Ultrasound
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Dx: Small Bowel Obstruction

The patient’s bedside ultrasound of his abdomen demonstrates large, dilated loops of small bowel throughout his entire abdomen (Image 2). The loops of bowel are > 3 cm in diameter and are present diffusely in all four quadrants. Right on cue, the patient notes that he hasn’t had a normal bowel movement all week and that he stopped passing gas yesterday. He hasn’t had an appetite over the past few days, and he feels like the sharp, cramping pain he is experiencing, is going to make him vomit.

 

Your resident changes his tune after seeing the bedside ultrasound images and offers the patient IVF’s, IV pain medications, IV antiemetics, a surgical consultation plus an admission to the hospital for SBO. The surgeons would like a CT scan of the patient’s abdomen before he goes upstairs (of course) and the patient would like an IV cocktail of Dilaudid, Phenergan, and Benadryl (no surprise).

Your shift is coming to an end so you invite your resident out to grab a late night snack to unwind and debrief. Over drinks, you discuss the issues surrounding burn-out in the field of emergency medicine and you offer him some tips on how to keep it at bay:

  1. Remember and remind yourself why you became a physician.
  2. Congratulate yourself on the differences you have already made, and the ones you will continue to make in your daily work.
  3. Make time to take care of yourself and your family.
  4. Our career as EM physicians should be thought of as a marathon, and not a sprint. Pace yourself and continue to train accordingly.
  5. Set personal and professional goals and re-evaluate these goals regularly.


Your resident thanks you for the mentoring and the advice, and leaves with a new hop in his step. You take your own advice, order dessert, and reflect about all the good you were able to accomplish in just one ED shift. One day at a time…

 

Pearls & Pitfalls for performing Ultrasonography to Diagnose Small Bowel Obstruction

01 Save Some Time
Compared to CT or abdominal X-rays, ultrasound can be performed in less than 5 minutes and can significantly increase your pre-test probability for a small bowel obstruction, as well as easily identify ascites in a patient presenting with a distended abdomen. Recent studies suggest that dilated bowel on US had a sensitivity of 91% and specificity of 84% for SBO.

Decreased bowel peristalsis on US was less sensitive (24%) but more specific (98%)1. Use bedside ultrasound to expedite the patient’s emergency department treatment plan. Remember that it is very difficult to determine if the patient has free air on bedside ultrasound. If you are suspicious for perforation, order an upright abdominal or chest x-ray to look for free air under the diaphragm.

02 Getting Started
Use the low frequency (5 to 1 MHz) phased array or curvilinear transducer. You may want to start with a quick FAST scan to ensure there is no free fluid and to identify some intra-abdominal landmarks. Next scan the patient’s abdomen in a systemic manner looking for dilated loops of bowel. It often helps to have the patient point to where it hurts the most and start your scan at that spot.

03 Know What You Are Looking For
In general, large fluid-filled small bowel is relatively easy to see on ultrasound. Experienced ultrasonographers can usually identify these dilated loops based on clinical experience alone. More specifically, previous criteria used for a positive ultrasound includes dilated loops of bowel greater than 25mm in the jejunum or 15mm in the ileum over a length of at least 3 loops. Decreased bowel peristalsis may also be seen, but this can be difficult to identify if you are a novice ultrasonographer.2

04 Avoid Pitfalls
Remember that sensitivity and specificity of ultrasound diagnosis is operator dependent. If your clinical suspicion for SBO remains high after your bedside ultrasound, obtain appropriate imaging and consultation per your department’s protocol. Air-filled loops of bowel can scatter the ultrasound waves and also make it more difficult to identify bowel borders. Remember to use your acoustic windows (spleen, liver, bladder, etc.) and be flexible in how you angle your beam to obtain to the best images possible.

References
1. Jang TB, Schindler D, Kaji AH. Bedside ultrasonography for the detection of small bowel obstruction in the emergency department. Emerg Med J. 2011;28(8):676-8.
2. Unluer EE, Yavasi O, Eroglu O, et al. Ultrasonography for emergency medicine and radiology residents for the diagnosis of small bowel obstruction. Eur J Emerg Med. 2010;17(5):260-4.

Brady Pregerson (@TheSafetyDoc) manages a free online EM Ultrasound Image Library and is the editor of the Emergency Medicine Pocketbook series. For more info visit EMresource.ORG.

Teresa S. Wu (@TeresaWuMD) is the Associate Residency Director, and Director of Ultrasound and Simulation Programs and Fellowships, for the Maricopa EM Program in Phoenix, Arizona. Dr. Wu is the creator of SonoSupport, an ultrasound app for smartphones and tablets.



 



 

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