Imaging

Large Bowel Obstruction

Preliminary Diagnosis: Large Bowel Obstruction

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

  • CT with IV and PO contrast

II. Describe the advantages and disadvantages of this technique for diagnosis of large bowel obstruction.

Advantages

  • High sensitivity and specificity for large bowel obstruction

  • Identifies transition point of obstruction

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

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

  • May identify cause of large bowel obstruction (e.g., neoplasm, inflammatory disorder, volvulus), which will often affect clinical management

Disadvantages

  • Exposure to ionizing radiation

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.

  • Due to radiation exposure, CT should be used conservatively in the pediatric population and is contraindicated in pregnancy.

IV. What alternative imaging techniques are available?

  • Plain radiograph

  • Barium enema

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of large bowel obstruction.

Plain radiograph

Advantages

  • May show large bowel dilatation, which can be diagnostic of large bowel obstruction

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

Disadvantages

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

  • Often not diagnostic

Barium enema

Advantages

  • Can clearly identify transition point in sigmoid originating large bowel obstructions.

Disadvantages

  • Does not provide any information on extracolonic abnormalities, which would identify cause of large bowel obstruction

  • Does not provide evidence of mural changes or complications from obstruction

  • Exposure to ionizing radiation

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

Plain radiograph

  • No significant contraindications; may require consent for pregnant patients at some institutions

Barium enema

  • Contraindicated if perforation suspected

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