Gastroduodenal Diseases

Published on 16/04/2015 by admin

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Last modified 22/04/2025

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10 Gastroduodenal Diseases

Anatomy of the Stomach and Duodenum

image

Stomach in Situ

Parts of the Stomach

• Cardia(c) portion joins the abdominal esophagus.
• Fundus: uppermost curvature to the left of the cardia
• Greater curvature, lesser curvature, inferior and superior borders (respectively) of the voluminous body of the stomach
• Pyloric region

image Angular incisure (notch): distal end of the lesser curvature and start of the antrum
image Antrum: entryway to the pyloric canal, very muscular and peristaltic
image Pylorus: thickened circular muscle layer

• Rugae: folds in the mucosal surface of the relaxed stomach

Functional Anatomy and Motility

• Receptive relaxation and accommodation occur in the proximal 1/3 of the stomach, with swallowing and entry of food.
• True peristalsis occurs in the distal 2/3, with waves of contraction driving the contents back and forth between the body and antrum (trituration).
• Small amounts of triturated stomach contents pass through the pylorus with successive peristaltic waves.
• Myoelectric pacemaker for peristalsis is located high on greater curvature.

Gastric Microscopic Anatomy

Mucosa

• Epithelium

image Mucus-secreting cardia glands
image Oxyntic glands in the fundus and body

image Chief cells secrete pepsinogen.
image Parietal cells secrete H+ and intrinsic factor.

image Antrum and pylorus glands

image Both secrete HCO3 and mucus.
image G cells release gastrin.
image D cells secrete somatostatin, inhibiting release of gastrin and H+.

• Lamina propria: supportive, loose connective tissue deep to epithelium
• Muscularis mucosae: layer of smooth muscle at the boundary between mucosa and submucosa

Submucosa

• Strongest layer
• Connective tissue
• Meissner’s plexus (neuronal network)

Muscularis (Smooth Muscle)

• Auerbach’s plexus: myenteric neurons
• Inner circular muscle
• Outer longitudinal layer

Serosa

• Peritoneum
image

Duodenum in Situ

Anatomy of the Duodenum

• Most fixed portion of small bowel, surrounds head of the pancreas
• Superior (first) part

image Length ~5 cm, lies anterolateral to L1 body
image Overlain by liver and gallbladder
image Ampulla (cap)—first 2 cm—bears a mesentery, the hepatoduodenal ligament, part of the lesser omentum.
image Distal 3 cm retroperitoneal

• Descending (second) part

image Length 7-10 cm, lies along right sides of L1-L3 bodies
image Receives the outflow from bile and pancreatic ducts via the hepatopancreatic ampulla (Vater) through the greater duodenal papilla (Vater)
image Receives outflow from the accessory pancreatic duct through the lesser duodenal papilla

• Horizontal (third) part

image Length 6-8 cm, crosses the L3 body
image Lies posterior to the main trunk of the superior mesenteric artery

• Ascending (fourth) part

image Length ~5 cm, left of L3 to the upper border of L2

• Ligament of Treitz (suspensory ligament of the duodenum): marks duodenal-jejunal junction
• Plicae circulares: internal circular folds of the wall due to circular muscle, increase surface area per length

Duodenal Microscopic Anatomy

Mucosa

• Epithelium: enterocytes (absorptive), goblet cells, Paneth cells, enterochromaffin cells,
• Lamina propria: contains Peyer’s patches (lymphoid aggregations with B cells in germinal centers and T cell in interfollicular zones)
• Muscularis mucosa
• Water and nutrients absorbed across the mucosa

Submucosa

• Strongest layer
• Connective tissue
• Meissner’s plexus (parasympathetic ganglion cells and neuronal network)

Muscularis

• Inner circular muscle
• Outer longitudinal layer
• Auerbach’s plexus: myenteric neurons and parasympathetic ganglion cells

Serosa

• Peritoneum

Inner Surface

• Mucosal surface area specializations: microvilli, villi, plica circulares (valvulae conniventes)
• Total absorptive surface: 200-550 cm2

Gastroduodenal Embryology

• Stomach has two mesenteries during development.

image Dorsal mesogastrium, attached to the greater curvature, grows very redundant, overlaps, and becomes the greater omentum.
image Ventral mesogastrium, part of the original septum transversum, becomes the following.

image Lesser omentum (hepatogastric ligament)
image Peritoneal serosa of liver, gallbladder
image Falciform ligament, with embedded round ligament of the liver

• Greater curvature is initially dorsal, then the stomach rotates along its longitudinal axis until the dorsal curve lies to the left.
• Stomach also rotates around an axis through the gastroesophageal junction, until the greater curvature lies in its final left inferolateral position.
• Duodenum also rotates with the stomach, as well as around an anteroposterior axis, so that it surrounds the pancreas.

image First two parts of the duodenum (down to the bile duct), the terminal portion of the foregut: supplied by the celiac axis
image Lower second through fourth parts of the duodenum, the initial segment of the midgut: supplied by the proximal superior mesenteric artery

image

Nerves of the Stomach and Duodenum

Innervation

• Parasympathetic

image Left vagal trunk lies anterior as it crosses the gastroesophageal junction and runs anteriorly along the lesser curvature toward the duodenum.
image Right vagal trunk lies posterior as it crosses the gastroesophageal junction and runs posteriorly along the lesser curvature toward the duodenum.
image Ganglion cells are located in myenteric (Auerbach’s) and submucosal (Meissner’s) plexuses in stomach and duodenum.

