|Year : 2015 | Volume
| Issue : 3 | Page : 116-120
Correlation between functional outcomes and postoperative pelvic magnetic resonance imaging in children with anorectal malformation
Venkat Shankar Raman1, Sandeep Agarwala1, Veereshwar Bhatnagar1, Arun Kumar Gupta2
1 Department of Pediatric Surgery, All India Institute of Medical Sciences, New Delhi, India
2 Department of Radiodiagnosis, All India Institute of Medical Sciences, New Delhi, India
|Date of Web Publication||18-Jun-2015|
Prof. Sandeep Agarwala
Department of Pediatric Surgery, All India Institute of Medical Sciences, New Delhi - 110 029
Source of Support: None, Conflict of Interest: None
| Abstract|| |
Background: Though the outcomes in operated children with anorectal malformation (ARM) have greatly improved, postoperative soiling and constipation remain major issues. Among the various factors described for poor outcomes; misplaced bowel, hypoplastic sphincters and obtuse anorectal angle bear special mention. The aim of this study was to compare the stooling outcomes, type of anomalies and surgical procedure with postoperative pelvic magnetic resonance imaging (MRI). Materials and Methods: This was a cross-sectional study involving operated children of ARM who had at least 2 years of follow-up, and who were at least 3 years of age. The subtypes of ARM, surgical procedures, and functional outcomes were documented using the Krickenbeck classification. All children were subjected to a pelvic MRI. Results: Thirty-three eligible children were part of this study. Twenty-two patients underwent posterior sagittal anorectoplasty, seven patients underwent abdominoperineal pull-through (APPT) and four patients underwent perineal operations. Local abnormalities were present in 66% patients, and 34% had abnormalities of the spine detected on MRI. Poorer stooling outcomes were twice as common in children with local pelvic MRI abnormalities as compared to asymptomatic children. The highest incidence of local abnormalities were seen in patients treated with APPT (P = 0.0001). No significant difference in the pelvic MRI was seen among children who were constipated and those who had soiling. Conclusion: MRI is a useful imaging modality in operated children of ARM with poor stooling outcomes. Local abnormalities were the most common in children undergoing abdominoperineal pull-through procedure.
Keywords: Anorectal malformations, constipation, fecal soiling, magnetic resonance imaging scan, sacral abnormality, spinal abnormality, stooling outcome
|How to cite this article:|
Raman VS, Agarwala S, Bhatnagar V, Gupta AK. Correlation between functional outcomes and postoperative pelvic magnetic resonance imaging in children with anorectal malformation. J Indian Assoc Pediatr Surg 2015;20:116-20
|How to cite this URL:|
Raman VS, Agarwala S, Bhatnagar V, Gupta AK. Correlation between functional outcomes and postoperative pelvic magnetic resonance imaging in children with anorectal malformation. J Indian Assoc Pediatr Surg [serial online] 2015 [cited 2020 Feb 24];20:116-20. Available from: http://www.jiaps.com/text.asp?2015/20/3/116/159017
| Introduction|| |
Despite surgical advances,  fecal incontinence and constipation remain major postoperative problems that plague children with anorectal malformations (ARM). In 1996, a small sample of adolescents operated for ARM revealed a significant number of mental (58%) and psychological problems (73%) in patients with adverse stooling outcomes.  Hypoplastic sphincter complex, abnormal anorectal angle, and misplacement of neorectum in relation to the sphincter complex have been implicated as causes of poor stooling outcomes.  However, reports are scarce and do not shed sufficient light either on the types of anomalies or the surgical procedure performed to correct ARM. The purpose of this study was to compare the stooling outcomes, types of anomalies and surgical procedure to the postoperative pelvic magnetic resonance imaging (MRI) in children with ARM.
| Materials and Methods|| |
This cross-sectional study was conducted between 2010 and 2012 and involved children with ARM who had at least 2 years of follow-up after completing all stages of surgery and who were at least 3 years of age at the time of the study. The patients were either contacted on the telephone and requested to attend the outpatient clinic for the interview or interviewed during routine follow-up. Children who had undergone redo pull-through procedures, and permanent fecal diversion was excluded. All relevant clinical data, diagnosis, operative details, and findings were collected from the departmental ARM registry, and the missing data were obtained from the hospital archive section. Clearance from the hospital ethics committee was obtained for the study. A written informed consent was taken from both the children and parents.
