Infrarenal inferior vena cava agenesis presenting as acute abdomen and hydronephrosis - case report.

The inferior vena cava agenesis (IVCA) is a rare and often asymptomatic malformation due to the abundant development of the collateral circulation. However, it is frequently found in young people and carries a significant risk of deep venous thrombosis (DVT). It is estimated that about 5% of patients under 30 years of age presenting with DVT have this condition. We report a case of a previously healthy 23-year-old patient presenting with signs of acute abdomen and hydronephrosis due to the thrombophlebitis of an unusual iliocaval venous collateral, which developed secondary to IVCA. After treatment, the iliocaval collateral and hydronephrosis completely regressed on a 1-year follow-up. To our knowledge, this is the first such case reported in the literature.