Preliminary Diagnosis: Large Bowel Obstruction
I. What imaging technique is first-line for this diagnosis
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CT with IV and PO contrast
II. Describe the advantages and disadvantages of this technique for diagnosis of large bowel obstruction.
Advantages
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High sensitivity and specificity for large bowel obstruction
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Identifies transition point of obstruction
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Identifies degree of obstruction (low grade, high grade, or complete)
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Can identifiy complications from obstruction (i.e., perforation, bowel ischemia)
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May identify cause of large bowel obstruction (e.g., neoplasm, inflammatory disorder, volvulus), which will often affect clinical management
Disadvantages
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Exposure to ionizing radiation
III. What are the contraindications for the first-line imaging technique?
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If a complete or high grade obstruction is suspected, then PO contrast should not be given.
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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?
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Plain radiograph
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Barium enema
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of large bowel obstruction.
Plain radiograph
Advantages
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May show large bowel dilatation, which can be diagnostic of large bowel obstruction
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Can also demonstrate signs of complications from obstruction (e.g., pneumoperitoneum)
Disadvantages
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Typically does not provide the cause, degree, or precise location of obstruction, which would often affect clinical management
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Often not diagnostic
Barium enema
Advantages
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Can clearly identify transition point in sigmoid originating large bowel obstructions.
Disadvantages
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Does not provide any information on extracolonic abnormalities, which would identify cause of large bowel obstruction
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Does not provide evidence of mural changes or complications from obstruction
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Exposure to ionizing radiation
VI. What are the contraindications for the alternative imaging techniques?
Plain radiograph
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No significant contraindications; may require consent for pregnant patients at some institutions
Barium enema
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Contraindicated if perforation suspected
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