Page 153 - Feline diagnostic imaging

154 9 Normal Radiographic Anatomy

Figure 9.1 Lateral thoracic radiograph of a normal cat. The lungs extend from the thoracic inlet caudally to L1. The longus coli
muscle (arrow) interposes between the thoracic vertebrae and lungs.

(b)

(a)

Figure 9.2 Lateral (a) and ventrodorsal (b) thoracic radiographs of an adult cat taken under general anesthesia. The lungs are
underinflated, extending only to the caudal aspect of T12. On the ventrodorsal image (b), the heart occupies most of the incompletely
expanded lung field. The lungs have an overall increase in opacity.

The mediastinum is not a closed space but opens into Most of the soft tissue anatomy visible on thoracic radio-
the cervical soft tissues via the thoracic inlet, and into the graphs is located within the mediastinum (heart and great
retroperitoneal space via the aortic hiatus. Although the vessels, cranial and caudal vena cava, esophagus, thymus,
mediastinum is separate from the pleural space, fenestra- trachea, lymph nodes). The mediastinum extends from the
tions allow pleural fluid and air to move freely to both left ventral aspect of the spine to the sternum (entire dorsal‐
and right thoracic cavities. Pleural fluid that is thick or ventral dimension of the thorax), but is seen as a soft tissue
viscous (such as pyothorax) may not pass beyond the opacity only in the cranial thorax, ventral to the trachea
mediastinal fenestrations, resulting in a unilateral pleural (Figure 9.6). This opacity is created by border effacement
effusion. of several structures, including esophagus, cranial vena