BACKGROUND
A 30-year-old man presents to the hospital
with an insidious onset of vague upper abdominal pain. On examination, the patient is afebrile. His cardiovascular and respiratory systems are normal. Abdominal examination does not reveal any masses or tenderness. No abnormalities are detected on upright and recumbent abdominal radiographs. CT is performed to identify the cause of his abdominal pain.
 

What is the diagnosis?

Hint
The CT scan shows a normal variant.
 

 

Answer
Double inferior vena cava (IVC): The CT scan depicts an oval structure anterior to the abdominal aorta and near the renal vessels (Image A). Scans obtained at levels inferior to Images B and C show this oval structure continuing as a round structure to the left of aorta; it can be traced in lower images (not shown) to the left common iliac vein.

This structure is an anatomic variant, the double IVC, and is due to the abnormal development of fetal veins. The other veins, such as the renal, gonadal, suprarenal, azygos, and hemiazygos veins, are normal and drain normally.

Normal development of the IVC is complex and involves the sequential formation and regression of 3 paired venous channels: the posterior cardinal veins, the subcardinal veins, and the supracardinal veins. The paired posterior cardinal veins usually regress, and the left parts of the subcardinal and supracardinal vein disappear. The persistent right subcardinal vein forms the suprarenal part of the IVC, and the right supracardinal vein forms the infrarenal part. Persistence of the left supracardinal vein occurs in 0.2-3% of individuals and results in the double IVC. The left-sided IVC usually begins from the left common iliac vein and runs to the left of the abdominal aorta. This left-sided IVC crosses at the level of the renal vein, anterior to the aorta, to join the normal right-sided IVC; however, the junction can occur at higher or lower levels. Usually, the 2 IVCs are of equal size, but 1 may be dominant. This anomaly does not produce any symptoms.

Careful analysis of the CT scans is necessary to avoid confusing this condition with enlarged lymph nodes. Unlike lymph nodes, the IVC is a contiguous structure depicted on multiple sections and may cross over the aorta to join the normal IVC. Multiplanar reconstructions are helpful in cases of suspected double IVC.

A double IVC can be associated with other conditions, such as a horseshoe kidney, cloacal extrophy, a circumaortic renal vein, a retroaortic left renal vein, and a retroaortic right renal vein with hemiazygos continuation of the IVC.

In patients with pulmonary embolism, the failure to recognize this anomaly and the placement of a filter in only the normal, right-sided IVC may result in recurrent pulmonary embolism.