3 CE Credits
Idiopathic Chylothorax: Pathophysiology,
Diagnosis, and Thoracic Duct Imaging
Ameet Singh, DVM, DVSc, DACVS
Brigitte Brisson, DMV, DVSc, DACVS
Stephanie Nykamp, DVM, DACVR
University of Guelph
Guelph, Ontario
Canada
Abstract: Idiopathic chylothorax is a debilitating disease that can lead to respiratory and metabolic compromise and fibrosing pleuritis.
Previous investigation has provided theories for the etiology of this poorly understood disease. This article provides an overview of the
pathophysiology and diagnosis of chylothorax. Thoracic duct imaging, including minimally invasive techniques, is also discussed, as
it is frequently performed in the perioperative period. A companion article reviews nonsurgical and surgical techniques for treating and
managing idiopathic chylothorax in dogs and cats.
For more information, please see the companion article, “Idiopathic
Chylothorax in Dogs and Cats: Nonsurgical and Surgical Management”
C
hylothorax is a debilitating disease that occurs when disruption
of the thoracic duct (TD) results in chyle leakage into the
pleural space (FIGURE 1). Trauma to the TD during cardiothoracic surgery is the most common cause of chylothorax in
humans. While traumatic causes of chylothorax have been reported
in veterinary patients, most cases in dogs and cats are considered
idiopathic because a predisposing cause cannot be identified.1
lymph to the vascular system by emptying into the venous system
(lymphaticovenous anastomosis) at the level of the jugulocaval
angle3 (FIGURE 2). This maintains fluid balance and prevents tissue
edema by returning interstitial fluid to the vascular system, thereby
acting as an adjunct to the cardiovascular system.
The Lymphatic System
The human anatomist Gaspar Aselli is credited with the indirect
discovery of the lymphatic system in a dog in 1622.2 In his
experiments, he noted that “a great number of cords […] were spread
over the whole mesentery and intestine.”2 Aselli first believed these
white cords were nerves, but he realized this was not the case
when incising the largest cord yielded a “white milk- or creamlike
liquid.”2 This fluid was not seen after incision of a white cord in a
subsequent experimental dissection of a dog that had been fasted,
and Aselli linked digestion to the formation of the milky fluid.2
The lymphatic system has three primary roles: (1) maintain
fluid balance, (2) generate an immune response, and (3) perform
uptake and transport of dietary fats.3 Approximately 10% of fluid
extravasated into the interstitial space enters blind-ended lymphatic
capillaries and becomes lymph.3 These capillaries connect to
larger lymphatic vessels that arborize into the TD. The TD, which
is the largest lymphatic vessel in the body and located in the tissues
dorsal to the aorta and ventral to the thoracic vertebrae, returns
Figure 1. Intraoperative image of a dog after right fifth intercostal thoracotomy.
The patient’s head is to the right, and the abdomen is to the left. Finochietto rib
retractors have been applied to improve visualization. Chyle is seen bathing the
heart and lungs within the pleural space.
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Idiopathic Chylothorax: Pathophysiology, Diagnosis, and Thoracic Duct Imaging
Figure 2. Lateral thoracic radiograph after contrast lymphangiography in a normal
dog. The cisterna chyli (arrow) is highlighted in the cranial abdomen; its extension
is the thoracic duct (arrowheads).
Figure 4. Lateral thoracic radiograph after contrast lymphangiography in a dog
The lymphatic system
plays a key role in many
immune functions in the
body, including creating
immune cells and defending
the body against infection
and the spread of cancer.
The TD provides a conduit
for immune cells as well as
an entry point to the systemic circulation.4
Dietary fats are absorbed
from small intestinal enterocytes in the form of chylomicrons, which are large
lipoprotein molecules (75 to
1200 nm).3 Chylomicrons
Figure 3. Characteristic “milky” appearance of
predominantly consist of trifluid retrieved from the pleural space of a dog
glycerides but also contain
with chylothorax.
phospholipids, cholesterol,
and other proteins. After
they are expelled from enterocytes, they are collected by villous
lacteals via exocytosis and eventually empty into the cisterna
chyli (CC). The CC is the abdominal lymphatic reservoir located
in the craniodorsal abdomen, and its cranial extension is the TD3
(FIGURE 2). The “milky” appearance of intestinal lymph, or chyle,
is proportional to the concentration of chylomicrons3 (FIGURE 3).
and mediastinal and pulmonary neoplasia.1 Cardiac diseases,
including constrictive pericarditis, dirofilariasis, right ventricular
failure, double-chambered right ventricle, and tricuspid dysplasia,
have also been reported as causes of chylothorax.5 However, in
veterinary patients, a predisposing cause is rarely identified and
chylothorax is most often deemed idiopathic.1 Idiopathic chylothorax is poorly understood.
