UOTW #20 Answer

Answer: Small bowel obstruction

Small bowel obstruction (SBO) has been reported to be present in 2% of all patients presenting to the E.D. with abdominal pain.¹ A delay in diagnosis is associated with worsening morbidity and mortality,² and the vast majority of patients with SBO are first seen in the E.D.³ Bedside imaging methods for the diagnosis of an SBO include abdominal X-ray (AXR) and ultrasound (US). A recent meta-analysis by Taylor et al⁴ compared those diagnostic modalities and found surprising results. AXR has a paultry +LR of 1.6 and a –LR of 0.43. Ultrasound, however, was found to have a +LR of 14.1 and a –LR of 0.13 when performed in the radiology department, and a +LR of 9.5 and a –LR of 0.04 when performed by emergency physicians.⁴

• When scanning the abdomen, you should use a systematic approach so critical findings are not missed.  One such method is called moving the lawn:

• The main finding diagnostic of SBO on US is the visualization of dilated loops of bowel >2.5 cm.⁴
• Other findings that increase the likelihood of SBO include thickened bowel walls >3mm⁵ and hyperechoic material moving back and forth within thickened bowel loops.
• Concomitant abdominal free fluid has been demonstrated to be associated with higher grade obstruction.⁶ The tanga sign⁷ represents abdominal free fluid between loops of bowel.

Post and Scan by: Jacob Avila, MD, RDMS

1. Hastings RS, Powers RD. Abdominal pain in the ED: a 35 year retrospective. Am J Emerg Med. 2011; 29:711–6. [pubmed]
2. Bickell N, Federman A, Aufses AH. Influence of time on risk of bowel resection in complete small bowel obstruction. J Am Coll Surg. 2005; 201:847–54. [pubmed]
3. Foster NM, McGory ML, Zingmond DS, Ko CY. Small bowel obstruction: a population-based appraisal. J Am Coll Surg. 2006; 203:170–6. [pubmed]
4. Taylor MR, Lalani N. Adult small bowel obstruction. Acad Emerg Med. 2013;20(6):528-44. [pubmed]
5. Hefny AF, Corr P, Abu-zidan FM. The role of ultrasound in the management of intestinal obstruction. J Emerg Trauma Shock. 2012;5(1):84-6. [pubmed]
6. Grassi R, Romano S, D’amario F, et al. The relevance of free fluid between intestinal loops detected by sonography in the clinical assessment of small bowel obstruction in adults. Eur J Radiol. 2004;50(1):5-14. [pubmed]
7. Mizio, Roberto. Small Bowel Obstruction CT Features with Plain Film and US Correlations. Milan: Springer, 2007. Print. [Amazon]