**4.1 Simple and low abscesses and fistulas**

The 2 most common fistulas described by Park in 1976 were intersphincteric fistula and transphincteric fistula, which accounts for 75% of his series. Eisenhammer in 1966 also reported that 80% in his series were low intermuscular type. Infection arising from anal gland forms suppuration in the intersphincteric space, forming an intersphincteric abscess. Alternatively, it can track along the potential intersphincteric space caudally to the intersphincteric groove or along the subcutaneous external sphincter fibers/septaes to form a perianal abscess. This forms an intersphincteric fistula once it ruptures outwards. However, if it spreads between subcutaneous and superficial external sphincter, it forms a low transphincteric fistula and results in a perianal or ischiorectal abscess. These 2 patterns are the most common findings reported and can occur anteriorly or posteriorly [1, 5–7, 12].
