Figure 5a. Horseshoe fistula and rectal opening missed at surgery. (a-d) Coronal T2-weighted two-dimensional turbo SE (3,427/150) MR images from posterior (a) to anterior (d) show two hyperintense fluid collections that cross the midline, one located infralevatorly (arrow in a and b) and the other at the level of the pelvic floor (arrowhead in a and b). A secondary track (arrow in c) ascends from the highest collection toward the rectal lumen. The rectal opening (arrowhead in d) is clearly visualized. MR imaging findings suggested the presence of two horseshoe fistulas at different levels, with connection to the rectal lumen. The surgeons identified the lower horseshoe fistulas but missed the higher extensions because the problem was thought to have been solved by draining the lower extension. Because of the additional MR imaging information, surgical exploration was extended, and the higher extensions were found and properly treated.