This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Thorax- wall and Bronchopulmonary segment, Subject name: Anatomy
[{'content': 'In IVC obstruction, all of the following collaterals help EXCEPT: \nSelect and explain. \nA. Superior epigastric and inferior epigastric vein, B. Superficial epigastric and iliolumbar vein, C. Azygos and ascending lumbar vein, D. Lateral thoracic and preveebral vein', 'role': 'user'}, {'content': 'Answer: B \nExplanation: In IVC obstruction, collaterals open up to drain blood into SVC and then to the hea (right atrium). Since, superficial epigastric and iliolumbar vein both drain into IVC, they are not helping the cause. Superior epigastric and inferior epigastric form collateral in rectus sheath. Superior epigastric drain into internal thoracic then into SVC which open into right atrium, hence blood can be drained from IVC into SVC . Superficial Epigastric vein forms collaterals with Lateral Thoracic vein thoracoepigastric vein in case of either IVC or SVC obstruction', 'role': 'assistant'}]