Page 399 - Atlas of Small Animal CT and MRI

4.1

Thoracic wall and diaphragm

Thoracic wall margins are poorly defined. Abscesses typically have a
fluid‐attenuating center as well as a thick surround-
Developmental disorders ing soft‐tissue rim on unenhanced CT images and
Clinically significant developmental anomalies of the tho- peripherally enhance following contrast administration
racic wall and sternum are uncommon and can usually be (Figure 4.1.4).
adequately characterized by clinical evaluation, survey Osteomyelitis of the ribs or sternum usually appears
radiographs, and ultrasound examination. CT is some- as a mixed destructive and productive lesion on CT
times useful for definitive diagnosis or treatment planning. images, with moderate to marked, ill‐defined contrast
enhancement (Figure 4.1.5).
Trauma
Fractures of the ribs and sternum are a common sequela Neoplasia
to thoracic trauma. Rib fractures can also occur from Neoplasms of the thoracic wall can be benign or malig-
cyclic stress injury in patients with respiratory disorders nant and of either soft‐tissue or bone origin. Soft‐tissue
that lead to increased respiratory effort. This is tumors include lipomas, benign mesenchymal neo-
1
more often seen in cats. Acute fractures have sharply plasms, sarcomas, and round cell tumors.
demarcated fracture margins on CT images and may be Lipomas have a homogeneous fat‐attenuating appear-
displaced depending on the type and severity of injury ance on CT images, do not significantly enhance, and
(Figure 4.1.1). Chronic or healed fractures usually have a usually have encapsulated margins. Some lipomas can
productive bridging or nonbridging bony callus be invasive, dissecting along fascial planes or infiltrating
(Figure 4.1.2). Callus can be exuberant with displaced muscle (Figure 4.1.6). Lipomas are T1 and T2 hyperin-
fractures or fracture site motion. tense on MR images.
Penetrating thoracic wall injuries from bite wounds or Malignant soft‐tissue neoplasms can be uniformly or
foreign bodies are also common but usually manifest heterogeneously attenuating on unenhanced CT images
with pleural or pulmonary clinical signs (Figure 4.1.3). and can run the spectrum from well encapsulated to
poorly defined (Figure 4.1.7). Vaccine‐associated fibro-
Inflammatory disorders sarcomas are particularly invasive. The degree and
Thoracic wall cellulitis or abscess can be seen as a sequela homogeneity of contrast enhancement is variable and
to regional infectious inflammatory disease. Cellulitis depends on tumor type.
manifests as thoracic wall thickening, associated with Benign bone tumors, such as osteomas and chondro-
a loss of fascial plane definition on unenhanced CT mas, are rare. These neoplasms alter normal bone anatomy
images. Affected regions moderately to markedly but typically have a nonaggressive appearance, showing no
enhance following contrast administration, and lesion evidence of active bone destruction or rapid rate of change.

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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