Medicine by the Numbers

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Accuracy of Ultrasonography for the Diagnosis of Small Bowel Obstruction

 

Am Fam Physician. 2021 Aug ;104(2):135-136.

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Details for This Review

Study Population: 1,178 patients, across 11 trials, with suspected small bowel obstruction

Efficacy End Points: Diagnosis of small bowel obstruction

Harm End Points: Data on harms not reported

Narrative: Small bowel obstruction comprises 2% of all patients presenting to the emergency department (ED) with abdominal pain, with more than 300,000 hospitalizations per year.1,2 If not appropriately diagnosed, small bowel obstruction can result in intestinal ischemia, necrosis, and perforation.3  Traditional methods for diagnosing the condition, such as plain radiography, have poor sensitivity and specificity (Table 14,5) and expose patients to radiation.4 Other imaging modalities include computed tomography (CT) and magnetic resonance imaging (MRI). However, they may be expensive, they are not available at all institutions, and CT is associated with radiation exposure.

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TABLE 1.

Accuracy of Imaging Tests for the Diagnosis of Small Bowel Obstruction

ModalityLR+ (95% CI)LR− (95% CI)Sensitivity(95% CI)Specificity(95% CI)

Computed tomography*4

3.6 (2.3 to 5.4)

0.18 (0.09 to 0.35)

87 (83 to 90)

81 (74 to 87)

Magnetic resonance imaging4

6.7 (2.1 to 21.5)

0.11 (0.04 to 0.26)

92 (80 to 98)

89 (65 to 99)

Plain radiography 4

1.6 (1.1 to 2.5)

0.43 (0.24 to 0.79)

75 (68 to 80)

66 (55 to 76)

Ultrasonography5

27.5 (7.7 to 98.4)

0.08 (0.06 to 0.11)

92 (89 to 95)

97 (88 to 99)


LR− = negative likelihood ratio; LR+ = positive likelihood ratio.

*— This summary estimate incorporates several generations of computed tomography and different slice sizes (0.75 mm to 50 mm). Studies with smaller slice sizes and current generation scanners demonstrate significantly higher test characteristics.

Information from references 4 and 5.

TABLE 1.

Accuracy of Imaging Tests for the Diagnosis of Small Bowel Obstruction

ModalityLR+ (95% CI)LR− (95% CI)Sensitivity(95% CI)Specificity(95% CI)

Computed tomography*4

3.6 (2.3 to 5.4)

0.18 (0.09 to 0.35)

87 (83 to 90)

81 (74 to 87)

Magnetic resonance imaging4

6.7 (2.1 to 21.5)

0.11 (0.04 to 0.26)

92 (80 to 98)

89 (65 to 99)

Plain radiography 4

1.6 (1.1 to 2.5)

0.43 (0.24 to 0.79)

75 (68 to 80)

66 (55 to 76)

Ultrasonography5

27.5 (7.7 to 98.4)

0.08 (0.06 to 0.11)

92 (89 to 95)

97 (88 to 99)


LR− = negative likelihood ratio; LR+ = positive likelihood ratio.

*— This summary estimate incorporates several generations of computed tomography and different slice sizes (0.75 mm to 50 mm). Studies with smaller slice sizes and current generation scanners demonstrate significantly higher test characteristics.

Information from references 4 and 5.

Ultrasonography has demonstrated promise in the diagnosis of small bowel obstruction,6,7 and a meta-analysis including prospective observational studies evaluated the accuracy of ultrasonography for this use.5 The reference standard confirmatory test was determined by individual study definition and included CT, enteroclysis, diagnosis at surgery or discharge, or diagnosis at clinical follow-up. The primary outcome was diagnostic accuracy of ultrasonography for small bowel obstruction, with a subgroup analysis based on specific clinical setting (ED vs. non-ED setting). The authors of the meta-analysis also conducted a sensitivity analysis that categorized inconclusive ultrasound results as false-negatives.

The authors of the meta-analysis identified 9,774 records, of which 11 prospective observational studies (n = 1,178) met the inclusion criteria.5 These studies enrolled patients with signs and symptoms of suspected acute small bowel obstruction, with most studies using a convenience sample. Five studies were conducted in the ED, and six were conducted in other settings, including gastroenterology or radiology clinics, or the setting was not reported. The ultrasonography was performed by an ED clinician in three studies and a radiologist in five studies, and the sonographer was not described in the remainder of studies. The mean age of patients was 50 years, and 74% of patients were male.

Overall, ultrasonography was 92.4% sensitive (95% CI, 89.0% to 94.7%) and 96.6% specific (95% CI, 88.4% to 99.1%), with a positive li

Author disclosure: No relevant financial affiliations.


Copyright © 2021 MD Aware, LLC (theNNT.com). Used with permission.

This series is coordinated by Christopher W. Bunt, MD, AFP assistant medical editor, and the NNT Group.

A collection of Medicine by the Numbers published in AFP is available at https://www.aafp.org/afp/mbtn.

References

show all references

1. Irvin TT. Abdominal pain: a surgical audit of 1190 emergency admissions. Br J Surg. 1989;76(11):1121–1125....

2. Hastings RS, Powers RD. Abdominal pain in the ED: a 35 year retrospective. Am J Emerg Med. 2011;29(7):711–716.

3. Paulson EK, Thompson WM. Review of small-bowel obstruction: the diagnosis and when to worry. Radiology. 2015;275(2):332–342.

4. Taylor MR, Lalani N. Adult small bowel obstruction. Acad Emerg Med. 2013;20(6):528–544.

5. Gottlieb M, Peksa GD, Pandurangadu AV, et al. Utilization of ultrasound for the evaluation of small bowel obstruction: a systematic review and meta-analysis. Am J Emerg Med. 2018;36(2):234–242.

6. 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):676–678.

7. Suri S, Gupta S, Sudhakar PJ, et al. Comparative evaluation of plain films, ultrasound and CT in the diagnosis of intestinal obstruction. Acta Radiol. 1999;40(4):422–428.

8. Becker BA, Lahham S, Gonzales MA, et al. A prospective, multicenter evaluation of point-of-care ultrasound for small-bowel obstruction in the emergency department. Acad Emerg Med. 2019;26(8):921–930.

 

 

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