CXR Signs: Golden S, Sail Sign, Deep Sulcus
- Crack Medicine
- 1 hour ago
- 4 min read
TL;DR
MRCP Part 1 frequently tests classic radiological patterns rather than subtle imaging interpretation. CXR Signs: Golden S, Sail Sign, Deep Sulcus are high-yield chest X-ray findings that indicate important pathological processes including lobar collapse, thymic anatomy or pneumomediastinum in children, and occult pneumothorax. Learning the mechanism, differentials and common examination traps behind each sign can secure easy marks in respiratory and radiology questions.
Why this matters
Radiological questions in MRCP rarely require memorising every abnormality on a chest radiograph. Instead, they focus on recognising distinctive patterns that strongly suggest a diagnosis.
Understanding these signs helps candidates:
Diagnose common respiratory conditions quickly
Recognise medical emergencies
Differentiate normal anatomical variants from pathology
Avoid common examination traps
Improve confidence when interpreting chest radiographs
Core sections
The five most tested CXR signs and related concepts
1. Golden S Sign
The Golden S sign is a classic feature of right upper lobe collapse caused by a central obstructing mass, most commonly bronchogenic carcinoma.
As the upper lobe collapses, the minor fissure becomes elevated. A hilar mass creates a convex bulge in the fissure, producing the characteristic reversed S-shaped contour.
Causes
Bronchogenic carcinoma (most common)
Endobronchial tumour
Enlarged hilar lymph nodes
Rarely mucus plugging
Key examination point
A Golden S sign should always prompt suspicion of an obstructing central lesion rather than simple atelectasis.
2. Sail Sign
The term Sail sign has two important meanings, making it a favourite examination trap.
A. Normal thymic sail sign (infants)
The normal thymus projects into the right upper mediastinum as a triangular opacity resembling a sail.
Features include:
Smooth borders
No mass effect
Normal infant finding
No treatment required
B. Spinnaker sail sign
When air enters the mediastinum (pneumomediastinum), both thymic lobes become elevated away from the heart.
This appearance resembles the sails of a boat.
Associated with:
Neonatal pneumomediastinum
Birth trauma
Mechanical ventilation
Positive-pressure ventilation
3. Deep Sulcus Sign
The Deep Sulcus sign is seen in supine pneumothorax.
Instead of air rising to the lung apex, intrapleural air accumulates anteriorly and basally, making the lateral costophrenic angle appear:
Unusually deep
More lucent
Sharply outlined
This sign is particularly important in:
Intensive care patients
Trauma patients
Ventilated patients
Failure to recognise it may delay diagnosis of a life-threatening pneumothorax.
4. Lobar Collapse
Understanding collapse patterns helps interpret both the Golden S sign and other chest radiographs.
Typical features include:
Increased opacity
Volume loss
Fissure displacement
Mediastinal shift towards collapse
Elevated diaphragm
Right upper lobe collapse is the classical association with the Golden S sign.
5. Pneumothorax Patterns
MRCP candidates should distinguish:
Upright pneumothorax
Supine pneumothorax
Tension pneumothorax
The Deep Sulcus sign specifically indicates a supine pneumothorax, often in critically ill patients.
High-yield revision table
Sign | Classical association | Mechanism | Common MRCP clue |
Golden S sign | Right upper lobe collapse due to bronchial carcinoma | Obstructing hilar mass distorts minor fissure | Think lung cancer |
Sail sign (thymus) | Normal infant thymus | Normal thymic contour | Normal variant |
Spinnaker sail sign | Pneumomediastinum | Air elevates thymus | Neonatal emergency |
Deep Sulcus sign | Supine pneumothorax | Air collects anteriorly | Trauma or ICU patient |
Upper lobe collapse | Endobronchial obstruction | Volume loss | Shift towards lesion |
10 high-yield examination facts
Golden S sign almost always suggests an obstructing hilar lesion.
Bronchogenic carcinoma is the commonest cause.
The thymic sail sign is normal in infants.
