Causes of Duodenal Ulcers
The two predominant causes of duodenal ulcers are Helicobacter pylori infection and nonsteroidal anti-inflammatory drug (NSAID) use, with H. pylori accounting for approximately 94% of cases and NSAIDs representing the most common identifiable risk factor in the remaining cases 1, 2, 3.
Primary Etiologic Factors
Helicobacter pylori Infection
H. pylori gastritis is the dominant cause of duodenal ulcers, with approximately 94% of duodenal ulcer patients testing positive for this infection 3. Among those infected with H. pylori, the lifetime risk of developing peptic ulcer disease is approximately 1 in 6 (17%) 1. The infection is typically acquired in childhood through familial transmission, which explains the clustering of peptic ulcer disease within families 1.
The mechanism involves H. pylori-induced gastritis leading to increased gastric acid secretion, which when combined with duodenal mucosal exposure creates the conditions for ulcer formation 1, 4. Importantly, cure of H. pylori infection transforms peptic ulcer from a chronic relapsing disease into a curable condition, preventing ulcer recurrences 1.
NSAID and Aspirin Use
NSAID use has now surpassed H. pylori as the most commonly identified risk factor among patients presenting with bleeding ulcers, found in 53% of such patients 5. NSAIDs increase the risk of serious gastrointestinal complications 3- to 5-fold compared to non-users 5. Even low-dose aspirin (81-325 mg/day) increases the risk of duodenal ulcers 2-4 times 5.
The risk is dose-dependent and linear across all NSAID classes, including non-selective NSAIDs, COX-2 inhibitors (coxibs), and aspirin 5. Concurrent use of multiple NSAIDs (including low-dose aspirin with another NSAID) increases the relative risk of GI bleeding to more than 10 times baseline 5.
Secondary and Less Common Causes
H. pylori-Negative, NSAID-Negative Ulcers
Approximately 6% of duodenal ulcers are H. pylori-negative 3. Within this subset:
- NSAID use remains the largest subgroup (8 of 18 patients in one series), even when H. pylori is absent 3
- Recent antibiotic use (which may temporarily suppress H. pylori detection) accounts for another significant proportion 3
- Rare causes include:
Additional Risk Factors That Modify Ulcer Risk
When NSAIDs or aspirin are used, the following factors substantially increase duodenal ulcer risk:
- History of previous peptic ulcer (odds ratio as high as 13.5—the single strongest risk factor) 5
- Advanced age (approximately 4% increased risk per year) 5
- Concomitant use of:
- High-dose NSAID therapy 5
Clinical Implications
When evaluating a patient with duodenal ulcer, the diagnostic approach should focus on identifying H. pylori status and obtaining a detailed medication history, particularly regarding NSAID and aspirin use 6, 2. Testing for H. pylori should include histology, culture, and urease testing to minimize false negatives 3.
For patients who are both H. pylori-negative and not using NSAIDs, consider the rare causes listed above, but recognize that recent antibiotic exposure may have temporarily suppressed H. pylori detection 3.
The critical pitfall to avoid is assuming all duodenal ulcers are H. pylori-related without obtaining a thorough NSAID/aspirin history, as this represents an increasingly common and entirely preventable cause 5, 6.