Anatomy Atlases: Illustrated Encyclopedia of Human Anatomic Variation: Opus II: Cardiovascular System: Veins: Head, Neck, and Thorax: Hemiazygos Veins

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Illustrated Encyclopedia of Human Anatomic Variation: Opus II: Cardiovascular System: Veins: Head, Neck, and Thorax

Hemiazygos Veins

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD
Peer Review Status: Internally Peer Reviewed

The hemiazygos vein arises from one or more of three possible roots (lateral, intermediate and medial). The lateral root arises in 85% of individuals from the left subcostal and left ascending lumbar vein at the head of the twelfth rib. The intermediate root occurs in only 28% of individuals and arises from the dorsal side of the left renal vein. The medial root has an incidence of 40% and arises in a plexiform manner from small veins on the anterior side of upper lumbar veins and communicates with the inferior vena cava, renal vein, and possibly from the second and third lumbar segmental.

The hemiazygos vein usually receives the ninth to eleventh posterior intercostal veins, and may include the eighth. The hemiazygos vein passes behind the aorta from the left side to join the right-sided azygos. The communication may be doubled.

The hemiazygos veins have been found passing to the right side of the body ventral to (cross over) the aorta. In situs inversus and persistent left superior vena cava, the hemiazygos may switch sides with the azygos vein. In 40% of cases the hemiazygos is continuous above with an accessory hemiazygos vein.

The vein may open into the right atrium, brachiocephalic trunk, internal thoracic vein, left subclavian vein (ascribed to an elongated embryonic left common cardinal vein), or left brachiocephalic (after receiving abnormally the azygos vein).

Lejars found the left azygos (hemiazygos) vein communicating with the left renal vein in 88% of subjects studied.

Unusual tributaries include the superior phrenic, gonadal, renal, and suprarenal veins.

See also Azygos Vein

Left Cardinal (Persistant)

Image 260

References

See Azygos Vein and Accessory Azygos Vein

Lejars, -. (1888) Les voies de sûreté de la veine rénale. Bull. et Mem. de la société Anatomique de Paris.

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