Chylous reflux in the lungs and pleurae.

Lymphangiectasis of varying extent may be present in some cases of chronic pulmonary disease. Often the dilated lymphatic channels are not identified because pulmonary fibrosis and emphysema together with secondary inflammatory changes obscure the lymph vessel pathology. When chylothorax is associated with such chronic pulmonary pathology, attention may be drawn to the lymphatic system. The presence of a chylothorax is usually attributed to obstruction or injury of the thoracic duct, whereas in some cases chylous reflux into the lungs and pleurae via abnormal lymph channels in the lungs and pleurae as well as in the mediastinum may cause the chylothorax. In rare instances a patient may actually expectorate chylous fluid which seeps into the bronchi from the abnormal peribronchial lymphatics. A detailed analysis of reported cases together with some personal experience has demonstrated that pathological changes in the pulmonary and pleural lymphatic vessels are more common than is usually appreciated. The normal remarkable regenerative potential which is usually evident after experimental interruption of the lymphatics apparently is lacking in some humans due to genetic and other factors. Thus pathological changes, difficult to simulate experimentally, may be encountered. Lymphangiectasis is often found not to be limited to a single organ if complete studies of the lymphatic system are made.