A 36-year-old woman with history of ulcerative colitis, status post-ileoanal J-pouch anastomosis, and total proctocolectomy presented with leakage of stool from her vagina. The fistula tract could not be fully visualized directly or identified on endoanal ultrasonography, but was diagnosed by peroxide-enhanced endovaginal ultrasound.The use of peroxide-enhancement while performing 3-dimensional endovaginal sonographic imaging may be of benefit to patients with rectovaginal fistulas that cannot be fully evaluated by physical examination or more typical use of endoanal ultrasonography.