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296 SECTION II III The Mammals

because of its undulant growth plate and deeply
indented femoral fossa (Figure 26-9). The point is that
this normal morphological variant must not be mis-
taken for a femoral head fracture.
Mature Hip. Generally, the hips of rabbits are deeply
set in their sockets, an appearance accentuated by
a large overhanging cranial acetabular lip, as seen in
ventrodorsal (VD) projections (Figure 26-10). Because
it is relatively easy to manipulate the hind limbs of a
rabbit during radiography, overrotation often occurs,
making it appear as if the femurs are bowed medially,
a phenomenon termed projectional curvature (Figure
26-11).

Thorax
Immature Thorax. The immature rabbit thorax is char-
acterized by an extremely wide cranial mediastinum,
due in large part to the thymus (Figure 26-12). This
normal organ and the fat that surrounds it must not be
mistaken for a tumor such as a thymoma.

Mature Thorax. The thorax of a mature rabbit, espe-
cially a pet, is characterized by reduced contrast, which
is most often the result of perithoracic fat combined
with expiratory filming (Figure 26-13). This normal

appearance may be misinterpreted as representing
interstitial lung disease, which of course it is not. The
cranial and precardiac portions of the mediastinum are
usually vague in appearance, the result of localized fat Figure 26-9 • Ultraclose view of the normal left hip of an
immature rabbit.

Figure 26-10 • Close-up view of normal hips in a mature rabbit.

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