A chylothorax's a type of pleural effusion. It results from lymphatic fluid accumulating in the pleural cavity. Causes Its cause's usually leakage from the thoracic duct or one of the main lymphatic vessels that drain to it. The most common causes are lymphoma and trauma caused by thoracic surgery. The effusion's characteristically white and milky in appearance and contains high levels of triglycerides. In animals, chylothorax usually results from diseases that cause obstruction to the thoracic… (More on Chylothorax)