Pediatric Fistula-in-Ano Clinical Presentation

Updated: Aug 27, 2021
  • Author: Jayant Deodhar, MD; Chief Editor: Harsh Grewal, MD, FACS, FAAP  more...
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History and Physical Examination

Congenital fistula-in-ano

Newborns with fistula-in-ano may or may not have an anus as part of the spectrum of imperforate anus. Male neonates may pass meconium per the urethra through a fistula located in the perineum, usually anterior to the normally located anus. In female neonates, meconium can be passed through the vagina, vestibule, or perineum. Both boys and girls present with recurrent urinary tract infection if fistula-in-ano is untreated.

Acquired fistula-in-ano

More than 96% of cases occur in infants younger than 1 year. The usual presentation involves a recurrent perianal abscess, which may or may not have been surgically treated. [7, 8]

Two distinct views have been expressed regarding perianal abscess and fistula-in-ano. In the first view, perianal abscess is regarded as a precursor to fistula-in-ano. More than 95% of patients with perianal abscesses that lead to fistula-in-ano are boys younger than 1 year. The second view is that perianal abscess and fistula-in-ano are two distinct entities. Perianal abscesses are seen in 22% of girls with fistula-in-ano, 68% of whom present after age 2 years.

Examination of the perineum may reveal an external opening of the fistula, with an outpouching of granulation tissue or purulent discharge. The fistula may appear as a perianal abscess. An internal opening may be felt as a nodule on the wall of the anal canal. The opening is invariably single. Probing the fistula should be done with the patient under anesthesia to avoid creating false passages.



Fistula-in-ano has commonly been divided into types according to the Parks classification [9]  (see the image below), as follows:

  • Superficial
  • Intersphincteric
  • Transsphincteric
  • Suprasphincteric
  • Extrasphincteric

In 2003, an American Gastroenterological Association technical review on perianal Crohn disease described another approach to classifying fistula-in-ano, whereby these lesions would be broadly categorized as either simple or complex. [10]  In this schema, a simple fistula is characterized as follows:

  • Lesser involvement of anal sphincters (superficial, intersphincteric, or low transsphincteric fistulas)
  • Only one opening
  • No association with an abscess or connection to an adjacent structure (eg, vagina or bladder)

The following are characteristics of a complex fistula:

  • Involvement of more of the anal sphincters (high transsphincteric, extrasphincteric, or suprasphincteric fistulas)
  • Multiple openings
  • Horseshoe configuration (crossing the midline anteriorly or posteriorly)
  • Association with a perianal abscess, connection to an adjacent structure, or both