An experimental model of chylothorax developed by ligating
the cranial vena cava has been used to help determine the pathophysiology of idiopathic chylothorax.6 In dogs with experimentally
induced chylothorax, and in dogs and cats with naturally occurring
idiopathic chylothorax, injection of contrast medium into a mesenteric lymphatic vessel (mesenteric lymphangiography) reveals
large, tortuous, dilated lymphatic vessels in the cranial mediastinum6
(FIGURE 4). These abnormal vessels in the cranial mediastinum
are characteristic of lymphangiectasia. It has been theorized that
lymphangiectasia of the TD, its tributaries, and/or the cranial
mediastinal lymphatic vessels leads to transmural leakage of chyle
into the pleural space, causing chylothorax.6 Why the spontaneous
occurrence of a flow disturbance in the TD results in thoracic
lymphangiectasia has not been determined and is the focus of
ongoing research.
Pathophysiology of Chylothorax
Numerous causes of chylothorax have been reported in the veterinary literature, all resulting in obstruction or impedance of TD
outflow at the lymphaticovenous anastomosis. They include fungal
granuloma, trauma, cranial vena caval thrombosis, congenital
abnormalities of the TD, diaphragmatic hernia, lung lobe torsion,
with idiopathic chylothorax. Dilated and tortuous cranial mediastinal lymphatic
vessels (circle) are common in animals with idiopathic chylothorax.
Role of Venous Hypertension in Chylothorax
Several diseases that could elevate right-sided venous pressures,
such as restrictive pericarditis, cranial vena caval thrombosis, and
right ventricular failure, have been reported to cause chylothorax.
However, it has not been determined why all patients with elevated
right-sided venous pressures do not develop chylothorax (e.g., all
cases of right ventricular failure do not lead to chylothorax). In two
independent studies, ligation of the TD at its entry into the venous
system at the level of the jugulocaval angle did not lead to chylothorax.6,7 This was thought to be a result of redirected lymphatic flow
through collateral channels that enter the cranial vena cava caudal
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Idiopathic Chylothorax: Pathophysiology, Diagnosis, and Thoracic Duct Imaging
Figure 5. Fluoroscopic image of the cranial thorax after contrast lymphangiography
in a normal dog. Multiple collateral TD branches (arrowheads) are seen entering
into circular structures (presumably lymph nodes) or the venous system caudal
to the entry point of the main TD (arrow) at the lymphaticovenous anastomosis.
Figure 6. Lateral thoracic radiograph of a canine thorax demonstrating soft-tissue
opacity in the pleural space. Note the retraction and scalloping of lung lobes
(arrowheads). Also, the cardiac silhouette is obscured.
to the lymphaticovenous anastomosis (FIGURE 5). These findings
provide evidence for the presence of, or the ability to recruit,
collateral lymphatic channels within the thoracic cavity and could
explain why chylothorax secondary to elevated central venous
pressure is rare.6–8
Diagnosis
Physical Examination
A complete physical examination often leads the clinician to
diagnose pleural effusion. The color of the patient’s mucous
membranes can vary from normal to pale blue, according to the
level of respiratory compromise. Thoracic auscultation may reveal
reduced heart and lung sounds in the ventral thorax from the
gravity-dependent accumulation of pleural fluid. Increased bronchovesicular sounds have been found in 45% and 50% of dogs9 and cats10
with chylothorax, respectively. Some patients exhibit respiratory
compromise when placed in lateral recumbency (orthopnea).
Thoracic percussion in a patient with pleural effusion produces a
dull, low, hyporesonant sound. Most patients with chylothorax
are normothermic.9,10
Chyle comprises proteins, dietary fats, electrolytes, fat-soluble
vitamins, and cells of the immune system. Chronic loss of chyle into
the pleural space can lead to metabolic compromise characterized
by hypoproteinemia, electrolyte abnormalities (hyponatremia
and hyperkalemia), fat depletion, and immunocompromise from
lymphocyte loss.1,9–11 Patients with chylothorax may also present
with a history of anorexia, lethargy, and weight loss.1,10 Additional
diagnostic evaluation should only be performed once the patient
is in stable condition.
