STOMACH

Anatomic Relationships and Gross Morphology

• The stomach is readily recognizable as the asymmetrical, pear-shaped, most proximal abdominal organ of the digestive tract

• The part of the stomach attached to the esophagus is called the cardia• Just proximal to the cardia at the gastroesophageal (GE) junction is the anatomically

indistinct but physiologically demonstrable lower esophageal sphincter• At the distal end, the pyloric sphincter connects the stomach to the proximal duodenum• The stomach is relatively fixed at these points, but the large midportion is quite mobile• The superior-most part of the stomach is the distensible floppy fundus, bounded superiorly

by the diaphragm and laterally by the spleen• The body of the stomach contains most of the parietal (oxyntic) cells, some of which are also

present in the cardia and fundus• The body is bounded on the right by the relatively straight lesser curvature and on the left by

the more curved greater curvature• At the angularis incisura, the lesser curvature turns rather abruptly to the right, marking the

anatomic beginning of the antrum, which comprises the distal 25 to 30% of the stomach

Arterial and Venous Blood Supply

• The stomach is the most richly vascularized portion of the alimentary tube• The large majority of the gastric blood supply is from the celiac axis via four named arteries • The left and right gastric arteries form an anastomotic arcade along the lesser curvature, and

the right and left gastroepiploic arteries form an arcade along the greater gastric curvature• The consistently largest artery to the stomach is the left gastric artery, which usually arises

directly from the celiac trunk and divides into an ascending and descending branch along the lesser gastric curvature

• Approximately 15% of the time, the left gastric artery supplies an aberrant vessel that travels in the gastrohepatic ligament (lesser omentum) to the left side of the liver

• The second largest artery to the stomach is the right gastroepiploic artery, which arises consistently from the gastroduodenal artery behind the first portion of the duodenum

• The left gastroepiploic artery arises from the splenic artery, and, together with the right gastroepiploic artery, forms the rich gastroepiploic arcade along the greater curvature

• The right gastric artery usually arises from the hepatic artery near the pylorus and hepatoduodenal ligament, and runs proximally along the distal stomach

• In the fundus along the proximal greater curvature, the short gastric arteries and veins arise from the splenic circulation.

• The richness of the gastric blood supply and the extensiveness of the anastomotic connections have some important clinical implications

• Erosion of a peptic ulcer or gastric cancer into a large perigastric vessel may cause life-threatening hemorrhage

• Because of the rich venous interconnections in the stomach, a distal splenorenal shunt, which connects the distal end of the divided splenic vein to the side of the left renal vein, can effectively decompress esophagogastric varices in patients with portal hypertension

• At least two of the four named gastric arteries may be occluded or ligated which is done routinely when the stomach is mobilized and pedicled on the right gastric and right gastroepiploic vessels to reach into the neck as an esophageal replacement

Lymphatic Drainage

Innervation

• Both the extrinsic and intrinsic innervation of the stomach play an important role in gastric secretory andmotor function

• The vagus nerves provide the extrinsic parasympathetic innervation to the stomach, and acetylcholine is the most important neurotransmitter

Physiology• The stomach stores food and facilitates digestion through a variety of secretory and motor

functions• Important secretory functions include the production of acid, pepsin, intrinsic factor, mucus,

and a variety of GI hormones• Important motor functions include food storage (receptive relaxation and accommodation),

grinding and mixing, controlled emptying of ingested food, and periodic interprandial "housekeeping."

Acid Secretion• Hydrochloric acid in the stomach hastens both the physical and (with pepsin) the biochemical

breakdown of ingested food• In an acidic environment, pepsin and acid facilitate proteolysis. Gastric acid also inhibits the

proliferation of ingested pathogens, which protects against both infectious gastroenteritides and intestinal bacterial overgrowth

• Long-term acid suppression with proton pump inhibitors (PPIs) has been associated with an increased risk of community acquired Clostridium difficile colitis and other gastroenteritides, presumably because of the absence of this protective germicidal barrier

Gastric Mucosal Barrier

Gastric Hormones Gastrin• Gastrin is produced by antral G cells and is the major hormonal stimulant of acid secretion during the gastric

phase. Gastrin is also trophic to GI epithelial and enterochromaffin cells Somatostatin• Somatostatin is produced by D cells located throughout the gastric mucosa. The predominant form in humans

is somatostatin 14, though somatostatin 28 is present as well• The major stimulus for somatostatin release is antral acidification; acetylcholine from vagal nerve fibers

inhibits its release• Somatostatin inhibits acid secretion from parietal cells and gastrin release from G cells• It also decreases histamine release from ECL cells Gastrin-Releasing Peptide• GRP is the mammalian equivalent of bombesin• In the antrum, GRP stimulates both gastrin and somatostatin release by binding to receptors on the G and D

