Gastric Secretion

Introduction

Gastric secretion supports digestion through acid production, intrinsic factor release, and antimicrobial action, alongside the stomach’s roles in storage and motility. It is influenced by diet, stress, and neural factors, with H. pylori and gastrin levels holding clinical significance.

• The stomach is a key organ of the gastrointestinal system. It primarily stores ingested food temporarily. It regulates the controlled emptying of contents into the duodenum.
• Mechanical mixing and grinding convert food into chyme.
• Chyme formation facilitates efficient digestion and absorption in the small intestine.

Functions And Functional Anatomy Of Stomach

Functions of Stomach

• The stomach acts as a temporary reservoir, allowing ingestion of large meals and gradual processing of food. It accommodates food through receptive relaxation without a marked rise in intragastric pressure.
• Mechanical activity includes rhythmic contractions that grind and mix ingested material with gastric secretions. This process reduces particle size and produces a semi-fluid mixture called chyme.
• The stomach ensures controlled gastric emptying, delivering chyme to the duodenum at a regulated rate. This regulation prevents overload of the small intestine and supports efficient digestion and absorption.
• Gastric glands secrete hydrochloric acid, creating a highly acidic environment with a pH of approximately 1.5 to 3.5. This acidic medium facilitates protein digestion and maintains optimal conditions for enzyme activity.
• Hydrochloric acid converts dietary iron from the ferric to the ferrous form, which is essential for intestinal absorption.
• Reduced acid secretion can impair iron absorption and contribute to anemia.
• The acidic environment provides a protective role by destroying ingested microorganisms. This function reduces the risk of infections entering through the gastrointestinal tract.
• The stomach secretes pepsinogen, which is activated by acid into pepsin, a proteolytic enzyme.
• Pepsin initiates protein digestion by breaking peptide bonds to form smaller peptides. Its activity is optimal in strongly acidic conditions, ensuring efficient enzymatic function.
• The gastric mucosa produces intrinsic factor, which is necessary for vitamin B12 absorption in the terminal ileum.
• Vitamin B12 binds with intrinsic factor to form a complex that is absorbed via receptor-mediated endocytosis.
• Deficiency of intrinsic factor leads to impaired absorption and results in megaloblastic anemia.
• The stomach also contributes minimally to absorption, particularly of water, alcohol, and lipid-soluble drugs.
• Although limited, this absorption can have physiological and clinical significance. ·  Overall, the stomach integrates storage, mechanical processing, secretion, protection, and regulated delivery of contents to optimize digestive efficiency.

Functional Anatomy

• The stomach is anatomically divided into cardia, fundus, body, and antrum.
• The esophagus opens into the stomach at the gastroesophageal junction, guarded by the lower esophageal sphincter, which prevents reflux.
• The cardia is the region adjacent to this junction and serves as the entry point for ingested food.
• The fundus forms the proximal dome-shaped portion and mainly participates in storage.
• The body or corpus constitutes the largest region and is the principal site for secretion and mixing.
• The antrum is the distal part that regulates grinding and controls emptying into the duodenum.
• The pylorus connects the stomach to the duodenum and contains the pyloric sphincter, which regulates gastric emptying.
• The storage capacity of the stomach varies with age, sex, and dietary habits.
• In adults, the average capacity is approximately 1.5 liters, with a range of 1 to 4 liters.
• The inner lining consists of a thick mucosal membrane arranged into folds called gastric rugae. These folds are prominent when the stomach is empty and flatten during distension.
• The rugae allow expansion without a significant rise in intragastric pressure.
• The mucosa is lined by simple columnar epithelial cells. These cells secrete mucus and alkaline substances that form a protective barrier. This barrier prevents damage from acid, enzymes, and mechanical stress.
• The surface of the mucosa contains numerous gastric pits, which are small invaginations.
• Gastric glands open into these pits and extend deep into the mucosa. These glands contain specialized cells responsible for secretion of acid, enzymes, and intrinsic factor.
• Overall, the structural organization of the stomach supports its roles in storage, secretion, protection, and controlled delivery of chyme.