Thoracic Radiography
Small volumes of pleural effusion may form radiopaque pleural
fissure lines from the peripheral margin of the lungs toward the
hilar region. Large amounts of pleural effusion lead to retraction and
“scalloping” of lung lobes (FIGURE 6). Pleural effusion can obscure the
cardiac silhouette, and repeat thoracic radiography after pleural
evacuation may be required to evaluate cardiac size. Chyle is a
bacteriostatic fluid that irritates the pleural and pericardial surfaces, and chronic
Key Points
chylous effusion can lead to
• Although numerous causes of
life-threatening fibrosing
chylothorax have been reported in
pleuritis and pericarditis.12
the veterinary literature, an underlying
Fibrosing pleuritis should
cause is rarely identified.
be suspected when the lungs
are rounded in the presence
• Although chyle has a characteristic
of minimal pleural fluid or
“milky” appearance, a definitive
when pneumothorax develdiagnosis of chylothorax can be made
ops after thoracocentesis
only if triglyceride levels in the pleural
(FIGURE 7).
fluid are greater than those in serum.
Pleural Fluid Evaluation
Thoracocentesis and retrieval of pleural fluid is recommended for diagnostic
purposes and to relieve the
patient’s respiratory compromise. Chyle has a characteristic milky appearance;
however, this appearance
alone cannot be used to
make a definitive diagnosis
of chylothorax because other
effusions, including pyothorax, may have a similar
appearance.1 In anorectic
patients, chyle may have an
uncharacteristically clear
appearance that can be
• Chronic chylous effusion can lead to
life-threatening fibrosing pleuritis
and pericarditis. Fibrosing pleuritis
should be suspected when the lungs
are rounded in the presence of
minimal pleural fluid.
• TD imaging is recommended before
and after TD ligation. Preoperatively,
it provides the surgeon with a view of
TD anatomy, and postoperatively, it
confirms occlusion of all TD branches.
• Minimally invasive TD imaging
techniques are associated with less
morbidity and shorter procedure
times compared with traditional
imaging techniques.
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Idiopathic Chylothorax: Pathophysiology, Diagnosis, and Thoracic Duct Imaging
fluid samples is recommended if
chylothorax is suspected.
Further Diagnostic Evaluation
A
Figure 7. Lateral (A) and dorsoventral (B) thoracic radiographs of a cat
with fluid opacity in the pleural space. The caudal lung lobes are
rounded compared with the normal caudal subsegment of the left
cranial lung lobe, which maintains a triangular shape. This is indicative
of fibrosing pleuritis, in which fibrin deposition on the pleural surface
prevents normal expansion and contraction of the lungs.
B
misleading.1 If chylous effusion is suspected, further diagnostic
tests should be performed to confirm the diagnosis.1,13–15 These
tests include cytologic, physical, and biochemical evaluation of
the sampled effusion.1,13–15
Cytologically, chylous effusion contains large numbers of
small, mature lymphocytes and lower numbers of macrophages
that contain lipid droplets1,14,15 (FIGURE 8). Chylomicrons should
be evident on a wet mount preparation of a chylous effusion.14 In
patients with chronic chylothorax that have undergone multiple
thoracocenteses, the effusion can be laden with nondegenerate
neutrophils.14,15 This finding could also be a result of the inflammatory effect of chyle on the pleura and pericardium. Biochemical
evaluation includes measuring triglyceride, cholesterol, and total
protein levels; performing a total cell count; measuring specific
gravity; and assessing for the presence of chylomicrons.13–15 A
definitive diagnosis of chylothorax is made by comparing triglyceride
levels in paired pleural fluid and serum samples.13–15 In cases of
chylous effusion, the level of triglycerides in the pleural fluid is
greater than that in the serum.13 It is common for the ratio of
triglycerides in pleural fluid to triglycerides in serum to be 10:1 to
20:1 or higher.13–15 The specific gravity and total protein concentration of feline chylous effusion have been reported to be 1.030
to 1.032 and 5.0 to 5.32 g/dL, respectively.9,14 Historically, several
other diagnostic tests have been performed to determine whether
an effusion is chylous.14 These include the ether clearance test and
Sudan II stain, which provide crude estimates of lipid content in
the fluid; however, these tests are seldom used at our institution.
