Imaging

Small Bowel Obstruction

Preliminary Diagnosis: Small Bowel Obstruction

I. What imaging technique is first-line for this diagnosis?

CT with IV and PO contrast. If a complete or high-grade obstruction is suspected, then PO contrast should not be given.

II. Describe the advantages and disadvantages of this technique for diagnosing small bowel obstruction.

Advantages

  • High sensitivity and specificity for small bowel obstruction. Sensitivity of CT decreases for low-grade obstruction, but is highest when PO contrast is given.

  • Identifies transition point of obstruction.

  • Identifies degree of obstruction (low grade, high grade, or complete).

  • Can identify complications from obstruction (i.e., perforation, bowel ischemia).

  • May identify cause of small bowel obstruction (e.g. adhesion, hernia, neoplasm, inflammatory disorder), which may affect clinical management.

Disadvantages

  • Exposure to ionizing contrast.

III. What are the contraindications for the first-line imaging technique?

  • If a complete or high grade obstruction is suspected, then PO contrast should not be given.

  • Contraindicated for use during pregnancy.

  • Relative contraindication of contrast use in patients with renal failure.

  • Relative contraindication of contrast use in patients with contrast allergy.

IV. What alternative imaging techniques are available?

  • Plain radiograph

  • Small bowel follow-through

V. Describe the advantages and disadvantages of the alternative techniques for diagnosing small bowel obstruction.

Plain radiograph

Advantages

  • Can be diagnostic of small bowel obstruction.

  • Can demonstrate signs of complications from obstruction (e.g., pneumoperitoneum).

Disadvantages

  • Typically does not identify the cause, degree, or precise location of obstruction, which would often affect clinical management.

Small bowel follow-through/enteroclysis

Advantages

  • There is less radiation exposure than in CT.

Disadvantages

  • Does not provide extraluminal information which may identify cause of obstruction and affect clinical management.

  • Similar sensitivity and specificity to CT in identifying low-grade obstruction.

VI. What are the contraindications for the alternative imaging techniques?

Plain radiograph

No significant contraindications. Some institutions may require consent for pregnant patients.

Small bowel follow-through/enteroclysis

Contraindicated in suspected complete or high-grade obstruction.

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