Abstract: Methods and materials involved in assessing and treating a mammal having a rectovaginal fistula (RVF) are provided herein. For example, the methods and materials described herein can be used for determining if a mammal having a RVF is likely to experience a successful outcome after surgical repair of the RVF, or if the mammal is likely to experience recurrence. Methods and materials for modulating the rectal and/or vaginal microbiome of mammal having a RVF also are provided herein.