Last revised by Raymond Chieng on 13 Jul 2023

The stomach is a muscular organ that lies between the esophagus and duodenum in the upper abdomen. It lies on the left side of the abdominal cavity caudal to the diaphragm at the level of T10.

The stomach ("normal" empty volume 45 mL) is divided into distinct regions:

  • cardia: the area that receives the esophagus (gastro-esophageal junction)

  • fundus: formed by the upper curvature; portion of stomach above GEJ level 17

  • body (corpus): the main central region of the organ; central two-thirds portion from the cardia to the incisura angularis 17

  • pylorus (antrum): the lower section of the stomach that facilitates emptying into the small intestine, located on the right of the midline at the level of L1.

The lesser curvature forms the shorter concave border and the greater curvature forms the longer convex border of the stomach. The lesser omentum attaches the lesser curvature to the liver, while the greater omentum attaches to the greater curvature of the stomach 17

There are two smooth muscle sphincters, esophageal and pyloric, that dictate entry into and exit from the stomach. These are under the control of several mechanisms including stimulant (parasympathetic) and inhibitory (orthosympathetic) control from the anterior gastric, posterior, superior and inferior celiac plexus and myenteric nerve plexuses.

The inner mucosal surface has many rugal folds that act to increase the surface area of the stomach lining and increase its efficiency.

  • incisura angularis: small anatomical notch on the stomach located on the lesser curvature of the stomach near the pyloric end, which marks the junction between the body and the antrum 17

  • fornix gastricus: refers to the arch-shaped superior margin of the fundus of the stomach

Stomach has its own lymph nodes stations. Routes of flow of lymph from perigastric nodes to para-aortic lymph nodes include 4-6

It is suggested that the most likely route for para-aortic lymph node metastases is from the left gastric artery nodes accompanying the celiac artery 4.

  • sympathetic innervation is from the T5 to T12 segments of the sympathetic chain via the greater and lesser splanchnic nerves which synapse in the celiac plexus.

    • sympathetic supply causes vasoconstriction, inhibition of gastric motility and pyloric constriction

    • afferents run with the sympathetic fibers (visceral pain sensation)

  • parasympathetic innervation is from the vagus nerves 

    • the anterior vagal trunk supplies the anterior surface of the upper body and fundus, antrum, parts of the lesser curvature and the pylorus

    • the posterior vagal trunk supplies the cardiac orifice and posterior surface of the body and antrum

    • parasympathetic supply is secretomotor to the gastric mucosa, promotes gastric motility and relaxes the pyloric sphincter during gastric emptying

Akin to other areas of the gastrointestinal (GI) tract, the stomach walls are composed of the following layers:

  • mucosa: internal layer of epithelium, the lamina propria (loose connective tissue and gastric glandular tissue) and the muscularis mucosae

  • submucosa: a fibrous layer of connective tissue under the mucosa

  • muscularis externa: this is the muscular layer of the stomach wall and is comprised of three layers (inner oblique, middle circular and outer longitudinal) unlike other GI organs which only have two layers

  • serosa: the outermost layer of the stomach wall consisting of connective tissue which is continuous with the peritoneum

The stomach wall contains several different types of glandular tissue. The cardia, fundus and pylorus all have different types of glands and are composed of a variety of different cells:

  • mucous cells: secrete a mucus gel layer and are found throughout the stomach

  • parietal (oxyntic) cells: secrete gastric acid and intrinsic factor throughout the stomach

  • chief (zymogenic) cells: secrete pepsinogen and rennin in the fundus and body 17

  • enteroendocrine (APUD cells): secrete a variety of products and are found throughout the stomach

Control of the stomach relates to the autonomic nervous system and various digestive system hormones:

  • gastrin: causes an increase in the secretion of hydrochloric acid (HCl), pepsinogen and intrinsic factor from parietal cells in the stomach; it also causes increased motility in the stomach; released by G-cells in the stomach to distension of the antrum, and digestive products; inhibited by a pH normally <4 (acidic), as well as the hormone somatostatin

  • cholecystokinin (CCK): greatest effect on the gallbladder, but it also decreases gastric emptying and increases release of pancreatic juice which is alkaline and neutralizes the chyme

  • secretin: has most effects on the pancreas, but will also diminish acid secretion in the stomach

  • gastric inhibitory peptide (GIP): decreases both gastric acid and motility

  • enteroglucagon: decreases both gastric acid and motility

  • glycogen: produced in the brain and stomach, affects the liver and level of glucose in the stomach

The stomach is not usually well visualized on the plain film although a gastric bubble (gas outlining the fundus of the stomach) is often visible on an erect chest or abdominal x-ray.

Gastric rugae is readily identified on supine abdominal radiograph 20,21.

Analogous to the abovementioned histological architecture, the gastric walls will consist of five concentric layers of alternating echogenicity when viewed with an appropriately high frequency transducer, characteristic of the sonographic gut signature 16.

Sonographic localization of the stomach is typically performed with epigastric transducer placement with the patient in a supine or right lateral decubitus position. The gastric antrum is commonly visualized just to the right of anatomic midline using the following sonographic landmarks; 11

Visualization of the gastric body is often possible by sweeping leftward of the gastric antrum. Visualization of the gastric fundus may require using the spleen as a sonographic window, using a left intercostal probe position.​ The sonographic appearance of the stomach, most notably the gastric antrum, may differ based on the patient's prandial status as follows;

  • fasting patient

    • gastric antrum may appear as a flattened ovoid with absent to minimally appreciable luminal contents 11

      • targetoid or "bulls eye" appearance 12

    • may also appear round, with homogenous anechoic fluid filling the lumen

  • post-prandial patient

    • viscous fluid ingestion results in luminal contents appearing uniformly hyperechoic 

    • recent solid food ingestion results in a heterogeneous appearance of luminal contents, with posterior acoustic shadowing

      • may be indicative of higher aspiration risk for patients under general anesthesia 10

When well distended, the normal gastric wall will have a thickness of 5-7 mm in the antrum and 2-3 mm in the body 17

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Cases and figures

  • Figure 1
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  • Figure 2: histology
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  • Figure 3: histology (high power)
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  • Case 1: stomach outlined on fluoroscopy
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  • Figure 4a: lymphatics of the stomach and foregut (Gray's illustrations)
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  • Case 2: areae gastricae in a gastric antrum
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  • Figure 4b: lymphatics of the stomach and foregut (Gray's illustrations)
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