cells Leptin• Leptin is a protein primarily synthesized in adipocytes• It is also made by chief cells in the stomach, the main source of leptin in the GI tract• Leptin works at least in part via vagally mediated pathways to decrease food intake in animals Ghrelin• Ghrelin is a potent secretagogue of pituitary growth hormone (but not adrenocorticotropic hormone, follicle-

stimulating hormone, luteinizing hormone, prolactin, or thyroid-stimulating hormone)• Ghrelin appears to be an orexigenic regulator of appetite (i.e., when ghrelin is elevated, appetite is stimulated,

and when it is suppressed, appetite is suppressed)• Resection of the primary source of this hormone (i.e., the stomach) may partly account for the anorexia and

weight loss seen in some patients following gastrectomy

Gastric Emptying

Liquid Emptying• The gastric emptying of water or isotonic saline follows first-order kinetics, with a half

emptying time around 12 minutes• Thus, if one drinks 200 mL of water, about 100 mL enters the duodenum by 12 minutes,

whereas if one drinks 400 mL of water, about 200 mL enters the duodenum by 12 minutes• This emptying pattern of liquids is modified considerably as the caloric density, osmolarity,

and nutrient composition of the liquid changes Solid Emptying• Normally, the half-time of solid gastric emptying is <2 hours

Diagnosis of Gastric Disease

Signs and Symptoms• The most common symptoms of gastric disease are pain, weight loss, early satiety, and

anorexia. Nausea, vomiting, bloating, and anemia also are frequent complaints• Several of these symptoms (pain, bloating, nausea, and early satiety) are often described by

physicians as dyspepsia, synonymous with the common nonmedical term indigestion• Common causes of dyspepsia include gastroesophageal reflux disease (GERD) and disorders

of the stomach, gallbladder, and pancreas Diagnostic Tests• Esophagogastroduodenoscopy

Radiologic Tests• Plain abdominal x-rays may be helpful in the diagnosis of gastric perforation

(pneumoperitoneum) or delayed gastric emptying (large air-fluid level)• Double-contrast upper GI series may be better than EGD at elucidating the following:

diverticula, fistula, tortuosity or stricture location, and size of hiatal hernia

Computed Tomographic Scanning and Magnetic Resonance Imaging Endoscopic Ultrasound Gastric Secretory Analysis• This test may be useful in the evaluation of patients with hypergastrinemia, including the

Zollinger-Ellison syndrome (ZES), patients with refractory ulcer or GERD, and patients with recurrent ulcer after operation

Scintigraphy• Nuclear medicine tests can be helpful in the evaluation of gastric emptying and duodenogastric

reflux• The standard scintigraphic evaluation of gastric emptying involves the ingestion of a test meal

with one or two isotopes, and scanning the patient under a gamma camera Tests for Helicobacter Pylori • It is present in most patients with peptic ulcer disease (PUD), and has been associated with

gastric lymphoma and adenocarcinoma• A positive serologic test is presumptive evidence of active infection if the patient has never

been treated for H. pylori. Histologic examination of an antral mucosal biopsy using special stains is the gold standard test

Antroduodenal Motility Testing and Electrogastrography• Antroduodenal motility testing and electrogastrography (EGG) are performed in specialized

centers and may be useful in the evaluation of the patient with anomalous epigastric symptoms

Peptic Ulcer Disease• Peptic ulcers are focal defects in the gastric or duodenal mucosa that extend into the

submucosa or deeper• They may be acute or chronic and, ultimately, are caused by an imbalance between mucosal

defenses and acid/peptic injury • It is now recognized that the large majority of duodenal and gastric ulcers are caused by H.

pylori infection and/or NSAID use

FIVE TYPES OF GASTRIC ULCER

1. Johnson type I gastric ulcer, most common, is typically located near the angularis incisura on the lesser curvature, close to the border between the antrum and the body of the stomach

- Patients with Type I gastric ulcer usually have normal or decreased acid secretion2. Johnson Type II gastric ulcer is associated with active or quiescent duodenal ulcer disease3. Johnson Type III gastric ulcer is prepyloric ulcer disease - Both type II and type III gastric ulcers are associated with normal or increased gastric acid secretion4. Johnson Type IV gastric ulcers occur near the GE junction, and acid secretion is normal or below normal5. Johnson Type V gastric ulcers are medication induced and may occur anywhere in the stomach.

Medical Treatment of Peptic Ulcer Disease

Surgical Treatment of Peptic Ulcer Disease• The indications for surgery in PUD are bleeding, perforation, obstruction, and intractability or

nonhealing• Gastric cancer must always be considered in patients with gastric ulcer or gastric outlet

obstruction

HSV, also called parietal cell vagotomy or proximal gastric vagotomy, is safe (mortality risk <0.5%) and causes minimal side effects. The operation severs the vagal nerve supply to the proximal two thirds of the stomach, where essentially all the parietal cells are located, and preserves the vagal innervation to the antrum and pylorus, and the remaining abdominal viscera

Truncal vagotomy and pyloroplasty, and truncal vagotomy and gastrojejunostomy are the paradigmatic vagotomy and drainage procedures

• HSV may be substituted for truncal vagotomy• The advantage of V+D is that it can be performed safely and quickly by the experienced

surgeon• The main disadvantages are the side effect profile (10% of patients have significant dumping

and/or diarrhea).

