Compressive symptoms due to thrombosed or hypertrophic collateral circulation in infrarenal inferior vena cava agenesis.

Agenesis of the infrarenal segment of inferior vena cava is an uncommon and often asymptomatic congenital abnormality with an approximate incidence of 0.005-1% in the general population. Presentation of this condition as deep venous thrombosis associated with symptoms secondary to thrombosis or hypertrophy of collateral vessels is a rare clinical form. Two cases of this rare form are described, and an analysis of the related literature is presented. The first case was that of a 35-year-old man with symptoms of acute obstructive pyelonephritis with no apparent cause and swelling of the lower limb. The second case involved a 30-year-old man with lower limb swelling associated with paresthesia and motor deficit. Both patients were found to have infrarenal inferior vena cava agenesis associated with iliofemoral deep venous thrombosis and compression of anatomic structures by collateral vessels (ureteral compression due to thrombosis of an ectatic gonadal vein and L5 nerve root compression due to a hypertrophic epidural venous plexus). Patients were conservatively managed with anticoagulation therapy, with a favorable outcome and no recurrence in either case. In a young patient with iliac deep venous thrombosis of uncertain etiology, and particularly in those with atypical associated symptoms (mainly abdominal or neurologic), it is important to investigate congenital vena cava anomalies and carry out diagnostic imaging studies. Anticoagulation therapy is currently considered the best treatment option for this condition, but it should be individualized. The need for long-term anticoagulation should also be assessed in each case.