Gastric Glands

• The gastric mucosa contains surface mucous cells in pits and deeper gastric glands within mucosal folds.
• Cardiac glands, near the lower esophageal sphincter, secrete mucus and bicarbonate to protect the mucosa.
• Oxyntic glands, located in the fundus and body, contain parietal cells that produce hydrochloric acid and intrinsic factor.
• Pyloric glands, in the antrum, include mucous cells and G cells that release gastrin.
• Gastrin regulates acid secretion and gastric motility.

Oxyntic Gland

• The oxyntic gland is a straight, tubular gland located mainly in the fundus and body of the stomach. It is divided into three regions: neck, body, and base, each containing distinct cell types.
• The neck region contains mucous cells, which secrete mucus and bicarbonate.
• These secretions form a protective barrier against acid and enzymatic injury.
• The body of the gland is rich in parietal cells, also called oxyntic cells.
• These cells secrete hydrochloric acid and intrinsic factor, essential for vitamin B12 absorption.
• The base of the gland contains chief cells, which release pepsinogen.
• Pepsinogen is converted into pepsin in an acidic environment and initiates protein digestion.
• The gland also contains enteroendocrine cells that regulate gastric function.
• Enterochromaffin-like cells release histamine, which stimulates acid secretion.
• Other endocrine cells produce somatostatin, vasoactive intestinal peptide, glucagon, and enkephalins.
• Gastrin-secreting cells are located mainly in the antral region, while somatostatin-secreting cells modulate secretion.

Structure of Oxyntic Cells

• Parietal cells have a specialized structure adapted for acid secretion. They possess an extensive tubulovesicular system and intracellular canaliculi.
• The apical surface faces the gland lumen, allowing secretion into the gastric cavity.
• In the resting state, tubulovesicles are abundant and microvilli are poorly developed.
• These vesicles contain the hydrogen-potassium adenosine triphosphatase pump, responsible for acid secretion.
• Upon stimulation, tubulovesicles fuse with the apical membrane. This fusion increases the surface area and forms prominent microvilli within canaliculi.
• The increased membrane area enhances pump activity and facilitates rapid acid secretion. This structural adaptation enables efficient and regulated production of gastric acid under physiological conditions.

Nerve Supply of Stomach

• The stomach receives autonomic innervation from parasympathetic and sympathetic divisions.
• The vagus nerve provides parasympathetic supply and enhances secretion and motility.
• Sympathetic activity reduces gastric secretion and inhibits motility.

Gastric Juice

Composition of Gastric Juice

• Daily gastric secretion ranges from 1 to 2.5 liters and is highly acidic, with a pH of 0.7 to 4. It consists of about 99.5 percent water and 0.5 percent dissolved solids.
• The inorganic components include chloride, phosphate, sulfate, and bicarbonate ions, along with hydrogen, sodium, potassium, calcium, and magnesium ions. These ions maintain acidity and electrolyte balance within the gastric lumen.
• The organic components include pepsinogen, intrinsic factor, mucin, gastric lipase, and antimicrobial substances.

Functions of Constituents

• Hydrochloric acid is present at a concentration of about 40 to 60 milliequivalents per liter and may rise to 150 milliequivalents per liter.
• Pepsinogen, secreted by chief cells, is converted into pepsin in an acidic environment.
• Pepsin initiates protein digestion and is most active at a pH between 2 and 4.
• Mucin, secreted by mucous cells, forms a protective gel layer over the gastric epithelium. This layer traps bicarbonate and prevents damage from acid and enzymes.
• Intrinsic factor, secreted by parietal cells, is essential for vitamin B12 absorption in the terminal ileum.
• Overall, gastric juice supports digestion, mucosal protection, and nutrient absorption through coordinated chemical activity.

