Retrocrural Space Obliteration as CT Diagnostic Sign of Massive Chylothorax in Thoracic Injuries

Purpose: Blunt traumatic chylothorax could be distinguished in CT (Computer Tomography) scan as low attenuated fluid, due to chylomicrons inside, however blood intermixture in chylous effusion could make densitomery higher and hide chylothorax, due to the possible presence of an underlying hemothorax. The objective of the study is to demonstrate the specificity of retrocrural space obliteration, as additional CT sign to quickly identify and treat chylothorax.
Materials and Methods: This retrospective study was undertaken since May 2012 until May 2013 and included patients scheduled for MDCT (Multi Detector CT) scan before a thoracentesis procedure diagnostic for hemothorax and chylothorax. Were used as a controls, MDCT scans performed for thoracic or thoracic-abdominal trauma, or after a thoracic surgery procedure.
Results: Comparison of CT findings revealed significant difference in densitometry between the two groups of effusions (P=0,003), a difference in inability of visualization of retrocrural space (P=0,0002) and cisterna chily (P=0,0009). Inability to observe thoracic duct was not different between the two groups (P=0,8805).
Conclusion: Negative density (-16,7+8HU) in effusions, due to the presence of fat inside, was usually observed in almost 6 anterior regions or at least 2 upper anterior regions and it’s the best way to distinguish a chylo-thorax to hemo-thorax. Most accurate CT scan differentiation between post traumatic massive bloody and chylous leakage can be done after assessment of a lower densitometry of effusion and inability in observing chylous structures and fat in retrocrural space due to chylous leakage inside.