Page 371 - Clinical Small Animal Internal Medicine

34 Pleural Effusion 339

thickened, and inflamed by chronic effusions, thus inhib- Pyothorax
VetBooks.ir iting reexpansion of the lungs once the effusion is Pyothorax is the accumulation of purulent exudative
removed. In humans, this is termed lung entrapment as
the intrapleural pressure has become negative, but the
lungs cannot expand due to the formation of a visceral effusion in the pleural space caused by infection. Young
(3–6 years) male dogs are more likely to be diagnosed
pleural peel and persistent pleural effusion. This imparts with pyothorax, with performance breeds being overrep-
a large negative pressure on the diseased visceral pleural resented. Dyspnea, tachypnea, pyrexia, lethargy, and
surface, which may cause pain or increase risk of sponta- anorexia are the most common clinical signs in dogs. In
neous pneumothorax. cats, pyothorax is more common in young (2–4 years)
Intrapleural pressure can be measured during thoraco- domestic shorthairs, with no sex predilection, and the
centesis with several techniques, including a U‐shaped most common initial clinical signs include hyporexia or
water manometer, an “overdamped” water manometer,
or electronic pressure transducer systems such as those
used for invasive blood pressure monitoring. The role of
intrapleuaral pressure monitoring in veterinary medi-
cine is an expanding area of interest and research.

Thoracoscopy
Thoracoscopy is a minimally invasive technique which is
becoming more widespread in veterinary medicine and
can be used as both a diagnostic and therapeutic tech-
nique in veterinary patients with pleural effusion.
Advantages of thoracoscopy include obtaining pleural
biopsies, visualization of intrathoracic pathology, and
minimally invasive approach (Figure 34.1).
Properly collected thoracoscopic pleural biopsies are
adequate in quality and quantity to obtain a definitive
histopathologic diagnosis (Figure 34.2). Disadvantages
include general anesthesia, risk of pneumothorax, hem-
orrhage, infection, and potential need for thoracotomy if
unable to achieve definitive treatment (depending on Figure 34.1 Normal pleura visualized via thoracoscopy. Source:
underlying disease) with thorascoscopy alone. Photo courtesy of Brad Case, DVM, DACVS, University of Florida CVM.

(a) (b)

Figure 34.2 (a,b) Thoracoscopic biopsy in a dog with mesothelioma. Source: Photo courtesy of Brad Case, DVM, DACVS, University of
Floriday CVM.