Spinnaker sail sign indicates pneumomediastinum.
Deep Sulcus sign occurs in supine patients.
Supine pneumothorax may lack an apical pleural line.
Lobar collapse produces volume loss.
Mediastinum shifts towards collapse.
Tension pneumothorax shifts the mediastinum away.
Always interpret chest radiographs alongside the clinical presentation.
Practical examples / mini-cases
Mini-case
A 67-year-old smoker presents with weight loss, persistent cough and haemoptysis.
Chest radiograph demonstrates elevation of the minor fissure with a characteristic reverse S-shaped contour.
Question
What is the most likely diagnosis?
A. Pulmonary embolism
B. Bronchogenic carcinoma causing right upper lobe collapse
C. Pleural effusion
D. Left ventricular failure
E. Sarcoidosis
Answer
Correct answer: B. Bronchogenic carcinoma causing right upper lobe collapse
Explanation
The reverse S-shaped appearance represents the Golden S sign, indicating right upper lobe collapse secondary to a central obstructing tumour. This is a classic MRCP imaging appearance.
Practical study-tip checklist
Use this checklist during revision:
â–¡ Memorise the three classical signs.
â–¡ Learn the underlying mechanism, not just the appearance.
â–¡ Differentiate normal thymic sail sign from Spinnaker sail sign.
â–¡ Associate Golden S sign with bronchogenic carcinoma.
â–¡ Remember that Deep Sulcus sign occurs in supine patients.
â–¡ Revise common causes of lobar collapse.
â–¡ Practise image-based MCQs regularly.
â–¡ Compare normal and abnormal chest radiographs.
â–¡ Review respiratory emergencies involving pneumothorax.
â–¡ Attempt timed radiology questions before the examination.
Common pitfalls (5 bullets)
Confusing a normal thymic sail sign with mediastinal pathology.
Assuming every upper lobe collapse is infective rather than obstructive.
Missing a pneumothorax on a supine chest radiograph because there is no apical pleural line.
Forgetting that Golden S sign implies an underlying central obstructing lesion.
Ignoring mediastinal shift when interpreting collapse versus tension pneumothorax.
FAQs
What is the Golden S sign?
The Golden S sign is a reverse S-shaped deformity of the minor fissure caused by right upper lobe collapse around a central obstructing mass, usually bronchogenic carcinoma.
Is the Sail sign always abnormal?
No. In infants, the thymic sail sign is a normal anatomical appearance. The Spinnaker sail sign, however, indicates pneumomediastinum.
What does the Deep Sulcus sign indicate?
It indicates a supine pneumothorax, where pleural air accumulates anteriorly rather than at the lung apex, making the lateral costophrenic angle appear unusually deep.
Why are these signs important for MRCP Part 1?
They are classic radiological appearances that repeatedly feature in image-based and clinical reasoning questions. Recognition often leads directly to the diagnosis.
How should I revise chest radiology for MRCP Part 1?
Combine systematic chest X-ray interpretation with repeated image-based practice. Using the MRCP Part 1 overview, Free MRCP MCQs, MRCP lectures, and mock tests helps reinforce these high-yield patterns under examination conditions.
Ready to start
Chest radiology becomes much easier when you recognise classic patterns instead of memorising isolated facts. Build a systematic approach by studying the MRCP Part 1 overview:
Practise image-based questions using the free QBank:
Test your knowledge under exam conditions:
For structured respiratory teaching, explore:
Sources
MRCP(UK). Examination syllabus. https://www.mrcpuk.org/
Royal College of Radiologists. Standards for interpretation of chest radiographs. https://www.rcr.ac.uk/
Radiopaedia. Golden S sign. https://radiopaedia.org/articles/golden-s-sign
Radiopaedia. Deep sulcus sign. https://radiopaedia.org/articles/deep-sulcus-sign
Radiopaedia. Thymic sail sign. https://radiopaedia.org/articles/thymic-sail-sign
Grainger & Allison's Diagnostic Radiology.
Felson's Principles of Chest Roentgenology.