Page 433 - Atlas of Small Animal CT and MRI

4.4

Heart, pulmonary vasculature, and great vessels

Pericardium on CT images. The pericardium may be well defined on
unenhanced images and will mildly enhance following
The normal parietal pericardium is thin (1–2 mm) and contrast medium administration.
is therefore inconsistently seen on CT images. The peri­
cardial sac holds only a small volume of fluid but can Pericarditis
contain a significant amount of fat that accentuates both Pericarditis can include an exudative pericardial effusion
the parietal pericardial and the epicardial margins.
that is fluid attenuating on unenhanced CT images,
although density may be greater with high cellularity.
Peritoneopericardial diaphragmatic hernia The pericardium can be markedly thickened, and the
Peritoneopericardial diaphragmatic hernia is the result of pericardium and epicardium moderately to intensely
incomplete development of the diaphragm, leading to the enhance following contrast administration (Figure 4.4.3). 6
formation of a window between the pericardial sac and
the peritoneal cavity. The disorder appears to be more Neoplasia
common in cats than in dogs, and Himalayan, Maine Neoplasms that can cause a pericardial mass or
Coon, and other longhaired cats as well as Weimaraner hemorrhagic/malignant pericardial effusion include
dogs are predisposed. The CT appearance of peritoneo­ cardiac hemangiosarcoma, chemodectoma, mesotheli­
1,2
pericardial diaphragmatic hernia depends on the specific oma, lymphoma, rhabdomyosarcoma, and fibrosarcoma.
4
viscera and visceral volume that has migrated into the Hemorrhagic pericardial effusion from erosive right
pericardial sac. Displaced omentum will appear primarily atrial hemangiosarcoma is reported to be the most com­
fat attenuating unless it is strangulated and edematous. mon cause of pericardial effusion in dogs. As with exu­
7
Liver lobes often herniate, and liver parenchyma and dative effusions, hemorrhagic and malignant effusions
hepatic veins have a characteristic appearance on contrast‐ can be highly cellular and will therefore have a density
enhanced CT images (Figure 4.4.1). Small intestinal her­ somewhat greater than a transudative effusion on CT
niation appears as a tubular, fluid‐ and gas‐attenuating images. The CT imaging appearance of neoplastic peri­
collection. Peritoneopericardial diaphragmatic hernias cardial masses will vary depending on cell type, complex­
are often associated with anomalies of the sternum. ity, and vascularity, but they often appear as mural and/or
intraluminal masses that are isoattenuating compared to
Pericardial effusion myocardium and enhance following contrast administra­
Pericardial fluid may be transudative, exudative, or tion (Figure 4.4.4). Cardiac MR has been compared to
hemorrhagic, and the underlying causes of pericardial transthoracic and transesophageal echocardiography for
effusion are idiopathic, inflammatory, neoplastic, trau­ evaluation of pericardial effusion caused by cardiac neo­
8
matic, or cardiovascular in origin (Figure 4.4.2). Simple plasia. Cardiac MR did not improve diagnostic accuracy
3–5
transudative pericardial effusions are fluid attenuating but did yield additional anatomical information. Imaging
Atlas of Small Animal CT and MRI, First Edition. Erik R. Wisner and Allison L. Zwingenberger.
© 2015 John Wiley & Sons, Inc. Published 2015 by John Wiley & Sons, Inc.
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