What Is Your Diagnosis?

Ilana C. Zuckerman School of Veterinary Medicine, University of California-Davis, Davis, CA 95616.

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Michelle I. Dulake VCA West Los Angeles Animal Hospital, 1900 S Sepulveda Blvd, Los Angeles, CA 90025.

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Reid K. Nakamura Southern California Veterinary Specialty Hospital, 1371 Reynolds Ave, Irvine, CA 92614.

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History

A 12-year-old castrated male Himalayan cat was referred for evaluation because of a 1-week history of tachypnea. The cat lived indoors only and was the only cat in the household. No known history of trauma existed. Hematologic evaluation by the referring veterinarian revealed that the cat had a regenerative anemia with an Hct of 15.9% (reference range, 29% to 45%) and a reticulocyte count of 199,000 reticulocytes/μL (reference range, 3,000 to 50,000 reticulocytes/μL). The cat had a platelet count of 454,000 platelets/μL, which was within the reference range of 170,000 to 600,000 platelets/μL. No abnormalities had been identified on serum biochemical analysis. Radiographs of the thorax were obtained (Figure 1).

Figure 1—
Figure 1—

Right lateral (A) and ventrodorsal (B) radiographic views of the thorax of 12-year-old castrated male Himalayan cat with a 1-week history of tachypnea.

Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.885

Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →

Radiographic Findings and Interpretation

Severe pleural effusion is evident; it obscures the cardiac silhouette completely on the lateral projection and partially on the ventrodorsal projection. Parts of the cardiac silhouette are visible and are normal in appearance. The pleural effusion appears more severe in the right hemithorax than on the left, as evident by the severe retraction of the lung margins and obscuring of the cranial mediastinum. The trachea does not appear dorsally displaced, and the cranial and middle lung lobes are not aerated. The thoracic skeleton is radiographically normal, and the diaphragm is partially obscured (Figure 2).

Figure 2—
Figure 2—

Same radiographic images as in Figure 1. Notice severe pleural effusion that is obscuring the cardiac silhouette. Pleural effusion appears more severe in the right hemithorax than on the left; lung margins are retracted (arrows) and the cranial mediastinum is obscured.

Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.885

Thoracic ultrasonography revealed a large mixed echogenic mass lateral to the base of the heart in the area of the right cranial lung lobe (Figure 3) with a suspicion of tracheobronchial lymph node enlargement. The mass did not appear to invade the adjacent cardiac structures, which had a normal ultrasonographic appearance. Severe anechoic pleural effusion was evident as well. The primary differential diagnosis for the pleural effusion was pulmonary neoplasia. Other less likely differential diagnoses included lung lobe torsion, pulmonary thromboembolism, or unknown thoracic trauma.

Figure 3—
Figure 3—

Right parasternal long-axis 4-chamber echocardiographic view of the same cat as in Figure 1. Severe anechoic pleural effusion and a large mixed echogenic mass (arrows) lateral to the base of the heart are evident. The mass was suspected to originate from the right cranial lung lobe. Images were obtained with a 12-MHz probe. Scale on the left indicates depth in centimeters. LA = Left atrium. LV = Left ventricle. RA = Right atrium. RV = Right ventricle.

Citation: Journal of the American Veterinary Medical Association 245, 8; 10.2460/javma.245.8.885

Treatment and Outcome

Thoracocentesis was performed to obtain pleural fluid samples. Results of laboratory analysis of the fluid revealed a hemorrhagic effusion with a PCV of 26% and total solids concentration of 4.2 g/dL, compared with a peripheral blood PCV of 14% and total solids concentration of 7.2 g/dL. Hemostatic testing revealed a prothrombin time (18 seconds; reference range, 15 to 22 seconds) and activated partial thromboplastin time (81 seconds; reference range, 65 to 119 seconds) within reference range, thereby consistent with a diagnosis of noncoagulopathic spontaneous hemothorax. Given the suspected neoplastic process, the owners declined further treatment and diagnostic testing and elected to have the cat euthanatized. A necropsy was declined.

Comments

Hemothorax is defined as an effusion in the pleural cavity with a PCV that is at least 25% of peripheral blood.1 Clinically, traumatic injuries and coagulopathies appear to be the most common causes of hemothorax in veterinary medicine.2 When no evidence of trauma or coagulopathy is found, the hemothorax is classified as a noncoagulopathic spontaneous hemothorax, which is usually reported in association with thoracic wall neoplasia in dogs.2 Diagnostic imaging modalities such as thoracic ultrasonography or CT are necessary to identify the underlying cause of the hemothorax in approximately 90% of affected dogs.2 In the cat of the present report, the hemothorax obscured the intrathoracic pathological lesion on radiographs, necessitating the use of thoracic ultrasonography to identify the underlying neoplastic process. Another diagnostic imaging option would include repeating thoracic radiography after removal of the pleural effusion. However, the authors do not recommend this when a hemothorax is identified because a potential for exsanguination and hypovolemic shock exists, particularly if active bleeding is occurring into the thoracic cavity.

To the authors' knowledge, this is the first reported case of noncoagulopathic spontaneous hemothorax in a cat. Pulmonary masses in people can result in hemothorax by direct invasion of pulmonary vessels, compression or ischemic necrosis of adjacent lung tissues by the tumor, tumor-induced angiogenesis, or rupture of a well-vascularized tumor.2,3 As a necropsy and further diagnostic imaging were declined for the cat of the present report, the origin of the mass and histologic diagnosis is unknown, although it was suspected to originate from the right cranial lung lobe. Lung lobectomy is recommended for all cats with a primary lung tumor, with differentiated and undifferentiated adenocarcinomas reportedly the most commonly identified lung tumors.4 Prognosis depends on histologic type and tracheobronchial lymph node enlargement; cats with undifferentiated tumors and tracheobronchial lymph node involvement have a poorer long-term prognosis.4

  • 1. Johnson RF, Green RA. Pleural diseases. In: Gauma GL, Wolinsky E, eds. Textbook of pulmonary diseases. 3rd ed. Boston: Little, Brown and Co, 1983;13161317.

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  • 2. Nakamura RK, Rozanski EA, Rush JE. Non-coagulopathic spontaneous hemothorax in dogs. J Vet Emerg Crit Care 2008; 18: 292297.

  • 3. Chou SH, Cheng YJ & Kao EL, et al. Spontaneous haemothorax: an unusual presentation of primary lung cancer. Thorax 1993; 48: 11851186.

  • 4. Hahn KA, McEntee M F. Prognosis factors for survival in cats after removal of a primary lung tumor: 21 cases (1979–1994). Vet Surg 1998; 27: 307311.

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