Page 44 - Feline Cardiology

38 Section B: Diagnostic Testing

Diagnostic Testing

A

C

B

Figure 6.1. A cat correctly restrained for lateral and VD radiographs. The use of sandbags over the hips (A) and neck (B) and a trough
(C) are helpful to minimize the need for restrainers and radiation exposure. Similarly, using roll gauze to draw the forelimbs cranially
(panels A–C) allows the radiographic exposure to be made without manual restraint.

correspond with peak inspiration whenever possible, to comfort and respiratory and hemodynamic stability.
provide maximal separation between the caudal cardiac Straight DV or VD projections will have the dorsal
border and the diaphragm. In the lateral view, the dorsal spinous processes of the thoracic vertebrae centered
heads of the ribs should be superimposed. If they are over the vertebral bodies along the entire length of the
not (barring a vertebral abnormality), the projection is thoracic spine, and the sternebrae should also be super-
oblique and the cardiac silhouette will be distorted. In imposed. As stated above, the radiograph should be
the cat, the lungs are normally better inflated in the taken during full inspiration, as evidenced radiographi-
ventrodorsal (VD) view because the thorax is more cally by the presence of aerated lung between the caudal
completely expanded; it may also be easier to pull the cardiac margin and the cupula of the diaphragm.
forelimbs cranially in this view. However, results from Whenever possible, radiographic positioning should be
one study suggest there is more variability in the cardiac standardized in a veterinary hospital (either the right or
silhouette in a VD position compared to the dorsoven- left lateral and the DV or VD views should be used rou-
tral (DV) projection (Carlisle and Thrall 1982). tinely) so that slight differences between views are not
Moreover, mild pleural effusion may be missed in the misinterpreted as abnormalities.
VD view because the fluid gravitates to the paravertebral In a dyspneic or otherwise unstable cat, a DV projec-
fossae (termed by some the “gutters”) formed by the rib tion may be much more readily obtained than a lateral
curvature, where it may not be apparent radiographi- view, because the dyspneic patient is in sternal recum-
cally. On the other hand, cardiac size and shape may be bency, the natural posture cats choose when in respira-
better characterized because the fluid is less likely to tory distress. Therefore, the “lateral-only” approach for
obscure the cardiac silhouette. Although all these vari- obtaining thoracic radiographs in dyspneic cats is not
ables should be considered, the most important goal is appropriate, and either a DV view should be considered,
a straight symmetric projection and, above all, patient or radiography should be postponed altogether until the