Low-type anorectal malformations in the male: Extent of deviation from the norm.

PURPOSE: To define the degree of deviation from the norm among boys with minor forms of anorectal malformations (ARM).

PATIENTS AND METHODS: Between March 2015 and January 2016, we studied the preoperative MRI of nine boys with low-type ARM. For comparison, we included another nine boys (control group) who underwent MRI pelvis for causes other than ARM (e.g. impalpable testes).

RESULTS: In boys with low-type ARM, the rectum descends forwards to touch the back of the prostate (as in the norm), but then goes downwards (with little or no backward deflection) keeping intimately attached to the bulb of the corpus spongiosum and displacing it downwards and forwards. The striated sphincter muscles do not follow the anterior displacement of the bowel termination, but remain orthotopically compacted at the normal predestined site of the anal canal.

CONCLUSION: Among boys with low ARM, the minor abnormalities at the external anal orifice are associated with deeper anatomical aberrations in the form of anterior misplacement of the anorectum. These findings may help in understanding the disturbed act of defecation among these patients, and provide guidance to the best way of surgical correction.