Texas Equine Veterinary Association

www.texasequineva.com • Page 17 MICHELLE BESSIRE, DVM Brock Veterinary Clinic History An eleven-year-old Quarter Horse gelding used for roping presented to Brock Vet Clinic with a history of weight loss over two to three months duration and poor performance of two weeks duration. Diagnostics and Treatment e horse had a temperature of 102.9F, a respiratory rate of 18 bpm, and heart rate of 44 bpm. His BCS was 3.5/9. In-house blood work showed mild anemia (Hct 27%), leukocytosis (WBCs 13.2 x 109/L), hyperfibrinogenemia (1030 mg/dL), and hyperglobulinemia (5.1 g/dL). oracic ultrasound revealed diffuse, bilateral comet tails with increased severity cranioventrally, and mild pleural effusion. Abdominal ultrasound was unremarkable and there was no evidence of lymphadenopathy. e depth of the pleural fluid was approximately 2cm. e patient was hospitalized and started on flunixin meglumine (1.1 mg/kg IV SID), penicillin G procaine (20,000 IU/kg/ IM BID), and gentamicin (6.6 mg/kg IV SID). He was also started on a probiotic. On day four of treatment, the patient was afebrile but ultrasound showed no improvement in the pleural effusion. His antibiotics were switched to TMS (30mg/kg PO BID) and metronidazole (15mg/kg PO TID). e horse maintained a good appetite and remained afebrile. An ultrasound exam was repeated on day 14 of treatment and revealed an increased amount of pleural effusion measuring 5cm in depth bilaterally. Antibiotics were discontinued for 72 hours and a transtracheal wash was performed to obtain bacterial culture and sensitivity results. e lab isolated E. coli and Enterobacter from the transtracheal wash but reported the isolates as contaminants. e horse was started on enrofloxacin (7.5 mg/kg PO SID) and sensitivity was requested on the contaminants. Sensitivity showed the E. coli to have an extremely resistant pattern. C A S E O F P L E U R A L E F F U S I O N No improvement was seen by day 28 of treatment so a thoracocentesis was performed and submitted for cytology and culture. e pleural fluid was a mixed cell exudate with an orange/hazy color and a protein of 5.0 g/dL. ere were 21,000 cells/L. It contained "a mixed population of leukocytes; predominately nondegenerate neutrophils and small lymphocytes. e lymphocytes had a high N:C ratio with clumped chromatin and moderately basophilic cytoplasm. Pyknotic cells were occasionally found. Occasional plasma cells and macrophages were noted. e cause of the exudate is uncertain. Overtly neoplastic cells and discrete infectious agents were not observed. e lymphocyte count, approximately 40%, seemed increased over what is typically seen. Whether this indicated an underlying lymphocytic inflammatory or neoplastic process (exfoliating lymphoma) was uncertain. e lymphocytes were not blastic appearing, but relatively monomorphic. Considered evaluation for possible underlying mass. No bacteria were isolated on culture. At this time the owner was given a poor prognosis but agreed to rule out a fungal infection so serum was submitted for Coccidioides immitis titers. e horse's BCS had dropped to 2.5/9 despite still having a good appetite. e titers for Coccidioides were negative. By day 40, bilateral pleural effusion was still present and the horse's condition continued to deteriorate (BCS 2/9) so the owner elected euthanasia. Necropsy revealed a large (20cm x 20cm x 30cm) mediastinal mass. e majority of the lung field appeared grossly normal. e mass was submitted for histopathology. It was described as, "the normal pulmonary architecture was completely effaced and replaced by a solid sheet of cells with a delicate fibrovascular stroma. ere was a "starry sky" appearance because of single cell necrosis. e cells had large round but variable sized basophilic nuclei with dense

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