Imaging

Colitis

Preliminary Diagnosis: Colitis

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

CT of the abdomen and pelvis with IV and oral contrast.

II. Describe the advantages and disadvantages of this technique for diagnosing colitis.

Advantages

  • A relatively quick imaging procedure that requires minimal patient cooperation.

  • The imaging may suggest certain pathogens when infectious colitis is suspected.

  • Modality of choice for patients suspected of having neutropenic colitis, due to the high risk of perforation with endoscopy.

  • Complications of colitis, including pneumatosis, abscess, perforation, toxic megacolon and peritonitis can be detected with a contrast enhanced CT.

Disadvantages

  • Findings of colitis can be nonspecific, and the final diagnosis often needs confirmation with stool/blood cultures, endoscopy and serologic testing.

  • Differentiation between TB colitis and Crohn’s disease may be difficult.

  • Exposes the patient to ionizing radiation.

  • Exposes the patient to intravenous contrast and the risk of renal injury.

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

  • 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.

  • Relatively contraindicated in pregnant women, especially during 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?

  • Acute abdominal series x-rays.

  • Barium fluoroscopy.

V. Describe the advantages and disadvantages of the alternative techniques for diagnosing colitis.

Acute abdominal series x-rays

Advantages

Can quickly provide information regarding bowel dilation, obstruction and possible free air.

Disadvantages

  • Evaluation for pneumoperitoneum is limited in patients who cannot tolerate upright or decubitus films.

  • Although the dose is low, abdominal radiographs use ionizing radiation and caution should be used in pregnant or young patients.

Barium fluoroscopy

Advantages

May offer better visualization of the bowel mucosa in double contrasted barium.

Disadvantages

Barium enemas have limited utility in infectious colitis and have been largely replaced by CT.

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

Acute abdominal series x-rays

  • No contraindications to plain radiographs.

Barium fluoroscopy

  • Barium studies are contraindicated in patients with peritoneal signs due to risk of bowel perforation.

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