Page 82 - Problem-Based Feline Medicine

74 PART 2 CAT WITH LOWER RESPIRATORY TRACT OR CARDIAC SIGNS

that produce exudates from leaking blood ves- decreased oncotic pressure as a result of hypoal-
sels such as neoplasia, and vasculitis associated buminemia (protein-losing enteropathy, protein-
with feline infectious peritonitis, uremia, pancre- losing nephropathy or hepatic failure).
atitis or neoplasia. ● Chylothorax is usually idiopathic and associated
● Pyothorax is pus in the chest cavity from bacterial with lymphangiectasia, or may occur in association
infection. Protein is high (30–70 g/L) and nucleated with congestive heart failure, mediastinal neoplasia
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cell counts are high (5–300 × 10 /L). or thoracic duct rupture.
● Chylothorax is a lipid-rich tissue fluid from ● Pyothorax is most often associated with mixed
obstruction or trauma to the thoracic duct. Protein bacterial infections presumed from a penetrating
content ranges from 25–60 g/L and cell counts from wound or foreign body.
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1.0–20 × 10 /L. ● Thoracic exudates are most commonly associated
with feline infectious peritonitis, but may also occur
The fluid from these various forms of pleural effusion
with neoplasia, pancreatitis and uremia.
encroaches on the space generally occupied by the
● The most common forms of hydrothorax in the
lungs, and creates hydraulic pressure that opposes the
cat are pyothorax, neoplastic effusions, transuda-
expansion of the lungs. Fluid volumes greater than 50
tion from cardiac disease and chylothorax.
ml/kg result in dyspnea.
DIAGNOSIS
WHERE?
For cats with mild to moderate clinical signs, thoracic
Hydrothorax is the result of conditions that affect the
radiography may be diagnostic. Pleural fissure lines,
pleural space, especially conditions affecting the blood
separation of the lung borders from the thoracic wall,
vessels or lymphatics of the pleura.
loss of cardiac detail, blunting of the costophrenic
Blood vessel problems that contribute to hydrothorax angles (lateral and VD views), widening of the medi-
include: astinum (DV view) can all indicate the presence of fluid
● Increased hydrostatic pressure from congestive in the pleural space.
heart disease or vascular obstruction.
With severely affected cats in respiratory distress,
● Decreased oncotic pressure from hypoalbuminemia
radiography should be delayed until after thoracocen-
secondary to liver disease, kidney or gastrointesti-
tesis (cats with pleural effusions die in radiology!).
nal protein loss.
● Increased vascular permeability from inflammation An algorithm for the approach to the dyspneic cat fol-
(vasculitis). lows;
● Vascular rupture and hemorrhage (trauma, neoplasia). ● A – Airway – establish a patent airway.
● B – Breathing – be certain the patient is ventilating.
Lymphatic diseases that contribute to hydrothorax
● C – Centesis – if the dyspnea has not resolved with
include:
steps A and B, then evaluating for the presence of
● Obstruction from congestive heart disease, lym-
pleural space disease via thoracocentesis is not only
phangiectasia or neoplasia.
diagnostic, but therapeutic for both hydrothorax
● Rupture from trauma.
and pneumothorax. A negative tap would suggest
the presence of a mass lesion or primary parenchy-
WHAT? mal disease such as status asthmaticus.
The following conditions are most commonly associ- Thoracocentesis
ated with the different forms of hydrothorax in cats: ● In the acute, emergency setting, a butterfly set may
● Hemothorax usually results from trauma or coagu- be rapidly introduced to alleviate life-threatening
lopathy. accumulations.
● Transudation results from either increased hydro- ● In chronic or more stable cases, a polypropylene or
static pressure (mediastinal mass, lymphatic infil- Silastic IV catheter on an IV extension set with a
tration or obstruction, and cardiac disease) or from three-way stopcock attached to a 20–60 ml syringe