopsy or thoracoscopy
- Recurrent symptomatic malignant effusion: talc pleurodesis or an indwelling pleural catheter, chosen with the patient (BTS 2023)
- Stage the primary: lung cancer staging is marked 'Essential' in LO Appendix 1 §J
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Q9 Draft the key sentences of your report.
Reveal answer
- 'Near-complete opacification of the left hemithorax with rightward mediastinal shift, consistent with a massive left pleural effusion. The underlying lung and pleura cannot be assessed.'
- 'Recommend thoracic ultrasound with guided aspiration and contrast-enhanced CT chest. Given age, smoking history and weight loss, malignancy is a concern.'
End of questions. Reveal the diagnosis, key takeaways and syllabus mapping below.
Reveal diagnosis, key takeaways & syllabus mapping
Diagnosis Massive left pleural effusion (malignant)
Key takeaways
- Mediastinal position is the key to the opaque hemithorax: away = fluid or mass; towards = collapse or pneumonectomy.
- Ultrasound first: it confirms fluid, guides aspiration and shows pleural nodularity.
- Contrast-enhanced CT ideally before complete drainage; think malignancy with weight loss.
- Watch for re-expansion oedema with large-volume drainage.
Syllabus mapping
| OSCER station | Thoracic and Cardiovascular |
|---|---|
| Learning Outcomes section | §6.5 Cardiothoracic (LO 6.5.1 thoracic US) |
| Appendix 1 condition | Pleural effusion including transudative, exudative and malignant (Appendix 1 E, Pleural, diaphragm and chest wall conditions excluding trauma, p71) |
| Category | Category 1 |
| Key Condition | No |
| Core marks by domain | Observation 3 · Interpretation 3 · Management/Safety 2 · Applied sciences 2 (= 10) |
| Learning objectives | Use mediastinal position to work through the opaque hemithorax; Choose US-guided aspiration and correctly timed CT; Know Light's criteria and the malignant effusion pathway |
Mapped to the RANZCR Clinical Radiology Learning Outcomes v1.3 (January 2024), section 6 and Appendix 1.
Further reading
- Roberts ME, Rahman NM, Maskell NA, et al. British Thoracic Society Guideline for pleural disease. Thorax. 2023;78(Suppl 3):s1–s42. PMID 37433578.
- Hooper C, Lee YCG, Maskell N. Investigation of a unilateral pleural effusion in adults: British Thoracic Society Pleural Disease Guideline 2010. Thorax. 2010;65(Suppl 2):ii4–ii17. PMID 20696692.
- Light RW, Macgregor MI, Luchsinger PC, Ball WC Jr. Pleural effusions: the diagnostic separation of transudates and exudates. Ann Intern Med. 1972;77(4):507–513. PMID 4642731.
- RANZCR. Clinical Radiology Learning Outcomes, v1.3 (January 2024), §6 and Appendix 1. Sydney: RANZCR.
- RANZCR. Clinical Radiology Phase 2 OSCER Sample Questions, v1.6 (4 May 2026). Sydney: RANZCR. (Format reference only; no RANZCR images reproduced.)
Always check current Australian/local guidelines.
Image credits
- A by Yale Rosen, CC BY-SA 2.0, via Wikimedia Commons. Changes: top banner cropped; resized and re-encoded (WebP/JPEG). Teaching arrows and labels are a separate overlay added by this site. Adapted image shared under the same licence.
Original file titles are listed on the image credits page (they may reveal the diagnosis).