A 52-year-old man with a 10-year history of epigastric pain presents with acute haematemesis and melaena. He is haemodynamically stable after resuscitation. Upper endoscopy reveals a large bleeding ulcer in the duodenal bulb with a visible vessel. After endoscopic haemostasis, which investigation is most appropriate to identify the underlying aetiology and guide long-term management?

Explanation

## Investigation of Choice for Peptic Ulcer Aetiology ### Clinical Context This patient presents with acute peptic ulcer bleeding requiring endoscopic haemostasis. After stabilisation and treatment of the acute bleed, identifying the underlying cause is essential for secondary prevention and long-term management. ### Why Urea Breath Test or Stool Antigen Test? **Key Point:** Helicobacter pylori infection is the most common cause of peptic ulcer disease (90% of duodenal ulcers), and testing for H. pylori is the standard investigation after acute bleeding is controlled. **High-Yield:** The urea breath test (UBT) and stool antigen test (SAT) are non-invasive, highly sensitive (>95%) and specific (>95%) methods to diagnose active H. pylori infection. These should be performed after acute bleeding is managed and before starting eradication therapy. **Clinical Pearl:** Testing should be done at least 2 weeks after completion of any antibiotic course and ideally after stopping proton pump inhibitors (PPIs) for 2 weeks, as these agents suppress H. pylori and may cause false-negative results. ### Diagnostic Algorithm for Peptic Ulcer ```mermaid flowchart TD A[Peptic ulcer bleeding controlled]:::outcome --> B[Identify aetiology]:::decision B -->|H. pylori suspected| C[Urea breath test or stool antigen]:::action B -->|NSAID use history| D[Stop NSAID + PPI]:::action B -->|Refractory/multiple ulcers| E[Serum gastrin + secretin test]:::action C --> F[If positive: eradication therapy]:::action E --> G[If gastrin >1000: Zollinger-Ellison]:::outcome ``` ### Why Not the Other Options? | Investigation | Indication | Why Not First-Line Here | |---|---|---| | **Serum gastrin + secretin stimulation** | Zollinger-Ellison syndrome (gastrinoma) | Reserved for refractory/multiple ulcers or atypical presentation; no clinical clues here | | **Abdominal ultrasound/CT** | Complications (perforation, obstruction) | Patient is haemodynamically stable post-endoscopy; imaging not needed for aetiology | | **Serum calcium + PTH** | Hyperparathyroidism-associated ulcers | Rare cause; no hypercalcaemia symptoms; not routine screening | **Mnemonic:** **HELP** — H. pylori (most common), NSAID, Zollinger-Ellison (gastrin), Hyperparathyroidism (rare causes of peptic ulcer). [cite:Harrison 21e Ch 297]