Thrombosis of the deep leg and pelvic veins in congenital agenesis of the inferior vena cava

History and admission findings: Severe pain and increasing swelling in the region of the right lower leg occurred after unaccustomed physical activity in a 29-year-old man. Physical examination showed painful swelling and livid discoloration of the right lower leg. Investigations: Laboratory tests were consistent with an acute inflammation. Colour Doppler duplex sonography of the leg and pelvic veins bilaterally revealed complete thrombosis of the deep leg and pelvic veins on the right. Spiral computed tomography of the abdomen confirmed deep pelvic vein thrombosis and also demonstrated complete agenesis of the inferior vena cava (IVC), Treatment and course: The patient was fully heparinized and compression bandage applied to the right leg, which was kept elevated, Ibuprofen, 3 x 400 mg daily, was given for pain relief. Anticoagulation treatment with phenprocoumon (Marcumar(R)) was initiated. The patient was discharged much improved after ten days. Duplex sonography after 3 months demonstrated partial recanalization of the right pelvic and deep leg veins. Conclusion: Congenital malformations of the IVC are rare. Phlebothrombosis often results in affected patients. Treatment or prevention of thrombosis of the deep veins by anticoagulation is indicated. Additional risk factors for thrombosis - smoking, hormonal contraceptives, immobilization and unusual physical activity - should be strictly avoided.