On plain abdominal radiograph, what is the significance of the 'coffee bean' sign?

Explanation

## Coffee Bean Sign — Sigmoid Volvulus **Key Point:** The coffee bean sign is a characteristic radiographic appearance of sigmoid volvulus, showing a single massively dilated loop of colon twisted on its mesentery, resembling a coffee bean in shape. ### Radiographic Appearance - **Shape:** Single, elongated, dilated loop with a twisted appearance - **Location:** Pelvis and lower abdomen (sigmoid colon) - **Axis:** Loop twisted around its mesentery, creating a "bent" or "bean-like" contour - **Associated findings:** Absence of gas distal to the volvulus, "bird's beak" appearance at the site of torsion on contrast studies ### Pathophysiology Sigmoid volvulus occurs when the sigmoid colon (which has a long mesentery in some individuals) twists 180–360° around its vascular pedicle, causing: 1. Mechanical obstruction 2. Vascular compromise (if prolonged → ischemia and perforation) 3. Abdominal distension and pain ### Clinical Context - **Incidence:** More common in elderly, institutionalized, or chronically constipated patients - **Geography:** Higher in Africa, Middle East, India (dietary factors) - **Presentation:** Acute onset of abdominal pain, distension, constipation, vomiting - **Management:** Rigid or flexible sigmoidoscopy for decompression (first-line); surgery if failed decompression or perforation ### Comparison with Other Volvulus Types | Type | Radiographic Sign | Location | Frequency | |------|-------------------|----------|----------| | **Sigmoid volvulus** | Coffee bean sign | Pelvis/lower abdomen | 60% of colonic volvulus | | **Caecal volvulus** | Kidney bean or "bird's beak" | Right lower quadrant | 25–30% of colonic volvulus | | **Small bowel volvulus** | Whirl sign (CT) | Central abdomen | Rare on plain film | **High-Yield:** Coffee bean sign is pathognomonic for sigmoid volvulus on plain radiograph. Recognition is critical because early decompression prevents perforation. **Clinical Pearl:** Sigmoid volvulus is the most common type of colonic volvulus in adults; caecal volvulus is more common in children and young adults. **Mnemonic:** **COFFEE** = **C**olon **O**bstruction **F**rom **F**lexed **E**longated loop (sigmoid volvulus).