Equine Internal Medicine Q&A 18

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A 12-year-old pony gelding is presented with a three week history of weight loss, inappetence, intermittent fever (up to 38.7°C) and ventral thoracic and abdominal oedema. Auscultation of the chest reveals bilateral absence of ventral lung sounds, and a pleural effusion is confirmed by ultrasonography. Thoracocentesis yields a large volume of blood-stained watery fluid. A tracheal wash did not reveal any any infectious cause.

Question	Answer		Article
What is the most likely diagnosis?	Thoracic neoplasia. The commonest type of thoracic neoplasia in the horse is mediastinal lymphosarcoma.		Link to Article
How can the diagnosis be confirmed?	Cytology of pleural fluid may reveal neoplastic cells. Similar fluid may be present in the peritoneal cavity. Neoplastic masses may be identifiable by thoracic radiography or ultrasonography. Mediastinal masses may sometimes extend through the thoracic inlet and be palpable externally at the base of the jugular groove; in this situation they may be amenable to biopsy. In the case of lymphosarcoma, peripheral lymph nodes may be enlarged due to neoplastic infiltration, and these may be biopsied.		Link to Article