A 45-year-old woman presents with sudden-onset severe epigastric pain radiating to the back, accompanied by vomiting and hypotension. On examination, she is in severe distress with a rigid abdomen and absent bowel sounds. Plain abdominal radiograph shows pneumoperitoneum with a single large air collection under the diaphragm. What is the most appropriate next investigation to confirm the diagnosis and assess for complications?

Explanation

## Clinical Scenario: Perforated Viscus The presentation of sudden severe epigastric pain, vomiting, hypotension, and pneumoperitoneum on plain radiograph is classic for **perforated peptic ulcer disease (or other visceral perforation)**. While pneumoperitoneum itself is diagnostic of perforation, CT imaging is essential to identify the site of perforation, assess for complications, and guide surgical planning. ### Why CT Abdomen and Pelvis with IV Contrast is Correct **Key Point:** CT with IV contrast is the investigation of choice in perforated viscus because it: - Identifies the site and size of perforation - Detects the source (peptic ulcer, malignancy, inflammatory bowel disease, trauma) - Assesses for peritonitis, abscess formation, and sepsis - Evaluates for associated complications (hemorrhage, fistula) - Guides surgical vs. conservative management decisions **High-Yield:** CT has superior sensitivity (90–95%) compared to plain radiography for detecting perforation and identifying the source. Even when pneumoperitoneum is evident on plain films, CT provides critical information about the underlying cause and extent of contamination. **Clinical Pearl:** In hemodynamically unstable patients with clear clinical signs of perforation, some centers proceed directly to surgery without CT. However, in stable or equivocal cases, CT is invaluable for confirming the diagnosis and planning the surgical approach. ### Comparison with Other Investigations | Investigation | Sensitivity for Perforation | Identifies Source | Assesses Complications | Guides Management | | --- | --- | --- | --- | --- | | Plain radiograph (upright) | 60–80% | No | Limited | No | | Erect chest radiograph | 60–80% | No | Limited | No | | Abdominal ultrasound | 40–60% | No | Limited | No | | CT abdomen/pelvis | 90–95% | Yes | Yes | Yes | **Mnemonic: PERFORATION** — **P**erforation needs **E**xact **R**adiological **F**indings for **O**ptimal **R**ecovery **A**nd **T**reatment **I**nterventions **O**ver **N**on-operative options