• Sympathetic

image Preganglionic fibers from T8-T10 lateral column distributed via splanchnic nerves.
image Postganglionic fibers are distributed from ganglion cells in celiac and superior mesenteric ganglia, traveling along respective arterial branches.

• Sensory fibers (general visceral afferent)

image Vagal afferents, including stretch, chemo-, and “satiety” receptors
image Segmental afferents travel back parallel to sympathetics, through the celiac and superior mesenteric plexuses and the splanchnic nerves to thoracic spinal nerves, dorsal root ganglia, and spinal segments.

Arteries, Veins, and Lymphatics

image

Arteries of the Stomach

image

Arteries of the (Pancreas) Duodenum (Spleen)

Arteries

Celiac Trunk (Axis) Branches (Highly Variable)

• Left gastric artery: typically the largest gastric branch, to left side of lesser curvature
• Splenic artery branches

image Posterior gastric artery: to posterior body and fundus
image Left gastro-omental (gastroepiploic) artery

image To left side of greater curvature
image Anastomoses with right gastroomental

image Short gastric arteries: to fundus region

• Common hepatic artery branches

image Right gastric artery: to right side of lesser curvature (may be off left or right hepatic)
image Proper hepatic artery
image Gastroduodenal artery

image Right gastro-omental (gastroepiploic) artery: to right side of greater curvature
image Superior pancreaticoduodenal: to first and upper second part of duodenum

Superior Mesenteric Artery

• Inferior pancreaticoduodenal artery

image Anterior and posterior branches anastomose with superior pancreaticoduodenal branches.
image Supply duodenum distal to bile duct

image

Veins of the Stomach, Duodenum, Pancreas

Venous Drainage

• Gastric and duodenal veins parallel arterial branches.
• Portal vein tributaries

image Right gastric (lesser curvature)
image Left gastric (coronary; prominent in varices)
image Superior mesenteric vein (right portal)

image Pancreaticoduodenal veins
image Right gastro-omental (gastroepiploic) vein

image Splenic vein (left portal)

image Short gastric vein
image Left gastro-omental (gastroepiploic)

image

Lymph Vessels and Nodes of Stomach

Lymphatic Drainage

• Parallels the venous drainage (see figure)

Clinical Correlates

Upper Gastrointestinal Bleeding

• Differential diagnosis includes gastritis, ulcer, and cancer.

Gastritis

• Stress gastritis occurs 3-10 days after event; lesions first appear in fundus.
• Chronic

image Type A: in fundus, associated with autoimmune disease and pernicious anemia
image Type B: in antrum, associated with Helicobacter pylori

image

Peptic Ulcer Disease

Peptic Ulcer

image 70%-80% in lesser curvature of the stomach
image Type I: in lesser curvature of the stomach
image Type II: in lesser curvature of the stomach and in the duodenum
image Type III: prepyloric ulcer
image Type IV: in lesser curvature in cardiac region
image Type V: ulcer associated with NSAIDs
• Most (type I and IV) are due to loss of mucosal defensive function with normal acid secretion.
• Duodenal ulcers are most common in the superior part, in the posterior superior wall, and within ~3 cm of the pylorus.
• Duodenal ulcer usually results from mucosal defense being overcome (decreased secretion of mucus and bicarbonate).
• Risk factors: male gender, tobacco, ethanol consumption, NSAIDs, H. pylori infection, uremia, stress, steroids, chemotherapy
• Hemorrhage associated with higher mortality
image

Hiatal Hernias

Hiatal Hernia

• Type I

image Dilation of hiatus with sliding hernia
image Most common
image May be associated with GERD, although most type I patients do not reflux

• Type II

image Paraesophageal, hole in diaphragm next to the esophagus
image Symptoms: dysphagia, chest pain, early satiety

• Type III: combined
• Type IV: entire stomach in thorax, other organs may be included (e.g., spleen or colon)
image

Gastric Carcinoma

Cancer

• Adenocarcinoma of the small bowel

image Most common small bowel malignancy
image Rare, but occurs more commonly in duodenum
image Risk factors: familial adenomatous polyposis, Gardner’s syndrome, polyps, adenomas, von Recklinghausen’s syndrome

• Adenocarcinoma of the stomach

image More than 20,000 new U.S. cases per year (rate declining)
image Dietary risk factors might include spicy and smoked food.
image Associated with atrophic gastritis with hypoacidity
image Chronic H. pylori infection is a major risk factor.
image 7%-10% of ulcers associated with an adenocarcinoma
image Hyperplastic gastric polyps (most common, 80%) have little risk.
image Adenomatous gastric polyps have a 15% risk of developing malignancy.
• Polyps of either kind may be asymptomatic or associated with vague abdominal discomfort.

• Lymphoma

image Can occur as a manifestation of diffuse lymphoma (more common)
image Isolated gastric disease
image 50% of all lymphomas occur in the stomach
image Primary gastric lymphoma can be treated by partial gastrectomy.

• Gastrointestinal stromal tumor (GIST): 3% of gastric malignancies

Billroth Procedures

• Billroth I: antrectomy with gastroduodenal anastomosis
• Billroth II: antrectomy with gastrojejunal anastomosis
• Increased marginal ulceration with diarrhea with Billroth procedures, compared with Roux-en-Y gastrojejunostomy

Zollinger-Ellison Syndrome

• Tumors may be multiple and metastatic.
• Pancreatic tumors may be surgically enucleated from the gastric wall.
• Enucleation and resection are considered necessary for effective palliation and reduced need for drug treatment.
• Total gastrectomy is indicated with nonresectable tumors for best long-term quality of life.
• See figure on page 210 for more information.

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