Anatomy - Gastrectomy, subtotal, robotically assisted

• The stomach is a muscular hollow organ located between the esophagus and the duodenum. It is situated in the left and middle upper abdomen directly beneath the diaphragm. When moderately filled, the stomach is on average 25-30 cm long and has a storage capacity of 1.5 liters and in extreme cases up to 2.5 liters. The position, size, and shape of the stomach vary significantly depending on age, state of filling, and body position. There are large interindividual differences.
• The stomach can be divided into different sections:
  • Cardia (stomach entrance, upper stomach mouth, Ostium cardiacum):
    The cardia is an area of 1-2 cm where the esophagus opens into the stomach. Here is the sharp transition from the esophageal mucosa to the gastric mucosa, which can usually be well recognized with an endoscope.
  • Fundus gastricus (stomach fundus):
    Above the stomach entrance, the fundus arches upwards, also called the "stomach dome" or Fornix gastricus. The fundus is usually filled with air that is involuntarily swallowed during eating. In an upright standing person, the fundus forms the highest point of the stomach, so that in an X-ray image the collected air can be recognized as a "stomach bubble." Opposite the stomach entrance, the fundus is demarcated by a sharp fold (Incisura cardialis).
  • Corpus gastricum (stomach body):
    The main part of the stomach is formed by the stomach body. Here lie deep longitudinal folds of the mucosa (Plicae gastricae), which extend from the stomach entrance to the pylorus and are also referred to as the "stomach street."
  • Pylorus (Pars pylorica, stomach gatekeeper):
    This section begins with the expanded Antrum pyloricum, followed by the gatekeeper canal (Canalis pyloricus) and ends with the actual stomach gatekeeper (Pylorus). Here lies the stomach sphincter muscle (M. sphincter pylori), which is formed by a strong circular muscle layer and closes the lower stomach mouth (Ostium pyloricum). The pylorus closes the stomach exit and periodically allows some food pulp (chyme) to pass into the subsequent duodenum.
• The stomach is located intraperitoneally and thus shows a covering of serosa, only the dorsal cardia is free of serosa. The embryonic mesogastria move from their former sagittal position to a frontal one through the rotation of the stomach: The lesser omentum extends from the lesser curvature to the liver hilum, the greater omentum spreads from the greater curvature to the transverse colon, the spleen, and the diaphragm.
• The stomach is stabilized and fixed in the abdominal cavity by ligaments that extend, among other things, to the liver and spleen. It forms the greater curvature (greater stomach curvature/ Curvatura major) with its convex side and the lesser curvature (lesser stomach curvature/ Curvatura minor) with its concave side. Its anterior wall is referred to as Paries anterior, its posterior wall as Paries posterior. The greater omentum extends from the greater curvature. The lesser omentum stretches between the left liver lobe and the lesser curvature.

Gastric Wall
Under the microscope, the gastric wall shows a characteristic layering from inside to outside:

• The Tunica mucosa is the mucosal layer lining the stomach from the inside. The gastric mucosa is divided into three sublayers: The Lamina epithelialis mucosae produces a viscous neutral mucus that protects the gastric mucosa from mechanical, thermal, and enzymatic damage. Below it follows the Lamina propria mucosae, a shifting layer into which the gastric glands (Glandulae gastricae) are embedded. Finally, there is a narrow Lamina muscularis mucosae, a thin initial muscle layer that can alter the relief of the mucosa.
• The Tela submucosa follows the gastric mucosa from the inside out. It represents a loose shifting layer consisting of connective tissue. In the Tela submucosa runs a dense network of blood and lymph vessels, as well as a nerve fiber network, the Plexus submucosus (Meissner's plexus), which controls gastric secretion. This plexus operates independently of the central nervous system (CNS) and is influenced by the autonomic nervous system.
• Next is a strong Tunica muscularis, divided into three sublayers with fibers running in different directions: an inner layer of small obliquely running muscle fibers (Fibrae obliquae), then a circular muscle layer (Stratum circulare), and an outer longitudinal muscle layer (Stratum longitudinale). This musculature ensures the peristalsis of the stomach, responsible for the constant mixing of the chyme with gastric juice. Between the circular and longitudinal muscle layers runs a nerve fiber network, the Plexus myentericus (Auerbach's plexus), which controls the function of the musculature. Like the Plexus submucosus, this plexus operates largely autonomously but is influenced by the autonomic nervous system.
• Another connective tissue shifting layer follows (Tela subserosa).
• The final layer is the Tunica serosa. The serosa is also divided into several layers. Following the Tela subserosa is the Lamina propria serosae. In this layer run the blood and lymph vessels as well as nerves. Additionally, cells of the immune defense, known as milk spots (Macula lactea), are found in the Lamina propria. The Lamina epithelialis serosae is directed towards the body cavity and consists of a single-layered squamous epithelium, the serosa epithelium. This layer is shiny, transparent, and ensures good mobility of the stomach relative to adjacent organs through a thin film of fluid.

