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A case of the left innominate vein passing behind the ascending aorta
Insights
A rare anatomical variation, the postaortic left innominate vein, was observed. This vein passes behind the ascending aorta, with few reported cases worldwide.
Area of Science:
- Anatomical variations
- Human embryology
- Vascular anatomy
Background:
- The left innominate vein (LIV) typically forms anterior to the great arteries arising from the aortic arch.
- Anatomical variations in venous return can have clinical significance.
Observation:
- A postaortic left innominate vein was identified during a dissection of a 69-year-old Japanese male.
- The anomalous vein passed posterior to the ascending aorta, with no evidence of a typical anterior LIV.
Findings:
- This case represents a rare anomaly, with only ten previous reports found in the literature.
- The observed postaortic left innominate vein was classified as Type I, passing ventral to the ligamentum arteriosum.
- Embryologically, this anomaly is attributed to the transposition of a venous connection during development.
Implications:
- Understanding rare vascular anomalies is crucial for accurate interpretation during medical imaging and surgical procedures.
- This case contributes to the limited literature on postaortic left innominate veins, aiding in anatomical knowledge.
- Awareness of such variations can prevent misdiagnosis and guide surgical planning in thoracic interventions.
Abstract:
The authors observed the postaortic left innominate vein, which passed behind the ascending aorta, in the body of a 69-year-old Japanese male during dissection in 1979. In this case, no rudiment of the ordinary left innominate vein could be found in front of the arteries arising from the arch of the aorta. There are few reports of this anomaly and an extensive search of the available literature revealed only ten cases, including three in Japan. Adachi classified the postaortic left innominate vein into two types, types I and II, on the basis of the positional relation between the left innominate vein and the ligamentum arteriosum. Our case was of type I, in which the left innominate vein passed ventral to the ligamentum arteriosum and ran across from left to right behind the ascending aorta to join the right innominate vein. The embryological explanation which generally is accepted for the postaortic left innominate vein lies in the transposition of a transverse connection, which becomes the left innominate vein in a later stage of development, between the left and right anterior cardinal veins from the ventral to dorsal sides of the rudiment of the ascending aorta.