What is the role of MRI in the workup of enterovesical fistula?

Updated: Dec 24, 2020
  • Author: Joseph Basler, MD, PhD; Chief Editor: Bradley Fields Schwartz, DO, FACS  more...
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MRI can be used to identify enterovesical fistulae. In a study of 25 patients with Crohn disease, 16 patients had enterovesical, deep perineal, or cutaneous fistulae. One false-negative result occurred in a patient who had a colovesical fistula. [48] Some authors recommend MRI evaluation in patients with Crohn disease given the presence of chronic inflammation and superior anatomic detail in relation to the anal sphincter. Another benefit is that this study does not expose the patient to additional radiation. [49]

T1-weighted images delineate the extension of the fistula relative to sphincters and adjacent hollow viscera and show inflammatory changes in fat planes.

T2-weighted images show fluid collections within the fistula, localized fluid collections in extra-intestinal tissues, and inflammatory changes within muscles.

MRI may be useful in identifying deep perineal fistulae but is not generally used in the routine workup of colovesical fistulae. In a study of 22 patients who presented with symptoms suggestive of colovesical fistula, MRI was performed in conjunction with cystoscopy. Afterward, 19 of the patients underwent laparotomy and repair. They found that MRI correctly identified 18 cases of fistula. Fistula was ruled out in the remaining patient. This data showed MRI to be a highly sensitive and specific study for colovesical fistula.

Although MRI is an excellent study, the increasing image quality of CT scanning, together with the high cost and limited availability of MRI, limit the practical application MRI as a diagnostic study for enterovesical fistulae. [50]

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