Gastric Secretion

Mechanism of HCl Secretion

• Parietal cells, located in the fundus and body, are responsible for hydrochloric acid secretion.
• The apical membrane contains hydrogen-potassium adenosine triphosphatase pumps, which actively transport hydrogen ions into the gastric lumen. This transport occurs against a concentration gradient and requires energy from adenosine triphosphate hydrolysis.
• Hydrogen ions are generated from carbonic acid within the cell.
• Carbonic acid is formed by the reaction of carbon dioxide and water, catalyzed by carbonic anhydrase.
• Carbon dioxide is supplied from cellular metabolism and the bloodstream.
• Carbonic acid dissociates into hydrogen ions and bicarbonate ions.
• Hydrogen ions are secreted into the lumen, while bicarbonate ions are exchanged for chloride ions across the basolateral membrane.
• Chloride ions enter the cell and then diffuse into the gastric lumen.
• In the lumen, hydrogen and chloride ions combine to form hydrochloric acid.
• For each hydrogen ion secreted, one bicarbonate ion enters the bloodstream. This process increases blood pH after meals, producing the postprandial alkaline tide. As a result, urine may also become temporarily alkaline.
• Potassium ions entering the cell through the pump are recycled back into the lumen.
• Additional potassium ions are also secreted from the basolateral side. This recycling maintains adequate potassium levels for continuous pump activity.
• The coordinated function of ion transporters and enzymes ensures efficient and regulated acid secretion required for digestion.

Secretion of Other Constituents

Pepsinogen Secretion

• Pepsinogen is secreted by chief cells and stored in zymogen granules before release.
• Two forms exist: type one in fundus and body, and type two throughout the stomach. It is converted to pepsin by hydrochloric acid.
• Pepsin is a proteolytic enzyme that initiates protein digestion.
• Secretion of pepsinogen is stimulated by gastrin and histamine.

Mucus Secretion

• Mucus is secreted by mucous cells located mainly in the neck of gastric glands. It includes insoluble and soluble mucin, distributed across different gastric regions.
• Mucin forms a viscous protective barrier over the gastric epithelium. This layer traps bicarbonate and maintains an alkaline microenvironment. It protects the mucosa from acid and enzymatic injury.
• Mucus secretion increases with enhanced mucosal blood flow.

Intrinsic Factor Secretion

• Intrinsic factor is a glycoprotein secreted by parietal cells along with acid.
• Its secretion is stimulated by the same factors that increase acid production.
• It binds vitamin B12 and enables its absorption in the terminal ileum.
• These coordinated secretions ensure digestion, mucosal protection, and nutrient absorption.

Factors that Influence HCl Secretion

Factors that Stimulate Gastric Acid Secretion

• Gastric acid secretion is primarily regulated by acetylcholine, gastrin, and histamine. These mediators act on specific receptors on parietal cells and increase intracellular second messengers.
• This process enhances the activity of acid-secreting mechanisms.

Acetylcholine

• Acetylcholine is released from vagal nerve endings supplying the stomach.
• It binds to M3 receptors on parietal cells and increases intracellular calcium levels.
• It directly stimulates acid secretion and indirectly promotes release of histamine and gastrin.

Gastrin

• Gastrin is a major hormonal stimulator of acid secretion. It is produced by G cells located in the antral mucosa.
• Gastrin binds to receptors on parietal cells and raises intracellular calcium concentration.
• It also stimulates histamine release from enterochromaffin-like cells, which amplifies acid secretion.
• Gastrin release is enhanced by gastric distension and intake of protein-rich meals.
• Neural stimulation through vagal pathways also increases gastrin secretion via gastrin-releasing peptide.
• Circulating catecholamines can further augment gastrin release under certain conditions.

Table 39.1: Stimuli that alter gastric acid secretion.

