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MRI anatomy of anteriorly displaced anus: what obstructs defecation?

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Abstract

Background

Anteriorly displaced anus is an anomaly that is debated with regard to its nomenclature, diagnosis and management.

Objective

To describe MRI anatomy of the anal canal in children with anteriorly displaced anus and its impact on the process of defecation.

Materials and methods

We prospectively examined ten children (7 girls, 3 boys; age range 7 months to 8 years, mean 3 years) with anteriorly displaced anus between August 2009 and April 2012. Noncontrast MRI examinations were performed on a 1.5-T magnet. T1- and T2-weighted turbo spin-echo images were acquired in axial, sagittal and coronal planes of the pelvis. The anorectal angle and the relative hiatal distance were measured in mid-sagittal images, and compared with those of a control group using the Mann–Whitney test.

Results

In children with anteriorly displaced anus, no anatomical abnormality was depicted at the level of the proximal anal canal. However, the distal anal canal was displaced anteriorly, running out its external muscle cuff, which remained un-displaced at the usual site of the anus. This changes the orientation of the central axis of the anal canal by passing across instead of along the fibers of the longitudinal muscle coat. Children with anteriorly displaced anus had a more obtuse anorectal angle (mean 112.1°), which was significantly greater than that of the control group (mean 86.2°).

Conclusion

MRI is a valuable tool in studying the anatomy of the anal canal in children with anteriorly displaced anus. The abnormal orientation of the longitudinal muscle across the anal canal can explain the obstructed defecation in these children. Based on this study, it might be of interest to use MRI in studying equivocal cases and children with unexplained constipation.

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References

  1. Kashyap P, Bates N (2004) Magnetic resonance imaging anatomy of the anal canal. Australas Radiol 48:443–449

    Article  CAS  PubMed  Google Scholar 

  2. Tang ST, Cao GQ, Mao YZ et al (2009) Clinical value of pelvic 3-dimensional magnetic resonance image reconstruction in anorectal malformations. J Pediatr Surg 44:2369–2374

    Article  PubMed  Google Scholar 

  3. Eltomey MA, Donnelly LF, Emery KH et al (2008) Postoperative pelvic MRI of anorectal malformations. Am J Roentgenol 191:1469–1476

    Article  Google Scholar 

  4. Hendren WH (1978) Constipation caused by anterior location of the anus and its surgical correction. J Pediatr Surg 13:505–512

    Article  CAS  PubMed  Google Scholar 

  5. Leape LL, Ramenofsky ML (1978) Anterior ectopic anus: a common cause of constipation in children. J Pediatr Surg 13:627–630

    Article  CAS  PubMed  Google Scholar 

  6. Schuster T, Joppich I, Schneider K et al (2000) A computerised vector manometry study of the so-called ectopic anus. Pediatr Surg Int 16:8–14

    Article  CAS  PubMed  Google Scholar 

  7. Pakarinen MP, Rintala RJ (2010) Management and outcome of low anorectal malformations. Pediatr Surg Int 26:1057–1063

    Article  PubMed  Google Scholar 

  8. Taccone A, Martucciello G, Dodero P et al (1992) New concepts in preoperative imaging of anorectal malformation. Pediatr Radiol 22:196–199

    Article  CAS  PubMed  Google Scholar 

  9. Nievelstein RAJ, Vos A, Valk J (1998) MR imaging of anorectal malformations and associated anomalies. Eur Radiol 8:573–581

    Article  CAS  PubMed  Google Scholar 

  10. Thambidorai CR, Raghu R, Zulfiqar A (2008) Magnetic resonance imaging in anterior ectopic anus. Pediatr Surg Int 24:161–165

    Article  CAS  PubMed  Google Scholar 

  11. Alves JC, Sidler D, Lotz JW et al (2013) Comparison of MR and fluoroscopic mucous fistulography in the pre-operative evaluation of infants with anorectal malformation: a pilot study. Pediatr Radiol 43:958–963

    Article  PubMed  Google Scholar 

  12. Holschneider A, Hutson J, Pena A et al (2005) Preliminary report on the international conference for the development of standards for the treatment of anorectal malformations. J Pediatr Surg 40:1521–1526

    Article  PubMed  Google Scholar 

  13. Boechat MI (1992) Magnetic resonance imaging of the pediatric pelvis. Radiol Clin North Am 30:807–816

    CAS  PubMed  Google Scholar 

  14. Van Beers BE, Kartheuser A, Delos MA et al (1996) MRI of the anal canal: correlation with histological examination. Magn Reson Imaging 14:151–156