Gastrojejunostomy is a good choice in patients with gastric outlet obstruction or a severely diseased proximal duodenum

• The anastomosis is done between the proximal jejunum and the most dependent portion of the greater gastric curvature, in either an antecolic or retrocolic fashion

• Marginal ulceration is a potential complication

Pyloroplasty is useful in patients who require a pyloroduodenotomy to deal with the ulcer complication (e.g., posterior bleeding duodenal ulcer), in those with limited or focal scarring in the pyloric region, or when gastrojejunostomy is technically difficult

• The most commonly performed pyloroplasty is the Heineke-Mikulicz type

Vagotomy and antrectomy• The advantages of vagotomy and antrectomy (V+A) are the extremely low ulcer recurrence

rate and the applicability of the operation to many patients with complicated PUD (e.g., bleeding duodenal and gastric ulcer, obstructing peptic ulcer, nonhealing gastric ulcer, and recurrent ulcer

• The disadvantage of V+A is the higher operative mortality risk (when compared with HSV or V+D), and its irreversibility

• Following antrectomy, GI continuity may be re-established with a Billroth I gastroduodenostomy or a Billroth II loop gastrojejunostomy

• Choice of Operation for Peptic Ulcer

APPENDIX • Anatomy and Function• The appendix first becomes visible in the eighth week of embryologic development as a

protuberance off the terminal portion of the cecum• The relationship of the base of the appendix to the cecum remains constant, whereas the tip

can be found in a retrocecal, pelvic, subcecal, preileal, or right pericolic position• The three taeniae coli converge at the junction of the cecum with the appendix and can be a

useful landmark to identify the appendix• The appendix can vary in length from <1 cm to >30 cm; most appendices are 6 to 9 cm long• It is now well recognized that the appendix is an immunologic organ that actively participates

in the secretion of immunoglobulins, particularly immunoglobulin A

Acute Appendicitis

Incidence• The lifetime rate of appendectomy is 12% for men and 25% for women, with approximately 7% of all people

undergoing appendectomy for acute appendicitis during their lifetime• Appendicitis is most frequently seen in patients in their second through fourth decades of life, with a mean age of

31.3 years and a median age of 22 years• There is a slight male:female predominance (1.2 to 1.3:1) Etiology and Pathogenesis• Obstruction of the lumen is the dominant etiologic factor in acute appendicitis• Fecaliths are the most common cause of appendiceal obstruction• The frequency of obstruction rises with the severity of the inflammatory process• Fecaliths are found in 40% of cases of simple acute appendicitis, in 65% of cases of gangrenous appendicitis

without rupture, and in nearly 90% of cases of gangrenous appendicitis with rupture• The proximal obstruction of the appendiceal lumen produces a closed-loop obstruction, and continuing normal

secretion by the appendiceal mucosa rapidly produces distention• Distention of the appendix stimulates the nerve endings of visceral afferent stretch fibers, producing vague, dull,

diffuse pain in the midabdomen or lower epigastrium• Distention of this magnitude usually causes reflex nausea and vomiting, and the diffuse visceral pain becomes

more severeAs pressure in the organ increases, venous pressure is exceeded• Capillaries and venules are occluded, but arteriolar inflow continues, resulting in engorgement and vascular

congestion.• The inflammatory process soon involves the serosa of the appendix and in turn parietal peritoneum in the region,

which produces the characteristic shift in pain to the right lower quadrant

Bacteriology

Clinical Manifestations Symptoms• Abdominal pain is the prime symptom of acute appendicitis• Anorexia nearly always accompanies appendicitis• Vomiting Signs• The Rovsing sign—pain in the right lower quadrant when palpatory pressure is exerted in the

left lower quadrant—also indicates the site of peritoneal irritation• The psoas sign indicates an irritative focus in proximity to that muscle• The test is performed by having the patient lie on the left side as the examiner slowly

extends the patient's right thigh, thus stretching the iliopsoas muscle• The test result is positive if extension produces pain• positive obturator sign of hypogastric pain on stretching the obturator internus indicates

irritation in the pelvis• The test is performed by passive internal rotation of the flexed right thigh with the patient

supine.

Laboratory Findings• Mild leukocytosis, ranging from 10,000 to 18,000 cells/mm3, usually is present in patients

with acute, uncomplicated appendicitis and often is accompanied by a moderate polymorphonuclear predominance

• Patients with scores of 9 or 10 are almost certain to have appendicitis• Patients with scores of 7 or 8 have a high likelihood of appendicitis• Patients with scores of 5 or 6 are compatible with, but not diagnostic of, appendicitis

• Acute Appendicitis during Pregnancy

Treatment

• Open Appendectomy• Laparoscopic Appendectomy