Radiographic findings:
On thoracic radiographs, increased opacity was noted in the ventral portion of the thorax. The opacity, characteristic of fluid seemed to fill up the chest half way, moving the lungs in to the dorsal part of the thorax. The lung lobes were easily visualized due to the fluid surrounding them.
Tentative diagnosis: Pleural effusion.
Further diagnostic tests: Thoracocentasis, cytology, chemistry.
Pleural effusion is an accumulation of fluid in the space between the membrane encasing the lung and that lining the thoracic cavity. The normal pleural space contains only a small amount of fluid to prevent friction as the lung expands and deflates. There are several types of fluids that can accumulate in the pleural space including; transudate, modified transudate, nonseptic exudates, septic exudates, chylous exudates, and hemorrhagic.
Transudate is colorless/ pale yellow clear fluid with protein <1.5g/dl class="Apple-style-span" style="font-style: italic;">caused by hypoproteinemia and rarely early chronic heart failure.
Modified transudate is yellow/pink in color, clear to cloudy fluid with a protein count of 1.5-3.0g/dl and a nucleated cell count of 1,000-5,000/µl. Predominant cells found on cytology are macrophages, mesothelial cells, and possibly neoplastic cells. Modified transudate can develop with the diseases: chronic heart failure, neoplasia, and diaphragmatic hernia.
Nonseptic exudate is yellow/pink in color, clear to cloudy fluid with a protein count of 2.5-6.0 g/dl and a nucleated cell count of 1,000-20,000/µl. Predominant cells found on cytology are non-degenerate neutrophils, macrophages, and possibly neoplastic cells. Fibrin can also be found on cytology. The disease processes causing nonseptic exudates are neoplasia, diaphragmatic hernia, and lung lobe torsion (also FIP in cats).
Septic exudates is yellow/red-brown in color, cloudy to opaque fluid with a protein count of 3.0-7.0 g/dl and a nucleated cell count of 5,000-3000,000/µl. Predominant cells found on cytology are degenerated neutrophils and macrophages. Bacteria and fibrin are also found on cytology. Septic exudates is caused by septic pleuritis and called pyothorax.
Hemorrhagic exudates is a red opaque fluid with a protein count >3.0 g/dl the nucleated cell count is the same as peripheral blood and on cytology RBC’s, WBC’s and fibrin will be found. Hemothorax is caused by trauma, hemostatic disorders, and neoplasia.
Chylous exudate is a milky white opaque fluid with a protein count of 2.5-6.0 g/dl with a nucleated cell count of 500-20,000/µl. The major cells seen on cytology are small mature lymphocytes, with chronicity neutrophils and macrophages can be found. Chylothorax can be caused by an obstructed duct, ruptured duct, chronic right sided heart failure, neoplasia, and heartworm disease.
Chyle can be differentiated from pseudochyle by comparing the triglyceride and cholesterol levels of the exudates to the patient’s serum. Chyle will have a higher triglyceride level and lower cholesterol level than the patients serum while pseudochlye would be opposite with a lower triglyceride level and higher cholesterol level than the patients serum.
Treatment and management:
Thoracocentesis was performed which yielded 1700ml of a chyle like fluid that was whitish pink in color. Post-thoracocentesis radiographs were taken as shown below (click on the image to enlarge):
The treatments suggested for a chylothorax are; thoracentesis, identify and treat underlying cause, chest tubes (only for patients with chylothorax secondary to trauma with rapid accumulation or after surgery), and with unsuccessful medical management surgery is considered. The surgery suggested is a thoracic duct ligation and pericardectomy, if this is not successful pleuroperitoneal or pleurovenous shunts and can be considered.
A change in diet could help; a low fat diet may decrease the amount of fat in the effusion, which may allow the patient to resorb the fluid from the thoracic cavity easier. The prognosis is guarded on these patients therefore euthanasia is often performed on the patients that do not respond to medical or surgical treatment.
The patient was cage rested and monitored for respiratory distress with thoracentesis performed to keep the patient comfortable.
