- Union of superior vena cava (SVC) or inferior vena cava (IVC) with the left atrium (LA).
- Persistent left SVC.
- Absent hepatic segment of IVC.
Union of SVC or IVC with LA
It is a very rare anomaly.
All cases are cyanotic.
If both SVC & IVC join LA, the right heart is hypoplastic.
Once diagnosed, surgery is indicated: An intra-atrial baffle is placed to direct the caval blood to RA.
Persistent left superior vena cava
This anomaly is hemodynamically insignificant.
It may, however, cause difficulties during cardiac catheterization from the left arm.
It may also cause a bloody field during open heart surgery and complicate matters.
A persistent left SVC usually joins left innominate vein or coronary sinus.
Rarely it joins LA, in association with: asplenia, or polysplenia, or an atrial septal defect (ASD).
Mirror-image venous system:
Rarely the venous system in the neck is a mirror image of normal:
The right innominate vein crosses to the left side, joins the left vein & forms a left SVC that drains into the coronary sinus.
Absent hepatic segment of IVC
Definition and pathology:
In absent hepatic segment of IVC (also called: Continuity of IVC with the Azygos or hemi-Azygos veins, or Candy-Cane deformity), the hepatic segment of IVC is absent, the rest of IVC joins either the Azygos or the hemi-Azygos vein which then joins SVC.
The hepatic veins join together and form a trunk that joins RA in place of IVC.
Anatomy and tributaries of the inferior vena cava.
Inferior vena cava and Azygos and Hemi-Azygos veins.
- The hepatic (pre-renal or upper) segment of IVC is formed by the right vitelline vein.
- The renal (middle) segment of IVC is formed by the right sub-cardinal vein.
- The post-renal (lower) segment of IVC is formed by the right supra-cardinal (sacro-cardinal) vein.
Segments of the inferior vena cava.
- With drainage to Azygos vein: Fullness of right side of superior mediastinum.
- With drainage to hemi-Azygos vein: Fullness of left side of superior mediastinum.
Diagnosis and significance:
Leg venography is diagnostic.
The anomaly has no clinical significance but may cause difficulties during cardiac catheterization.