Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

Chapter Three The Abd omen 259
Fig. 3-10 Longitudinal sonograms
of the stomach of a 10-year-old
spayed female Yorkshire Terrier with
a history of mammary tumors. The
abdominal ultrasonography was performed
to investigate the possibility
of abdominal metastasis. The dog
was clinically normal. The stomach
is normal. The gastric wall is well
defined and uniform in thickness.
Gas can be identified within the
stomach. The five layers of the gastric
wall can be identified with the
hypoechoic mucosa and muscularis
and the hyperechoic serosa, submucosa,
and mucosal or luminal surface.
Diagnosis: Normal stomach.
right. The stomach wall thickness varies from 3 to 5 mm, with larger breeds having a
thicker wall. Five layers may be identified starting with a hyperechoic serosa, a hypoechoic
muscularis, a hyperechoic submucosa, a hypoechoic mucosa, and a hyperechoic lumen or
mucosal surface (Figs. 3-10 and 3-11). The luminal gas produces reverberation artifacts,
which are useful in identifying the stomach. The rugal folds may be identified if the stomach
is relatively empty, but they disappear when the stomach is distended. Fluid and gas
may be seen swirling around within the stomach as a result of normal peristalsis. Water
may be administered by stomach tube in order to improve examination of the gastric
wall. 12,18
Pancreas. The pancreas is immediately caudal to the stomach and medial to the duodenum.
The pancreas has two parts, (1) the left lobe or limb, which is immediately caudal to
the stomach and extends from the gastroduodenal junction to the cardia, and (2) the right
lobe, which is immediately medial to the descending duodenum and extends caudally from
the gastroduodenal junction. In normal animals, the pancreas usually cannot be identified
radiographically because of its small dimensions and the large number of superimposed
structures of similar density. In a very fat cat, a triangular soft-tissue density may be
observed on the ventrodorsal view just caudal to the stomach and medial to the spleen.
This may represent the tip of the left limb of the pancreas.
Identifying the pancreas during an ultrasonographic examination may be a challenge
even for the expert ultrasonographer. This organ can be identified in a cooperative small
patient when using a high-frequency transducer or in animals with peritoneal fluid.
Infusion of 60 ml of isotonic saline per kg of body weight into the peritoneal cavity has
been recommended in order to visualize the pancreas. No complications were encountered
with this technique. 19 The pancreas is usually isoechoic when compared with the mesentery,
similar in echogenicity to abdominal fat, and hyperechoic when compared with the
liver (Figs. 3-12 and 3-13). 12,19,20 It is most often identified adjacent to the duodenum and