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Superior segmental artery of left lung

The superior segmental artery of the left lung (A6) is a branch of the left lower lobar pulmonary artery, supplying the superior segment (S6) of the left lower lobe. This segment lies posteriorly in the lung and corresponds anatomically to the superior segment of the right lower lobe, making it clinically and surgically significant in segmental lung resections.

The A6 artery usually arises as the first major branch of the left lower lobar artery after its bifurcation from the interlobar pulmonary artery. It travels dorsally, coursing posteriorly to accompany the superior segmental bronchus (B6) and is accompanied by the superior segmental vein (V6), forming the classic bronchovascular bundle of S6.

Anatomical variations are common: A6 may arise as a single trunk or as two branches (A6a and A6b), and in some cases, it shares a common origin with basal segmental arteries. Due to its dorsal course and relation to the pulmonary hilum, precise identification of A6 is critical during pulmonary segmentectomy, lobectomy, and pulmonary embolism evaluation.

Synonyms

  • A6 artery

  • Superior segmental branch of left lower lobar artery

  • Arteria segmenti superioris pulmonis sinistri

Function

  • Supplies oxygen-poor blood to the superior segment (S6) of the left lower lobe for gas exchange

  • Supports the bronchovascular anatomy of the dorsal lung region

  • Serves as a surgical landmark in segmental resections and thoracic surgery

  • Plays a role in embolism localization and interventional procedures

Branches

  • Typically divides into anterior and posterior branches supplying subsegments of S6

  • May arise as a single trunk or share origin with basal arteries (variant anatomy)

MRI Appearance
T1-weighted images:

  • A6 lumen appears as a signal void (black) due to fast arterial flow

  • Surrounded by hypointense vessel wall and hyperintense lung parenchymal fat planes

T2-weighted images:

  • Lumen remains a signal void

  • Adjacent pathology (edema, consolidation, tumor) appears hyperintense

T2 TRUFISP (cardiac/respiratory-gated):

  • A6 artery appears as a bright vascular channel with sharp contrast to lung parenchyma

  • Provides cine-like dynamic imaging of branching and flow patterns

STIR:

  • Fat suppression highlights the artery within lung hilum

  • Useful for detecting inflammation, edema, or perivascular pathology

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • A6 artery enhances brightly and homogeneously

  • Filling defects represent thromboembolic disease or stenosis

MRI Non-Contrast Cardiac-Gated 3D Imaging:

  • Demonstrates the origin and posterior course of A6 from the left lower lobar artery

  • Useful for preoperative segmental mapping and embolism evaluation without contrast

  • Shows relationship to bronchus (B6) and vein (V6)

MRA (Magnetic Resonance Angiography):

  • Contrast-enhanced MRA visualizes branching pattern and anatomical variations

  • Important for segmentectomy planning and embolism detection

CT Appearance
CT Pulmonary Angiography (CTPA):

  • Contrast opacifies A6, clearly showing its origin from the left lower lobar artery and posterior course to S6

  • Multiplanar reconstructions demonstrate relation to bronchus B6 and vein V6

  • Detects pulmonary embolism, stenosis, or anatomical variation

  • Essential for thoracic surgical planning and interventional radiology

CT image

Superior segmental artery of left lung anatomy ct axial image -img-00000-00000

MRI image

Superior segmental artery of left lung mri axial image