A 58-year-old man from Delhi presents to the emergency department with acute onset severe epigastric pain radiating to the back, accompanied by vomiting. He has a history of peptic ulcer disease and stopped taking his proton pump inhibitor 3 months ago. On examination, he is febrile (38.2°C), tachycardic (HR 110/min), and has severe tenderness in the epigastrium with guarding. Upright chest X-ray shows pneumoperitoneum. Which imaging finding on CT abdomen would be most specific for identifying the site of perforation in this clinical scenario?

Explanation

## Imaging Diagnosis of Gastric Perforation ### Clinical Context The patient presents with classic acute peptic ulcer perforation: sudden severe epigastric pain, peritonitis signs (guarding), fever, and pneumoperitoneum on upright CXR. History of PUD off PPI is a major risk factor. ### CT Findings in Gastric Perforation **Key Point:** The **sentinel clot sign** (localized blood clot adjacent to the perforation site) is a highly specific CT marker for acute gastric perforation. Combined with a focal defect in the gastric wall and perilesional fat stranding, this triad is pathognomonic. | Finding | Sensitivity | Specificity | Clinical Significance | |---------|-------------|-------------|----------------------| | Pneumoperitoneum alone | High | Low | Non-specific; seen in any perforation | | Focal gastric wall defect | Moderate | High | Localizes perforation site | | Sentinel clot sign | Moderate | Very High | Indicates acute bleeding/perforation | | Perilesional fat stranding | High | Moderate | Suggests acute inflammation | | Contrast extravasation | Moderate | High | Confirms active leak | ### Why Gastric Antrum? In peptic ulcer disease, the **anterior wall of the gastric antrum** (prepyloric region) is the most common site of perforation (~60% of cases), followed by the duodenal bulb. The anterior location makes perforation more likely than posterior penetration. **High-Yield:** The **sentinel clot sign** is the single most specific CT finding for acute gastric perforation and helps differentiate it from other causes of pneumoperitoneum (e.g., perforated colon, iatrogenic). ### Clinical Pearl In acute gastric perforation, CT with IV contrast (not oral) is preferred. Oral contrast is contraindicated due to risk of aspiration and mediastinitis if perforation is confirmed. ### Differential Imaging Patterns - **Duodenal perforation:** Air may track into the retroperitoneum (right paracolic gutter), but sentinel clot is less prominent - **Colonic perforation:** Free air in pelvis with colonic wall thickening and pericolonic stranding - **Iatrogenic perforation (post-ERCP):** Often retroperitoneal air without prominent sentinel clot