Effect on Secretion	Category	Key Factors
Increase HCl	Luminal	Gastric distension; peptides from protein digestion
	Hormonal	Acetylcholine, gastrin, histamine
	Neural	Vagal stimulation (cholinergic and peptide-mediated)
	Circulatory	Epinephrine
Decrease HCl	Luminal	Highly acidic chyme
	Hormonal	Somatostatin
	Circulatory	Secretin, gastric inhibitory peptide, glucagon

Histamine

• Histamine strongly stimulates gastric acid secretion by acting on H2 receptors of parietal cells.
• It increases intracellular cyclic adenosine monophosphate, which activates protein kinase and enhances hydrogen-potassium adenosine triphosphatase activity.
• Histamine is released from enterochromaffin-like cells. Its release is promoted by acetylcholine and gastrin, making it a key mediator of acid secretion.
• H2 receptor antagonists reduce acid secretion and are used in peptic ulcer management.

Mechanical and Chemical Factors

• Gastric distension increases acid secretion by stimulating gastrin release.
• Peptides and amino acids from protein digestion further enhance gastrin secretion.
• Spicy food can augment gastric acid secretion.

Factors that Inhibit Gastric Acid Secretion

Gastric acid secretion is reduced by low luminal pH, somatostatin, and acidic chyme entering the duodenum.

pH of Gastric Luminal Content

• A fall in gastric pH below 2 initiates negative feedback regulation of acid secretion. This autoregulation prevents excessive acid accumulation and mucosal injury.
• Inhibition is mediated indirectly through hormonal pathways rather than direct suppression of parietal cells.
• Highly acidic contents suppress gastrin release from G cells.
• At the same time, they stimulate D cells to release somatostatin. Somatostatin reduces gastrin secretion and thereby decreases acid production.

Somatostatin

• Somatostatin acts as a key inhibitory regulator within the gastric mucosa. Its secretion increases significantly when intragastric acidity rises.
• Reduced gastrin levels lead to diminished stimulation of parietal cells.
• Acidic chyme in the duodenum further inhibits gastric secretion through enterogastric reflexes and hormonal signals. These coordinated mechanisms maintain acid balance and protect the gastrointestinal mucosa from injury.

Chyme in the Duodenum

• Entry of acidic chyme into the duodenum stimulates secretin release from intestinal mucosa.
• Secretin inhibits gastric acid secretion, motility, and gastrin release.
• Products of carbohydrate and fat digestion increase gastric inhibitory peptide secretion.
• Increased osmolarity of duodenal contents further suppresses acid secretion.
• Additional enterogastrones also contribute to inhibition of gastric activity.

Regulation of Gastric Secretion

• Gastric secretion is regulated by coordinated neural and hormonal mechanisms.
• Neural control includes autonomic influences, local reflexes, and central inputs via the vagus nerve.
• Regulation varies across three phases: cephalic, gastric, and intestinal.

Cephalic Phase

• The cephalic phase is initiated by sight, smell, taste, thought, and chewing of food.
• Sensory inputs activate the dorsal motor nucleus of the vagus in the medulla. This phase is mediated predominantly by vagal pathways.
• Vagal fibers directly stimulate parietal cells through cholinergic mechanisms. They also stimulate G cells via noncholinergic pathways using gastrin-releasing peptide.
• Gastrin release further enhances acid secretion.
• Noncholinergic effects are more prominent, so blocking cholinergic pathways alone is insufficient to suppress secretion.
• Gastric juice secretion begins before food enters the stomach, so it is termed the pregastric phase. This phase contributes approximately 40 to 50 percent of total gastric secretion.

Experimental Design to Study Cephalic Phase

• The integrity of this phase can be evaluated using sham feeding. In this method, food is chewed and swallowed but does not reach the stomach.
• Gastric secretions are collected simultaneously for analysis.
• Persistence of secretion during sham feeding indicates intact vagal stimulation.
• Surgical interruption of vagal pathways abolishes secretion in this phase. This confirms that the cephalic phase depends primarily on vagal neural activity.
• Overall, the cephalic phase prepares the stomach for digestion by initiating acid secretion in anticipation of food intake.