The subtype of ARM, surgical procedure performed, and the stooling outcomes were assessed using the Krickenbeck classification.  Pelvic MRI imaging was done under sedation or general anesthesia and was done with high resolution phased array coils using a 3 Tesla machine. The protocol included T1- and T2-weighted images in the axial, coronal, and sagittal planes. A 20 Fr Foley catheter was advanced into the rectum, and a small amount of saline was instilled to delineate the bowel in relation to the sphincter. Special attention was paid to the position of the neorectum, sphincter muscle complex, perianal fat, anorectal angle, and spine. Assessment of muscle quality was subjective and based on internal comparison for symmetry and comparison with pelvic MRI of healthy persons. To look for mesenteric fat pulled-through inadvertently with the bowel, axial T1- and T2-weighted images without fat saturation was performed which showed fat as a halo of high signal intensity surrounding the wall of the pulled-through bowel. Anorectal angle was measured as the angle formed between the rectum and the anal canal, and T2-weighted sagittal images were used to capture this angle. The normal angle is <90° and any angle, which was obtuse was deemed abnormal. The statistical analysis was done using the SPSS version 15 (Chicago, Illinois, USA) software. Chi-square and Fischer exact tests were used for analyzing the data and P < 0.05 was considered significant.
| Results|| |
Thirty-three patients who fulfilled the inclusion criteria were included in the study. Twenty patients were contacted telephonically, and the remaining 13 were interviewed during regular follow-up. There were 18 males and 15 females (M:F = 1.2:1). The median age of the patients at the time of the study was 7.5 years (range 4-14 years). The median age at the time of definitive procedure was 7 months (range 25 days-12 months), and the median period after completion of all surgeries for ARM was 4.5 years (range 2-11 years).
Thirteen patients underwent primary definitive repair (39.4%) while the remaining 20 (60.6%) underwent staged repair. All the patients were operated upon by the two senior authors (SA, VB) and the decision to do a staged or single stage repair was based solely on standard clinical criteria. Twenty-two patients (66%) underwent posterior sagittal anorectoplasty (PSARP), 7 patients (21%) underwent abdominoperineal pull-through (APPT), and 4 patients (13%) underwent perineal operations. The perineal operations were an excision of H-type fistula along with perineal body repair in one patient and anoplasty in three patients.
Voluntary bowel movement (VBM) was absent in 18 patients with all cases of rectovaginal fistula (without pouch colon) and 88% of pouch colon having absent VBM. Twenty-eight patients had soiling; all patients with rectovaginal fistula, rectovesical fistula, no fistula, and pouch colon had soiling. Twelve patients had constipation; >50% patients with perineal lesions, rectovaginal fistula, rectovesical fistula, and no fistula had constipation [Table 1].
Abnormal local findings on MRI were seen in 22 patients (66.7%). Both the patients of rectovaginal fistula and 63% of pouch colon patients had misplaced neorectum [Figure 1] with only one patient in this group having undergone PSARP, the rest had undergone APPT (86%). This difference was statistically significant (P = 0.0001). Of the children who had undergone APPT, 57% had atrophic muscle complex compared to 9% in the PSARP group and none in the perineal operation group. This was also found to be statistically significant (P = 0.02) [Table 2].
|Figure 1: Axial T2-weighted magnetic resonance imaging of the pelvis showing eccentric placed neorectum (arrowhead) to the right of sphincter muscle complex|
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|Table 2: MRI local abnormalities (n = 22) in ARM subtypes and surgical procedure|
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Twelve (36.4%) patients had abnormal findings on MRI imaging of the lumbosacral spine. The bony abnormalities were sacral agenesis (>2 vertebrae absent) and hemivertebrae, and the cord abnormalities were diastometamyelia in one and low-lying tethered cord in seven patients [Figure 2]. Only two patients with tethered cord had cutaneous stigmata of occult spinal dysraphism. None of the perineal lesions had spinal abnormalities while only one patient with vestibular anus had cord abnormality in the form of tethered cord [Table 3].
