Formation of the inferior vena cava (IVC) is a complex process that involves multiple steps. Three entire venous systems develop (supracardinal, sub-cardinal and posterior cardinal) and selectively regress to complete formation of the inferior vena cava and its large tributaries. Caval development begins in the sixth week of fetal life and progresses rapidly, with formation of all three percursor venous systems by the eighth week.
Many different anomalies are described, usually as incidental and infrequent findings: left-sided IVC, double IVC, azygos continuation of the IVC, circunaortic left renal vein, retroaortic left renal vein, circuncaval ureter, absence of the entire IVC and finally, absence of the infra-renal segment of the IVC when there is selective injury to the supracardinal system. Recognition of these anatomical variants can avoid significant morbidity during abdominal surgical procedures, liver or renal transplantation, placement of caval filters and varicocele scleroterapy. Agenesis of the infra-renal segment of the IVC is a rare anomaly (15 cases described by imagiology in the english language literature between 1957 and 1999). Of these, only two reports described persistence of the suprarenal segment, such as in this case.
Absence of the IVC was found to be associated with 5% of cases of deep venous thrombosis in patients below 30 years of age, thus representing a rare risk factor for idiopathic deep venous thrombosis.
In this particular case, CT was sufficient for diagnosis. Angiography, which remains the most accurate diagnostic technique, may provide further characterisation of these malformations.