    Article  PubMed  Google Scholar 

  15. McHugh K (1998) The role of radiology in children with anorectal anomalies; with particular emphasis on MRI. Eur J Radiol 26:194–199

    Article  CAS  PubMed  Google Scholar 

  16. Piloni V, Fioravanti P, Spazzafumo L et al (1999) Measurement of the anorectal angle by defecography for the diagnosis of fecal incontinence. Int J Colorectal 14:131–135

    Article  CAS  Google Scholar 

  17. Mohammad SA, AbouZeid AA (2013) MRI of persistent cloaca: can it substitute conventional imaging? Eur J Radiol 82:241–251

    Article  PubMed  Google Scholar 

  18. Fielding JR (2002) Practical MR imaging of female pelvic floor weakness. Radiographics 22:295–304

    Article  PubMed  Google Scholar 

  19. Tang S, Tong Q, Mao Y et al (2006) Magnetic resonance imaging of the anorectal striated muscle complex in normal children. J Pediatr Surg 41:1549–1555

    Article  PubMed  Google Scholar 

  20. Pena A (2004) Comment on anterior ectopic anus. Pediatr Surg Int 20:902

    Article  CAS  PubMed  Google Scholar 

  21. Reisner SH, Sivan Y, Nitzan M et al (1984) Determination of anterior displacement of the anus in newborn infants and children. Pediatrics 73:216–217

    CAS  PubMed  Google Scholar 

  22. Herek O, Polat A (2004) Incidence of anterior displacement of the anus and its relationship to constipation in children. Surg Today 34:190–192

    Article  PubMed  Google Scholar 

  23. Penninckx F, Debruyne C, Lestar B et al (1990) Observer variation in the radiological measurement of the anorectal angle. Int J Colorect Dis 5:94–97

    Article  CAS  Google Scholar 

  24. Penninckx F, Debruyne C, Lestar B et al (1991) Intraobserver variation in the radiological measurement of the anorectal angle. Gastrointest Radiol 16:73–76

    Article  CAS  PubMed  Google Scholar 

  25. Upadhyaya P (1984) Mid-anal sphincteric malformation, cause of constipation in anterior perineal anus. J Pediatr Surg 18:183–186

    Article  Google Scholar 

  26. Lunniss PJ, Phillips RK (1992) Anatomy and function of the anal longitudinal muscle. Br J Surg 79:882–884

    Article  CAS  PubMed  Google Scholar 

  27. Shafik A (1976) A new concept of the anatomy of the anal sphincter mechanism and the physiology of defecation III. The longitudinal anal muscle: anatomy and role in sphincter mechanism. Invest Urol 13:271–277

    CAS  PubMed  Google Scholar 

  28. Petros P, Swash M, Bush M et al (2012) Defecation 1: testing a hypothesis for pelvic striated muscle action to open the anorectum. Tech Coloproctol 16:437–443

    Article  CAS  PubMed  Google Scholar 

  29. Deutekom M, Dobben AC, Terra MP et al (2007) Clinical presentation of fecal incontinence and anorectal function: what is the relationship? Am J Gastroenterol 102:351–361

    Article  PubMed  Google Scholar 

  30. Boyadzhyan L, Raman SS, Raz S (2008) Role of static and dynamic MR imaging in surgical pelvic floor dysfunction. Radiographics 28:949–967

    Article  PubMed  Google Scholar 

  31. Campbell AM, Murphy J, Charlesworth PB et al (2013) Dynamic MRI (dMRI) as a guide to therapy in children and adolescents with persistent full thickness rectal prolapse: a single centre review. J Pediatr Surg 48:607–613

    Article  PubMed  Google Scholar 

  32. Yong C, Ruo-yi W, Yuan Z et al (2013) MRI findings in patients with defecatory dysfunction after surgical correction of anorectal malformation. Pediatr Radiol 43:964–970

    Article  PubMed  Google Scholar 

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Correspondence to Amr Abdelhamid AbouZeid.

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AbouZeid, A.A., Mohammad, S.A. & Khairy, K.T. MRI anatomy of anteriorly displaced anus: what obstructs defecation?. Pediatr Radiol 44, 831–838 (2014). https://doi.org/10.1007/s00247-014-2897-0

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  • DOI: https://doi.org/10.1007/s00247-014-2897-0

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