Anus & perianal
Congenital defects

Topic Completed: 1 April 2005

Minor changes: 20 August 2019

Copyright: 2002-2019,, Inc.

PubMed Search: Anus perianal congenital defects

Nat Pernick, M.D.
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Page views in 2020 to date: 121
Table of Contents
Definition / general
Cite this page: Pernick N. Congenital defects. website. Accessed May 24th, 2020.
Definition / general
  • Occur in one per 5,000 births

  • High (supralevator) anomalies (40%):
    • Also called anorectal agenesis
    • No anal canal, rectum ends above levator ani muscle
    • Causes severe obstruction
    • Associated with anomalies in vertebrae and urinary tract, defective innervation of pelvic muscles, fistulas from rectum to bladder, urethra or vagina
    • Complicated surgery is needed for reconstruction

  • Low (translevator) anomalies (40%):
    • Includes ectopic (perineal, vestibular or vulvar) anus, anal stenosis and covered (imperforate) anus (failure of cloacal diaphragm to rupture)
    • Simple surgery is curative
    • No severe obstruction, no / rare associated anomalies, normal pelvic innervation

  • Intermediate anomalies (15%):
    • Includes anal agenesis (may be associated with Larsen syndrome, Hum Pathol 1991;22:1055), anorectal stenoses, anorectal membrane
    • Need complicated surgery

  • Other (5%):
    • Perineal groove, persistent anal membrane
    • Also persistence of cloaca (bladder, genital tract and bowel empty into single narrow channel that opens onto perineum with small orifice)
    • Exstrophy of cloacal membrane (Arch Pathol Lab Med 1987;111:157)
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