Congenital anomalies of the caval vein are often associated with other abnormities such as heart defects, situs inversus or a polysplenia-asplenia-syndrome. An isolated, congenital malformation like aplasia of the inferior vena cava is a rare finding. A review of the embryology and abnormities, diagnostics, clinical signs and treatment is given together with the histories of two patients having thrombosis of the lower extremities and pelvic veins, caused by aplasia of the inferior vena cava. After thrombotic complications caused by vena cava aplasia there is high risk of recurrence. Those patients should be anticoagulated for lifetime.
