Page 87 - Problem-Based Feline Medicine

6 – THE CAT WITH HYDROTHORAX 79

● Cholesterol and triglyceride levels of the serum and Chylous effusions may occur as part of congestive
the effusion may be measured and compared to heart failure. If cardiac abnormalities are detected, than
definitively diagnose true chylous effusion, but a complete cardiac diagnostic evaluation should be per-
these findings rarely change the prognosis or the formed (see Cardiomyopathy section in this chapter).
management. True chylothorax has higher triglyc-
eride and lower cholesterol levels than serum.
Treatment
● So-called pseudochylous effusions have the same
gross appearance but with higher cholesterol and Emergency thoracocentesis should be performed
lower triglyceride concentrations than serum. immediately in cats with severe respiratory distress.
Pseudochylous effusion has been discussed in the ● A 23 G butterfly infusion set on a 60 ml syringe is
veterinary literature for years, but there is little evi- introduced at the 5th–7th intercostal space (ICS) on
dence that this exists as a clinical entity in cats. the right, just above the costochondral junction.
Remove as much fluid as possible, or until breath-
Thoracic radiography should be performed after thora-
ing improves. This can usually be performed with-
cocentesis.
out sedation or local anesthetic block with the cat
● If cardiac or pulmonary vessel abnormalities are evi-
standing or in sternal recumbancy. Drainage at mul-
dent radiographically, this indicates the pleural effu-
tiple locations below the costochondral junction
sion may be secondary to congestive heart failure.
between the 4th and 6th intercostal space is some-
● Chronic chylothorax may result in fibrosing pleuri-
times more effective.
tis evidenced by rounded or collapsed lung lobes on
● Placement of a chest drain is recommended for all
radiography.
patients except those that are very debilitated.
● Contrast lymphangiography may be performed if no
● Fluid should be aspirated 1–2 times/day and the
underlying cardiac disease or neoplasia is detected.
tube removed once less than 1–2 ml/kg daily is
– A mesenteric lymphatic vessel is cannulated via
obtained.
celiotomy, and iodinated contrast media are
● Intermittent thoracocentesis may be required until
injected. Thoracic duct lymphangiectasia is the
definitive therapy has been effective.
most common finding with primary chylothorax
in cats. Radiographically, dilated, tortuous lym- Definitive therapy if congestive heart failure is diag-
phatics are found in the cranial mediastinum of nosed is based upon ultrasonographic characterization
affected cats. This procedure adds significant of the type and severity of the cardiomyopathy present
time under anesthesia, and may be technically (see page 128 The Cat With Abnormal Heart Sounds
difficult to perform without intraoperative radi- and/or an Enlarged Heart).
ography or fluoroscopy capabilities. There is
Removal of the jugular catheter and drainage of the
current debate whether this finding of lym-
chlye usually results in resolution of the chylothorax in
phangiectasia is the cause or an effect of tho-
those cases associated with an indwelling jugular
racic lymphatic hypertension.
catheter.
Echocardiography is the definitive modality for ruling
For idiopathic primary chylothorax, both medical and
out cardiomyopathy, pericardial effusion, or other
surgical management have been advocated.
causes of congestive heart failure.
Medical management
If the cat is only mildly dyspneic, ultrasound should be
● This is based around decreasing the lymphatic
performed before the pleural fluid is drained as the
flow through the thoracic duct. Restricting
fluid aids in the detection of a mediastinal mass.
dietary fats is the cornerstone of medical manage-
Severely dyspneic cats should have some fluid drained
ment. Parenteral intravenous feeding is used in
first, as the stress of ultrasound can be fatal.
humans, but is not a practical long-term solution in
cats. Low-fat-reducing diets, commercial or home-
Differential diagnosis
made, help reduce chyle flow, but must be formu-
Other forms of pleural effusion may have similar clin- lated to meet the nutritional needs of the patient.
ical signs but the appearance of the fluid is different. MCT oil (medium chain triglycerides) is a way to