## Anatomical Distribution of Peptic Ulcers **Key Point:** The first part of the duodenum (D1) is the most common site of peptic ulcer disease, accounting for approximately 60–80% of all PUD cases in India and worldwide. ### Why D1 is Most Vulnerable 1. **Acid exposure**: The duodenum receives highly acidic chyme from the stomach, and D1 lacks the protective mucus layer present in the stomach 2. **Reduced bicarbonate secretion**: Duodenal mucosa has lower bicarbonate buffering capacity compared to the antrum 3. **H. pylori colonization**: The organism preferentially colonizes the gastric antrum and extends to the duodenal bulb, causing ulceration at the junction 4. **NSAID effect**: NSAIDs cause ulcers at the pyloric channel and D1 more frequently than the fundus ### Site-Specific Features | Site | Frequency | Key Features | |------|-----------|---------------| | **D1 (First part duodenum)** | 60–80% | Most common; associated with H. pylori and NSAIDs; anterior wall perforates | | **Gastric antrum** | 15–20% | Second most common; H. pylori-associated; lesser curvature involvement | | **Gastric fundus** | 5–10% | Rare; usually NSAID-related; high malignancy risk | | **Pyloric channel** | Rare | NSAID-related; can cause gastric outlet obstruction | **Clinical Pearl:** Duodenal ulcers typically cause epigastric pain 2–3 hours after meals (relieved by food), whereas gastric ulcers cause pain immediately after eating or at night. **High-Yield:** In India, H. pylori seropositivity is 50–60%, making it the leading cause of duodenal ulcers. The antrum is the primary site of H. pylori colonization, but ulceration occurs at the gastroduodenal junction (D1).
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