Page 80 - Problem-Based Feline Medicine

72 PART 2 CAT WITH LOWER RESPIRATORY TRACT OR CARDIAC SIGNS

QUICK REFERENCE SUMMARY
Diseases causing hydrothorax
DEGENERATIVE

● Congestive heart failure (cardiomyopathy)* (p 83)
Pleural effusion may result from right-sided or biventricular failure, most commonly associated
with cardiomyopathies. Cardiac tamponade from pericardial effusion may cause pleural effusion.
Abnormal heart sounds (gallops, murmurs, arrhythmias) are commonly noted. Cardiomegaly, pul-
monary venous congestion and pulmonary edema may be seen radiographically. Effusion fluid is
commonly a modified transudate or chylous effusion. Rarely, heartworm disease has been associ-
ated with pleural effusion of a clear transudate.
ANOMALY
● Chylothorax** (p 77)
Milky white, lipid-rich lymphatic fluid accumulates in the pleural space secondary to thoracic duct
hypertension. Idiopathic chylothorax is the most common form. Less commonly chylothorax is
associated with cardiomyopathy, or mediastinal neoplasia. Affected cats are often chronically ill
for several months prior to the onset of dyspneic signs of pleural space disease.
MECHANICAL

● Pleural/mediastinal masses (p 84)
Malignancies like thymoma or thymic lymphoma may cause obstruction of the lymphatic drainage
of the pleural cavity, leading to hydrothorax and dyspnea. Mass lesions may be observed radi-
ographically, especially after thoracocentesis. Dyspnea rarely may not improve significantly after
drainage. Transudate or exudate found on fluid analysis.
● Hemothorax (p 87)
Trauma or bleeding diatheses from congenital coagulopathies (hemophilia, Chediak–Higashi) or
acquired coagulopathies (rodenticide toxicity) may create hemothorax. Fluid is pink to frankly red
in color, but often defibrinated and does not clot. Evidence of blunt or penetrating chest trauma is
common. There may be other signs of coagulopathy (scleral hemorrhages, hematoma formation,
epistaxis, etc.).

METABOLIC
● Hypoproteinemia (p 88)
Protein-losing enteropathy, protein-losing nephropathy, and hepatic failure are common
causes of low serum protein, specifically hypoalbuminemia, which may result in decreased oncotic
pressure and transudation. This fluid is clear to lightly straw-colored. Signs include dyspnea,
weight loss, especially loss of muscle mass +/− icterus.
NEOPLASTIC

● Airway / Pulmonary neoplasia (p 87)
Tracheal adenocarcinomas (i.e., Siamese), primary pulmonary masses (pulmonary adenocarci-
noma) or secondary metastatic disease from distant neoplasms may create effusions. Fluid is often
modified transudate and is often grossly opaque. It is more common in middle-aged to older cats.