MR Imaging Finding Sensitivity Specificity PPV NPV Primary track 96(52/54) 96(54/56) 96(52/54) 96(54/56) Abscess 100(20/20) 100(20/20) 100(20/20) 100(20/20) Horseshoe fistula 100(5/5) 100(5/5) 100(5/5) 100(5/5) Internal opening 96(52/54) 96(54/56) 96(52/54) 96(54/56)

Table 2: Accuracy of MR Imaging for the detection of a Primary track, Abscess, Horseshoe fistula and Internal opening.