Page 84 - Problem-Based Feline Medicine

76 PART 2 CAT WITH LOWER RESPIRATORY TRACT OR CARDIAC SIGNS

● Penetrating wound as a result of a fight, a foreign ● Thoracocentesis should be performed in all
body or thoracic surgery. acutely dyspneic animals, especially trauma
patients, prior to radiography. These patients are
Fibrinous exudation and cellular infiltration occurring
extremely fragile, and even the minimal restraint
in response to bacterial infection results in obstruction
involved in radiography may be excessive, and they
of the parietal pleural stomata, which further reduces
may die during the procedure!
drainage of the exudation.
● A negative tap for air or fluid suggests solid pleu-
Clinical signs of systemic illness result from the ral space disease (mass or herniated viscus), pri-
chronic sepsis. Eventually respiratory signs become mary pulmonary (i.e., contusion in the trauma
evident as fluid reaches critical volume (estimated in patient) or cardiac disease. If the tap is positive,
cats to be 50 ml/kg). remember that small animals may accommodate
up to 50 ml/kg free fluid in the chest prior to
becoming dyspneic.
Clinical signs ● Be certain to remove as much fluid as possible, do
not stop after you have a diagnostic sample.
Pyothorax is more common in intact males, and there
is a history of fight wounds several weeks prior to Cytology
presentation.
Cytology and Gram stain are important in identifica-
Heart and lung sounds are dull ventrally. Breathing tion of the pathogen, as culture is often negative.
sounds are harsh dorsally in standing or sternal
Pyothorax is characterized by a thick, fetid, septic sup-
recumbency. Chest wall percussion may be dull ven-
purative exudate. Cytology reveals a high protein fluid
trally.
9
(TP > 30 g/L), highly cellular (TNCC > 7.0 × 10 /L)
Dyspnea is characterized by marked chest wall excur- with mostly degenerative neutrophils, often with intra-
sions with minimal airflow. Orthopnea, or positional cellular bacteria. Macrophages and reactive mesothelial
dyspnea is common. Dyspnea is worsened in lateral cells are common.
recumbency and cats often are reluctant to lie in lat- ● Bacterial infection is characterized by suppurative
eral recumbency. inflammation involving degenerative neutrophils
with intracellular bacteria.
Signs of chronic disease are often evident. The cat
● Fungal and mycobacterial diseases have pyogranu-
may appear sick, septic, thin and unkempt.
lomatous inflammation, with characteristic organ-
Fever or, in the latter stages, hypothermia may be isms seen on routine or special stains.
present.
Bacteriology
There may be caudal displacement of the liver due to
Bacterial culture for aerobic and anaerobic bacteria is
pleural fluid pressure on the diaphragm.
important, but negative cultures are not surprising, as
many bacteria have been killed or had their growth
inhibited by the lysozymes present in the exudate.
Diagnosis
Gram staining is an excellent way to document the ini-
Typically there is a vague history of being unwell for tial categories of bacteria present, as well as following
weeks, with inappetance, weight loss and recent onset the response to therapy.
of dyspnea.
Thoracic radiographs show significant pleural effusion Hematology
with pleural fissure lines and loss of the cardiac silhou- Blood smear may reveal neutrophilia with or without
ette. Effusions are usually bilateral, although not a left shift and toxic neutrophils (Doehle bodies,
always. etc.).
Thoracocentesis may be both diagnostic and therapeu- A low-grade non-responsive anemia and monocytosis
tic in pleural space disease. may support chronicity.