What causes tram-tracking in the lungs on chest X-ray?
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Answer:
Parallel linear opacities representing thickened bronchial walls due to bronchiectasis, a condition characterized by irreversible bronchial dilatation from recurrent infection, inflammation, or obstruction.
Why is it called so?:
Named for the resemblance to parallel tramway tracks formed by the two thickened walls of a dilated bronchus seen in tangential projection.
Pathophysiology:
Chronic inflammation and infection lead to bronchial wall fibrosis and smooth muscle hypertrophy, causing parallel wall thickening visible as tram-lines when the bronchus is viewed longitudinally on CXR; less commonly, represents calcified parallel vascular walls in chronic venous thrombosis.
Alternative names: Tram track sign
Other associated named signs: Signet-ring sign, finger-in-glove sign
Access all radiology signs posted so far: https://radiogyan.com/radiology-signs/
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