Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

84 Small Animal Radiolo g y and Ultrasono graphy
the opposite crus. Asymmetry between diaphragmatic crura may be a normal variation;
however, if one crus is located consistently cranial to the opposite crus despite position
changes, the possibility of a functional diaphragmatic abnormality should be considered.
Displacement of one or both diaphragmatic crura may result from adhesions or diaphragmatic
paralysis (Fig. 2-59). 115-118 It also may result from pulmonary, pleural, or abdominal
diseases. Optimal functional evaluation of the diaphragm requires fluoroscopy.
Comparison of inspiratory and expiratory lateral radiographic views can suggest a lack of
parallel motion of the diaphragmatic crura. Although usually traumatic in origin,
diaphragmatic motion abnormalities may arise from other causes. A posttraumatic
condition called synchronous diaphragmatic flutter also may be seen as a diaphragmatic
dysfunction.
PLEURAL ABNORMALITIES
Pleural abnormalities that can be detected include intrapleural and extrapleural masses
and air or fluid accumulation in the pleural space. Pleurography has been described for the
purpose of evaluating the pleural space. 119,120 Because the technique is difficult to perform
and interpret, it has been used infrequently. Sonography has proven to be marginally easier
and a great deal more specific since its introduction.
P L E U R A L A N D E X T R A P L E U R A L M A S S E S
Masses that involve the thoracic wall may extend into the thorax, although they may not
penetrate the pleura. These chest wall masses often are referred to as extrapleural masses.
The intact pleural covering produces a smooth, distinct margin over the inner surface of
these masses. A convex interface with the adjacent lung and concave edges at the point of
attachment to the chest wall, referred to as a shoulder, may be seen. These masses are usually
widest at their point of attachment. Rib destruction, bony proliferation, soft-tissue
mineralization, and distortion of intercostal spaces may be seen (Fig. 2-60). Although the
presence of a bony lesion suggests that a mass is extrapleural, the absence of bone lesions
does not exclude that possibility. The often smaller, external portion of the mass also may
be identified. Pleural fluid, more often observed with pleural than extrapleural or pulmonary
masses, may be minimal unless the mass becomes rather large and causes intercostal
vascular erosion. Most extrapleural masses are neoplastic, often arising from the rib
FIG. 2-58 A 9-year-old neutered
female Beagle had a history of panting
and an enlarged cardiac silhouette
on thoracic radiographs. A right
lateral view reveals the presence of a
lobe of liver (LIVER) and gall
bladder (GB) in the right side of
the pericardial sac. Diagnosis:
Peritoneopericardial diaphragmatic
hernia.