Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

250 Small Animal Radiolo g y and Ultrasono graphy
Fig. 3-1 A 4-year-old male Cocker
Spaniel (A) and a 3-year-old male
domestic short-haired cat (B). Both
animals were clinically normal. The
right lateral abdominal radiographs
revealed normal anatomy. Diagnosis:
Normal abdomen. Continued
controversy over linear versus sector transducers, they each offer advantages and disadvantages.
Linear transducers offer a wider near field but are less useful for examining structures
through an intercostal window or beneath the rib cage. Most sector transducers (pieshaped
image with the narrowest field of view at the point of patient contact) have a
smaller footprint and therefore can be directed between and under the ribs or into the
pelvic inlet. For small animal medicine, either mechanical sector or curved linear- and
radial-array scanners are preferable provided the footprint, or area of patient contact, is
small. A consistent, systematic search pattern is recommended. Usually this means starting
in the anterior abdomen and continuing along the left side to the posterior abdomen and
returning on the right side. All organs should be evaluated in at least two planes.
Longitudinal and transverse planes are customary, although oblique planes are extremely
useful. Because the organs may be moveable and not oriented along the transverse, or sagittal,
plane of the animal, the planes used are related to the organ being examined and not
the patient. In some areas (e.g., adrenal glands, retroperitoneal great vessels, and certain
lymph node groups) dorsal plane imaging may be very helpful.
P O S I T I O N I N G A N D V I E W
The routine views of the abdomen are the lateral and ventrodorsal views (Figs. 3-1 and
3-2). It is our preference to take the lateral view with the animal’s right side down. This usually
causes the pylorus to be fluid filled, and in some animals it will appear radiographically
as a perfectly round tissue density suggestive of a mass or ball. The other commonly used
positions are the left lateral and dorsoventral views (Figs. 3-3 and 3-4). On the left lateral
position the pylorus usually will contain air and may appear as a radiolucent, round structure.
1 The choice between the right and left lateral as the routine view is a matter of personal
preference. The ventrodorsal view is clearly preferable to the dorsoventral view when
evaluating abdominal structures, because positioning for the ventrodorsal view causes the
abdomen to be stretched to its fullest possible length and the abdominal viscera are distributed
evenly throughout the abdomen. Positioning for the dorsoventral view results in
the abdomen being somewhat bunched up, and the viscera are tightly crowded into a minimized
space. This crowding makes identification of various structural and pathologic
changes (loss of detail or masses) much more difficult.
A