Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Two The Thorax 73
Fig. 2-46 A 9-year-old male Old English Sheepdog with a 2-month
history of coughing. The ventrodorsal radiograph reveals a large tissue-density
mass in the area of the cranial portion of the left cranial
lung lobe. Close examination reveals lysis of the left third rib (arrow)
suggesting the mass is arising from the rib and extending into the
thoracic cavity. Diagnosis: Chondrosarcoma of the left third rib.
thoracic diameter, which is increased markedly at the xiphoid when compared with the
manubrium.
Sternal abnormalities are frequent and usually without clinical significance. Soft-tissue
infection, tumors, and trauma may affect the sternebrae. Few sternal anomalies are significant.
Absence, splitting, or malformation of the xiphoid cartilage has been associated with
peritoneopericardial diaphragmatic hernia, and this can be a useful radiographic feature in
distinguishing that condition from other pericardial diseases. 80
An acute bony lesion rarely occurs without an associated soft-tissue injury; consequently
the evaluation of the bony structures cannot be divorced from the evaluation of the adjacent
soft tissues. In the absence of a soft-tissue lesion most bony deformities can be ignored.
DIAPHRAGMATIC ABNORMALITIES
The variation in appearance of the normal diaphragm due to variations in breed, species,
position, x-ray beam geometry, phase of respiration, and abdominal content make recognition
of diaphragmatic abnormalities difficult. Although the basic shape of the diaphragm
is fairly constant, contour alterations occur frequently.
Diaphragmatic abnormalities that may be recognized radiographically include changes
in shape, width, outline, and position. The diaphragmatic outline may be deformed from
masses arising from the diaphragm, from the pleural space, or from abdominal masses that
protrude through the diaphragm. The diaphragm’s outline and position may change with
diaphragmatic hernia or diaphragmatic paralysis.
M A S S E S
Masses may arise from or involve the diaphragm; pleural or mediastinal tumors may metastasize
to or involve the diaphragm. Solitary or multiple masses may protrude from the
diaphragm, altering its normal shape. Diaphragmatic granulomas or adhesions may occur in