Endoanal probe technology provides high-resolution soft-tissue imaging for periluminal anal and rectal disease, most notably in complex perirectal sepsis and in patients presenting with fecal incontinence and sphincter damage. The trend is a movement away from direct sphincter repair toward sacral neuromodulation in external anal sphincter (EAS) injury. However, endoanal magnetic resonance imaging (EAMRI) has shown clear accuracy in the delineation of both EAS defects suitable for surgical treatment and in the definition of internal anal sphincter (IAS) damage potentially suitable for bioimplant deployment. Moreover, endoanal MR images have shown a correlation with histopathologically defined sphincter atrophy, which in turn has been predictive of relatively poor postsphincteroplasty outcomes. The role of EAMRI in the hierarchy of imaging modalities for use in an incontinence algorithm is somewhat unclear in the absence of comparative randomized clinical trials. However, it has a definitive place in defining sphincter atrophy in equivocal cases that are perhaps best treated nonoperatively or initially by temporary neuromodulatory stimulation.
Imaging Atlas of the Pelvic Floor and Anorectal Diseases p. 39-48