Felis ISSN 2398-2950

Anus: atresia

Synonym(s): Atresia ani, imperforate anus

Contributor(s): Ed Hall, Cheryl Hedlund, Philip K Nicholls

Introduction

  • Cause: congenital absence of anal opening +/- absence caudal rectum.
  • Signs: tenesmus, bulging of the perineum, absence of feces, abdominal distension and discomfort.
  • Diagnosis: physical examination, history of tenesmus, lack of feces and restlessness.
  • Treatment: surgical.
  • Prognosis: guarded - post-operative fecal incontinence, megacolon Megacolon, suture line breakdown and infection, rectal stricture Rectum: stricture.

Pathogenesis

Etiology

  • Congenital.

Pathophysiology

Type I

  • A membrane over the anal opening remains, with the rectum ending as a blind pouch just cranial to the closed anus.

Type II

  • The anus is closed as in Type I but the rectal pouch is located somewhat cranial to the membrane overlying the anus.

Type III

  • The rectum ends as a blind pouch cranially within the pelvic canal (rectal atresia), while the terminal rectum and anus are normal.

Type IV

  • In females, atresia ani exists with a persistent communication between the rectum and the vagina (rectovaginal fistula). This fistula can occur with a normal anal opening as well. The cause of this condition is failure of the cloacal membrane to resorb or rupture by the second month of embryonal development; hence, continuity between the rectum and anus is maintained. The result of this defect is an altered defecation behavior resulting in outpouching of the anal region and abnormal vaginal discharges (rectovaginal fistula).

All Types

  • All types usually have an intact external anal sphincter and its associated nerve supply, although the sphincter may be poorly developed.

Diagnosis

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Treatment

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Prevention

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Outcomes

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Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • van den Broek A H M, Else R W & Hunter M S (1988) Atresia ani and urethrorectal fistula in a kitten. JSAP 29 (2), 91-94 VetMedResource.


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