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Lateral segmental artery of right Lung

The lateral segmental artery of the right lung is a branch of the right middle lobar pulmonary artery. It supplies the lateral segment (segment 4) of the right middle lobe, which lies adjacent to the lateral chest wall. The artery typically arises after the middle lobar artery divides into medial and lateral segmental branches, traveling laterally within the pulmonary parenchyma to accompany the corresponding segmental bronchus (B4).

Anatomically, the artery runs parallel to the lateral chest wall, providing perfusion to the lateral portion of the right middle lobe. Its venous drainage occurs via tributaries of the middle lobe pulmonary vein, and lymphatic drainage follows the bronchovascular bundles toward hilar lymph nodes.

Clinically, the lateral segmental artery is relevant in pulmonary embolism (PE), segmentectomy, and lobectomy planning, where precise vascular mapping is required. It may also be involved in congenital vascular anomalies or pulmonary arteriovenous malformations.

Synonyms

  • Right middle lobe lateral segment artery

  • Artery to lateral segment (S4)

  • A4 branch of right pulmonary artery

Function

  • Supplies oxygen-poor blood to the lateral segment (S4) of the right middle lobe for gas exchange

  • Works with the corresponding bronchus and vein as part of the bronchopulmonary segment unit

  • Provides a critical anatomical landmark in thoracic surgery and pulmonary angiography

MRI Appearance

T1-weighted images:

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

  • Surrounded by intermediate-signal parenchyma and hyperintense mediastinal fat

T2-weighted images:

  • Vessel lumen appears as a signal void

  • Adjacent parenchymal pathology (e.g., infarction, pneumonia, or edema) may appear hyperintense

T2 TRUFISP (cardiac/respiratory-gated):

  • Displays the artery as a bright, well-defined vascular channel

  • Allows dynamic evaluation of flow and segmental branching within the right middle lobe

STIR (Short Tau Inversion Recovery):

  • Fat suppression improves delineation against lung tissue and mediastinal fat

  • Perivascular edema or inflammation appears hyperintense

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • The artery enhances homogeneously

  • Filling defects indicate embolus, thrombosis, or vascular malformation

MRI Non-Contrast 3D Cardiac/Respiratory-Gated Imaging:

  • Whole-lung 3D imaging demonstrates the lateral segmental artery and its relation to bronchus B4

  • Useful for mapping in patients with renal impairment or contrast contraindication

CT Appearance

CT Pulmonary Angiography (CTPA):

  • Gold standard for visualization of segmental pulmonary arteries

  • Lateral segmental artery appears as a contrast-opacified branch from the middle lobar artery, coursing laterally to supply S4

  • Detects pulmonary emboli, stenosis, aneurysm, or vascular anomalies

  • Multiplanar and 3D reconstructions provide precise mapping for segmentectomy or lobectomy planning

CT Image

Lateral segmental artery of right lung anatomy CT axial image -img-00000-00000

MRI image

Lateral segmental artery of right lung mri image