I read with interest the article by Nadolski and Itkin1 in CHEST (January 2013) on thoracic duct embolization (TDE) for nontraumatic chylous effusion. The authors are to be applauded for approaching a difficult topic with poorly established standards and a high mortality rate. This is an important condition for chest physicians to understand and manage. Unfortunately, and despite the authors’ vast experience in the management of >160 patients with this frequently devastating disorder, the etiology of spontaneous or idiopathic chylothorax remains unexplained. What are the mechanisms for the thoracic duct undergoing obstruction in patients with no previous disease and normal MRI thoracic examinations? Up to 20% of patients with nontraumatic chylous effusions present with lymphatic anomalies (lymphatic malformations, generalized lymphatic disease [lymphangiomatosis], or Gorham-Stout disease).2 Children with massive lymphatic malformations in the neck, axilla, or groin do not develop lymphatic duct obstruction with lymphedema. We do not have information regarding compared outcomes of TDE in patients with or without associated lymphatic malformations.