Introduction
A fistula is an abnormal communication between 2 epithelial-lined organs. The communication is usually between the anal canal and the perineal skin. In the congenital varieties, the fistulous tract may extend from the anal canal to the vestibule, vagina, or urethra.
History of the Procedure
As a clinical entity, fistula-in-ano has well been recognized from ancient times. Hippocrates (460 BC) used a seton to cure fistula-in-ano. The great Indian surgeon Sushruta (1600 BC) used a caustic ligature (Kshara sutra) to treat fistula-in-ano. In 1337, John Anderne was the first to surgically lay open a fistula-in-ano.
Problem
Fistula-in-ano is a fistulous connection between the anal canal and the perineum. It is usually secondary to perianal infections and, rarely, secondary to a congenital defect.1
Frequency
Fistula-in-ano is not common in children compared with adults; most cases occur in adults. Fistula-in-ano is more common in boys than in girls, and 96% of cases occur in infants younger than 1 year.
At King Edward Memorial (KEM) Hospital in Pune, India, this condition is present in 0.18% of admitted patients.
Etiology
The congenital type is an uncommon developmental defect. The acquired type is secondary to a perianal abscess, tuberculosis (in developing countries), Crohn disease, or immunocompromise.
Pathophysiology
In the congenital form, the fistulous tract is lined with stratified squamous epithelium, columnar epithelium, or both. The acquired form manifests with repeated perianal abscesses and has an inflamed fibrous tract lined by granulation tissue and no epithelial lining upon microscopic examination.
In the infected form of fistula-in-ano, the crypts of Morgagni are deeper (3-10 mm) than normal (1-2 mm). This abnormality facilitates the trapping of bacteria, which cause cryptitis that leads to perianal abscess formation and fistulae. Abnormal anal glands2 and hormonal imbalances have also been proposed as causes of fistula-in-ano. Androgen excess may stimulate the sebaceous glands, resulting in secondary infection.
Presentation
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.
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 2 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.
Indications
Surgery is required if pain is severe, if medical treatment fails, or if the fistula-in-ano recurs.
Relevant Anatomy
The anal canal is the part of the hind gut that extends from the anal ring to the anal verge. The dentate line, which is the site of the cloacal membrane, divides the anal canal into the proximal part, lined by columnar epithelium, and the distal part, lined by squamous epithelium. At the level of the dentate line, transverse folds of mucosa form a ring of valves with pockets called the crypts of Morgagni. The anal glands open in the crypts. The glands branch out and lie in the submucosal plane or, most frequently, in the intersphincteric plane.
Contraindications
Associated severe medical conditions may contraindicate surgical procedure or anesthesia.
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References
Fitzgerald RJ, Harding B, Ryan W. Fistula-in-ano in childhood: a congenital etiology. J Pediatr Surg. Feb 1985;20(1):80-1. [Medline].
Parks AG. Pathogenesis and treatment of fistuila-in-ano. Br Med J. Feb 18 1961;5224:463-9. [Medline].
Deshpande PJ, Pashak SN, Sharma BN, Singh LM. Treatment of fistula-in-ano by Kshara Sutra. Indian J Med Res. 1968;2:131-9.
Bennett RC. A review of the results of orthodox treatment for anal fistulae. Proc R Soc Med. Sep 1962;55:756-7. [Medline].
Deshpande PJ, Sharma KR, Sharma SK, Singh LM. Ambulatory treatment of fistula in ano: results in 400 cases. Indian J Surg. 1975;37:85-9.
Hermann G, Desfosses L. Fistula in ano in childhood: A congenital etiology. Acad Sci. 1990;1301, 1880.
Mishra BS. Bhavamishra's Bhave Prakash (Hindi). Vol 2. 3rd ed. Varanasi, India: Chowkhamba Sanskrit Series Office; 1961:66.
Nadkarni AK. Nadkarni's Indian Materia Medica. Vol 1. 2nd ed. Panwel, India: Dhoorapapeshwar Prakashan Ltd; 1954:524.
Stephens FD, Donnellan WL. "H-type" urethroanal fistula. J Pediatr Surg. Feb 1977;12(1):95-102. [Medline].
Further Reading
Keywords
fistula-in-ano, fistula in ano, anal fistula, anal fistulae, perianal abscess, perineal fistula, perineal opening, rectal fistula, rectal opening, perianal infection, Kshara sutra, seton, tuberculosis, Crohn disease, immunocompromise, perianal abscess, cryptitis, congenital fistula-in-ano, imperforate anus, urinary tract infection, acquired fistula-in-ano, ulcerative colitis, submucosal fistula, intersphincteric fistula, transsphincteric fistula
