Chylothorax occurs when chyle, or lymph fluid containing fatty acids, leaks into the pleural space surrounding the lungs. It is uncommon in dogs and cats and usually secondary to other conditions like trauma, cancer, or heart disease. Diagnosis involves identifying milky white fluid in the chest that contains high levels of triglycerides. Treatment aims to drain the fluid and reduce lymph flow through dietary changes, medications, or duct ligation surgery, but prognosis is generally poor.

1. Chylothorax
Dr. Rekha Pathak (Sr. Scientist)
Division of Surgery,
Indian Veterinary Research Institute, Izatnagar,
Bareilly, India

2.  Duct – dorsal mediastinum –
close to vertebral bodies
 Passes cranially from the
cisterna chyle- on the rt. Side
of aorta- 6th thoracic
vertebra- crosses to left of
oesophagus- continues
cranially – thoracic inlet-
turns ventrally and enters the
left brachiocephalic vein.

4. Chylothorax in dogs and cats
 Chylothorax – chyle(a high
concentration of
chylomicrons and lymph)
-effuses from the thoracic
duct
 Chylothorax is fairly
uncommon in dogs and cats,
is usually secondary to other
conditions or diseases, and
can be difficult to treat.

5.  Chylous effusion
 - milky-white pleural fluid
 - fails to become clear upon
centrifugation.

6.  Pseudochylous effusion -
chronic inflammatory thoracic
disease.
 Pseudochylous effusions do not
contain chylomicra, clear upon
centrifugation,

7.  Dietary lipids- break to form chylomicrons –
finally absorbed by lymphatics (chyle)- carried to
different body parts.

8.  Chylous effusions
may result from
leakage of chyle from
intact lymph vessels
or
 thoracic duct
perforation.
 Obstruction of
lymphatic flow
commonly causes
lymphatic
hypertension,
 dilation of lymphatics,
and subsequent
leakage of lymph.

9. Different causes for chylothorax in
dogs
 Congenital
abnormalities of the
thoracic duct
 Diaphragmatic hernia
 Fungal infections
 Heartworm disease
 Idiopathic
 Violent
coughing/vomiting .

10.  Lung lobe torsion
 Lymphangiectasia
 Neoplasia
 Trauma and rupture
of thoracic duct
 Venous thrombi
 Mediastinal neoplasia

11.  Incidence:
 No gender predisposition
 Age does seem to be a factor,
4. trauma-related,
5. idiopathic, and
6. congenital causes of chylothorax tend to
occur in younger dogs.
 Chylothorax associated with neoplasia
and heart disease tend to occur in older
animals.

12.  A breed predisposition
 purebred cats,
 Afghan Hounds, and
 Mastiffs

13. Diagnosis
 Diagnosis is made based on
 Physical examination,
 Clinical signs,
 Thoracic radiographs, and
 Pleural fluid analysis.

14. Diagnosis
1. clinical signs,
 dyspnea and coughing.
 weight loss,
 anorexia, lethargy

15.  regurgitation,
 vomiting,
 exercise intolerance, and salivation.
Abnormal physical findings most
commonly include dyspnea, muffled
heart sounds,

16. Diagnosis
 Physical examination,
 Bronchovesicular sounds, and tachycardia.
 Thoracic radiographs
 Radiographs typically reveal pleural effusion
which may be unilateral or bilateral,

17.  Imaging Studies
 Chest radiographic findings are nonspecific for chylothorax and
indistinguishable from other causes of pleural effusion.
 Determine if effusion is bilateral.
 Look for a mediastinal shift.

18. Left sided effusions

19.  . Ultrasonography and echocardiography
may be useful in identifying an underlying
cause of the effusion, such as
cardiomyopathy or mediastinal neoplasia.

20. Lab diagnosis
 The complete blood count
 mature neutrophilia due to inflammation
 lymphopenia from the loss of lymphocytes into
the fluid.

21.  The serum chemistry profile
 Hypoalbuminemia,- protein loss in the
fluid
 Hyponatremia- electrolyte loss in fluid
 Hyperkalemia. Hyperkalemia may be due
to hypovolemia and/or renal secretion
defects of potassium.

22.  Pleural fluid analysis
is required for the
diagnosis of
chylothorax. Grossly,
chylous effusion is
milky white or pink,
depending on the
degree of hemorrhage
associated with the
effusion

23.  Chylous effusions
should not clot or
have an odor, and
should be free of
particulate
matter.

24.  Collecting the
fluid into an
EDTA tube
allows for cell
counts on the
sample.

25.  A culture and sensitivity
 The effusion should form a cream layer
 Upon centrifugation, the sample should become
white following centrifugation if red blood cells
are present (although the presence of hemolyzed
erythrocytes will result in a fluid that remains red
or pink following centrifugation), and should
remain opaque.

26. Cytologic and Chemical Characteristics
 Laboratory analyses that may be performed on the fluid
include determination of
 specific gravity,
 TP
 TLC,DLC
 cholesterol and triglyceride concentrations
 ratio of cholesterol to triglyceride.

27.  Predominance of small
lymphocytes - considered
characteristic of chylous
effusion;
 However, increase in
neutrophils and macrophages
may be associated with
chronicity.(chyle is irritant to
pleura)

28.  Pseudochylothorax
 Chylothorax must be distinguished from
pseudochylothorax, or cholesterol pleurisy,
which results from accumulation of
cholesterol crystals in a chronic existing
effusion.
 The most common cause of
pseudochylothorax is chronic pneumonia,
pleuritis and lymphosarcoma

29. Serum/chylous/pseudochylous
 . Chylous effusions
 Less cholesterol more triglycerides than serum
C:T= <1
 Fluid: serum triglycerides = >3:1,
 Usually encountered 10-20:1
 Pseudochylous – more cholesterol and
triglycerides less or equal to serum

30.  An ether clearance test
 take effusion in 2 tubes+ 10% KOH
 First tube+equal water (control)
 Second tube+equal ether
 Invert- chylomicrons dissolve completely in ether
 The first tube should appear diluted, but second
tube should become clear. This test is not
routinely performed.

31. Treatment and Prognosis
 depends on the underlying cause
 Medical therapy:
 Thoracocentesis-needle/ chest tube drainage
 Dietary management- low fat diet-to decrease
lipids in intestinal absorption

32.  Drug therapy
 loss of fat-soluble vitamins, lipids, and protein-
rich lymph fluid may contribute to a state of
malnourishment in the animal.
 Parenteral nutrition can bypass the
gastrointestinal system and decrease lymphatic
flow.

33. Surgical management
 Not v. successful
 ligation of the thoracic duct-feed fat/oil prior-
canulate superficial lymphatic in hindlimb- inject
dye- locate the duct and point of rupture

34.  1% Evans blue dye can either be injected
into the web space of the toes for uptake
into the lymphatic space to increase
visualization.

35.  9th i.c.(right) space-an open right
thoracotomy or through a thoracoscope.
 locate duct- ligate cranial and caudal to
rupture
 Collaterals build
 Place the chest tube and close
 pleuroperitoneal or pleurovenous shunts.

36.  Positive contrast mesenteric lymphangiography
is useful to determine lymphatic anatomy and
post-ligation success.
 Pleuroperitoneal or pleurovenous shunts may
be beneficial, but are associated with
complications such as infection, adhesions, and
clogging of the implants

37. Poor prognosis
 Regardless of the cause, chylothorax has been
associated with poor survival rates in dogs and
cats.
 A common sequela to chylothorax is restrictive
pleuritis, resulting in an inability to expand the
lungs.