Clinical Cases - Posterior Mediastinum

Your service has been called to provide consultative support to a patient who has become unstable during his postoperative phase of surgery. The patient is currently recovering from a modified radical neck procedure for squamous cell carcinoma of the tongue. The patient presents tachycardic and hypotensive with decreasing urinary output and poor skin turgor. He is intermittently combative and semi-conscious. On physical exam, you note the incision line on the left side of his neck to be intact with a bulb suction device protruding through the incision. The surrounding region of the neck is edematous, and a palpable mass roughly 8 cm in diameter is felt. You connect the bulb suction to the wall suction apparatus and approximately 600 ml of milky white fluid is immediately aspirated from the wound with a subsequent diminution in the size of the mass. Over the next few hours, you notice that the patient continues to have worsening hypotension, and the wound has now drained over 1 liter of milky white fluid in the period of six hours. The resident diagnosed a chylothorax . The plan for management includes contacting the thoracic surgery team and replacing the patient's lost fluid volume.

Questions to consider:

1. What is chylothorax?
   

   A pleural effusion composed of lymphatic fluid due to disruption of the thoracic duct.

2. How would you explain the milky white fluid following this kind of operation? Which lymphatic channel/duct would be involved?
   

   The fluid is lymph, which contains lipids and hence presents as milky white drainage.
   
   Given the location of the surgical procedure - dissection of the left neck - there is a danger of injuring the thoracic duct or its major tributaries, particularly the jugular trunk found within the neck.

3. How would a definitive diagnosis be made?
   

   First, by microscopic analysis of the pleural fluid output for lipid or lymphocytes. Secondly, one could give a lipid challenge, by administering a high lipid content meal and looking for an increase in the amount or change in the appearance of the fluid effusion.

4. What is the course of the thoracic duct?
   

   The thoracic duct begins at the cisterna chyli in the abdomen and extends cranially on the anterior surface of the vertebral bodies. It passes thru the diaphragm along with the aorta at the T12 level. It then shifts to the left at T5 to T7, and then empties into the left subclavian vein.

5. What structures drain into the thoracic duct?
   

   The thoracic duct receives branches from the intercostal spaces, and the jugular, subclavian, and bronchomediastinal trunks of the lymphatic system.

6. What lymph nodes can be found in the posterior mediastinum?
   

   The posterior mediastinal lymph nodes lie posterior to the pericardium. These lymph nodes receive lymph from the esophagus, the posterior aspect of the pericardium, and the middle posterior intercostal spaces.

References:

Moore's Clinical Anatomy 4th Edition pp. 150 - 157.
Advanced Surgical Recall pp. 1048 - 1049.
Woodburne & Burkel, p. 421-31