Pleural and serum cholesterol levels can also be compared, with
cholesterol levels being lower in a chylous effusion than in serum.1,14
Although chyle is a bacteriostatic substance, multiple thoracocenteses for pleural evacuation can increase the risk of developing
pyothorax. Bacterial culture and sensitivity testing of pleural
Once a diagnosis of chylothorax
has been made, the clinician
should attempt to determine
whether there is an underlying
cause. In addition to a complete
blood cell count, serum biochemistry panel, heartworm antigen testing, and coagulation
evaluation, the diagnostic evaluation should include thoracic
ultrasonography (ideally before
thoracocentesis, to provide an
acoustic window) and threeview thoracic radiography (after
pleural evacuation has been performed) to determine if there is
underlying pathology. Thoracic
computed tomography (CT) provides three-dimensional detail of thoracic structures and can be
combined with preoperative TD imaging.16 As cardiac diseases
are reported causes of chylothorax, a complete cardiac evaluation,
including echocardiography, is warranted in all cases. In cats,
FeLV and FIV testing should also be performed.
Thoracic Duct Imaging
Kagan and Breznock17 first described the use of aqueous contrast
medium injected directly into a mesenteric lymphatic vessel
(mesenteric lymphangiography) for imaging the TD in normal dogs
Figure 8. A cytologic smear (40× magnification) prepared from pleural fluid of a
dog with idiopathic chylothorax. The nucleated cells consist of well-preserved
neutrophils (A ), macrophages (B), medium to large lymphocytes (C), and large
numbers of small lymphocytes (D). Courtesy of Dr. Emmeline Tan
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Idiopathic Chylothorax: Pathophysiology, Diagnosis, and Thoracic Duct Imaging
Figure 9. Intraoperative photo of a dog with idiopathic chylothorax. A celiotomy has
been performed for TD imaging. A mesenteric lymphatic vessel has been cannulated
with an over-the-needle catheter that is sutured in place. Contrast medium can be
injected into the catheter for TD imaging using radiography or CT.
(FIGURE 9). Since that landmark study, several published reports
have described the use of mesenteric lymphangiography to highlight the TD in dogs and cats undergoing surgical treatment for
idiopathic chylothorax.1,6,18,19 The most common surgical treatment for idiopathic chylothorax in dogs and cats is TD ligation.20
TD imaging has been recommended before and after TD ligation.18–20 Preoperative imaging of TD anatomy can allow the surgeon
to ligate the TD at a location with minimal branching in the caudal
thorax, which may optimize surgical success (FIGURE 10). Postoperative lymphangiography can confirm successful occlusion of all
TD branches with no flow of contrast cranial to the ligation site
so that if postoperative effusion persists, the surgeon can be more
certain that it is not from a failure to occlude all TD branches at
the time of surgery. If postoperative lymphangiography reveals
persistent TD flow, ligation for the missed TD branch(es) should
be reattempted or chylothorax will persist.18,19
Some authors21 have reported concern with the accuracy of postTD ligation lymphangiography in confirming occlusion of all TD
branches. In an experimental study in eight cats, six cats had TD
ligation performed and two cats had the TD dissected but not ligated
as a sham procedure.21 Immediate postoperative lymphangiography
showed no contrast flowing cranial to the site of dissection in all
cats, including the two that did not undergo TD ligation.21 Repeat
lymphangiography in the two nonligated cats 4 weeks postoperatively
revealed a patent TD. The authors concluded that simply dissecting
around the TD was sufficient to cause short-term occlusion of the
TD.21 Additional studies are required in dogs to determine if dissection of the TD alone is sufficient to obstruct the flow of contrast at
the time of lymphangiography. Lymphangiography is challenging to
perform in cats and is associated with several limitations, including
difficulty in locating and injecting mesenteric lymphatic vessels.