Gastric Phase

• The gastric phase begins when food enters the stomach and is the major contributor to acid secretion. It accounts for approximately 50 to 60 percent of total gastric secretion.
• The primary stimulus is gastric distension, which activates both neural and hormonal pathways.
• Distension triggers local enteric reflexes and central vagovagal reflexes. These reflexes increase acetylcholine release, which directly stimulates parietal cells.
• Chemical stimuli also play an important role in this phase.
• Peptides and amino acids formed during protein digestion stimulate G cells.
• G cells release gastrin, which enhances acid secretion.
• Gastrin further promotes histamine release from enterochromaffin-like cells.
• Histamine acts synergistically with acetylcholine and gastrin to increase hydrochloric acid production. Thus, acid secretion during this phase is regulated by mechanical, neural, and chemical mechanisms.
• As gastric acidity increases, a feedback mechanism limits further secretion.
• When intragastric pH falls below 2, acid secretion is reduced. This occurs through inhibition of gastrin release and increased somatostatin secretion. This process is termed autoregulation and prevents excessive mucosal damage.

Experimental Designs to Study Gastric Phase

• Gastric secretion in this phase has been studied using isolated gastric pouches.
• An innervated pouch helps assess combined neural and chemical influences.
• A denervated pouch helps isolate hormonal effects. These experimental methods are now largely of historical importance but provide insight into regulatory mechanisms.

Intestinal Phase

• The intestinal phase begins when chyme enters the duodenum and represents the postgastric phase. It contributes approximately 10 percent of total gastric secretion.
• The early part of this phase produces mild stimulation of acid secretion.

Stimulation of Secretion

• Duodenal distension activates vagovagal reflexes that transiently increase secretion.
• Peptides and amino acids in chyme stimulate endocrine cells in the upper intestine. These cells release mediators that briefly enhance gastric acid production.
• The later phase is predominantly inhibitory and regulates gastric activity.

Inhibition of Secretion

• Acidic chyme in the duodenum activates the enterogastric reflex, which suppresses secretion.
• Low duodenal pH stimulates release of secretin from intestinal mucosa.
• Secretin inhibits gastrin release and reduces parietal cell responsiveness.
• Fat digestion products, including fatty acids, stimulate release of cholecystokinin and gastric inhibitory peptide. These hormones suppress acid secretion and slow gastric motility.
• Increased osmolarity of intestinal contents further contributes to inhibition.
• Additional enterogastrones also reduce gastric secretion.
• Overall, the intestinal phase ensures that gastric secretion is limited when the intestine is processing chyme. This coordination prevents excessive acid delivery and protects the intestinal mucosa.

Table 39.2: Mechanisms of gastric secretion in three different phases.

Phase	Primary Stimuli	Regulatory Mechanisms	Contribution
Cephalic phase	Sensory cues such as sight, smell, taste, and thought of food	Central nervous system activation via vagal pathways	About 30–50% of total secretion
Gastric phase	Gastric distension and protein digestion products	Local reflexes and gastrin-mediated stimulation	About 50–60% of total secretion
Intestinal phase	Entry of chyme into the duodenum	Intestinal reflexes and hormonal feedback including secretin and inhibitory peptides	Minor contribution, mainly inhibitory

Gastric Function Tests

• Gastric function tests evaluate secretory, hormonal, and motor functions of the stomach. They assist in diagnosing gastric and duodenal disorders and in monitoring treatment response.
• Examination of gastric contents assesses volume, pH, color, and acidity. It also detects abnormal constituents such as blood, mucus, and undigested food.
• Tests for acid secretion measure basal and stimulated acid output. These tests help identify hypersecretion or reduced acid production.
• Assessment of enzymes and protective factors includes pepsin, mucus, and intrinsic factor. These components are essential for digestion and mucosal protection.
• Measurement of serum gastrin levels aids in evaluating disorders associated with abnormal acid secretion.
• Visualization techniques such as endoscopy allow direct inspection of the gastric mucosa.
• Biopsy sampling helps confirm structural and pathological abnormalities.
• Tests of gastric motility and electrical activity provide information on functional disorders.

Classification

• Gastric analysis can be performed under different conditions.
• Basal state testing is done after overnight fasting to assess resting secretion.
• Postprandial testing follows a standardized meal to evaluate stimulated secretion.
• Stimulus-based tests involve agents that provoke maximal acid output for functional assessment. These approaches provide comprehensive evaluation of gastric physiology and pathology.

