Developmental interruption of the inferior vena cava with azygos and hemiazygos substitution. Unusual radiographic features.

Two cases of left paraspinous density are presented. An inferior vena cava anomaly was not considered in the initial case, resulting in surgical exploration. The second case was diagnosed angiographically and surgery was avoided. The importance of considering this entity in the differential diagnosis of paraspinous masses is obvious, and venography should be performed to delineate the anatomy. Concurrent cardiac catheterization should be used to rule out associated lesions such as intracardiac shunts, since there is an increased association of such lesions with this anomaly.