Changes

[[File:Chyle.jpg|right|200px|thumb|<center>Chylous effusion <br><small>(Courtesy of B. Stanikova)</small></center>]]

[[File:Chyle.jpg|right|200px|thumb|<center>Chylous effusion <br><small>(Courtesy of B. Stanikova)</small></center>]]

Chylous effusions are predominantly composed of chyle, the lymphatic fluid that flows through the lacteals of the small intestine and the thoracic duct in the chest.  Effusions occur when the normal flow of lymph is disrupted, either by alterations in the pressure gradient between the lymphatic and systemic venous systems or by physical disruption of the lymphatic vessels.  Chyle resembles milk and it is composed chiefly of fat globules (chylomicrons) with a high lymphocytic cellularity.  The vast majority of chylous effusions occur in the chest (producing chylothorax) but chylous ascites may occur.  The major causes of chylous effusions are:

Chylous effusions are predominantly composed of chyle, the lymphatic fluid that flows through the lacteals of the small intestine and the thoracic duct in the chest.  Effusions occur when the normal flow of lymph is disrupted, either by alterations in the pressure gradient between the lymphatic and systemic venous systems or by physical disruption of the lymphatic vessels.  Chyle resembles milk and it is composed chiefly of fat globules (chylomicrons) with a high lymphocytic cellularity.  The vast majority of chylous effusions occur in the chest (producing chylothorax) but chylous ascites may occur.  The major causes of chylous effusions are:

*Reduction of the pressure gradient from the lympahtic system to the major veins

*Reduction of the pressure gradient from the lymphatic system to the major veins

**'''Right-sided backward heart failure''' caused by [[Cardiac Tamponade|cardiac tamponade]], heartworm (''[[Angiostrongylus vasorum]]'' or ''[[Dirofilaria immitis]]''), [[Tricuspid Valve Dysplasia|tricuspid dysplasia]] or [[Cardiomyopathy|cardiomyopathy]].

**'''Right-sided backward heart failure''' caused by [[Cardiac Tamponade|cardiac tamponade]], heartworm (''[[Angiostrongylus vasorum]]'' or ''[[Dirofilaria immitis]]''), [[Tricuspid Valve Dysplasia|tricuspid dysplasia]] or [[Cardiomyopathy|cardiomyopathy]].

**'''Intrathoracic masses''' impeding venous return to the heart.  Commons types of mass are thymoma and thymic lymphoma.

**'''Intrathoracic masses''' impeding venous return to the heart.  Commons types of mass are thymoma and thymic lymphoma.