Use of MRI in evaluation of anorectal anomalies

Anal mucosal electric sensation in postoperative patients with anorectal malformations

“…Functional abnormality of defecation in postoperative patients with ARMs is caused by developmental lesions in the muscles of levator ani, especially the puborectal muscle, in addition to developmental lesions of internal and external anal sphincter muscles [1][2][3][4][5][6][7][8]. It has also been reported that in cases with additional malformation of the sacrum, pelvic neuropathy makes a contribution [9].…”

“…Investigations of postoperative defecation functions in patients with ARMs have mainly involved anal sphincter muscle tone, the new rectum storage ability, and the new sensory ability of the rectum at the time of an anorectal internal pressure test, when these have been reported to be in functional decline [1][2][3][4][5][6]. Morphologically, abnormalities in the growth of the puborectal muscle or the external anal sphincter muscle and abnormalities in the location of myotomes and in the rectum have been observed by barium enema examination, pelvic computed tomography, and magnetic resonance imaging [6][7][8].…”

MR imaging of anorectal malformations and associated anomalies

“…Multiplanar imaging capabilities and direct visualization of the rectal pouch and related musculature allow accurate determination of the level and type of anorectal malformations (Fig. 5) [20,24,28,30,31]. The level of anorectal malformation can be adequately depicted on T1-weighted images in most cases, but T2-weighted images are especially helpful in the evaluation of intermediate and low malformations, because the higher signal intensity of the anorectal mucosa allows better delineation of the anorectum with respect to the sphincter muscle complex and perineum ( Fig.…”

“…However, until recently, MRI has been unreliable in the detection of fistulae [6,24,31]. Adequate delineation of the fistula is of great clinical importance, as the definitive surgical approach depends largely on this additional information [7].…”

“…To overcome this problem, Taccone et al introduced MRI after injection of vaseline oil into the distal loop of the colostomy, thus demonstrating the fistula prior to reconstructive surgery [28]. When performing the MRI in the immediate newborn period, however, the hyperintense meconium inside the rectal pouch on T1-weighted images may serve as an excellent MRI contrast agent [24,31]. This T1 shortening and resultant increased signal intensity of meconium is thought to be due to the high mucoid and/ or lipid content.…”