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

Explanation

## Understanding Rigler's Triad and Perforation Imaging Signs **Key Point:** Rigler's triad is a classic radiological sign on **plain radiographs** for pneumoperitoneum, and its components are different from what is stated in Option A. ### Rigler's Triad — Correct Definition Rigler's triad (also called the **double wall sign** on plain X-ray) consists of: 1. **Pneumoperitoneum** — free air in the peritoneal cavity 2. **Liver edge sign** — visualization of the falciform ligament due to surrounding free air 3. **Double wall sign** — visualization of both the inner (mucosal) and outer (serosal) walls of the bowel loop because free intraperitoneal air outlines the outer wall while intraluminal gas outlines the inner wall **Option A is INCORRECT** because it states Rigler's triad consists of pneumoperitoneum, pneumomediastinum, and subcutaneous emphysema — this is NOT Rigler's triad. Pneumomediastinum and subcutaneous emphysema are features of esophageal perforation (Boerhaave syndrome) or severe barotrauma, not components of Rigler's triad [Grainger & Allison's Diagnostic Radiology, 6e; Dahnert's Radiology Review Manual, 7e]. ### CT Findings in Hollow Viscus Perforation | Finding | Definition | Correctness | |---------|-----------|-------------| | **Focal wall defect + adjacent free air** | Direct sign of perforation site on CT | ✅ TRUE (Option B) | | **Sentinel clot sign** | High-density blood clot adjacent to perforation/bleeding site | ✅ TRUE (Option C) | | **Double wall sign on CT** | Free fluid between two layers of bowel wall (bowel wall edema/thickening) | ✅ TRUE (Option D) | ### Why Option A is the EXCEPT Answer The triad described in Option A — pneumoperitoneum + pneumomediastinum + subcutaneous emphysema — describes findings in **esophageal perforation (Boerhaave syndrome)**, not Rigler's triad. Rigler's triad specifically refers to the plain radiograph finding of free intraperitoneal air outlining both walls of the bowel loop, along with visualization of the falciform ligament and free subdiaphragmatic air. **High-Yield:** On NEET PG/INI-CET, Rigler's sign = double wall sign on plain X-ray (both walls of bowel visible due to intraluminal + extraluminal air). Do NOT confuse with pneumomediastinum/subcutaneous emphysema, which are hallmarks of esophageal perforation. **Clinical Pearl:** In a patient with suspected hollow viscus perforation, upright CXR showing free air under the diaphragm is the first-line investigation. CT abdomen with contrast is the gold standard for localizing the perforation site via focal wall defect and adjacent extraluminal air.