Page 172 - BSAVA Manual of Canine and Feline Head, Neck and Thoracic Surgery, 2nd Edition

Chapter 12 · Pleural drainage techniques

cats, bradycardia), injected or pale mucous membranes Thoracocentesis
and bounding or weak pulses may be present. Recent Thoracocentesis (see above and Operative Technique 12.1)
VetBooks.ir body condition may be noted. Additional findings may is indicated as soon as a strong suspicion of pleural effu-
weight loss may be reported by the owner and a poor
sion is present. If the fluid is caused by a septic process, it
include depression and dehydration. Hypersalivation has
is often thick, opaque and foul-smelling and may be floc-
been reported in cats and was found to be associated with
a poorer outcome (Waddell et al., 2002). culant. Samples should be evaluated using biochemistry,
cytology, cell counts and culture (see the BSAVA Manual of
Canine and Feline Clinical Pathology).
Diagnostic imaging Cytology should look for the presence of neutrophils,
which are often degenerate and show signs of toxic
Radiography: Thoracic radiography is very useful for con-
firming the presence of pleural effusion (see above), but change. Bacteria, both intracellular and extracellular, are
care must be taken with patients in respiratory distress. If usually present (Figure 12.7). However, the absence of
respiratory compromise is severe, the patient will not be bacteria does not exclude pyothorax from the differential
able to tolerate restraint in lateral or dorsal recumbency for list, especially if the patient has already been treated with
thoracic radiography, and thoracocentesis should be per- antibiotics. Whenever an inflammatory exudate is present,
formed as both a diagnostic test and immediate stabilizing the fluid should be submitted for aerobic and anaerobic
therapy. Thoracic ultrasonography can be used instead to culture and sensitivity testing. Sulphur granules, which are
confirm the presence of fluid and help guide thoraco - actually macroaggregates of bacteria, may also be seen in
cen tesis. Thoracic radiography is often more helpful in the effusion with Actinomyces and Nocardia infections. If
searching for underlying causes once the pleural effusion the pyothorax has been chronic, increasing numbers of
has been removed and the pulmonary parenchyma can be macrophages and plasma cells may be seen in the fluid.
better visualized. It may also be useful in determining A complete blood count often shows a marked leuco-
whether disease is bilateral or unilateral, although careful cytosis, with or without an increased number of band
auscultation and percussion of the chest should determine neutrophils and toxic change. In severe cases, a leuco-
this. The majority of cats and dogs show bilateral effu- penia and degenerative left shift may be found. Anaemia
sions; occasionally, a patient has unilateral disease, which may be present if the pyothorax is chronic.
may be secondary to a more localized process or the Biochemical results may be normal or may show
ability to wall off a particular area of the pleural space changes consistent with sepsis, including hypoalbumin-
(Figure 12.6). Cats and dogs have both been reported to aemia, hypoglycaemia and increased alanine aminotrans-
have an anatomically complete mediastinum but, because ferase and total bilirubin: the last two are consistent with
of the frequency of bilateral thoracic effusions, it seems cholestasis. Changes consistent with dehydration and
unlikely that the mediastinum is intact in most cases. haemoconcentration are seen in some patients.
There may be individual anatomical variability in the Retrovirus testing is indicated for cats diagnosed with
completeness of the mediastinum in both species. pyothorax; although not thought to be an underlying
cause, positive retroviral status may certainly complicate
treatment and increase the risk of recurrence.
Ultrasonography: Thoracic ultrasonography can identify
abscesses or masses in the pulmonary parenchyma or
mediastinum, and can be used to help locate fluid for
thoracocentesis, particularly if the fluid is pocketed.
Unilateral pyothorax
12.6 in a cat, shown on a
ventrodorsal radiograph.

leural effusion from a cat ith pyothora . ote the
12.7 degenerative neutrophils, and intra- and extracellular bacteria.

Emergency treatment
Stabilization of the patient with pyothorax presenting in
respiratory distress should include oxygen supplementa-
tion, minimal handling and stress, thoracocentesis and
intra venous catheter placement. Fluid therapy, including
shock boluses, may be indicated depending on the
patient’s cardiovascular status at the time of presentation.

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