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==Introduction==

==Description==

[[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, heartworm (''[[Angiostrongylus vasorum]]'' or ''[[Dirofilaria immitis]]''), tricuspid dysplasia or 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.

*Direct disruption of lymphatic flow

*Direct disruption of lymphatic flow

|-

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| Nucleated cells

| Nucleated cells

| 1.5 - 20 x 10e9/L of which the majority are small [[Lymphocytes|lymphocytes]], mature [[Neutrophils|neutrophils]] and variable numbers of [[Macrophages|macrophages]].

| 1.5 - 20 x 10e9/L of which the majority are small [[Lymphocytes - Introduction|lymphocytes]], mature [[Neutrophils|neutrophils]] and variable numbers of [[Macrophages|macrophages]].

|}

|}

===Other Tests===

===Other Tests===

'''Pseudocyle''' is a type of fluid which has the same milky appearance as chyle but is actually composed of cellular debris, cholesterol micelles and lecithin globulin complexes.  Pseudochyle may represent an inflammatory or neoplastic process and, although rare in animals, it may be associated with ''Mycobacterium'' infection.  True chyle may be identified in the following ways:

'''Pseudochyle''' is a type of fluid which has the same milky appearance as chyle but is actually composed of cellular debris, cholesterol micelles and lecithin globulin complexes.  Pseudochyle may represent an inflammatory or neoplastic process and, although rare in animals, it may be associated with [[:Category:Mycobacterium species|''Mycobacterium'']] infection.  True chyle may be identified in the following ways:

*Chyle has a higher triglyceride concentration than plasma but a lower cholesterol concentration and it has a triglyceride: cholesterol ratio (C:T) of <1.  Pseudochyle has a higher cholesterol concentration than plasma but a lower triglyceride concentration.

*Chyle has a higher triglyceride concentration than plasma but a lower cholesterol concentration and it has a triglyceride: cholesterol ratio (C:T) of <1.  Pseudochyle has a higher cholesterol concentration than plasma but a lower triglyceride concentration.

*When chyle is left to stand overnight, an upper 'cream' layer will become evident due to the presence of chylomicrons in the fluid, whereas pseudochyle will remain homogenous.

*When chyle is left to stand overnight, an upper 'cream' layer will become evident due to the presence of chylomicrons in the fluid, whereas pseudochyle will remain homogenous.

If a tumour is found to be causing the clinical signs, resection may be attempted.

If a tumour is found to be causing the clinical signs, resection may be attempted.

[[Category:Effusions]]

[[Category:Effusions]]

 

[[Category:Expert_Review]]

[[Category:To_Do_-_James]]

[[Category:To_Do_-_Review]]