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Mnemonic

Hilar Position on the Chest Radiograph

A memory aid for the normal position of the lung hila on a chest film.

Anatomy Investigations Thorax Imaging Interpretation
Expansion

The left hilum is normally higher than the right, never lower

Expansion

  • The left hilum normally lies 0 to 2 cm higher than the right
  • It is never normally lower than the right

The reason is anatomical: the left pulmonary artery arches over the left main bronchus (Left Superior of the RALS mnemonic), while the right pulmonary artery lies anterior to the right main bronchus, so the left hilar point sits higher.

Displacement indicates volume change:

  • Upper lobe collapse pulls the hilum up
  • Lower lobe collapse pulls the hilum down

Hilar enlargement should then be characterised as vascular (pulmonary hypertension, usually bilateral and symmetrical) or nodal or mass (bronchial carcinoma, lymphoma, sarcoidosis, tuberculosis).