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Lateral vein of right lung

The lateral vein of the right lung is the segmental venous tributary draining the lateral segment (S4) of the right middle lobe. It courses anteriorly within the right middle lobe, paralleling the segmental bronchi and arteries of S4, and typically unites with the medial vein (V5) to form the middle lobe vein (MLV). The MLV empties into the right superior pulmonary vein (RSPV) at its anteroinferior aspect before entering the left atrium.

This venous anatomy is of particular clinical importance in pulmonary vein isolation for atrial fibrillation, pulmonary resection surgery (lobectomy/segmentectomy), and CT pulmonary venography, as variations in middle lobe venous drainage are common.

Synonyms

  • Right middle lobe lateral segment vein (V4)

  • Tributary of middle lobe vein → RSPV

Function

  • Returns oxygenated blood from the lateral segment (S4) of the right middle lobe

  • Forms the middle lobe vein (V4 + V5) draining into the RSPV → left atrium

  • Serves as an anatomical landmark in thoracic surgery and AF ablation procedures

Tributaries

  • Small intrapulmonary venules from the S4 subsegments, converging to form V4, which unites with V5

MRI Appearance

T1-weighted images:

  • V4 lumen appears as a signal void (black), seen at the anterior hilum with perihilar fat contrast

T2-weighted images (normal):

  • V4 visualized as a linear flow void against hyperintense background structures

  • Thrombus or slow flow would alter signal intensity

T2 TRUFISP (cardiac/respiratory-gated):

  • Depicts V4 as a bright continuous venous channel draining into the MLV and then the RSPV

  • Provides cine-like visualization of venous filling and confluence with V5

STIR:

  • Fat suppression improves visualization against hilar fat

  • Highlights perivascular edema or inflammatory involvement

T1 Post-Contrast (Gadolinium-enhanced MRI):

  • V4 enhances homogeneously, showing its convergence with V5 and drainage into the RSPV

  • Filling defects correspond to thrombosis or stenosis

MRI Non-Contrast Cardiac-Gated 3D (whole-heart):

  • 3D datasets delineate V4 joining V5 → middle lobe vein → RSPV

  • Useful for pre-ablation pulmonary vein mapping and segmentectomy planning without contrast

CT Appearance

CT Coronary Angiography (CCTA) / CT Pulmonary Venography:

  • Contrast-enhanced imaging shows V4 draining S4 → MLV → RSPV with high-resolution detail

  • Multiplanar and 3D reconstructions confirm ostial anatomy, common trunks, and variants

  • Essential for AF ablation, surgical resection planning, and detecting anomalous pulmonary venous return

CT images

Lateral vein of right lung anatomy CT axial image -img-00000-00000

CT images

Lateral vein of right lung anatomy CT axial image -img-00000-00000_00001

MRI image

Lateral vein of right lung mri axial image