Gastroduodenal Peptic Ulcer: Definition and Etiology
Definition
Gastroduodenal peptic ulcer (GDU) is a mucosal defect that breaches the muscularis mucosae of the stomach or duodenum, resulting from acid-peptic damage to the gastroduodenal mucosa that exposes underlying tissues to digestive secretions 1. This represents tissue loss beyond superficial erosion, distinguishing true ulceration from simple mucosal injury 2.
The condition affects approximately 1% of the US population with a lifetime prevalence of 5-10% globally 1, 3. Despite declining incidence over the past 30 years, complications still occur in 10-20% of patients, with hemorrhage being most common (73%), followed by perforation (9%) and pyloric obstruction (3%) 1, 3.
Etiology
Primary Etiologic Factors
The development of peptic ulcers fundamentally represents a disequilibrium between aggressive injurious factors (acid and pepsin) and defensive mucosa-protective factors (phospholipid surfactant layer, mucus-bicarbonate barrier, epithelial tight junctions) 2. Ulcers never develop spontaneously in healthy gastroduodenal mucosa 2.
1. Helicobacter pylori Infection
H. pylori is the leading cause of peptic ulcer disease, responsible for approximately 42% of cases 3. The infection causes chronic gastritis and disrupts normal mucosal defense mechanisms 4. In the absence of NSAIDs and gastrinoma, most gastric ulcers and all duodenal ulcers occur with H. pylori infection 5. The bacteria colonize gastric metaplasia in the duodenum, leading to inflammation that disrupts mucosal defense and regeneration, creating a cycle of injury and chronic ulceration 5.
2. NSAID and Aspirin Use
NSAIDs and aspirin account for approximately 36% of peptic ulcer cases 3. These medications cause ulceration primarily through inhibition of prostaglandin production, resulting in loss of protective effects on the gastroduodenal mucosa 2, 5. About half of ulcer patients have recent NSAID use, with three-fourths of these having concurrent H. pylori infection 6.
Secondary and Less Common Causes
- Hypersecretory states: Including Zollinger-Ellison syndrome (gastrinoma), though rare 6
- Vascular disorders: Interfering with mucosal perfusion 2
- Physicochemical injury: Including caustic ingestion 2
- Idiopathic ulcers: Approximately 13.6% of cases are negative for H. pylori, NSAID use, and hypersecretory illness 6. These "idiopathic" ulcers represent about one-tenth of all peptic ulcers 3, 6.
Pathophysiologic Mechanisms
The traditional concept of "no acid, no ulcer" has evolved to recognize that most gastric ulcers and many duodenal ulcers occur without increased acid secretion 5. The emphasis has shifted from pure acid hypersecretion to weakening of defensive factors:
Duodenal ulcers: Typically involve H. pylori-induced duodenitis, impaired duodenal bicarbonate secretion, and moderately increased peptic activity. Gastric metaplasia in the duodenum becomes colonized by H. pylori, leading to inflammation that disrupts defense and regeneration 5.
Gastric ulcers: Often occur with decreased acid-peptic activity, suggesting mucosal defensive impairments are more critical. The combination of inflammation, protective deficiencies, and moderate acid/pepsin levels induces ulceration 5.
Important Clinical Considerations
The epidemiology has shifted dramatically: H. pylori-induced ulcers are declining in the Western world, while drug-induced and idiopathic ulcers are increasing 2. With the advent of a super-aged society, aspirin-related ulcers have become increasingly prevalent as H. pylori cases decline 7. Approximately 10,000 people die annually from peptic ulcer disease in the US, with perforation causing about 40% of all ulcer-related deaths despite being less common than bleeding 1, 3.