Ultrasound Podcast with Mike and Matt on Small Bowel Obstruction

By Elizabeth Dei Rossi, MD

Please refer to The Ultrasound Podcast

Different modalities can be used for diagnosing SBO

  • CT scan is considered gold standard
    • sensitivity of 92% and a specificity of 93%
    • Mallo RD et al. CT diagnosis of ischemic and complete obstruction in SBO: a sys review. J Gastrointest Surg 2005
    • Abd xray is often used a rapid test in the ER but has very poor sensitivity/specificity
      • Looks for air fluid levels
      • sensitivity of 66-77% and specificity of 50-57%
      • Shrake PK, Rex DK, Lappas JC, et al. (1991) Radiographic evaluation of suspected small bowel obstruction.  Am J Gastroenterology 86:175-178
      • Ultrasound can be used for diagnosis of SBO
        • Sensitivity of 88% and specificity of 96%
        • Ogata M et al Prospective Evaluation of Abdominal Sonography for the diagnosis of bowel obstruction. Annals of surgery in 1996
        • can see SBO without air


Ultrasound findings in patients with SBO

  • Fluid filled bowel
  • Dilated bowel with back and forth peristalsis


Bedside ultrasonography of the detection of small bowel obstruction in the emergency department by Timothy B Jang, Danielle Schindler, and Amy H Kaji

  • Methods
    • Residents were given 10 min of training with 5 scans performed then patient’s with suspected small bowel obstruction had an US and XRAY, CT scan was used as the gold standard
    • Using a phased array probe bilateral colic gutters, epigastric and suprapubic areas were assessed for dilated loops of bowel with peristalsis (big loops of bowel with movement back and forth of bowel)
    • Results
      • Dilated bowel on US had a sensitivity of 91% and a specificity of 84%
      • Xray had a sensitivity of 46% and specificity of 67%
      • Some tips from Dr. Timothy Jang
        • Decreased peristalsis is a late finding and therefore not something for which to look
        • If you see dilated bowel also consider non-SBO etiologies like ileus
        • Study didn’t assess for transition point
        • Look for gallstones if you see dilated bowel (gallstone ileus)
        • In SBO bowel wall thickening is a prognostic sign and may suggest diagnosis like IBD and colitis

In summary US is potentially a quicker study without side effects of radiation that has a better sensitivity and specificity than XRAY.  Develop your own practice with this information: maybe use to rule out low risk patients.

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