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