Page 512 - Clinical Small Animal Internal Medicine

480 Section 6 Gastrointestinal Disease

duodenum. The stomach consists of four major anatomic is located in the fundus region and the fluid is located in
VetBooks.ir divisions: the cardia, fundus, body, and pylorus. There the gastric body/antrum. The fluid in the gastric body/
antrum creates a round, circular, soft tissue attenuating
are two sphincters, one each at the orad and aborad
aspects of the stomach. The caudal esophageal sphincter
taken for a foreign body in the pylorus or a mass in the
extends into the cardia, while the pylorus is located at area in the cranial abdomen, which is occasionally mis­
the junction between the stomach and duodenum. The cranial abdomen. In the left lateral recumbent view, gas
pylorus is divided into the pyloric antrum and canal. The is present in the pyloric region, appearing as a gas opac­
pylorus has an important gatekeeper function, only ity oval or triangle‐shaped structure in the cranioventral
allowing smaller sized particles to exit the stomach into aspect of the abdomen (Figure 48.10).
the small intestinal tract.
Ultrasound Examination of the Stomach
Radiographic Examination of the Stomach
An ultrasound examination of the stomach helps evalu­
In a survey radiographic study, the stomach is located ate the gastric mucosa and gastric content. If possible,
predominantly to the left of midline with the cardia patients should be fasted for 12 hours before an ultra­
located slightly to the left of midline, ventral to the 11th sound examination is performed as food in the stomach
and 12th thoracic vertebrae. The fundus is positioned might create artifacts. The stomach is positioned caudal
to the left of midline and just caudal to the liver and to the liver, predominantly central to left of midline, and
diaphragm. The fundus is the only aspect of the stom­ adjacent to the spleen. The cardia is located to the left of
ach which can be in direct contact with the diaphragm. midline and can usually be seen as a thick bulge with a
The antrum is usually not distinctly outlined and is smooth mucosal outline at the border of the thoracic
located between the fundus and pyloroduodenal junc­ esophagus to fundus. The pylorus is located to the right
tion. The pylorus is located on or to the left of midline in or on midline in the dog and is usually on or slightly to
the cat and on midline or to the right of midline in the the left of midline in the cat. The stomach wall thickness
dog. The gastric axis in the dog is usually perpendicular ranges from 3 to 5 mm in normal dogs and cats. The
to the spine or parallel with the ribs. In the cat, it is usu­ pyloric wall thickness in the cat is 3.8–5 mm, which is
ally more perpendicular to the spine. In a lateral radio­ similar to established gastric wall thickness measure­
graph, the pylorus is located approximately at the ventral ments of 3–5 mm. Under optimal conditions, five layers
aspect of the ninth rib. of the stomach and small intestine are visualized
Radiographic attenuation of the stomach is dependent (Figure 48.11). The innermost hyperechoic layer corre­
on its content. The stomach usually contains both gas sponds to the luminal surface of the mucosa. The next
and fluid, but if the stomach is empty or only a small hypoechoic layer is the mucosa, which is followed by
amount of fluid is present in the stomach, it may be another hyperechoic thin layer, the submucosa. The
difficult to visualize as it summates with the liver. The outer hypoechoic layer is the muscularis, which is adja­
stomach has rugal folds, which are usually best seen on a cent to the outermost hyperechoic layer, the subserosa/
contrast study or ultrasound evaluation. Rugal folds serosal layer.
within the fundus of the stomach often create a mosaic
pattern. In the body of the stomach, the rugal folds are Gastrography
more parallel and in the pylorus the number of rugal
folds is reduced. Subjectively, rugal folds in the cat are Indications for contrast studies of the stomach (gastrog­
less prominent than in the dog. raphy) include vomiting, regurgitation, a history of
Obtaining multiple projections in various positions of foreign body consumption, chronic weight loss, bloat­
the patient is important when evaluating the stomach ing, and anorexia. Contraindications for performing gas­
radiographically. Changing the position of the stomach trography include suspected gastric rupture, large
affects the position of the gas and fluid in the stomach. amounts of ingesta or large amounts of fluid in the stom­
In dorsal recumbency (VD view), gas is located in the ach. A potential contraindication could be a rigid stom­
gastric body and pyloric antrum and can be noted as a ach as overfilling of the stomach might cause vomiting,
gas opacity structure summating with the stomach at the resulting in aspiration. Before a gastrography is per­
right and left side of midline. In ventral recumbency (DV formed, survey radiographs of the abdomen should be
view), the gas is present in the fundus of the stomach, obtained. For all gastrography studies, 12 hours of fast­
which is then the most dorsal aspect of the stomach. In a ing of the patient is recommended to reduce the risk of
DV view, a gas opacity structure is noted summating artifacts caused by food or other material in the stomach.
with the left cranial aspect of the stomach in the location Most of the study can be performed without sedation of
of the fundus. In a right lateral recumbency view, the gas the patient; however, if the patient is not sufficiently