Likewise, a pleural effusion with attenuation of fat (approximately -90 to -115 HU) may suggest the presence of a pseudochylous
(or chyliform) pleural effusion, which has high lipid content and has been described with tuberculous pleurisy and rheumatoid arthritis.
In pleural fluids, chylous effusions are milky white or yellow-bloody and indicate damage or obstruction to the thoracic duct secondary to trauma, malignancy, or congenital abnormality; pseudochylous
effusions are also milky or green with a metallic sheen, contain cholesterol crystals and indicate chronic inflammation.
Effusions secondary to Collagen Vascular Disease -Effusions secondary to rheumatoid arthritis are predominantly mononuclear cell exudates, typically with low glucose levels (< 10 mg/dl), high titers of rheumatoid factor (> 640) and cloudy appearance (pseudochylous
or cholesterol effusions).
In the case of a pseudochylous
effusion of pleural fluid, cholesterol crystals may be seen.