Figure 4a. Abscess and fistula track missed at surgery. (a) Coronal and (b) transverse T2-weighted two-dimensional turbo SE (3,427/150) MR images show a hyperintense lesion with a hypointense rim (arrowhead in a) above the pelvic floor, which suggests a small abscess in the supralevator space. Note the layering of debris within the fluid collection (arrow in b). Also note the hyperintense structure between the sphincter muscles (arrow in a) that extends toward the abscess collection. MR imaging was used to correctly predict the presence of a left intersphincteric blind-ending fistula track leading toward a supralevator abscess collection on the left side. Both the track and abscess were missed at initial surgical exploration because the patient was thought to have only a sinus on the contralateral side (not shown).