Etiology of Duodenal Ulcer
The two primary causes of duodenal ulcer are Helicobacter pylori infection (responsible for approximately 75% of cases) and nonsteroidal anti-inflammatory drug (NSAID) use, with these factors accounting for the vast majority of duodenal ulcers. 1, 2
Primary Etiologic Factors
Helicobacter pylori Infection
- H. pylori gastritis is the dominant cause, with approximately 76% of duodenal ulcer patients testing positive for the infection using at least one diagnostic method 2
- Among those with H. pylori infection, the lifetime risk of developing peptic ulcer is approximately 17% (1 in 6 individuals) 1
- The infection is typically acquired in childhood through familial transmission, explaining the clustering of peptic ulcer disease within families 1
- H. pylori-positive duodenal ulcers represent approximately 94% of cases when NSAIDs are excluded 3
NSAID Use
- NSAIDs are the second major cause, with approximately 46% of duodenal ulcer patients reporting NSAID use within the preceding month 2
- Among NSAID users, H. pylori co-infection increases the risk of upper gastrointestinal complications by 2- to 4-fold 1
- In patients with both risk factors present, approximately three-fourths have ulcers attributable to the combined effect of H. pylori and NSAIDs 2
- NSAID use alone (without H. pylori) accounts for approximately 10% of duodenal ulcers 2
Risk Stratification for NSAID-Related Ulcers
The following factors increase ulcer risk in NSAID users 1:
- Prior ulcer disease or ulcer complications (strongest risk factor)
- Advanced age
- Cardiovascular disease
- Concomitant use of aspirin, antiplatelet drugs, corticosteroids, or anticoagulants
The annualized incidence of NSAID-related ulcer complications varies by risk factors 1:
- 0.8% with no risk factors
- 2% with one risk factor
- 7.6-8.6% with three risk factors
- 18% with four risk factors
Less Common Causes
Idiopathic Ulcers
- Approximately 13.6% of duodenal ulcers are classified as idiopathic, occurring in patients who are H. pylori-negative, do not use NSAIDs, and have no hypersecretory illness 2
- Some H. pylori-negative cases (approximately 6%) may have unusual etiologies requiring specific investigation 3
Other Rare Causes
In H. pylori-negative, NSAID-negative patients, consider 3:
- Recent antibiotic use (may mask H. pylori detection)
- Crohn's disease involving the duodenum
- Malignancy (penetrating pancreatic carcinoma)
- Alternative infections (e.g., Gastrospirillum hominis)
- Hypersecretory states (though gastrin levels are typically normal in routine peptic ulcer disease) 2
Clinical Implications
All patients requiring regular NSAID therapy should be tested for H. pylori given the synergistic increase in complication risk 1. The historical paradigm of duodenal ulcer as a chronic disease ("once an ulcer, always an ulcer") has been transformed by recognition that curing H. pylori infection prevents ulcer recurrence and development of new cases 1.
The improvement in stomach health from H. pylori eradication and resulting increase in acid secretion historically led to an increase in duodenal ulcers, while the decline in H. pylori prevalence in developed countries has contributed to decreased peptic ulcer disease overall 1.