Which radiological sign on plain abdominal X-ray is pathognomonic for small bowel obstruction and represents gas in both the small bowel and colon?

Explanation

## Rigler's Triad: The Classic Triad of Small Bowel Obstruction **Key Point:** Rigler's triad consists of three radiological findings on plain abdominal X-ray that are highly suggestive of small bowel obstruction: 1. **Pneumatosis intestinalis** — gas within the bowel wall (appears as a linear lucency outlining the bowel loop) 2. **Pneumoperitoneum** — free air in the peritoneal cavity (seen as a lucent crescent under the diaphragm or outlining abdominal organs) 3. **Portal venous gas** — gas within the portal venous system (appears as branching lucencies in the liver) ### Clinical Significance **High-Yield:** While Rigler's triad is pathognomonic (100% specific) for small bowel obstruction, it is **not sensitive** — present in only 5–15% of cases. When all three signs are present, the diagnosis is certain, but their absence does NOT exclude obstruction. **Clinical Pearl:** Rigler's triad typically indicates **advanced or complicated small bowel obstruction** with bowel ischemia, perforation, or necrosis. This is a **surgical emergency** requiring immediate intervention. ### Differential Features of Other Signs | Sign | Appearance | Condition | |------|-----------|----------| | **Rigler's triad** | Pneumatosis + pneumoperitoneum + portal venous gas | Advanced SBO with ischemia/perforation | | **Bird's beak** | Abrupt narrowing of bowel at transition point | Volvulus, adhesion | | **Coffee bean** | Twisted, coffee-bean-shaped loop of bowel | Sigmoid volvulus | | **Sentinel loop** | Single dilated small bowel loop near inflammation | Pancreatitis, appendicitis | **Warning:** Do not confuse Rigler's triad (three findings together) with individual signs like pneumoperitoneum alone, which has many causes (perforation, post-operative, incompetent sphincter). [cite:Sabiston Textbook of Surgery Ch 45]