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4. 1 and 3
Chylothorax results when the flow of lymph from the abdomen is interrupted during its normal passage along the thoracic duct before draining into venous system usually at the subclavian veins (1). About half the cases are secondary to trauma where the thoracic duct leaks chyle and about half are due to medical conditions or are congenital. Obstruction of the thoracic duct from direct obstruction (mediastinal masses, mediastinitis, and radiation therapy) or elevated right-sided heart pressures essentially resulting in thoracic duct obstruction may cause a chylothorax. The thoracic duct runs posteriorly along the esophagus and is rarely injured during coronary artery bypass grafting. Most surgical injuries are secondary to esophageal, head and neck or aortic operations.
Based on the above pathophysiology which of the following may be used to diagnose the cause of the chylous effusion? (Click on the correct answer to proceed to the fifth of seven pages)