Consolidation vs Collapse on Chest X-ray MCQ — NEET PG Practice Question | NEETPGAI
Consolidation vs Collapse on Chest X-ray
medium
scan Radiology
On chest X-ray, the most common site of lobar collapse in adults is which of the following?
A. Left lower lobe
B. Left upper lobe
C. Right upper lobe
D. Right lower lobe
Explanation
Atelectasis (Collapse): Most Common Site in Adults
Key Point
Left lower lobe collapse is the most common site of lobar atelectasis in adults, particularly in post-operative and critically ill patients, due to anatomical and physiological factors favouring left-sided dependent collapse.
Why Left Lower Lobe is Most Common
Table
Factor
Left Lower Lobe
Right Lower Lobe
Bronchial angle
More acute, longer path
More vertical, shorter
Cardiac compression
Heart lies on left side, compresses LLL
Less compression
Gravity dependence
Posterior/basal — most dependent
Also dependent but less compressed
Post-operative risk
Highest overall
High but less than LLL
Frequency of collapse
Most common (~40–50%)
Second most common (~25–35%)
High-YieldNEET PG
The left lower lobe bronchus is longer and more acutely angled than the right, and the overlying heart compresses the left lower lobe, impairing mucociliary clearance and predisposing to mucus plugging and collapse. This is the predominant reason LLL collapse is most frequent in adults (Felson's Principles of Chest Roentgenology; Grainger & Allison's Diagnostic Radiology).
Radiological Features of Left Lower Lobe Collapse
1.
Volume loss signs
Mediastinal shift toward left
Elevation of left hemidiaphragm
Approximation of left-sided ribs
2.
Silhouette sign
Loss of left hemidiaphragm outline (posterior segment collapses behind heart)
Preserved left heart border (distinguishes from lingular/LUL collapse)
3.
Opacity pattern
Triangular retrocardiac opacity (sail sign)
Visible on lateral film as posterior wedge
No air bronchograms (collapsed airways)
Relative Frequency of Lobar Collapse in Adults
Table
Lobe
Approximate Frequency
Left lower lobe
~40–50% (most common)
Right lower lobe
~25–35%
Right upper lobe
~10–15%
Left upper lobe
~5–10%
Mnemonic
LLL LEADS — Left Lower Lobe is the Leading (most common) site of lobar collapse in adults.
Clinical Causes of Left Lower Lobe Collapse
1.
Post-operative (most common overall)
Mucus plugging after general anaesthesia
Reduced diaphragmatic excursion after abdominal/cardiac surgery
2.
Cardiac compression
Cardiomegaly further compresses LLL bronchus
3.
Obstruction
Endobronchial tumour (left lower lobe bronchus)
Aspiration (less common on left due to bronchial angle)
4.
Pleural effusion / Compression
Left-sided effusion compressing LLL
Clinical Pearl
In a post-operative patient (especially after cardiac or upper abdominal surgery) with a new retrocardiac triangular opacity and loss of the left hemidiaphragm outline, left lower lobe collapse from mucus plugging is the first diagnosis to consider. Aggressive pulmonary hygiene (incentive spirometry, chest physiotherapy, early ambulation) is the key preventive measure.
