History
A 10-year-old 9.1-kg (20-lb) neutered male domestic shorthair cat was evaluated because of an acute onset of lethargy, vomiting, anorexia, and paradoxical breathing a few hours prior to hospital admission. Physical examination revealed mild tachypnea (40 breaths/min), paradoxical breathing, and absence of lung sounds ventrally on the right side of the thorax. Anemia (Hct, 17%; reference range, 30% to 45%), thrombocytopenia (140,000 platelets/μL; reference range, 300,000 to 700,000 platelets/μL), and a stress leukogram (neutrophil count, 19,500 neutrophils/μL; reference range, 2,500 to 12,500 neutrophils/μL; lymphocyte count, 1,100 lymphocytes/μL; reference range, 1,700 to 7,000 lymphocytes/μL) were detected on CBC. Mild hypoproteinemia (4.2 g/dL; reference range, 5.8 to 8.0 g/dL) was detected on serum biochemical analysis. Prothrombin time and partial thromboplastin time were within the reference ranges. Radiographs of the thorax were obtained (Figure 1).
Left lateral (A) and ventrodorsal (B) radiographic views of the thorax of a 10-year-old 9.1-kg (20-lb) neutered male domestic shorthair cat evaluated because of an acute onset of lethargy, vomiting, anorexia, and paradoxical breathing a few hours prior to hospital admission.
Citation: Journal of the American Veterinary Medical Association 247, 5; 10.2460/javma.247.5.475
Left lateral (A) and ventrodorsal (B) radiographic views of the thorax of a 10-year-old 9.1-kg (20-lb) neutered male domestic shorthair cat evaluated because of an acute onset of lethargy, vomiting, anorexia, and paradoxical breathing a few hours prior to hospital admission.
Citation: Journal of the American Veterinary Medical Association 247, 5; 10.2460/javma.247.5.475
Left lateral (A) and ventrodorsal (B) radiographic views of the thorax of a 10-year-old 9.1-kg (20-lb) neutered male domestic shorthair cat evaluated because of an acute onset of lethargy, vomiting, anorexia, and paradoxical breathing a few hours prior to hospital admission.
Citation: Journal of the American Veterinary Medical Association 247, 5; 10.2460/javma.247.5.475
Determine whether additional imaging studies are required, or make your diagnosis from Figure 1—then turn the page →
Diagnostic Imaging Findings and Interpretation
On the ventrodorsal view, there is a homogeneous soft tissue opacity affecting the entire right hemithorax. This soft tissue opacity causes complete border effacement with the caudal and right margins of the heart and the diaphragm. On the right side of the thorax, the airways and lungs are not evident. The trachea is displaced to the left. A discrete pleural fissure line is present between the cranial and caudal segments of the left cranial lung lobe. The caudal borders of the left caudal lung lobe are retracted from the thoracic wall, with the pleural space of soft tissue opacity (Figure 2). On the lateral view, the soft tissue opacity is ventrally distributed. There continues to be retraction of the caudal lung lobe margins from the thoracic wall.
Same radiographic images as in Figure 1. A—A homogeneous soft tissue opacity affecting the ventral aspect of the thorax is present (black arrows). The caudal borders of 1 caudal lung lobe appear retracted (white open arrow). B—A homogeneous soft tissue opacity affecting the entire right hemithorax is evident (black arrows). The trachea appears displaced to the left (black open arrows). A discrete pleural fissure line is observed between the cranial and caudal parts of the left cranial lung lobe (arrowhead).
Citation: Journal of the American Veterinary Medical Association 247, 5; 10.2460/javma.247.5.475
Same radiographic images as in Figure 1. A—A homogeneous soft tissue opacity affecting the ventral aspect of the thorax is present (black arrows). The caudal borders of 1 caudal lung lobe appear retracted (white open arrow). B—A homogeneous soft tissue opacity affecting the entire right hemithorax is evident (black arrows). The trachea appears displaced to the left (black open arrows). A discrete pleural fissure line is observed between the cranial and caudal parts of the left cranial lung lobe (arrowhead).
Citation: Journal of the American Veterinary Medical Association 247, 5; 10.2460/javma.247.5.475
Same radiographic images as in Figure 1. A—A homogeneous soft tissue opacity affecting the ventral aspect of the thorax is present (black arrows). The caudal borders of 1 caudal lung lobe appear retracted (white open arrow). B—A homogeneous soft tissue opacity affecting the entire right hemithorax is evident (black arrows). The trachea appears displaced to the left (black open arrows). A discrete pleural fissure line is observed between the cranial and caudal parts of the left cranial lung lobe (arrowhead).
Citation: Journal of the American Veterinary Medical Association 247, 5; 10.2460/javma.247.5.475
Radiographic findings of border effacement can be associated with both pleural and pulmonary diseases; it occurs when no air is present between pleural or pulmonary lesions and the heart or the diaphragm. The absence of air bronchograms in this patient makes pleural disease, such as pleural effusion or pleural mass, a more likely cause, although a pulmonary lesion cannot be excluded.
