Figure 11.45 A. Double inferior vena cava at the lumbar level arising from the persistence of the left sacrocardinal vein. B. Absent inferior vena cava. The lower half of the body is drained by the azygos vein, which enters the superior vena cava. The hepatic vein enters the heart at the site of the inferior vena cava.
A double inferior vena cava occurs when the left sacrocardinal vein fails to lose its connection with the left subcardinal vein (Fig. 11.45A). The left common iliac vein may or may not be present, but the left gonadal vein remains as in normal conditions.
Absence of the inferior vena cava arises when the right subcardinal vein fails to make its connection with the liver and shunts its blood directly into the right supracardinal vein (Figs. 11.44 and 11.45B). Hence the bloodstream from the caudal part of the body reaches the heart by way of the azygos vein and superior vena cava. The hepatic vein enters into the right atrium at the site of the inferior vena cava. Usually this abnormality is associated with other heart malformations.
Left superior vena cava is caused by persistence of the left anterior cardinal vein and obliteration of the common cardinal and proximal part of the anterior cardinal veins on the right (Fig. 11.46A). In such a case, blood from the right is channeled toward the left by way of the brachiocephalic vein. The left superior vena cava drains into the right atrium by way of the left sinus horn, that is, the coronary sinus.
A double superior vena cava is characterized by the persistence of the left anterior cardinal vein and failure of the left brachiocephalic vein to form (Fig. 11.46B). The persistent left anterior cardinal vein, the left superior vena cava, drains into the right atrium by way of the coronary sinus.
Right brachiocephalic vein
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