Fig. 14
Simple fistula (white arrows) shown on TSE T2-weighted (a) and STIR (b) images. The axial T1-weighted image after gadolinium contrast (c) shows avid contrast enhancement of the fistula (white arrow) but to lesser degree the anal sphincter. The sagittal T1-weighted image (d) a few minutes later (note the filling of the urinary bladder) demonstrates decreased distinction in degree of contrast enhancement between the fistula (white arrow) and the anal sphincter (hatched arrow), consistent with time intensity curve characteristics described by Horsthuis et al. [13]