Page 79 - Problem-Based Feline Medicine

6. The cat with hydrothorax

Robert Allen Mason

KEY SIGNS
● Dyspnea worsened in lateral recumbency.
● Dull heart and lung sounds ventrally.
● Fluid aspirated from chest (chyle, blood, transudate, modified transudate,
exudates).

MECHANISM?
● Accumulation of fluid (blood, transudate, modified transudate, exudate, chylous) in the pleural
cavity.
● There is a delicate balance of the normal fluid dynamics between the slight transudation across
the parietal pleura and the slight absorption across the visceral pleura.
● Factors which facilitate pleural effusion include decreased oncotic or increased hydrostatic
pressure within blood vessels, increased vessel wall permeability, and lymphatic obstruction.
● Excessive fluid in pleural cavity (chlye, blood, transudate, modified transudate, exudate).
● Pleural effusion encroaches on the space generally occupied by the lungs, and creates
hydraulic pressure opposing expansion of the lungs.

WHERE?
● Pleural space is the cavity between the visceral and the parietal pleura. Generally, this space
contains a few milliliters of fluid to act as a lubricant.

WHAT?
● Chylothorax – secondary to congestive heart failure, mediastinal neoplasia, lymphangiectasia,
or trauma.
● Hemothorax – secondary to trauma, coagulopathy, or neoplasia.
Pyothorax – from penetrating chest wound, ruptured lung abscess, or systemic bacteremia.
● Transudation – secondary to hypoalbuminemia from hepatic failure, protein-losing enteropa-
thy, or protein-losing nephropathy. May also occur from increased hydrostatic pressure from
congestive heart failure or lymphaticovenous obstruction from a neoplastic or granulomatous
disease of the chest.
● Modified transudates result either from causes of chronic transudates or occur early in dis-
eases, which cause exudates such as vasculitis secondary to feline infectious peritonitis, ure-
mia, neoplasia or pancreatitis.

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