A 68-year-old woman with a history of colorectal cancer (resected 2 years ago) presents with acute-onset abdominal pain, distension, and constipation. On examination, she has a tense, tender abdomen with absent bowel sounds. Plain abdominal X-ray shows a 'coffee bean' sign with a dilated loop of bowel. What is the most appropriate next investigation to confirm the diagnosis and assess viability?

## Investigation of Choice for Suspected Volvulus with Ischemia Risk **Key Point:** CT abdomen with IV contrast (and oral contrast if not contraindicated) is the investigation of choice for confirming volvulus and assessing bowel viability, as it can detect the 'whirl sign' and signs of ischemia. ### Clinical Context: Sigmoid Volvulus The 'coffee bean' sign on plain X-ray is pathognomonic for sigmoid volvulus. However, the key concern in this case is: - **Risk of bowel ischemia** (tense, tender abdomen; absent bowel sounds suggest advanced obstruction) - **Need to confirm diagnosis** before attempting decompression - **Assessment of viability** to guide surgical vs. endoscopic management ### Why CT with Contrast is Superior 1. **Confirms diagnosis**: Demonstrates the 'whirl sign' (twisted mesentery) with high specificity 2. **Assesses viability**: Detects signs of ischemia: - Abnormal bowel wall enhancement - Mesenteric edema - Free fluid (peritonitis) - Pneumatosis intestinalis (late ischemia) 3. **Guides management**: Determines if endoscopic decompression is safe or if surgery is needed 4. **Rapid**: Faster than other modalities in acute setting ### Comparison of Investigations for Volvulus | Investigation | Can confirm volvulus? | Detects ischemia? | Time to diagnosis | Guides management? | | --- | --- | --- | --- | --- | | **CT with contrast** | Yes (whirl sign) | Yes | 5–10 min | Yes | | Plain X-ray | Suggestive (coffee bean) | No | Immediate | No | | Ultrasound + Doppler | Limited | Possible (flow assessment) | 15–20 min | Limited | | Barium enema | Yes (bird's beak sign) | No | 30–45 min | No | | Diagnostic laparoscopy | Yes (direct visualization) | Yes | Variable | Yes (but therapeutic) | **Clinical Pearl:** In sigmoid volvulus, the 'whirl sign' on CT (twisted mesentery and vessels around the point of torsion) is highly specific and confirms the diagnosis. Absence of this sign makes volvulus unlikely. **High-Yield:** Signs of ischemia on CT (abnormal enhancement, free fluid, pneumatosis) mandate urgent surgical intervention, whereas viable bowel may be managed with endoscopic decompression (flatus tube placement). **Mnemonic: CT VOLVULUS** — **C**onfirms diagnosis, **T**wist visualized (whirl sign), **V**iability assessed, **O**rgan perfusion evaluated, **L**evel and extent determined, **V**ascular compromise detected, **U**rgency of surgery determined, **L**ow mortality with early diagnosis, **U**ltrasound/plain X-ray insufficient, **S**urgery vs. endoscopy decision guided.