Page 88 - Problem-Based Feline Medicine

80 PART 2 CAT WITH LOWER RESPIRATORY TRACT OR CARDIAC SIGNS

supply calories from fats that are absorbed directly and removed once the fluid production through
into the portal circulation and bypass the thoracic the tube falls below 1 ml/kg daily.
duct lymphatics. Whether this truly decreases tho- – There is current debate whether this procedure is
racic duct flow has come under question in the useful in idiopathic lymphangiectasia, or whether
dog, and information is still lacking in cats. MCT the lymphatic hypertension continues despite lig-
oil is generally reserved for extremely cachectic ation.
cats. It tastes terrible, and may worsen inap- – Pleuroperitoneal drainage, either with passive
petance. drains with diaphragmatic mesh implants, or
● Nutriceutical “fat binders” such as Chitin/ active sump drains between the pleural and peri-
Chitosan may be beneficial to decrease the fat- toneal cavities have been described, but there is
induced chlye flow. a lack of data on the outcomes of these proce-
● Rutin, another oral nutriceutical therapy, has dures in cats. Blockage of the drain is a problem.
shown mixed results in idiopathic chylothorax. – Some surgeons report success with pericardec-
● Rutin is a bioflavanoid and a derivative of vitamin tomy, as a means to decrease the underlying
C. It stimulates macrophage uptake of protein and lymphatic hypertension. Recent studies combin-
processing of inflammatory cells, thus improving ing pericardectomy with thoracic duct ligation
the absorption of the remaining fluid. Dose is 50 have resulted in 80% success in a group of ten
mg/kg tin, which can be mixed up with food. cats with chylothorax.
● Octreotide (Sandostatin, Novartis) a synthetic
somatostatin is being trialled in cats as a SQ injec-
tion tid, but its efficacy is currently unknown. Prognosis
● Medical management together with intermittent
The success of medical management has been docu-
thoracocentesis may be used during the treatment
mented at 20% or less. The author’s clinical experience
for the underlying disease (cardiac therapy, cancer
has been somewhat below that figure. Traumatic injuries
treatments, etc.).
to the thoracic duct may have a slightly better response
Surgical management. rate to medical management. Successful treatment of the
● Surgery should only be considered for patients who underlying disease process usually results in resolution
do not respond to medical management within 6–10 of the chylothorax for taurine-responsive dilated car-
days. Success following surgery is disappointingly diomyopathy and neoplasia. The poor success rate in
low. Surgery is best performed by a specialist with idiopathic chylothorax likely relates to persistence of the
experience in thoracic duct ligation. underlying pathophysiology.
– Ligation of the thoracic duct is the definitive
Prognosis for success of surgical ligation varies from
therapy for idiopathic chylothorax. Surgical
25–53%, and likely varies directly with the skill and
approaches and techniques are described in
experience of the surgeon. Continued effusion occurred
standard surgical texts. Some surgeons prefer
in 30% of cats after thoracic duct ligation in one study.
to give cream orally prior to surgery so that
Proponents of the primary lymphatic hypertension the-
the thoracic duct is filled with white chyle at
ory feel that surgical ligation does not change the under-
the time of surgery, for easier identification.
lying pathophysiology. New data regarding the success
Others prefer to perform a mesenteric lym-
rate of pericardectomy are very promising, with one
phatic dye study similar to what is described
report of an 80% remission rate in ten cats.
for lymphangiography, but using new methyl-
ene blue dye rather than radiographic contrast Chyle is a very irritating fluid to the pleura. Chylofibrosis
material. This dye is visible at the time of sur- and restrictive pleuritis may follow as a complication
gery to ease identification. even after successful surgical ligation. If the fibrosis is
– A postoperative contrast lymphangiogram may be severe, the lungs may fail to expand even after thoraco-
performed through the same mesenteric lymphatic centesis. Pleural stripping has been described, but is not
catheter to assess the success of the ligation. commonly performed in cats, so the success rate is
A thoracostomy tube is placed postoperatively unknown.