Respiratory Anatomy · Respiratory

Lung Anatomy

The hilum of each lung contains a defined set of structures arranged in a predictable pattern. Knowing hilar anatomy is essential for interpreting CT, planning lung surgery, and understanding hilar lymphadenopathy.

✦ The Mnemonic

"Brave Aviators Visit Lovely Narrows"

Bronchus, Artery, Veins, Lymphatics, Nerves — the five hilar structures

B Main Bronchus Most posterior hilar structure; left main bronchus passes under aortic arch
A Pulmonary Artery Anterior to bronchus; right PA passes anterior to right main bronchus
V Pulmonary Veins Two on each side (superior + inferior); most anterior and inferior at the hilum
L Lymphatics Hilar and mediastinal lymph nodes surround the hilum; drain to paratracheal nodes
N Autonomic Nerves Vagal and sympathetic fibres forming the pulmonary plexus; regulate bronchomotor tone

📚 Clinical Breakdown

At the right hilum, from superior to inferior: pulmonary artery (above right main bronchus) → right upper lobe bronchus (anterior) → right main bronchus → lower pulmonary veins (most inferior). The right pulmonary artery passes anterior to the right main bronchus.

At the left hilum, the left pulmonary artery arches over the left main bronchus (the 'pulmonary bay'). The left hilar structures are generally higher than the right — so the left hilum is normally at the same level or slightly higher than the right on a PA CXR.

Hilar lymphadenopathy causes: bilateral hilar enlargement = sarcoidosis until proven otherwise (also consider lymphoma, TB). Unilateral hilar enlargement = primary lung cancer or lymphoma most likely. The 1-2-3 sign (right paratracheal stripe + bilateral hila) on CXR is classic for sarcoidosis.

Right PA position Superior and anterior to right main bronchus
Left PA position Arches over left main bronchus
Normal hilar levels Left hilum slightly higher than right
Bilateral hilar enlargement Sarcoidosis first, then lymphoma, TB

⭐ Clinical Pearl

Pulmonary vein vs pulmonary artery on CT: pulmonary veins drain to the left atrium (posterolateral cardiac border) and run horizontally; pulmonary arteries run with the bronchi. Distinguishing them is critical for surgical planning and interventional procedures (especially pulmonary vein isolation for AF ablation).

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