History

A 7-year-old mixed-breed sexually intact female cat was evaluated for nonhealing bleeding wounds in both ears. The cat had a history of occasional coughing episodes and was not vaccinated. Physical examination revealed a hematoma in the left pinna and mild auricular injuries of probable traumatic origin in the right. Left-sided Horner syndrome was also found. A skin biopsy specimen was taken from the left ear, and a diagnosis of squamous cell carcinoma was made on the basis of histologic evaluation. Serum biochemical analysis, CBC, and urinalysis revealed mild anemia, mild hyperglycemia, hyperproteinemia, bilirubinuria, urine specific gravity of 1.030, hematuria, and proteinuria. Serologic test results were negative for feline infectious peritonitis, FIV, and FeLV. Cardiac auscultation was slightly attenuated in the left hemithorax without clinically relevant ECG findings. Radiographs of the thorax were made to rule out metastatic disease (Figure 1).

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Right lateral (A) and ventrodorsal (B) radiographic views of the thorax of a 7-year-old cat with an auricular squamous cell carcinoma. Thoracic radiographs were taken to rule out metastatic disease.

Citation: Journal of the American Veterinary Medical Association 238, 5; 10.2460/javma.238.5.569

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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 lateral radiographic view, well-defined soft tissue opacities with scalloped margins extend from the fourth intercostal space to the level of the eighth costochondral junction. These radiopaque structures are superimposed with the image of the caudoventral two-thirds of the heart and the cranioventral aspect of the diaphragm (Figure 2) and may represent pleural fluid, thickening of the pleural membranes, or a mass in the pleural cavity. On the ventrodorsal radiographic view, the left hemithorax is more radiopaque than is the right from the level of the fourth intercostal space to the diaphragm and from the cardiac silhouette to the central portion of the caudal lung field. The cardiac border is clearly visualized. In the left hemithorax, a sharply defined radio-lucent area is evident from the fifth intercostal space to the diaphragm immediately medial to the ribs. The soft tissue opacity that is evident along the thoracic wall on the left may be indicative of pleural effusion.

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Same radiographic images as in Figure 1. Notice the radiopaque structures (arrows) within the left hemithorax. In the ventrodorsal view, notice the retraction of lung from the fifth intercostal space to the area of the diaphragm, as evidenced by the sharply defined radiolucent area (asterisk). L = Left.

Citation: Journal of the American Veterinary Medical Association 238, 5; 10.2460/javma.238.5.569

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Ultrasonography of the ventral aspect of the thorax at the fifth to eighth left intercostal spaces revealed a heterogeneous, poorly echogenic linear structure separating the lung from the thoracic wall. Computed tomography of the thorax (Figure 3) revealed an ovoid tissue structure with a density measurement of −90 Hounsfield units. While the cat was in ventral recumbency, the tissue structure occupied the ventral caudal aspect of the left hemithorax, displacing the caudal lung lobe dorsally and the heart to the right. The caudal-most aspect of that structure was contiguous with the liver at its margin. The estimated density of the structure was consistent with fat-attenuating tissue.

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Transverse computed tomographic image (slice thickness, 5 mm) of the thorax of the same cat as in Figure 1. The image was obtained at the level of the sixth intercostal space. A large irregular fat-attenuating structure (white arrows) occupies the ventral aspect of the left hemithorax, displacing the heart (black arrows) toward the right. The image is displayed in a soft tissue window. L = Left.

Citation: Journal of the American Veterinary Medical Association 238, 5; 10.2460/javma.238.5.569

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Comments

During laparotomy, a long piece of falciform fat was found through a small (approx 15-mm-long) ovoid defect at the left ventral aspect of the diaphragm. The diaphragmatic discontinuity had rounded edges with smooth peritoneal and pleural layers. No signs of traumatic tears, muscular disruption, or hemorrhage were seen, indicating that the diaphragmatic hernia was congenital. The herniated falciform fat was relocated in the abdomen, and a suture was placed in the diaphragm. The cat recovered uneventfully.

Radiographic signs of diaphragmatic discontinuity include the absence of a complete diaphragmatic outline and cranial displacement of abdominal viscera contacting the diaphragm. A portion of consolidated or collapsed lung parenchyma may efface the diaphragmatic border. Similarly, large amounts of pleural effusion can also obscure the diaphragmatic silhouette. Therefore, lack of visualization of the position of the diaphragm is not a reliable radiographic sign of diaphragmatic rupture.¹ Ultrasonography failed to find any diaphragmatic abnormalities in the cat of this report.

To our knowledge, there are no reports on the usefulness of computed tomography in the diagnosis of diaphragmatic defects in dogs and cats. The diagnosis of a diaphragmatic hernia can be challenging in patients with no clear ultrasonographic or radiographic signs to support the diagnosis. Also, the presence of soft tissue opacities within the caudal lung fields can lead to misdiagnosis of severe pulmonary disease such as neoplasia.² For the cat of this report, computed tomography of the thoracic cavity offered a definitive diagnosis and allowed for determination of the nature of the herniated tissue and evaluation of the lungs and mediastinum for other lesions. By use of computed tomography, attenuation factors between −1,000 and +3,000 Hounsfield units allow for differentiation of fat tissue from soft tissue.