Anal fistula

A perianal abscess is caused by inflammation due to bacterial infection of the anal gland, which is located in the anal crypts along the dentate line, and is formed by tunneling under the skin of the anus. An anal fistula is formed when pus is discharged from an opening of the abscess to the skin (Fig. 42.1). The symptoms are more common in breastfed male infants aged less than 6 months. Abscesses and external fistulae (secondary openings) are more likely to be located to the side of the anus (at 3 and 9 o'clock). Abscess symptoms rapidly improve and are relieved by incision and drainage, but symptoms are likely to recur after some time. However, an anal fistula in infants generally resolves before 1 year of age. When the fistula is palpable and the symptoms recur, even at 1 year of age or older, radical surgery for the anal fistula is indicated.