Page 157 - Feline diagnostic imaging

158 9 Normal Radiographic Anatomy
projection to the left of the midline on VD/DV views and
should not be confused with a mass (Figure 9.9)

9.10 Pulmonary Parenchyma

Using the traditional lung pattern approach, the pulmonary
parenchyma is divided into four anatomic components:
alveoli, interstitium, pulmonary vessels, and bronchi. The
alveoli are air‐filled sacs, and do not contribute to normal
background pulmonary opacity. The interstitial tissue forms
alveolar septae, and provides a supporting framework for
the bronchial walls, lymphatics, and blood vessels. In the
normal feline thorax, the interstitial tissue contributes min-
imally to normal background opacity. Bronchial walls may
be seen toward the pulmonary hilus, but as they branch and
taper into the periphery, bronchial walls decrease in thick-
ness and are not typically visualized. Major bronchi are
located between their corresponding pulmonary artery and
vein, but do not necessarily occupy the entire space between
vessels. Pulmonary vessels (pulmonary arteries and veins)
provide most of the normal background opacity seen in nor-
mal feline thoracic radiographs (Figure 9.4).

9.11 Normal Vascular Anatomy

Figure 9.7 Ventrodorsal image of the thorax of a cat with a
mediastinal shift. The heart is shifted toward the left secondary Peripheral pulmonary arteries and veins are best visual-
to prolonged left lateral recumbency. The mediastinum (as noted ized individually as they extend into the cranial lung lobes
by the position of the heart) is shifted to the left side secondary (lateral view) and caudal lung lobes (DV/VD view). The
to atelectasis of the left lung lobes. The right lungs are right and left cranial lobar pulmonary vessels are best
overexpanded, and the left diaphragmatic crus is shifted
cranially, to compensate for the loss of volume. identified on lateral projections (Figure 9.10a). The artery

(b)

st
(a)

tb tb tb tb
cm cm

st

Figure 9.8 Lateral (a) and ventrodorsal (b) thoracic images of a normal adult cat. The approximate locations of the sternal, cranial
mediastinal, and tracheobronchial lymph nodes are noted. cm, cranial mediastinal; st, sternal lymph nodes; tb, tracheobronchial.