History 78-year-old woman with known ischaemic heart disease, acutely breathless overnight and unable to lie flat. SpO₂ 84% on room air; bibasal crackles.
Erect mobile AP 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
- Bilateral, fairly symmetrical airspace opacities, perihilar and lower-zone predominant; ill-defined nodular opacities tending to merge (1)
- Interstitial signs: peripheral septal (Kerley B) lines at the bases, peribronchial cuffing, indistinct vessels (1)
- Technique: erect mobile AP film, so heart size cannot be reliably assessed (0.5)
- External ECG leads only; no pneumothorax (0.5)
Examiner note Note the 'ERECT' and 'MOBILE' labels: the radiographer is telling you the projection.
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Q2 What is your preferred diagnosis? Give two differential diagnoses.
Reveal answer
2 marks Interpretation
- Preferred: acute cardiogenic pulmonary oedema (decompensated left heart failure) (1)
- Differentials (0.5 each, max 1): ARDS / non-cardiogenic oedema; fluid overload (renal failure); diffuse infection (viral, PJP); diffuse alveolar haemorrhage (1)
Examiner note Septal lines, effusions and a central distribution favour hydrostatic oedema; patchy peripheral opacities with few septal lines favour ARDS.
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Q3 What do you recommend next?
Reveal answer
2 marks Management/Safety
- Treat now: oxygen and ventilatory support (CPAP/NIV), diuretics and vasodilators as directed by the treating team; ECG and troponin for an ACS precipitant (1)
- Transthoracic echocardiography for LV and valve function; repeat CXR to monitor response; CT only if another diagnosis is suspected (1)
Examiner note NHFA/CSANZ 2018: echocardiography for suspected heart failure; natriuretic peptides help when the diagnosis is uncertain.
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Q4 Explain the physiological basis of the signs you described, and how they progress.
Reveal answer
3 marks Applied sciences
- Rising pulmonary venous pressure: upper-lobe blood diversion first (about 13–18 mmHg) (1)
- Interstitial oedema next (about 18–25 mmHg): septal lines, peribronchial cuffing, subpleural fluid, effusions (1)
- Alveolar flooding above about 25 mmHg: perihilar 'bat-wing' airspace opacities; clearing lags behind treatment (1)
Examiner note Thresholds are approximate (Gluecker 1999). Radiographic change can lag the haemodynamics in both directions.
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 Second patient: what do the original author's circle and arrow highlight?
B Second patient: frontal chest radiograph (circle and arrow are the original author's) Reveal answer
- Circle: upper-lobe vascular diversion (redistribution)
- Arrow: small left pleural effusion (blunted costophrenic angle); the author describes small bilateral effusions
- Also an enlarged cardiac silhouette (author's description: 'enlarged heart size')
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Q6 How do you separate cardiogenic oedema from ARDS on a plain film?
Reveal answer
- Cardiogenic: cardiomegaly, widened vascular pedicle, central/basal distribution, septal lines, effusions, peribronchial cuffing
- ARDS: normal heart size, patchy peripheral opacities, air bronchograms common, few septal lines or effusions
- Overlap is common: always correlate with the clinical setting, echo and time course
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Q7 What are the technical pitfalls?
Reveal answer
- AP projection magnifies the heart; supine positioning makes upper-lobe vessels look prominent (mimics redistribution)
- Poor inspiration crowds basal vessels and mimics oedema
- Asymmetric oedema: gravity/positioning, emphysema (destroyed lung is spared), acute mitral regurgitation (right upper lobe)
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Q8 Which Australian guideline applies, and what does it recommend for diagnosis?
Reveal answer
- NHFA/CSANZ Guidelines for the prevention, detection and management of heart failure in Australia 2018
- Echocardiography to confirm the diagnosis and classify HFrEF vs HFpEF
- BNP/NT-proBNP when the diagnosis is uncertain; the CXR supports but cannot exclude the diagnosis
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Q9 Draft the key sentences of your report.
Reveal answer
- 'Bilateral perihilar airspace opacity with septal lines and peribronchial cuffing, consistent with pulmonary oedema. Cardiac size cannot be assessed on this AP mobile film.'
- 'Correlate with echocardiography; follow-up radiograph to document response.'
End of questions. Reveal the diagnosis, key takeaways and syllabus mapping below.
Reveal diagnosis, key takeaways & syllabus mapping
Diagnosis Acute cardiogenic pulmonary oedema
Key takeaways
- Read oedema as a sequence: redistribution, then interstitial, then alveolar.
- State the projection: AP and supine films distort heart size and vessels.
- Treat the patient first; echo confirms, CXR monitors response.
- Cardiogenic vs ARDS: heart, pedicle, distribution, septal lines, effusions.
Syllabus mapping
| OSCER station | Thoracic and Cardiovascular |
|---|---|
| Learning Outcomes section | §6.5 Cardiothoracic |
| Appendix 1 condition | Pulmonary vascular congestion, oedema and fluid overload (Appendix 1 E, Pulmonary vascular conditions, p71); Cardiac failure, left and right (Heart and pericardial conditions, p71) |
| Category | Category 1 |
| Key Condition | Yes |
| Core marks by domain | Observation 3 · Interpretation 2 · Management/Safety 2 · Applied sciences 3 (= 10) |
| Learning objectives | Describe and stage pulmonary oedema on CXR; Separate cardiogenic oedema from ARDS; Recognise projection-related pitfalls |
Mapped to the RANZCR Clinical Radiology Learning Outcomes v1.3 (January 2024), section 6 and Appendix 1.
Further reading
- Gluecker T, Capasso P, Schnyder P, et al. Clinical and radiologic features of pulmonary edema. RadioGraphics. 1999;19(6):1507–1531. PMID 10555672.
- NHFA CSANZ Heart Failure Guidelines Working Group; Atherton JJ, Sindone A, De Pasquale CG, et al. National Heart Foundation of Australia and Cardiac Society of Australia and New Zealand: Guidelines for the prevention, detection, and management of heart failure in Australia 2018. Heart Lung Circ. 2018;27(10):1123–1208. PMID 30077227.
- 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 Frank Gaillard, CC BY-SA 3.0, via Wikimedia Commons. Changes: 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.
- B by James Heilman, MD, CC BY-SA 3.0, via Wikimedia Commons. Changes: resized and re-encoded (WebP/JPEG). Adapted image shared under the same licence.
Original file titles are listed on the image credits page (they may reveal the diagnosis).