Page 336 - Feline diagnostic imaging

344 21 Normal Gastrointestinal Anatomy
is empty, it has a star‐shaped or wagon wheel appearance 21.3.3 Normal Intestine
because of gas and mucus between the rugal folds. The Similar to the stomach, the small intestine has 4–5 layers:
submucosa contributes to this appearance where it
extends into the rugal folds. The thickness of the stomach an outer serosal layer, a thin hypoechoic muscularis, a thin
hyperechoic submucosa, and a thick hypoechoic mucosa
should be measured from the outside edge of the serosa to
the outside edge of the mucosal surface. The gastric wall (Figure 21.12) [16,17]. The inner mucosal luminal surface
is hyperechoic and is visible when the fluid is adjacent to
is approximately 3.0–5.0 mm when the stomach is full.
About 4–5 contractions occur per minute. The gastros- the wall. In one study, the average thickness of the small
intestine was 2.1 mm, with the duodenum having the great-
plenic ligament extends from the gastric fundus to the
proximal extremity of the spleen, which is immediately est thickness [18]. The duodenum is not always the thickest
region of the small intestine, however. In another study,
caudal.
The cardia and pylorus have been examined in 33 nor- the wall of the duodenum measured 2.0–2.4 mm (mean
mal cats. Both the pylorus and the esophagus at the cardia 2.2 mm) and the jejunum measured 2.1–2.5 mm (mean
had a muscularis that was thicker than in other parts of the 2.3 mm) while the ileum had the thickest wall at 2.5–
3.2 mm (mean 2.8 mm) [19]. Additionally, the ileum of the
GIT. The outer longitudinal muscle and inner circular
muscles of the esophagus could not be distinguished sono- cat has a thick hypoechoic muscularis that tends to be
more prominent than that of the dog. The hyperechoic
graphically. Unlike the cardia, the pylorus is a true sphinc-
ter. Histologically, there is a focal thickening of the inner mucosal–luminal interface was not always apparent in this
portion of the intestine in cats [19]. As with the stomach,
circular muscularis layer, which appears triangular when
sectioned longitudinally. This area was consistently hypo- clear fluids separate the wall, allowing visualization of the
hyperechoic mucosal–luminal interface. A significant
echoic on ultrasonography [15].
amount of gas results in reverberation artifact which

(a) (b)

(c) (d)

Figure 21.12 Ultrasonography of the normal feline small intestine. (a) Duodenum of a normal cat showing a variable amount of
ingesta within the lumen. Wall layers include the serosa, muscularis, submucosa, and mucosa. (b) Small intestine of another cat
showing ingesta filling the lumen of one segment. Calipers are shown measuring the intestinal wall in an area with less ingesta.
(c) Transverse sonographic image of the normal ileum (arrow) of a 16-year-old Maine Coon. The muscularis of the ileum is thicker than
that of other segments of the feline small intestine. (d) Longitudinal image of the ileum (arrow) of the cat in (c). Gas in the colon
(C) results in reverberation artifact causing shadowing of deeper structures.