Rectovaginal Fistulas

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.

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.