Gastrointestinal ❯ Small Bowel Obstruction (SBO)
| Problem | Evaluate suspected small bowel obstruction and define its cause to help with patient management |
| Protocol | The key to the protocol is to optimize the detection of pathology that is focused on the small bowel but also on the mesenteric vasculature with focus on the celiac and SMA as well as the portal vein and SMV. The ideal protocol is oral contrast (750-1000cc of water over a 30-45 minute period) and dual phase IV contrast study. The two phases are arterial (30 second delay) and venous phase imaging (70 second delay). The scans use thin section CT (ideally .75 mm) and interscan spacing (.5mm) for isotrophic datasets. Images are reviewed in axial and multiplanar reconstruction planes (coronal and sagittal) and 3D imaging with volume rendering and MIP imaging. |
| Pearls | The detection of small bowel obstruction is based on the review of the small bowel for distension, wall thickening, perfusion changes and/or abnormalities of the key arterial and venous phase imaging. 1. Review of the axial images shows whether bowel is dilated (over 2.5 cm) and whether there is thickening of the small bowel (3mm or greater). We also look carefully at the bowel for enhancement including whether or not there is increased or decreased bowel enhancement 2. When looking at the small bowel coronal views are ideal for looking at transition points while sagittal views are ideal to look at the Celiac, SMA and IMA origins 3. Looking for suspected bowel obstruction means to look for transition points ranging from an internal hernia with volvulus, to a small bowel tumor to narrowing due to crohns disease 4. The mesenteric arcade is important when looking at the branching of the SMA especially for ischemia. 5. The appearance of small bowel tumors ranges from adenocarcinoma to lymphoma to metastases to GIST tumors 6. When looking for the cause of SBO 3D MIP and VRT images can be helpful 7. When looking at inflammatory bowel disease like crohns it is important to also look at the mesenteric fat and mesenteric arcade 8. The presence of GI bleed can be due to tumor, ulcer or angiodysplasia. Careful looking at MIP images with thin slabs may be helpful 9. The presence of pneumatosis is always a concerning sign of bowel ischemia. This is not always the case but is of great concern. |