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172 Chylothorax

Chylothorax Client Education
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• Jugular vein distention/pulsation may be
BASIC INFORMATION
present in animals with CHF or pericardial achieved by fluid analysis and comparison of
serum and fluid triglyceride levels. Attempts
Definition disease. should be made to identify underlying disorders.
Accumulation of fluid with a high triglyceride ○ Large-volume pleural effusions can cause
concentration (chyle) within the pleural space increased central venous pressure (CVP) Differential Diagnosis
and jugular venous distention/pulsation. • Other causes of pleural effusion
Epidemiology ○ Radiation of a normal carotid pulse ○ Hypoalbuminemia
SPECIES, AGE, SEX through the overlying jugular vein should ○ CHF
Cats and dogs; some diseases associated with not be misinterpreted as jugular pulsation. ○ Intrathoracic neoplasia
chylothorax are more common in middle-aged • Peripheral lymphadenopathy with some ○ Lung-lobe torsion
to older patients. causes of intrathoracic neoplasia ○ Pyothorax
• ± Peritoneal effusion ○ Pseudochylothorax
GENETICS, BREED PREDISPOSITION • Decreased cranial thoracic compressibility ○ Hemothorax
Possible breed predispositions include Afghan (cats) if associated with mediastinal mass ○ Feline infectious peritonitis (FIP) in cats
hounds and Shiba inu dogs and purebred cats, or pleural effusion • Pneumothorax
especially Asian breeds. • Fever is uncommon • Pulmonary parenchymal disease

RISK FACTORS Etiology and Pathophysiology Initial Database
• Thoracic trauma • Chyle is formed from lymphatic drainage • Thoracic radiographs: pulmonary parenchy-
• Intestinal or generalized lymphangiectasia of the gastrointestinal tract and mesentery mal, mediastinal, or cardiac disease more
• Congestive heart failure (CHF); cats > dogs (composed of chylomicra, electrolytes, fat- likely to be identified after thoracocentesis.
○ Hyperthyroidism (cats) soluble vitamins, proteins, and lymphocytes), ○ Interlobar fissure lines
• Thoracic neoplasia/granulomas and collected in the cisterna chyli. The sole ○ Reduced visualization of the heart,
• Thoracic surgery (damage to the left bra- outflow of the cisterna chyli is the thoracic especially on dorsoventral views
chiocephalic vein) duct (TD), a single or paired structure that ○ Retraction of lung margins from the
• Pulmonary/caval thrombosis courses dorsally though the thorax and thoracic wall, with an interposed fluid
• Heartworm disease (HWD) empties into the cranial vena cava. opacity
• Pericardial disease • Impaired or disrupted lymphatic drainage ○ Blunting of lung margins at the costo-
• Peritoneopericardial diaphragmatic hernia ○ Traumatic rupture of the TD phrenic angles
(PPDH) ○ Neoplasia: mediastinal, thoracic wall, or any ○ Increased opacity dorsal to the sternum
• Cardiac disease (e.g., double-chamber right affecting TD (e.g., lymphangiosarcoma) on lateral views, with rounding of the
ventricle, tricuspid dysplasia, cardiomyopathy) ○ Thoracic lymphangiectasia (± intestinal lung margins ventrally
lymphangiectasia) ○ The diaphragm is often obscured.
ASSOCIATED DISORDERS ○ Fungal granulomas ○ Widened mediastinum
Fibrosing pleuritis ○ Congenital abnormalities of the TD ○ Avoid ventrodorsal views: increases the
• Increased CVP (TD empties into cranial risk of respiratory distress
Clinical Presentation vena cava) ○ Atelectatic lung lobes may give a false
HISTORY, CHIEF COMPLAINT ○ CHF (right sided in dogs, left or right impression of lung masses.
• Respiratory distress/increased respiratory effort sided in cats) ○ Fibrosing/constrictive pleuritis second-
• Lethargy, anorexia, weight loss, exercise ○ Pericardial disease: pericardial effusion, ary to chronic chylothorax may prevent
intolerance restrictive pericardial disease, PPDH complete re-expansion after drainage and
• History of thoracic trauma/surgery ○ Pulmonary thromboembolism can cause many of the same radiographic
• Some animals, especially cats, may show ○ HWD abnormalities seen with pleural fluid.
minimal clinical signs until effusion volume ○ Cranial vena caval thrombosis: may be • Thoracic ultrasonography: detect pul-
is quite large. associated with implantation of a device monary or mediastinal masses/lesions,
(e.g., pacemaker lead) in either jugular lymphadenopathy, pulmonary consolidation,
PHYSICAL EXAM FINDINGS vein. and lung-lobe torsion and confirm presence
• Respiratory: tachypnea, increased inspiratory • Chylothorax has occurred in a small number of effusion if in doubt.
effort, shallow respirations, restrictive or of dogs after lung-lobe torsion correction. ○ If the patient is stable, ultrasound is ideally
generalized paradoxical breathing pattern, ○ Chylothorax and lung-lobe torsion are performed before effusion is completely
± coughing often concurrent disorders, and it is removed to provide an acoustic window.
○ Severely affected patients may demonstrate often unclear which was the primary ○ Thoracic ultrasound can detect small-
orthopnea, open-mouth breathing, and/ abnormality. volume effusions, guide thoracocentesis
or cyanosis. • Often, the cause of chylothorax cannot be if fluid is compartmentalized, and guide
• Thoracic auscultation determined (idiopathic). fine-needle aspiration of masses (p. 1113)
○ Muffled ventral heart/lung sounds or other lesions.
○ Murmurs or arrhythmias (heart disease) DIAGNOSIS • Thoracocentesis (p. 1164): chyle is often
○ Displacement of point of maximal grossly white/pink and opaque and remains
intensity of heartbeat (mass effect) Diagnostic Overview so after centrifugation.
○ Increased bronchovesicular lung sounds Patients typically present with signs suggesting ○ Animals on low-fat diets may lack char-
dorsally pleural space disease. Effusion is confirmed acteristic color and opacity.
○ Thoracic percussion: hyporesonance ventrally by imaging (radiographs/ultrasonography) or ○ Chyle may be classified as a modified
○ Abnormalities can be very subtle in cats. thoracocentesis. A diagnosis of chylothorax is transudate (<3000-5000 nucleated cells/

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