Which of the following is the most specific radiological sign of hollow viscus perforation on plain abdominal radiography?

Explanation

## Rigler's Triad — The Classic Triad of Perforation **Key Point:** Rigler's triad is the pathognomonic radiological sign of hollow viscus perforation and consists of three findings: 1. **Pneumoperitoneum** (free air under diaphragm) 2. **Pneumatosis intestinalis** (air in bowel wall) 3. **Portal venous gas** (air in portal venous system) ### Specificity and Sensitivity | Finding | Sensitivity | Specificity | Notes | |---------|------------|------------|-------| | Pneumoperitoneum alone | 70–80% | Moderate | Can occur without perforation (post-op, incompetent sphincter) | | Rigler's triad | 5–15% | **Very high (>95%)** | Pathognomonic when present; indicates severe perforation with systemic spread | | Pneumatosis intestinalis | 30–40% | High | Suggests transmural necrosis; not always from perforation | | Portal venous gas | 10–20% | High | Indicates severe ischemia; poor prognostic sign | **High-Yield:** While pneumoperitoneum is the most common finding in perforation, Rigler's triad—when present—is the **most specific** indicator of hollow viscus perforation with systemic complications. **Clinical Pearl:** Portal venous gas and pneumatosis intestinalis indicate advanced ischemic injury and carry a poor prognosis; their presence warrants urgent surgical intervention. ## Why Other Signs Are Less Specific - **Sentinel loop:** Localized ileus around an inflamed viscus; non-specific (seen in pancreatitis, appendicitis, diverticulitis) - **Free fluid in pelvis:** Non-specific; can occur with peritonitis, ascites, or other inflammatory conditions - **Thumbprinting:** Indicates bowel wall edema; seen in ischemia, inflammatory bowel disease, and other conditions—not specific to perforation