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Posterior intercostal veins

The posterior intercostal veins form a venous network that drains the thoracic wall, intercostal spaces, and associated musculature. They run with the posterior intercostal arteries and nerves in the costal grooves of the ribs, coursing posteriorly to drain into the azygos venous system.

On the right side, the posterior intercostal veins drain into the azygos vein, while on the left side, the upper veins (2nd–4th) drain into the superior intercostal vein → brachiocephalic vein, and the lower veins drain into the hemiazygos or accessory hemiazygos veins, which then connect to the azygos vein. The 1st posterior intercostal vein typically drains into the brachiocephalic vein directly.

These veins have numerous anastomoses with the anterior intercostal veins, vertebral venous plexus, and epigastric veins, providing important collateral circulation between the superior and inferior vena cava systems.

Clinically, they are significant as collateral pathways in SVC obstruction, routes of spread for thoracic infections or metastasis, and as landmarks in thoracic surgery.

Synonyms

  • Intercostal veins (posterior group)

  • Thoracic wall venous network

Function

  • Drain posterior intercostal spaces and thoracic wall musculature

  • Connect systemic venous systems (SVC and IVC) via azygos system

  • Provide collateral venous return in caval obstruction

  • Participate in venous plexuses of spine and thoracic wall

Tributaries

  • Muscular branches from intercostal muscles

  • Cutaneous branches from thoracic wall skin

  • Vertebral venous plexus communications

MRI Appearance

T1-weighted images:

  • Veins appear as linear flow voids (dark lumens) between ribs in posterior thoracic wall

  • Surrounded by intermediate signal muscle and hyperintense fat

T2-weighted images:

  • Normal veins show as signal voids

  • Venous thrombosis appears as intermediate to high signal intraluminal content

STIR:

  • Suppresses fat to better outline venous channels

  • Highlights perivascular edema or inflammatory change as hyperintense

T1 Fat-Saturated (Pre-contrast):

  • Venous lumen shows intermediate signal intensity, contrasting with suppressed fat background

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Posterior intercostal veins enhance brightly and homogeneously in venous phase

  • Allows identification of small tributaries and azygos/hemiazygos connections

MRV (Magnetic Resonance Venography):

  • Depicts posterior intercostal venous drainage into azygos/hemiazygos veins

  • Shows collateral circulation in SVC obstruction or spinal venous plexus involvement

  • Useful for thoracic venous mapping

CT Appearance

CT Pre-Contrast:

  • Veins appear as tubular soft-tissue densities along intercostal spaces

  • Limited visualization without contrast

CT Post-Contrast:

  • Veins opacify in venous phase, showing their drainage into azygos, hemiazygos, and brachiocephalic veins

  • Detects thrombosis, dilation, or anomalous connections

CTV (CT Venography):

  • Best modality for non-invasive evaluation of intercostal veins and azygos system

  • 3D reconstructions highlight drainage pathways, collateral venous channels, and surgical landmarks

  • Essential in cases of venous obstruction, trauma, or planning thoracic surgery

CT images

Posterior intercostal veins CT axial 2

CT images

Posterior intercostal veins CT axial 1

CT images

Posterior intercostal veins CT axial