Although radiographic visualization of TD anatomy using
aqueous contrast material is advantageous before and after TD
Figure 10. Lateral thoracic radiograph after contrast lymphangiography in a dog
with idiopathic chylothorax. Branching of the TD is seen in the mid-thorax.
ligation, it does not provide the surgeon with intraoperative information about the TD and its branches. Injection of mesenteric
lymph nodes or lymphatic vessels with methylene blue is reported
to facilitate intraoperative visualization of the TD and its branches
during TD ligation.20,22 However, intravenous injection of methylene
blue can lead to toxicosis; reported complications include renal
failure, Heinz body anemia, and increased serum alkaline phosphatase levels.23,24 Preoperative administration of a fatty meal (oil
or 35% cream) to increase the chylomicron content of chyle has
also been reported to facilitate intraoperative identification of
lymphatic vessels and the TD.20
The standard imaging modality for mesenteric lymphangiography has been orthogonal view radiography.17,18 Some authors
question the accuracy of radiographs because superimposition of
TD branches and overlying spinal and soft tissue structures can
make interpretation challenging. In one study25 that compared
CT with radiography after direct mesenteric lymphangiography
in dogs, CT was found to identify a significantly greater number
of TD branches. The ability to observe TD branches in a threedimensional plane and the limited need for patient repositioning
for image acquisition were other advantages of CT identified in
this study.25 CT also has greater contrast resolution, and small,
poorly opacified branches can still be identified (FIGURE 11). The
study authors speculated that by improving the ability for surgical
planning, CT mesenteric lymphangiography would improve success
rates of resolving chylothorax with TD ligation.25
Minimally Invasive Techniques for Thoracic Duct Imaging
Traditional TD imaging techniques require an exploratory laparotomy and injection of contrast medium into a mesenteric lymphatic
vessel or lymph node, followed by either radiography or CT.17,18,25
The exploratory laparotomy required for mesenteric lymphangiography prolongs anesthesia time and can increase morbidity in
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Idiopathic Chylothorax: Pathophysiology, Diagnosis, and Thoracic Duct Imaging
Figure 11. Transverse CT image at the level
of the eighth thoracic vertebrae in a normal
dog after contrast lymphangiography. Three
branches of the thoracic duct (arrows) are seen
dorsal and lateral to the aorta (arrowhead ).
A
B
Figure 12. Lateral radiographs of the pelvic limb (A) and thorax and abdomen (B) after popliteal lymphangiography in a dog
with idiopathic chylothorax. In (A), small lymphatic vessels can be seen travelling from the popliteal lymph node (arrow)
to the medial iliac lymph node (arrowhead). In (B), lymphatic vessels from the medial iliac lymph node (arrowhead) and
abdomen arborize into the CC, from which the TD extends cranially.
an already metabolically compromised chylothorax patient. The
goal of developing minimally invasive TD imaging techniques is to
reduce morbidity and anesthesia times and to eliminate the need
for intraoperative patient transfer to the radiology suite while
providing optimal imaging studies to maximize success for the
veterinary surgeon.
Percutaneous Mesenteric Lymphadenography
Ultrasound-guided percutaneous injection of a mesenteric lymph
node with contrast medium followed by thoracic CT has been
reported to produce diagnostic lymphangiograms in dogs.26 The
success of this technique lies in the operator’s experience with
ultrasound-guided mesenteric lymph node injection.
Laparoscopic Mesenteric Lymphadenography
Laparoscopic surgery has several advantages over laparotomy,
including decreased morbidity, faster recovery, improved visualization, and improved cosmesis. Laparoscopic mesenteric lymphadenography followed by radiography has been described for
mesenteric lymph node injection for TD imaging in dogs.27 This
technique was less successful than direct mesenteric lymphadenography (performed via paracostal laparotomy) at producing
diagnostic lymphadenograms, which was attributed to the lack
of manual stabilization of the injected lymph node, allowing the
node to fall away from the needle during injection.27
Percutaneous Popliteal Lymphangiography
Percutaneous popliteal lymph node contrast injection has been
evaluated in dogs28 (FIGURE 12). Initial studies determined that
the TD could be seen radiographically after experimental injection
with 1 mL/kg of contrast medium injected at 2 mL/min in dogs.28
Major complications were not reported with percutaneous popliteal
lymph node injection.28 In a recent study, CT was used to identify
TD anatomy after percutaneous popliteal lymphangiography in
normal dogs.16 CT delineated a significantly greater number of
TD branches compared with both lateral and ventrodorsal radiographs.16
One concern with percutaneous or ultrasound-guided popliteal
lymphangiography is whether enough pressure is generated during
the injection to open all TD branches. This concern is based on
the fact that high injection pressures cannot be used during this
technique and the fact that the popliteal lymph node is much
farther away from the CC and TD compared with mesenteric
lymphatic branches. Millward et al29 did not find a significant difference in TD branches after direct mesenteric and popliteal
lymphangiography in normal dogs when CT was used to image
the lymphatic system. Studies support the use of percutaneous
popliteal lymphangiography in the perioperative period as a
minimally invasive alternative to mesenteric lymphangiography
or lymphadenography.16,28,29
Conclusion
The pathogenesis of idiopathic chylothorax remains poorly understood in veterinary patients. Advances in the diagnostic evaluation
of chylothorax patients will facilitate the generation of high-quality
images for presurgical planning with minimal patient morbidity.