Measurement of Acid Output

• Assessment of gastric secretion includes basal acid output and maximal acid output.
• These measurements reflect functional capacity and mass of parietal cells.

BAO

• Basal acid output is measured during the interdigestive period after overnight fasting.
• Gastric contents are aspirated for about 60 minutes using a nasogastric tube.
• Normal values range from 0.5 to 2 milliequivalents per hour.
• Elevated basal output suggests increased gastrin activity, as seen in hypersecretory states.
• A gastric pH above 2.5 generally excludes severe hypersecretion.

MAO

• Maximal acid output represents the highest acid secretion after stimulation. It is assessed by administering pharmacological stimulants and collecting gastric juice.
• Normal values range from 12 to 60 milliequivalents per hour.
• It helps evaluate parietal cell responsiveness and reserve capacity.

Special Test to Detect Acid Output

Histamine Test

• Histamine test uses subcutaneous histamine to stimulate acid secretion.
• Gastric samples are collected at regular intervals for quantitative analysis. It is useful in assessing severe hyposecretion and related neurological complications.

Histalog (Betazole) Test

• Betazole test is a safer alternative with fewer adverse effects.
• It follows a similar protocol without requiring additional protective medication.

Pentagastrin (Peptavlon) Test

• Pentagastrin test employs a synthetic gastrin analogue to strongly stimulate acid secretion.
• It provides reliable estimation of maximal acid output and parietal cell function.

Insulin Test (Hollander test)

• Insulin test induces hypoglycemia, which activates vagal pathways.
• This leads to increased acid secretion through neural stimulation. It is primarily used to assess completeness of vagal interruption after surgery.
• Absence of acid response indicates effective vagal denervation.
• These tests collectively provide detailed information on gastric secretory function and aid clinical decision making.

Fractional Test Meal Analysis

• Fractional test meal analysis evaluates gastric acid secretion after a standardized meal.
• Small samples of gastric content are collected every 15 minutes for about three hours.
• This method assesses acid secretion during the postprandial phase. It helps identify hyperchlorhydria, hypochlorhydria, and achlorhydria.

Tubeless Gastric Analysis

• Tubeless gastric analysis is a noninvasive alternative to tube-based methods.
• A diagnostic compound releases a dye in response to gastric acidity.
• The dye is absorbed, excreted in urine, and its intensity reflects acid levels.
• The test can be repeated after stimulation of gastric secretion.
• It is less accurate and contraindicated in renal impairment and malabsorption.

The Significance of BAO and MAO

• Interpretation of basal acid output and maximal acid output provides clinical insight.
• Values are usually normal or slightly reduced in gastric ulcer.
• Increased levels occur in duodenal ulcer, gastrin-secreting tumors, and anastomotic ulcer.
• Markedly reduced or absent acid secretion is seen in pernicious anemia and advanced gastric malignancy.
• Achlorhydria associated with ulcer strongly suggests malignancy.
• These investigations aid diagnosis, guide management, and improve understanding of gastric secretory disorders.

Tests for other Gastric Secretory Products

Assessment of non-acid components of gastric secretion provides additional clinical information.

Test for Pepsin

• Pepsin levels reflect activity of chief cells and protein digestion capacity.
• Reduced pepsin levels are observed in atrophic gastritis, indicating mucosal damage.
• Specialized inhibitors are used in research settings to quantify pepsin activity.

Test for Mucous

• Mucus secretion is evaluated by measuring its protein content.
• Normal gastric mucus protein concentration is about 1.8 milligrams per milliliter.
• Increased levels are seen in hypertrophic gastric conditions such as Menetrier disease.
• Mucus assessment helps evaluate mucosal protection and barrier function.

Test for Intrinsic factor

• Intrinsic factor is essential for vitamin B12 absorption in the terminal ileum.
• Deficiency leads to impaired absorption and megaloblastic anemia.
• Functional testing of intrinsic factor is performed using absorption studies of vitamin B12.
• These tests help diagnose pernicious anemia and gastric atrophy.

