Imaging

Abdominal fistulas

Preliminary Diagnosis: Abdominal Fistulas

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

CT with oral and intravenous contrast

II. Describe the advantages and disadvantages of this technique for diagnosis of abdominal fistulas.

Advantages

  • Quick examination after allowing oral contrast to migrate through the bowel

  • Specific examination in identifying a particular place of bowel abnormality and the exact length and location of the fistula. The type of fistula may be ascertained.

  • Ability to obtain mutiplanar reformats for further analysis as well as 3D reconstructions

Disadvantage

  • Exposure to ionizing radiation with relative contraindications in pregnant female patients

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

  • Relative contraindications in pregnant female patients; otherwise, no other significant contraindications exist

IV. What alternative imaging techniques are available?

  • Upper GI fluoroscopy

  • Contrast enema

  • Fistulagram

  • Radiography

  • MRI

V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of abdominal fistulas.

Upper GI fluoroscopy

Advantages

  • Inexpensive

  • Can specifically isolate and identify the fistula tract with barium or water-soluble oral contrast

  • Radiation level is overall low, but varies based on the operator.

Disadvantages

  • Takes a great deal of patient cooperation and maneuverability to conduct the exam successfully.

  • May not be diagnostic, especially if there are contrast-filled loops of bowel overlying the region of abnormality

  • Can take more than 24 hours to opacify distal loops of bowel

Contrast enema

Advantages

  • Inexpensive

  • Can specifically isolate and identify the fistula tract with barium or water-soluble oral contrast

  • Radiation level is overall low but varies based on the operator.

Disadvantages

  • Takes a great deal of patient cooperation and maneuverability to conduct the exam successfully. Often uncomfortable for the patient

  • May not be diagnostic, especially if there are contrast-filled loops of bowel overlying the region of abnormality

  • Frequently messy as there is leakage of contrast on the patient and the fluoroscopic table

Fistulagram

Advantages

  • Inexpensive

  • Can specifically isolate and identify the fistula tract with barium or water-soluble oral contrast

  • Fistula length and other characteristics of the fistula can be obtained.

  • Radiation level is overall low but varies based on the operator.

Disadvantages

  • Takes a great deal of patient cooperation and often maneuverability to conduct the exam successfully

  • Frequently messy as there is leakage of contrast on the table and patient

Radiography

Advantages

  • Inexpensive

  • May show ectopic gas

Disadvantages

  • Very nonspecific and difficult to identify and characterize a fistula

  • Only beneficial if oral contrast had been administered prior to the study.

MRI

Advantages

  • Identifies areas of hyperemic bowel and hyperenhancing granulation tissue around a fistulous tract after administration of contrast

Disadvantages

  • More expensive than obtaining a CT, fluoroscopic evaluation, radiographs

  • Requires patient cooperation during acquisition of the images to minimize artifact

  • Abundance of bowel gas limits resolution when interpreting MR images.

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

Upper GI fluoroscopy

  • Upper GI fluoroscopy has relative contraindications in pregnant female patients. Otherwise, no significant contraindications exist.

Contrast Enema

  • Contrast enema has relative contraindications in pregnant females. Otherwise, no significant contraindications exist

Fistulagram

  • Fistulagram has relative contraindications in pregnant female patients. Otherwise, no significant contraindications exist.

Plain films (radiographs)

  • Plain film (radiographs) has relative contraindications in pregnant female patients. Otherwise, no significant contraindications exist.

MRI

  • No significant contraindications exist. Relative contraindication to administer gadolinium-based contrast agent during pregnancy

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