Intestinal Obstruction & Volvulus: Radiology Essentials
1. Small Bowel Obstruction (SBO)
- Most Common Cause: Post-surgical adhesions.
- Radiology: Central dilated loops (>3 cm), “stack of coins” or “step-ladder” appearance, and absence of gas in the colon.
- Transition Point: The definitive CT finding identifying the exact location of the obstruction.
2. Large Bowel Obstruction (LBO)
- Most Common Cause: Malignancy (colon cancer).
- Radiology: Peripheral dilated loops (>6 cm; cecum >9 cm), presence of haustra (do not span the entire width of the bowel).
- Competent vs. Incompetent Ileocecal Valve: If incompetent, gas refluxes into the small bowel, increasing the risk of perforation in the cecum due to the Law of Laplace.
3. Volvulus: The “Classic” Signs
| Type | Radiological Sign |
|---|---|
| Sigmoid Volvulus | “Coffee Bean” sign (or bent inner tube); loop arises from the pelvis. |
| Cecal Volvulus | “Comma” or “Fetus” sign; loop arises from the RLQ. |
| Midgut Volvulus | “Whirlpool sign” on CT (mesentery and vessels twisting around the SMA). |
4. High-Yield Pearls
- Closed-Loop Obstruction: Obstruction at two points, creating a closed loop; high risk for strangulation and ischemia. Look for the “U-shaped” loop.
- Management: Sigmoid volvulus can often be decompressed via sigmoidoscopy; cecal volvulus usually requires surgery due to vascular compromise.