Test for Gastrin

• Gastrin is a hormone secreted by G cells in the antral mucosa and proximal duodenum.
• Normal fasting serum gastrin levels range from 20 to 150 picograms per milliliter.
• Elevated levels occur in atrophic gastritis, gastrin-secreting tumors, and after gastric surgery.
• Measurement is commonly performed using immunoassay techniques.
• Provocative tests help differentiate causes of hypergastrinemia.
• Secretin administration causing a significant rise in gastrin suggests gastrin-secreting tumors.
• Calcium infusion producing a similar increase supports this diagnosis.
• These investigations assist in diagnosing gastric disorders and guiding targeted management.

Other Tests

Barium-Meal X-Ray

• Barium meal radiography involves ingestion of contrast material followed by imaging of the upper gastrointestinal tract. It outlines the contour of the esophagus, stomach, and proximal small intestine.
• This method helps identify ulcers, masses, and structural abnormalities.

Endoscopy (Gastroscopy)

• Endoscopy allows direct visualization of the gastric mucosa using a flexible optical instrument. It provides detailed assessment of ulcers, inflammation, and suspected malignancy.
• Targeted biopsy can be obtained for histopathological examination.
• Biopsy samples also enable detection of Helicobacter pylori infection.
• A rapid urease test on biopsy material confirms infection by detecting urease activity.
• Endoscopy can be extended into the duodenum for further evaluation.
• These investigations are essential for accurate diagnosis and management of gastric disorders.

Applied Aspects

The common diseases related to gastric secretion are gastritis and peptic ulcer.

Gastritis

• Gastritis refers to inflammation of the gastric mucosa presenting with upper abdominal discomfort and dyspepsia. It is clinically important due to its association with peptic ulcer disease and gastric malignancy.
• Gastritis is broadly classified into acute and chronic types.

Etiopathogenesis

• Etiological factors include dietary habits, infections, medications, chemical agents, and severe stress.
• Nonsteroidal anti-inflammatory drugs and alcohol commonly damage the mucosal barrier.
• Infections, especially by Helicobacter pylori, play a major role in chronic gastritis.
• Persistent inflammation may impair mucosal integrity and predispose to ulcer formation.

Peptic Ulcers

• Peptic ulcer is a mucosal defect occurring in the stomach or duodenum due to acid-pepsin injury. It develops when aggressive factors outweigh protective mechanisms.

Pathophysiology

• The gastric mucosa is protected by a mucosal barrier composed of mucus, bicarbonate, and epithelial integrity.
• The mucus layer is a viscous gel approximately 0.2 millimeters thick. It traps bicarbonate and maintains a near-neutral pH at the epithelial surface.
• Disruption of this barrier increases susceptibility to acid and pepsin injury.
• Reduced mucus or bicarbonate secretion weakens mucosal defense.
• Mechanical or chemical injury can further compromise the barrier.
• Drugs such as nonsteroidal anti-inflammatory agents inhibit protective prostaglandins. This reduces mucus and bicarbonate secretion and impairs mucosal blood flow.
• Increased acid secretion or infection can enhance mucosal damage.
• Chronic stress elevates catecholamine levels, which reduce mucus production and promote ulcer formation.
• Thus, peptic ulcer disease results from imbalance between aggressive factors and protective mechanisms.

Table 39.3: Tests for gastric analysis.

Category	Tests Included
Gastric secretion tests	Histamine, betazole, pentagastrin, insulin stimulation; tubeless analysis
Enzymes and protective factors	Pepsin, mucus protein estimation, intrinsic factor assessment
Hormonal evaluation	Serum gastrin measurement; provocative tests using secretin and calcium infusion

Table 39.4: Classification of gastritis.

