A 58-year-old man from Delhi presents to the emergency department with acute onset severe epigastric pain and vomiting for 6 hours. He has a history of peptic ulcer disease and stopped his proton pump inhibitor 2 months ago. On examination, he is febrile (38.2°C), tachycardic (110/min), and has severe abdominal tenderness with guarding and rigidity. Upright chest X-ray shows a large pneumoperitoneum. CT abdomen with IV contrast reveals free air in the peritoneal cavity and a 5 mm defect in the anterior wall of the gastric antrum with surrounding inflammatory changes. What is the most likely diagnosis and imaging finding that confirms perforation?

Explanation

## Clinical Presentation & Imaging Correlation This patient presents with classic signs of **acute gastric perforation**: sudden severe epigastric pain, peritoneal signs (guarding, rigidity), and imaging evidence of pneumoperitoneum with a focal defect in the gastric antrum. ## Key Imaging Findings in Gastric Perforation **Key Point:** The **focal defect in the gastric wall** on CT is the pathognomonic finding that directly identifies the site of perforation. Combined with free air in the peritoneal cavity, this is diagnostic. **High-Yield:** Perforation imaging findings on CT include: - **Pneumoperitoneum** (free air in peritoneal cavity) — visible on upright CXR as lucency under diaphragm - **Focal defect or discontinuity** in the organ wall (stomach, duodenum, colon, small bowel) - **Perilesional fat stranding** and inflammatory changes around the defect - **Extravasation of oral contrast** (if given) through the defect ## Differential Imaging Features | Finding | Gastric Perforation | Appendiceal Perforation | Colonic Perforation | |---------|-------------------|------------------------|---------------------| | **Location of defect** | Anterior gastric wall (antrum/body) | Appendiceal tip | Sigmoid/cecum | | **Associated findings** | Peptic ulcer history, antral defect | Periappendiceal fat stranding, appendicolith | Diverticulosis, pericolic abscess | | **Peritoneal involvement** | Generalized peritonitis (rapid) | May be localized initially | Often localized, can be generalized | **Clinical Pearl:** Anterior wall gastric perforations (from peptic ulcers) are more common than posterior perforations because the anterior wall is exposed to gastric acid and is less protected by the omentum. ## Why This Answer Is Correct The combination of **pneumoperitoneum + focal defect in the gastric antral wall** directly confirms perforation at that anatomic site. This is the gold standard CT finding for identifying the organ of origin and the exact location of perforation. [cite:Robbins 10e Ch 17] [cite:Harrison 21e Ch 293]