In case of IVC obstruction the collaterals which open up are all except
Superior epigastric & inferior epigastric vein
Azygos & ascending lumbar vein
Superficial epigastric & iliolumbar vein
Lateral thoracic veins & preveebral vein
Superficial epigastric pain drains into great saphenous vein.Iliolumbar vein drains into internal iliac vein,so these two do not form collateral between SVC & IVC as both of them will be ultimately drained into IVC.All other choices form collaterals between SVC & IVC. Ref: Chapter 8. The Chest: Chest Wall, Pulmonary, and Cardiovascular Systems; The Breasts. In LeBlond R.F., Brown D.D., DeGowin R.L. (Eds),DeGowin's Diagnostic Examination, 9e.