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Internal thoracic veins

The internal thoracic veins (also called internal mammary veins) are paired veins that run alongside the internal thoracic arteries on each side of the sternum. They begin as venous tributaries in the superior epigastric and musculophrenic regions, ascend vertically along the posterior aspect of the anterior thoracic wall, and drain into the brachiocephalic veins near their junction with the superior vena cava (SVC).

Each internal thoracic vein is formed by the confluence of the superior epigastric vein and the musculophrenic vein. Along their course, they receive tributaries from the anterior intercostal veins, perforating veins, and mediastinal veins.

These veins are clinically important because they form collateral venous pathways in SVC obstruction, draining blood from the thoracic wall into systemic circulation. They are also landmarks in thoracic surgery and central venous catheterization, and their arterial counterparts are used in coronary artery bypass grafting (CABG).

Synonyms

  • Internal mammary veins

  • Venae thoracicae internae

Function

  • Drain venous blood from the anterior thoracic wall, anterior intercostal spaces, and superior epigastric region

  • Empty into the brachiocephalic veins bilaterally

  • Provide collateral drainage in SVC obstruction

  • Serve as surgical landmarks in thoracic and cardiac procedures

Tributaries

  • Superior epigastric veins

  • Musculophrenic veins

  • Anterior intercostal veins

  • Perforating veins

  • Mediastinal tributaries

MRI Appearance

T1-weighted images:

  • Internal thoracic veins appear as flow voids (dark tubular structures) adjacent to the sternum

  • Surrounded by hyperintense fat, aiding identification

T2-weighted images:

  • Veins appear as dark signal voids along the parasternal line

  • In venous congestion, may appear dilated with altered signal

STIR:

  • Fat suppression improves vein conspicuity

  • Highlights perivascular edema or inflammatory changes

T1 Fat-Saturated (Pre-contrast):

  • Venous lumen may appear as intermediate signal, standing out against suppressed fat background

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Veins enhance brightly and homogeneously in venous phase

  • Useful for detecting thrombosis, collateral pathways, or anomalous drainage

MRV (Magnetic Resonance Venography):

  • Provides 3D mapping of internal thoracic venous anatomy and variations

  • Demonstrates their drainage into brachiocephalic veins

  • Useful in assessing venous obstruction, thrombosis, and collateral circulation

CT Appearance

CT Pre-Contrast:

  • Veins appear as linear soft-tissue densities adjacent to the sternum

  • Difficult to differentiate from arteries without contrast

CT Post-Contrast:

  • Veins enhance and are visualized as contrasted tubular structures running alongside the internal thoracic arteries

  • Detects venous enlargement, thrombosis, or mediastinal venous anomalies

CTV (CT Venography):

  • Provides high-resolution imaging of the course, tributaries, and termination of the veins

  • 3D reconstructions highlight their drainage into brachiocephalic veins

  • Crucial for evaluating SVC obstruction, venous collateral pathways, and surgical planning

CT image

internal thoracic veins ct anatomy image -img-00000-00000

CT image

Internal thoracic veins CT axial image

MRI image

Internal thoracic veins MRI coronal anatomy image -img-00000-00000