Clinical Study Of MRI In Children With Postoperative Defecatory Dysfunction Of Congenital Imperforated Anus

Background:Congenital imperforated anus (CIA) is a common developmental malformation and defecatory dysfunction is the most common postoperative complication. Improper treatment will do harm to their health and life quality. Normal evacuation depends on4main factors:colonic motility, anorectal structure, developmental state of striated muscle complex (SMC) and pelvic floor function. Based on several advantages, such as multiplanar imaging capability, superb tissue characterization, lack of radiation and evaluation of the entire pelvis and pelvic floor in one examination, MRI has proven to be of considerable value in evaluating the anorectal structure and developmental state of SMC, in addition MR defecography can assess the pelvic floor function. MRI information help to establish the further surgical planning and significantly reduce the impairment to other structure.1. ObjectiveTo probe the clinic value of static MRI in postoperative anorectal structure and developmental state of SMC of CIA patients and compare the difference between constipation and incontinence. Also to probe the clinic value of dynamic MRI(MR defecography) in pelvic floor function of postoperative constipated patients.2. Material and methods52eligible patients were enrolled in this study,20constipated and32incontinent cases of them. MR findings of each patient were analyzed to evaluate the location and morphology of neorectum, peritoneal fat herniation,scarring, developmental state of SMC and other associated malformations. For every abnormality, the difference of constipated and incontinent patients was compared. MR defecography was performed in6constipated patients to evaluate their pelvic floor function. MRI findings were verified through clinical and operative observations. The statistical significance was determined by usingχ2-test.3. ResultsIn all52patients, we found14cases (26.92%) with abnormal location of neorectun,20cases (38.46%) with anorectal angle (ARA),17(32.69%) with peritoneal at herniation,29(55.77%) with dilation of neorectum,7(13.46%) with focal stenosis of neorectum, and41(78.85%) with extensive scarring. For abnormal location of neorectum, enlarged ARA and peritoneal fat herniation, the incidence in incontinent group were higher than that in constipated group (P<0.05);while for dilation of neorectom, the incidence in constipated group was higher than that in incontinent group (P<0.05); for fecal stenosis of neorectum and extensive scarring, there were no significant difference between2groups (P>0.05). As for developmental state of SMC, we found50patients with developmental agenesis, but there was no significant difference between2groups (P>0.05). Missed5fistulas,2tethered cords and3sacral teratoma were also present in this study.2anterior rectoceles,2cystoceles and6pelvic floor descents were found in6patients who undertook MR defecography.4. Conclusion(1) For abnormally located neorectum, enlarged ARA, peritoneal fat herniation, severe dilation or stenosis of neorectum and extensive scarring, further operation were inevitable. It was sure for missed fistula, tethered cord and tumor to be operated once again.(2) For developmental agenesis of SMC and fecal dysfunction caused by colonic hypomotility, conservative measures should be taken to alleviate the patients' complaint, such as biofeedback, laxatives and dietary manipulations.(3) Patients with abnormally located neorectum, enlarged ARA and peritoneal fat herniation were prone to suffer from fecal incontinence, while patients with rectal dilation were prone to constipation. (4) Developmental agenesis of SMC was not the key factor that caused incontinence, and anorectum could play more important role in this aspect.(5) MR defecography can reflect the function of pelvic floor and help to understand the mechanism of defecatory dysfunction in constipated patients.