A 3-year-old male cross-breed dog was presented with a one-day history of prostration. The dog lived in-and outdoors, was routinely vaccinated, and under heartworm prophylaxis. Physical examination revealed lethargy, depression, hypothermia (37.5°C), dyspnea, and jaundiced mucous membranes. A CBC showed mild thrombocytopenia (154,000 platelets/lL, reference interval [RI] 190,000-470,000/lL). A blood chemistry profile showed marked increase in liver enzyme activity (ALP 7640 IU, RI 0-180 IU; GGT 22 IU, RI 0-10 IU; ALT 260 IU, RI 0-110; AST 98 IU, RI 0-90 IU), moderate hyperbilirubinemia (4.65 mg/dL, RI 0-0.6 mg/dL), and moderate hyperglycemia (301 mg/dL, RI 80-130 mg/dL). Thoracic radiographs revealed moderate bilateral pleural effusion. Abdominal radiography showed the presence of an air gun pellet in the subcutis of the hypochondrium. Thoracocentesis was performed and yielded a brownish fluid characterized by a total nucleated cell count (TNCC) of 42,000/lL and a RBC count of 51,000/lL ( Figure 1). After centrifugation of the fluid at 100g, the supernatant color was the same as in the native effusion sample, and the total protein concentration was 3.1 g/dL. Smears from the sediment were made and stained with May-Gr€ unwald-Giemsa (MGG) and DiffQuick (Figures 2 and 3). Figure 3. Thoracic fluid, centrifuged preparation. Amorphous mucinous material with embedded inflammatory cells. Diff-Quick. 910 objective.Figure 1. Appearance of pleural effusion just after collection.Figure 2. Microscopic pattern of pleural fluid on sediment smear after concentration. May-Gr€ unwald-Giemsa. 9100 objective.