A 52-year-old man on long-term prednisolone (15 mg daily for 8 months) for rheumatoid arthritis develops acute severe abdominal pain, fever, and tachycardia. Abdominal examination reveals generalized tenderness and rebound. Which investigation is most appropriate to confirm the suspected diagnosis of steroid-induced peptic ulcer perforation?

## Investigation of Peptic Ulcer Perforation in Steroid-Induced Disease ### Clinical Context: Steroid-Induced Peptic Ulcer **Key Point:** Long-term corticosteroid use (especially >10 mg/day prednisolone equivalent for >3 months) increases risk of peptic ulcer disease by: - Increasing gastric acid secretion - Decreasing prostaglandin-mediated mucosal protection - Impairing mucosal blood flow - Masking pain sensation (leading to delayed presentation) This patient has acute peritonitis (fever, tachycardia, rebound tenderness), suggesting perforation. ### Why Erect Abdominal X-ray? **High-Yield:** Free air under the diaphragm is the hallmark of hollow viscus perforation and is best detected on ERECT chest X-ray or LEFT LATERAL DECUBITUS abdominal X-ray. 1. **Rapid and non-invasive:** Can be done at bedside; no delay for CT 2. **High specificity for perforation:** Free air is diagnostic of perforation (sensitivity ~70%, specificity >95%) 3. **First-line imaging:** In acute peritonitis with suspected perforation, plain X-ray is the standard initial investigation 4. **Guides urgent management:** Positive finding mandates immediate surgical consultation and laparotomy ### Diagnostic Features on X-ray - **Rigler's sign:** Free air under diaphragm (best seen on erect CXR) - **Pneumoperitoneum:** Air in peritoneal cavity - **Falciform ligament sign:** Air on both sides of falciform ligament (seen on CT, not plain film) ### Investigation Comparison for Acute Abdomen | Investigation | Sensitivity | Specificity | Time | Use | | --- | --- | --- | --- | --- | | Erect X-ray | 70% | >95% | <5 min | First-line for perforation | | CT abdomen | 95% | 95% | 15–30 min | When X-ray inconclusive; also shows source | | EGD | N/A | N/A | 30–60 min | Therapeutic (not diagnostic in acute perforation) | | Serum amylase/lipase | Variable | Low | 30 min | For pancreatitis, not perforation | **Clinical Pearl:** In acute perforation, the patient is too unstable for EGD. EGD is reserved for stable patients with chronic ulcer disease or when perforation is ruled out. **Mnemonic for Steroid Side Effects — GI Complications:** **ULCER-PLUS** - **U**lcer formation (increased acid, decreased protection) - **L**oss of pain sensation (delayed diagnosis) - **C**omplications (perforation, bleeding) - **E**rosions (multiple) - **R**isk with NSAIDs (additive) - **P**roton pump inhibitor (prophylaxis recommended) - **L**ong-term steroids (>3 months, >10 mg/day) - **U**nusual presentations (atypical pain) - **S**urgical emergency (perforation) **Warning:** Do NOT perform EGD in acute perforation — risk of extending perforation and converting closed perforation to open peritonitis. [cite:Harrison 21e Ch 307; KD Tripathi 8e Ch 58]