Preliminary Diagnosis: Rectovaginal Fistulas

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

Contrast enema with barium or water-soluble contrast.

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

Advantages

  • Specific examination as entry point with contrast near the diseased segment of bowel. Can easily and quickly identify the location, length, and quality of the fistula.

  • Inexpensive, quick examination.

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Disadvantages

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

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

  • May not see the abnormality, as there are contrast filled loops of bowel overlying the region of abnormality.

  • Can be messy, as there is leakage of contrast on the patient and the fluoroscopic table.

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

Relative contraindications in pregnant women.

IV. What alternative imaging techniques are available?

  • CT with oral and/or rectal contrast and with intravenous contrast.

  • Vaginography.

  • Radiographs.

  • MRI.

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

CT with IV contrast with additional oral and/or rectal contrast
Advantages

  • Specific, quick examination that allows one to obtain multiplanar reformats to better visualize the scanned structures.

  • Can visualize and identify fistulas (length, location, etc.)

  • Can appreciate enhanced characteristics of diseased segments of bowel (perifistular inflammation).

Disadvantages

  • Exposure to ionizing radiation.

Vaginography
Advantages

  • Inexpensive and can specifically isolate and identify the fistula tract with barium or water soluble oral contrast.

Disadvantages

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

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

  • Can be messy, as there is leakage of contrast on the patient and the fluoroscopic table.

Radiographs
Advantages

  • Inexpensive.

  • May show ectopic gas.

Disadvantages

  • Very nonspecific.

  • Difficult to identify and characterize a fistula using this imaging modality.

  • Only beneficial if oral/rectal or vaginal contrast is administered prior to the study.

MRI
Advantages

  • Provides excellent detail regarding fistulas.

Disadvantages

  • Expensive.

  • May be time consuming.

  • Requires significant patient cooperation to minimize motion artifact.

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

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

CT with IV contrast with additional oral and/or rectal contrast

  • Relative contraindication in pregnant patients.

Vaginography

  • Relative contraindication in pregnant patients.

Radiographs

  • No significant contraindication. Some institutions may require consent in pregnant patients.

MRI

  • Contraindicated in patients with non-MR compatible hardware.

  • Relative contraindication to administer gadolinium-based contrast agent during pregnancy or in patients with renal failure.

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