Thoracic ultrasonography was performed, which revealed a mild to moderate amount of anechoic pleural effusion and a 3.5-cm rounded, heterogeneous, mixed echoic mass in the right side of the midthoracic area. The mass moved in conjunction with the thoracic wall during respiration, indicating a pleural rather than a pulmonary location. One milliliter of microbubble ultrasound contrast agent, composed of a phospholipid shell surrounding a perfluorocarbon (sulfur hexafluoride) gas,a followed by 1 mL of saline (0.9% NaCl) solution flush, was injected IV for contrast harmonic ultrasonographic imaging of the mass. The periphery of the mass alongside the thoracic wall was slightly to mildly enhanced. There was only minimal central enhancement, and most of the mass was not enhanced (Figure 3). These features suggested neoplasia with possible central necrosis. Abscess, granuloma, and hematoma were less likely because contrast enhancement was present within the mass. The contrast-enhanced regions within the mass were aspirated twice (22-gauge needle) under ultrasound guidance.
Transverse ultrasonographic images of the thorax of the cat in Figure 1. A—Image obtained before IV administration of contrast agent for harmonic ultrasonographic imaging. A rounded, heterogeneous, and mixed echoic mass is observed in the right side of the midthoracic area (white arrows). B—Contrast harmonic ultrasonographic image of the mass in panel A. The contour of the mass is indicated by a white dashed line. Its periphery is slightly to mildly enhanced, and its center is only minimally enhanced after injection of a contrast agent (white open arrows). Images were obtained transthoracically with a 4- to 11-MHz microconvex transducer.
Citation: Journal of the American Veterinary Medical Association 247, 5; 10.2460/javma.247.5.475
Transverse ultrasonographic images of the thorax of the cat in Figure 1. A—Image obtained before IV administration of contrast agent for harmonic ultrasonographic imaging. A rounded, heterogeneous, and mixed echoic mass is observed in the right side of the midthoracic area (white arrows). B—Contrast harmonic ultrasonographic image of the mass in panel A. The contour of the mass is indicated by a white dashed line. Its periphery is slightly to mildly enhanced, and its center is only minimally enhanced after injection of a contrast agent (white open arrows). Images were obtained transthoracically with a 4- to 11-MHz microconvex transducer.
Citation: Journal of the American Veterinary Medical Association 247, 5; 10.2460/javma.247.5.475
Transverse ultrasonographic images of the thorax of the cat in Figure 1. A—Image obtained before IV administration of contrast agent for harmonic ultrasonographic imaging. A rounded, heterogeneous, and mixed echoic mass is observed in the right side of the midthoracic area (white arrows). B—Contrast harmonic ultrasonographic image of the mass in panel A. The contour of the mass is indicated by a white dashed line. Its periphery is slightly to mildly enhanced, and its center is only minimally enhanced after injection of a contrast agent (white open arrows). Images were obtained transthoracically with a 4- to 11-MHz microconvex transducer.
Citation: Journal of the American Veterinary Medical Association 247, 5; 10.2460/javma.247.5.475
Treatment and Outcome
Findings on cytologic evaluation of fluid in the pleural space were consistent with hemothorax. Cytologic evaluation of fine-needle aspirates of the mass only revealed a low cellularity. Surgical removal of the mass was offered, but declined by the owner. Because the prognosis without excision of the mass was assessed to be grave, euthanasia was elected and necropsy was performed. Postmortem examination of the pleural cavity confirmed the presence of a 9 × 6 × 3.5-cm encapsulated, dark red, soft, friable and necrotic mass attached to the parietal pleura on the right side at the level of the eighth intercostal space. Histologic evaluation of the mass was consistent with poorly differentiated leiomyosarcoma.
Comments
In people, radiographic findings of a homogeneously radiopaque hemithorax with mediastinal shift typically suggests unilateral pleural effusion.1,2 In the cat of the present report, a pleural lesion was also suspected on the basis of the presence of paradoxical breathing. Paradoxical breathing has been shown to be associated with pleural diseases, although it is not completely specific for pleural lesions.3 Thoracic ultrasonography has been used in human medicine to explore the causes of a radiopaque hemithorax: 83% of cases involved massive pleural effusion; 9% tumors; 3% fibrothorax, consolidation, or atelectasis; and 2% pseudocyst of the pleura.1 The ability of thoracic ultrasonography to detect underlying pleural or parenchymal lesions is comparable to that of CT.2 In the cat of the present report, thoracic ultrasonography was used to evaluate the mass responsible for the hemothorax. On the basis of the movement pattern of the mass, ultrasonography also was useful in determination of pleural location of the mass.4 However, the size of the mass was underestimated, most likely because only the portion alongside the thoracic wall (suspect pedicle location) was readily imaged. Away from the mass pedicle, the mass could not be ultrasonographically imaged if air was present between the mass and the ultrasound probe. Differential diagnoses for a pleural mass include neoplasia, pseudocyst, abscess, granuloma, or hematoma. Unlike the mass of the cat in the present report, pleural pseudocyst has a typical anechoic appearance on ultrasonography.5 Total absence of vascularization is present in contrast-enhanced ultrasonographic examination of hematomas and abscesses.6 The mass was peripherally contrast enhancing, consistent with neoplasia. The contrast enhancement alongside the thoracic wall may correspond to the pedicle of the mass providing blood supply from the thoracic wall. The poor global contrast enhancement of the mass was suggestive of sarcoma, as described for spindle cell sarcoma and hemangiosarcoma, although carcinomas may also have poor contrast enhancement.7 The suspicion of mesenchymal tumor was confirmed histologically.
In the case described in the present report, contrast harmonic ultrasonography was helpful in achieving an accurate premortem diagnosis.
SonoVue, Bracco, Italy.
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