<prompt> In case of IVC obstruction, the collateral which opens up are all exceptSuperior epigastric inferior epigastric veinAzygos ascending lumbar veinSuperficial epigastric ileolumbar veinLateral thoracic veins preveebral vein  <response>: Superficial epigastric vein drains into the femoral veinileo lumbar vein drains into common iliac vein Ref: Grays 39ep10 