|Figure 2: Sagittal T2-weighted magnetic resonance imaging showing a low-lying tethered cord (arrowhead)|
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Correlating the MRI findings with the stooling outcomes, in the patients with absent VBM, 12 (66.7%) had an abnormal local finding on MRI and 8 (44.4%) had an abnormal findings on MRI spine. Among the patients with soiling, 18 (64.3%) had abnormal local findings and 11 (39.3%) had abnormal spine findings. In the patients who had constipation, 8 (66.7%) had abnormal local findings and 3 (25%) had abnormal spine findings. Though the number of children with abnormal stooling outcomes and MRI abnormalities was twice the number of children with abnormal stooling outcomes and normal MRI findings, there was no statistical significance [Table 4]. Comparing the individual MRI parameters with poor stooling outcomes, more than half of the children (58%) with adverse stooling outcomes had atrophic muscle complex [Table 5], though there was no significant statistical difference.
| Discussion|| |
It is well-established that children with ARM have significantly worse bowel function compared with their peers.  The degree of functional impairment correlates with the severity of the ARM, and the late functional sequelae of fecal incontinence and/or constipation, which may frequently continue into adulthood. , A number of clinical scoring systems have been used to assess the functional and stooling pattern of children with ARM.  We have used the Krickenbeck scoring system for stooling outcome.  This is simple to use in routine clinical practice.
Of the available and relevant imaging modalities, MRI is superior because of excellent soft tissue characterization, multiplanar imaging, and lack of exposure to ionizing radiation. However, the disadvantages include the availability, cost, and the relatively frequent need for sedation or anesthesia. 
Children with ARM have variable degrees of striated muscle development from near-normal muscles to complete absence of the sphincter muscle.  The sphincter muscle complex is best seen on axial images at the level of the symphysis pubis and below.  After identification of the muscles of the sphincter mechanism, it is important to assess the relation between the sphincter and the pulled-through bowel. Malpositioning of the rectal pull-through can be identified on axial, coronal, and sagittal images. Axial and coronal images best show side-to-side displacement of the bowel. Sagittal images help in the assessment of anteroposterior displacement of the bowel in relation to the sphincter.  Children with incontinence are more likely to have the abnormal location of the neorectum, obtuse anorectal angle, and fat herniation compared to constipated children who have dilatation of the neorectum.  Even when the neorectum is positioned within the sphincter complex, fat herniation alone can interfere with the continence mechanism.  In addition, on long term follow-up, pelvic MRI studies of incontinent adults operated for ARM in childhood have shown normally positioned neorectum but atrophic levator ani and sphincter muscle complex. 
Abdominoperineal pull-through for ARM was associated with the highest incidence of local abnormalities reaching statistical significance with regard misplaced neorectum (P = 0.0001) and muscle atrophy (P = 0.02). Poorer stooling outcomes were noted in patients with abnormal local findings on MRI. Patients with local abnormalities had greater incidence of absent VBM (66.7% vs. 33.3%), soiling (80% vs. 20%), and constipation (66.7% vs. 33.3%) than those without these local abnormalities.
Severe sacral abnormalities have been associated with hypoplastic sphincters. If more than two sacral vertebrae are missing or there are other major sacral deformities, such as hemivertebrae and vertebral fusions, the functional outcome is worse than in patients with normal sacrum or lesser degree of sacral maldevelopment.  The spinal cord and bony abnormalities are also individual factors affecting continence independent of the location of the pulled-through bowel or muscle complex atrophy.  We had 12 children with bony and cord abnormalities. Interestingly, of the seven with tethered cord, only two had the cutaneous manifestation of occult spinal dysraphism. The incidence of absent VBM (44%) and soiling (39%) was higher than the incidence of constipation (25%) in children with spinal abnormalities.
| Conclusion|| |
Magnetic resonance imaging is a useful imaging modality in operated children of ARM with poor stooling outcomes. Local abnormalities were the most common in children undergoing APPT. The limitation of this study was the small sample size. In addition, the study was conducted over a limited period of time and hence it was not possible to determine whether surgical correction of a misplaced neorectum or detethering of the cord would help in improving the stooling outcomes in these children. A prospective study with larger numbers and longer follow-up may help us understand the effect of surgery in this subgroup of patients.
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[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]