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Chapter 20

The Torso

III NORMAL ANATOMY III THE EXTERIOR TORSO

Birds lack a diaphragm—at least in the mammalian The Thoracic Spine, Ribs, Keel, and
sense of the word—and instead have a thin sheet of Body Wall
connective tissue separating the lung from the remain-
ing viscera. This tissue is called the horizontal septum As with the radiographic assessment of any symmetri-
and serves no respiratory function. cal part or parts of the body, accurate positioning is
Thus there is no internal division into a thorax and the key to success. The exterior torso is no exception.
abdomen but rather a single large cavity termed the If equipped with well-positioned lateral and ventro-

celom or celomic cavity, which contains the abdominal dorsal (VD) views of the torso, the film reader is
organs, including air sacs. Figures 20-1 through 20-7 afforded the opportunity of comparing and contrast-
sequentially reveal the exposed viscera of a red-tailed ing either side of the rib cage, along with the interven-
hawk positioned on its back during the dissection. ing soft tissues and surrounding bones and joints.
The diagnostic benefits of a comparative radio-

graphic assessment cannot be overemphasized (Figure
III ANATOMICAL-RADIOLOGICAL 20-9).
CORRELATION Although lateral projections do not lend themselves
to right-left comparisons, they nevertheless constitute
Using conventional radiography, the abdominal viscera a valuable diagnostic asset, especially when projected
are necessarily displayed as a kind of two-dimensio- in a true lateral manner (Figure 20-10), thus reducing
nal montage, with the shadows of individual organs or eliminating geometric distortion, a potential source
superimposed on one another in a single fl attened of radiographic misdiagnosis.
layer (Figure 20-8, A). The resulting absence of depth Fractures of the thoracic spine and ribs are associ-
perception can be partially mitigated by the addition ated with high mortality, and as a consequence, few
of one or more right-angle (orthogonal) or oblique pro- such birds are radiographed. Sternal fractures, although
jections, but one should remember that not every organ not usually fatal in their own right, are often associated
may be seen in every view (Figure 20-8, B). with serious wing fractures and untreatable internal
In any event, it generally is the larger organs, such injuries leading to euthanasia.
as the heart and liver, or those containing natural con- The incidence of deep and superfi cial subcutaneous
trast, such as the gizzard and bowel, that are most emphysema in birds is surprisingly low given the
visible and thus are radiographically detectable. In frequent occurrence of wing fractures, probably a
effect, the diagnostic exercise becomes one of silhou- result of protection provided by the feathers. When
ette analysis, discussed later in this chapter. Text continued on p. 216.
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