Page 373 - Clinical Small Animal Internal Medicine

34 Pleural Effusion 341

considered once susceptibility data are available. Medical thoracic lavage, and nosocomial infection if aseptic tech-
VetBooks.ir management involves thoracocentesis alone (repeated as nique is not followed. Pleural lavage is performed by
slowly infusing 10–20 mL/kg of warmed, 0.9% saline into
needed) or placement of unilateral or bilateral indwelling
thoracostomy tubes with intermittent or continuous
drawing the fluid. If bilateral thoracostomy tubes are in
suction and thoracic lavage along with appropriate anti- the pleural space, waiting 10–15 minutes, and then with-
microbial therapy and supportive care. In general, large‐ place, some advocate for using one side as an infusion
bore trocar or surgically placed thoracostomy tubes are port and the opposite side as a withdrawal port.
preferred in larger patients; however, smaller thoracos- Thoracostomy tubes are generally removed when fluid
tomy tubes placed using a modified Seldinger technique production decreases to 3–5 mL/kg/day, in addition to
have been reported for management of pyothorax in clinical improvement of the patient and cytologic confir-
dogs. Surgical management involves exploratory thora- mation of absence of infectious organisms. Time to reso-
cotomy, usually by median sternotomy, to lavage and lution of disease is generally 5–8 days and patients should
debride the pleural space, and break down any adhesions be rechecked frequently as recurrence is possible.
causing pocketing of fluid, then insertion of thoracos-
tomy tubes for postoperative care, in addition to appro-
priate antimicrobial therapy and supportive care. Chylothorax
Appropriate treatment of pyothorax is controversial
and there is no consensus on ideal therapy for all cases. Chylothorax is a syndrome characterized by the accu-
Failure of medical therapy or presence of a focal lesion mulation of chyle, the milky fluid consisting of lymph
(abscess, tumor, or granuloma), foreign body, or evidence and emulsified fat formed in the small intestines during
of esophageal rupture found on imaging are indications digestion, in the pleural space and is often idiopathic in
for surgical management in dogs or cats. In dogs, some nature. Additional reported causes include traumatic or
advocate for early surgical treatment regardless of surgical thoracic duct rupture, cranial vena cava throm-
whether an underlying cause is identified, with the prem- bosis, lymphatic obstruction by cancer or fungal granu-
ise being that any other infectious disease such as perito- loma, cardiomyopathy, congenital defect, diaphragmatic
nitis, septic arthritis, or abscess is best treated by hernia, peritoneopericardial diaphragmatic hernia, lung
aggressive debridement and drainage. In a retrospective lobe torsion, pericardial effusion, tetralogy of Fallot, tri-
paper on medical versus surgical treatment canine cuspid dysplasia, cor triatriatum dexter, constrictive per-
pyothorax, medical management was 5.4 times more icarditis, and heartworm disease. Although trauma has
likely to fail compared to surgical treatment and more been a reported cause of chylothorax in the literature, it
dogs were free of disease at one year if treated surgically. could not be experimentally reproduced in dogs by lac-
In contrast, other studies have not shown a survival ben- eration or transection of the thoracic duct as the effusion
efit of surgery versus medical management and reported resolved within 10 days. Reported neoplasms associated
success of medical management has ranged from 29% to with lymphatic obstruction causing chylothorax include
100%. If Actinomyces spp. are suspected on cytology or thymoma, lymphosarcoma, lymphangiosarcoma, and
cultured from dogs with pyothorax, surgical manage- aortic body tumors. The rate of chyle production and
ment is warranted because medical treatment has a high drainage in normal dogs is approximately 2–4 mL/kg/h.
rate of failure and a grass awn foreign body is a likely Most of the body except the right forelimb and right
underlying cause. In cats, medical management with side of the head and neck drain into the thoracic duct in
indwelling thoracostomy tubes is reported to have a sur- dogs and cats. Intestinal lymphatics drain chyle into the
vival rate of 73–95%, whereas surgical management has mesenteric lymph nodes, which then form larger ducts
been reported to have a 100% survival rate. Successful that continue on to form the cisterna chyli, which is a
management of chronic pyothorax in cats with unilateral lymphatic reservoir located ventral to the first four lum-
pneumonectomy has been reported. bar vertebrae. The cisterna chyli continues cranially to
With medical management alone or during the post- become the thoracic duct and eventually empty into the
operative period, thoracic lavage is often recommended brachiocephalic trunk. In dogs, the cisterna chyli and
to facilitate drainage of exudative fluid; however, there caudal thoracic duct are located on the right side of the
are no large‐scale canine or feline studies to evaluate out- mediastinum; however, the duct crosses from right to
come with this method. Theoretical advantages of lavage left in the mid‐mediastinum to empty into the brachio-
include minimizing bacteria and inflammatory media- cephalic trunk. In cats, the thoracic duct is typically only
tors in the pleural space and dilution of exudative fluid, located to the left side of the mediastinum. Thoracic
which could clog the thoracostomy tube. Potential duct anatomy can vary within the same species.
disadvantages include electrolyte disturbances such as Obstruction of the thoracic duct or cranial vena cava
hypokalemia, which has been reported in a cat undergoing causes lymphatic flow stasis and dilation. It is thought