Rectovaginal fistula (MRI enema)

Case contributed by Dr Vikas Shah

Presentation

Anterior resection for adenocarcinoma. Assess anastomosis. Passing brown material from the vagina but not clear if it is fecal matter.

Patient Data

Age: 70 years
Gender: Female

Water soluble contrast enema

Fluoroscopy

Early and large volume leak of contrast from the anterior aspect of the rectum into vagina, indicating rectovaginal fistula. Contrast passes upstream to the side-to-end anastomosis into the distal sigmoid.

CT immediately after WSCE

CT

Limited CT volume acquired immediately after the water-soluble contrast enema confirms anterior rectovaginal fistula at the level of the anastomosis.

MRI enema 6 months later

MRI

MRI enema to check the status of fistula 6 months later.

Volume and standard T2 acquisitions, pre and post introduction of 120 ml of sterile ultrasound gel per anally.

Artefact in the posterior pelvis due to the staples just above the level of the anastomosis (also seen on the prior CT). A persistent rectovaginal fistula is discerned on the pre-gel sequences, with a small volume of high T2 signal in the lumen of the vagina at this level.

The gel causes distension of the rectum and secondary anterior displacement of the rectovaginal septum away from the artefact caused by the staples. Gel is seen to enter an anterior track (from the 12 o'clock position) between the rectum canal and the posterior vagina, indicating a persistent rectovaginal fistula. The fistula looks smaller than on the prior WSCE and CT.

Case Discussion

An MRI enema protocol utilizes the soft tissue resolution of MRI to delineate vaginal and anorectal anatomy, with the luminal gel insertion providing further data regarding the possibility of a fistula track. Multiplanar reformats of the volume T2 sequences aid in image analysis and reporting. The study can be acquired in 20 minutes and avoids the need for radiation from fluoroscopy or CT, of greater importance in younger patients undergoing investigation for obstetric anorectovaginal fistula.

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