Gastric Glands
The gastric glands (Glandulae gastricae) are located in the Lamina propria mucosae and can be found in the fundus and corpus of the stomach. Up to 100 glands are located on 1mm² of the mucosal surface. Various cells are located in the wall of the glandular tube:

• Mucous cells: They produce the same neutral mucus as the epithelial cells.
• Neck cells: These cells are located quite superficially in the gland and secrete alkaline mucus, meaning the pH is high due to the bicarbonate ions (HCO₃- ions) contained within. This property is important to control and, if necessary, regulate the pH of the stomach. The mucus coats the gastric mucosa, thus protecting it from self-digestion by the aggressive hydrochloric acid (HCl) and enzymes as self-digesting proteins. This cell type is found predominantly in the cardia and fundus of the stomach.
• Chief cells: These cells produce the inactive precursor enzyme pepsinogen, which is converted into the active enzyme pepsin by hydrochloric acid (HCl) and is responsible for the digestion of dietary proteins. Since the enzyme only comes into contact with hydrochloric acid at the surface of the gland, self-digestion of the glands by the enzyme is prevented. This cell form is mainly located in the corpus of the stomach.
• Parietal cells: These cells, found predominantly in the gastric corpus, produce abundant hydrogen ions (H+ ions), necessary for the formation of hydrochloric acid (HCl). Hydrochloric acid has a very low pH of 0.9-1.5. Additionally, parietal cells produce the so-called intrinsic factor. This substance forms a complex with vitamin B12 from food in the intestine, which can then pass through the intestinal wall. This vitamin is of particular importance in erythropoiesis (removal of the stomach can therefore lead to anemia).
• G cells: These cells, preferably located in the antrum of the stomach, produce gastrin to increase HCl production in the parietal cells.

The stomach serves as a reservoir for ingested food. Its function is to store and mix the food. In the stomach, acidic gastric juice (mucus and HCl) and enzymes are produced, which partially digest some components of the food. Subsequently, the chyme is gradually passed through the pylorus into the duodenum.

It can store food for hours, thus allowing us to meet our daily nutritional needs with a few larger meals.

The arterial supply of the stomach is provided by several blood vessels, all originating from the unpaired celiac trunk. These vessels run along the gastric curvatures as vascular arcades to supply the organ and form numerous anastomoses among themselves:

• Right gastric artery from the proper hepatic artery to the lower part of the lesser curvature,
• Left gastric artery to the upper part of the lesser curvature,
• Short gastric arteries from the splenic artery to the fundus,
• Right gastroepiploic (omental) artery from the gastroduodenal artery to the lower (right) part of the greater curvature,
• Left gastroepiploic (omental) artery from the splenic artery to the left side of the greater curvature,
• Posterior gastric artery from the splenic artery to the posterior wall.

Thus, the stomach is supplied by two vascular arcades between the left and right gastric arteries at the lesser curvature, and the left and right gastroepiploic arteries at the greater curvature.

Parallel to the arterial supply, the four major veins of the stomach run along the two curvatures. Collecting veins (left and right gastric veins directly into the portal vein, left gastroepiploic vein and short gastric veins to the splenic vein, and right gastroepiploic vein to the superior mesenteric vein) are formed from them, eventually all draining into the portal vein.

The nervous supply of the stomach is predominantly under the control of the autonomic nervous system. Additionally, there are sensory fibers: The sympathetic innervates the pyloric musculature, while the parasympathetic (vagus nerve X) innervates the rest of the gastric musculature and the glands of the stomach. The vagus nerve runs parallel to the esophagus on the right and left, passes through the diaphragm via the esophageal hiatus, reaching the anterior surface of the stomach on the left side (anterior vagal trunk), and the posterior surface on the right side (posterior vagal trunk). Sensory fibers from the stomach, on the other hand, run afferently via the greater splanchnic nerve to the thoracic spinal ganglia.

The draining lymphatic vessels of the stomach run parallel to the arterio-venous supply of the organ:

• The lymph from the lesser curvature drains parallel to the left/right gastric arteries into the left/right gastric lymph nodes,
• From the gastric fundus, the lymph flows parallel to the splenic artery into the splenic lymph nodes,
• The lymph from the greater curvature drains parallel to the attachment of the greater omentum to the right/left gastro-omental lymph nodes,
• From the pyloric region, the lymph drains into the pyloric lymph nodes.

From the aforementioned regional lymph nodes, the lymph subsequently flows into the celiac lymph nodes, the upper mesenteric lymph nodes, and the thoracic duct.
Another pathway for lymph drainage is represented by the pancreatic lymph nodes, allowing gastric tumors to potentially metastasize into the pancreas. A peculiarity of gastric carcinoma is the recurrent presence of a noticeable lymph node in the left lateral neck region (Virchow's node), indicating advanced metastasis.

For surgical reasons, the lymph node stations are divided into 3 compartments:

• Compartment I (LN Group 1-6): all LNs directly at the stomach: paracardial (Group 1+2), at the lesser and greater curvature (Group 3+4), supra- and infrapyloric (Group 5+6).
• Compartment II (LN Group 7-11/12): LNs along the major vessels: left gastric artery (Group 7), common hepatic artery (Group 8), celiac trunk (Group 9), splenic hilum (Group 10), splenic artery (Group 11), in distal carcinoma: LNs at the hepatoduodenal ligament (Group 12),
• Compartment III (LN Group 12/13-16): Lymph nodes behind the pancreatic head (Group 13), at the mesenteric root and mesentery (Group 14+15), and along the abdominal aorta (Group 16), in proximal carcinoma: LNs at the hepatoduodenal ligament (Group 12),

Note:

• Lymph node station 12: Hepatoduodenal ligament (including 12a – along the hepatic artery, 12b – along the common bile duct, and 12p – posterior).
• According to the Japanese Gastric Cancer Association (JGCA) classification, which serves as an international reference, the D2 lymphadenectomy includes:
• distal gastric carcinomas (e.g., antral or pylorus-near locations) also station 12a.
• proximal gastric carcinomas (cardia/fundus) usually do not include station 12 – here it is not part of the D2 dissection.

Japanese Gastric Cancer Association (JGCA). Japanese gastric cancer treatment guidelines 2021 (6th edition). Gastric Cancer. 2023.