A 52-year-old man presents to the emergency department with acute onset severe epigastric pain and abdominal rigidity. Upright chest X-ray shows pneumoperitoneum. Regarding the imaging findings in hollow viscus perforation, all of the following are true EXCEPT:

Explanation

## Rigler's Triad — Clarification **Key Point:** Rigler's triad of pneumoperitoneum consists of THREE findings, but NOT pneumomediastinum and subcutaneous emphysema. The correct triad is: 1. Pneumoperitoneum (free air in peritoneal cavity) 2. Pneumoretroperitoneum (air in retroperitoneal space) 3. Pneumatosis intestinalis (air within bowel wall) Pneumomediastinum and subcutaneous emphysema are NOT part of Rigler's triad; they occur in different pathologies (e.g., barotrauma, necrotizing fasciitis). ## Correct Imaging Findings in Hollow Viscus Perforation | Finding | Details | |---------|----------| | **Free air visualization** | Best seen on upright CXR or left lateral decubitus; as little as 1 mL can be detected | | **Retroperitoneal perforation** | Duodenal and antral perforations may show air confined to retroperitoneum (not diffuse peritoneal air) due to anatomic containment | | **Sentinel clot sign** | Blood collection adjacent to perforation site on CT; indicates active bleeding or recent perforation | | **Pneumatosis intestinalis** | Air in bowel wall; part of Rigler's triad | **High-Yield:** On CT, the location of free air can help identify the perforated viscus: - **Anterior perforation** → air in anterior peritoneal cavity, paracolic gutters - **Posterior/duodenal perforation** → air may be confined to retroperitoneum **Clinical Pearl:** In elderly or supine patients, free air may layer posteriorly and be missed on supine films; upright or decubitus views are essential. ## Why Option 0 Is Wrong Option 0 conflates Rigler's triad with findings seen in other conditions. Pneumomediastinum and subcutaneous emphysema are NOT components of Rigler's triad for pneumoperitoneum.