diagnosis of perianal fistula

This study investigated the effectiveness of magnetic resonance imaging (MRI) with rectal administration of the enteral contrast agent gadolinium diethylene triamine pentaacetic acid (Gd-DTPA) in the diagnosis of recurrent perianal fistulae, assessing the number, anatomical extent, location, and signal intensities of various lesions. Fistulas were examined by MRI before and after rectal administration of Gd-DTPA in 50 patients (excluding fistulas due to inflammatory bowel disease). Surgical findings were compared with both pre- and postcontrast T1-weighted, T2-weighted, and short T1 inversion recovery (STIR) sequences. Of the 68 fistulous tracts detected surgically, precontrast imaging identified 16 by TI-weighted images (hypointense), 27 by T2-weighted images (hyperintense or iso- to weakly hyperintense), and 54 by STIR. Postcontrast imaging identified 29 by T1-weighted images, 58 by T2-weighted, and 54 by STIR. MRI with rectal administration of Gd-DTPA thus facilitates determination of fistula tracts, which are better resolved by precontrast STIR than by either precontrast T1- or T2 weighted images. Postcontrast T2-weighted images were substantially superior to T1-weighted. Both noncontrast STIR and postcontrast T2-weighted sequences were adequate for classifying fistulas in ano, but in complex recurrent anal fistula postcontrast T2-weighted images were more helpful