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Right interlobar artery

The right interlobar artery is a major branch of the right pulmonary artery (RPA) that supplies the middle and lower lobes of the right lung. After the RPA gives off the right superior lobar artery, the vessel continues as the interlobar artery.

It descends between the right upper lobe bronchus (above) and the bronchus intermedius (below), coursing through the interlobar fissure toward the hilum of the middle and lower lobes. At the level of the hilum, it divides into the middle lobar artery and the lower lobar artery, which then branch into segmental arteries corresponding to bronchopulmonary segments.

The right interlobar artery is clinically significant as a frequent site for pulmonary embolism, which often lodges at lobar or interlobar levels. Its anatomy must also be carefully considered during lung resections, segmentectomy, and thoracic imaging interpretation.

Synonyms

  • Interlobar branch of right pulmonary artery

  • Right pulmonary interlobar artery

  • Arteria interlobaris dextra

Function

  • Delivers deoxygenated blood from the right pulmonary artery to the middle and lower lobes

  • Divides into middle lobar and lower lobar arteries

  • Supports gas exchange in right lung lobes

  • Key structure in thoracic surgery, pulmonary embolism diagnosis, and interventional radiology

Branches

  • Middle lobar artery → divides into segmental branches for medial (S5) and lateral (S4) segments of the middle lobe

  • Lower lobar artery → divides into segmental arteries (S6–S10) for superior, medial basal, anterior basal, lateral basal, and posterior basal segments

MRI Appearance

T1-weighted images:

  • Lumen appears as a signal void (black) due to rapid blood flow

  • Wall is hypointense; surrounding hilar fat provides contrast

T2-weighted images:

  • Appears as a signal void within the interlobar fissure

  • Intraluminal thrombus may appear as intermediate-to-high signal

STIR:

  • Suppresses fat, increasing visibility of the artery against the hilar fat and lung parenchyma

  • Highlights perivascular inflammation or edema

T1 Post-Gadolinium (Gd-enhanced MRI):

  • Interlobar artery enhances brightly and homogeneously

  • Filling defects represent emboli, thrombus, or stenosis

  • Useful in MR pulmonary angiography for embolism detection

MRA (Magnetic Resonance Angiography):

  • Depicts the interlobar artery branching pattern and its relation to middle and lower lobar arteries

  • Identifies occlusion, stenosis, aneurysm, or anomalous anatomy

CT Appearance

CT Pulmonary Angiography (CTPA):

  • Gold standard for interlobar artery imaging

  • Demonstrates the artery as a contrast-opacified branch descending from the RPA, between the right upper and bronchus intermedius

  • Multiplanar and 3D reconstructions clearly show division into middle and lower lobar arteries

  • Detects pulmonary emboli, vascular compression, stenosis, aneurysms, or extrinsic hilar mass effects

CT image

Right interlobar artery anatomy CT axial image -img-00000-00000

MRI image

Right interlobar artery MRI IMAGE