Type	Subtypes and Features
Acute gastritis	Helicobacter pylori–associated; other infectious causes including bacteria, viruses, fungi, and parasites
Chronic gastritis	Type A (autoimmune) – body and fundus predominant; Type B (H. pylori–related) – antral predominant; Type AB (mixed) – antrum and body; Chemical reflux gastritis; other less common variants

B. Hypersecretion of Acid

• Hyperchlorhydria refers to excessive gastric acid secretion that damages the mucosal barrier.
• Chronic stress and anxiety can increase acid secretion through neural mechanisms.
• Diets rich in spicy food may further augment gastric acid production.
• Sustained acid excess predisposes to peptic ulcer disease.
• Important causes include Zollinger–Ellison syndrome, gastric outlet obstruction, and systemic mastocytosis.
• Zollinger–Ellison syndrome involves a gastrin-secreting tumor, leading to marked acid hypersecretion.
• Histamine release in mast cell disorders also enhances acid production.

C. Helicobacter Pylori Infection

• Helicobacter pylori infection is a major etiological factor in peptic ulcer disease. It is a gram-negative bacterium that produces urease, generating ammonia to neutralize local acidity.
• The organism colonizes the antral mucosa and induces inflammation. It reduces somatostatin secretion, thereby increasing gastrin release and acid secretion. This results in moderately elevated serum gastrin levels, especially in duodenal ulcer.
• Infection initially causes gastritis and may progress to ulcer formation.
• Eradication therapy with antibiotics is effective in healing ulcers and preventing recurrence.

Features

• Peptic ulcers are most commonly located in the proximal duodenum, above the ampulla, where neutralization of acid is limited.
• The predominant symptom is epigastric pain, often described as burning or gnawing.
• Pain typically occurs during fasting and is relieved by food, water, or antacids.
• Progressive disease may lead to complications.
• Hematemesis indicates upper gastrointestinal bleeding.
• Melena presents as dark, tarry stools due to digested blood.
• Persistent vomiting may occur due to gastric outlet obstruction.
• Perforation of the ulcer can result in peritonitis, which is a surgical emergency.

Treatment

Specific Treatment

• Histamine-2 receptor antagonists reduce acid secretion by blocking histamine action on parietal cells.
• Common agents include ranitidine, cimetidine, famotidine, and nizatidine.
• Proton pump inhibitors inhibit hydrogen-potassium adenosine triphosphatase, the final step in acid secretion. These drugs, such as omeprazole, are highly effective in ulcer healing.
• Sucralfate forms a protective barrier over the ulcer surface and promotes mucosal healing.
• Muscarinic receptor blockers reduce cholinergic stimulation of acid secretion.
• However, their clinical use is limited due to modest efficacy.
• Gastrin antagonists aim to reduce acid secretion but have limited clinical utility.
• Antibiotic therapy is essential for eradication of Helicobacter pylori infection.
• Combination regimens improve healing rates and reduce recurrence.
• Effective management requires both reduction of acid secretion and enhancement of mucosal defense.

Nonspecific Measures

Antacids

• Antacids provide rapid but short-term relief by neutralizing gastric acid. They reduce epigastric pain but do not address the underlying cause.
• Reduction of stress is important, as it contributes to increased acid secretion.
• Lifestyle modifications improve symptom control and healing.

Yoga Therapy and Other Measures

• Yoga and relaxation techniques help decrease autonomic stimulation and acid output.
• Adequate sleep and regular rest support mucosal recovery.
• A balanced diet and avoidance of irritants such as alcohol and spicy food are beneficial.
• Discontinuation of ulcerogenic drugs, especially nonsteroidal anti-inflammatory agents, is essential.

Surgical Treatment

• Surgery is considered when medical therapy fails or complications develop.
• Vagotomy reduces acid secretion by interrupting vagal stimulation.
• Selective or highly selective procedures are preferred to minimize complications.
• Gastrectomy involves removal of the antral region, which contains gastrin-secreting cells. This reduces acid secretion but may impair gastric emptying.
• To prevent stasis, drainage procedures such as gastroduodenostomy or gastrojejunostomy are performed.
• Surgical management aims to reduce acid production and improve gastric drainage.