Preliminary Diagnosis: Ulcerative colitis
I. What imaging technique is first-line for this diagnosis
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Colonoscopy is the gold standard.
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CT of the abdomen and pelvis with IV and oral contrast is indicated in patients with abdominal pain in whom colitis is suspected or to evaluate for complications of known ulcerative colitis (e.g., abscess, perforation, toxic megacolon).
II. Describe the advantages and disadvantages of this technique for diagnosis of ulcerative colitis.
Advantages
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CT scan with IV and PO contrast is not diagnostic for ulcerative colitis, but can show the features associated with the disease that can guide further workup with colonoscopy and tissue biopsy
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Disadvantages
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Risks of CT imaging include exposure to ionizing radiation and renal injury from intravenous contrast agents. Assessment of renal function is required prior to administration of IV contrast.
III. What are the contraindications for the first-line imaging technique?
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Patients with allergic reactions (e.g., itching, rash) to intravenous contrast and more severe allergic reactions (e.g., angioedema) should be pretreated with steroids and antihistamines for a minimum of 13 hours prior to CT imaging with IV contrast. Anaphylaxis to prior contrast administration is an absolute contraindication to intravenous contrast.
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Relatively contraindicated in pregnant women, especially within the first two trimesters. In certain institutions, informed consent is required prior to imaging pregnant women with CT.
IV. What alternative imaging techniques are available?
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Acute abdominal series x-rays
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Barium enemas
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of ulcerative colitis.
Acute abdominal series x-rays
Advantages
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Can provide quick information regarding bowel dilation, obstruction and possible free air.
Disadvantages
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Limited diagnostic utility for ulcerative colitis
Barium enemas
Advantages
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Can show mucosal irregularity, benign stricturing, and haustral changes.
Disadvantages
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Limited utility in surveillance of ulcerative colitis.
VI. What are the contraindications for the alternative imaging techniques?
Acute abdominal series x-rays
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No contraindications to plain radiographs
Barium enemas
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Contraindicated in patients with bowel perforation.
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Acute inflammation, signs of toxic megacolon and peritonitis are also contraindications due to high risk of perforation during the study.
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