References
1. Birchard SJ, McLoughlin MA, Smeak DD. Chylothorax in the dog and cat: a review.
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2. Drinker CK. Lane Medical Lectures: the lymphatic system. In: University Series: Medical
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Microsc Res Tech 2001;55:92-99.
5. Fossum TW, Miller MW, Rogers KS, et al. Chylothorax associated with right-sided
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heart failure in five cats. J Am Vet Med Assoc 1994;204:84-89.
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chylothorax after ligation of the cranial vena cava in dogs. Am J Vet Res 1986;47:967-971.
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1986;188:1315-1318.
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with chronic chylothorax in five cats and two dogs. J Am Vet Med Assoc 1992;201:317-324.
13. Fossum TW, Jacobs RM, Birchard SJ. Evaluation of cholesterol and triglyceride concentrations in differentiating chylous and nonchylous pleural effusions in dogs and cats.
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Idiopathic Chylothorax: Pathophysiology, Diagnosis, and Thoracic Duct Imaging
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1. What is the most common cause of chylothorax in dogs and
cats?
6. Cytologic evaluation of chylous pleural effusion reveals
a. trauma
a. small, mature lymphocytes and lower numbers of
macrophages.
b. cranial vena caval thrombosis
b. degenerate neutrophils.
c. idiopathic
c. large, immature lymphocytes and lower numbers of
macrophages.
d. cardiac disease
2. Which of the following is/are not a function(s) of the
lymphatic system?
a. maintain fluid balance and act as an adjunct to the
cardiovascular system
b. generate an immune response against invading pathogens
c. transport dietary fats
d. regulate circadian rhythm
3. Which statement(s) is/are correct regarding chyle?
a. It comprises lymphocytes, fat-soluble vitamins, proteins,
and electrolytes.
b. Chronic loss of chyle into the pleural space can lead to
metabolic and immune compromise.
d. large, immature lymphocytes and higher numbers of
macrophages.
7. A definitive diagnosis of chylothorax can be made when
a. the ratio of triglycerides in pleural fluid to serum is 10:1
to 20:1.
b. the ratio of cholesterol in pleural fluid to serum is 10:1 to
20:1.
c. the ratio of triglycerides in serum to pleural fluid is 10:1
to 20:1.
d. sampled pleural fluid has a characteristic “milky” appearance.
8. Repeated thoracocentesis of chylothorax can lead to
a. restrictive pleuritis.
c. Chyle is an irritant, and chronic exposure of the pleural and
pericardial lining to chyle can lead to fibrosing pleuritis.
b. loculated fluid.
d. all of the above
d. hemothorax.
4. Which statement is correct regarding the TD?
c. pyothorax.
9. Which statement is true concerning TD imaging?
a. It is located in the tissues dorsal to the aorta and ventral
to the thoracic vertebrae.
a. It is recommended before and after TD ligation.
b. It transports chyle from the CC and empties it into the
venous system at the jugulocaval angle.
c. Radiographic and CT lymphangiography are equivalent
in delineating TD branching.
c. It can have variable anatomy at the lymphaticovenous
anastotomosis and along its course through the thoracic
cavity
d. It does not prolong anesthesia time in the operative
period.
d. all of the above
5. Which statement is correct regarding fibrosing pleuritis?
a. It is a benign condition.
b. It can be suspected on radiographs if the lung margins
are rounded in the presence of minimal pleural effusion.
b. Traditional techniques do not risk increased morbidity.
10. Which statement(s) is/are true concerning percutaneous
popliteal lymphangiography?
a. It represents a minimally invasive technique for TD imaging.
b. Followed by CT, it delineates a greater number of TD
branches than radiography.
c. It does not affect long-term prognosis.
c. It does not delineate as many TD branches as direct
mesenteric lymphangiography.
d. It occurs only in cats.
d. a and b
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