ENDOANAL MRI OF THE ANAL-SPHINCTER COMPLEX - CORRELATION WITH CROSS-SECTIONAL ANATOMY AND HISTOLOGY

The purpose of this study was to correlate the in vivo endoanal MRI fi ndings of the anal sphincter with the cross-sectional anatomy and hist ology. Fourteen patients with rectal tumours were examined with a rigi d endoanal MR coil before undergoing abdominoperineal resection. In ad dition, 12 cadavers were used to obtain cross-sectional anatomical sec tions. The images were correlated with the histology and anatomy of th e resected rectal specimens as well as with the cross-sectional anatom ical sections of the 12 cadavers. The findings in 8 patients, 11 recta l preparations, and 10 cadavers, could be compared. In these cases, th ere was an excellent correlation between endoanal MRI and the cross-se ctional cadaver anatomy and histology. With endoanal MRI, all muscle l ayers of the anal canal wall, comprising the internal anal sphincter, longitudinal muscle, the external anal sphincter and the puborectalis muscle were clearly visible. The levator ani muscle and ligamentous at tachments were also well demonstrated. The perianal anatomical spaces, containing multiple septae, were clearly visible. In conclusion, endo anal MRI is excellent for visualising the anal sphincter complex and t he findings show a good correlation with the cross-sectional anatomy a nd histology.