Do we need a new classification for fistula-in-ano?

Introduction
Identification of correct anatomy of the fistulous tract is important in the treatment of fistula-in-ano. Several classifications are available for this. Our objective was to identify the differences in the anatomy of fistula-in-ano in patients been treated at our hospital and compare it with commonly used classifications, namely Parks and St James University Hospital (SJUH) classifications.

Materials and Methods
Fifty one consecutive patient with diagnosed cryptoglandular fistula-in-ano were recruited from August 2017 to January 2020. All were examined under spinal or general anaesthesia by two experienced colorectal surgeons. Gentle probing with a fistula probe and injection of saline / Hydrogen peroxide was used to identify the internal opening and primary tract.

Results
There were 41 male patients and 10 female patients. Their median age was 42 years. Thirty-four (66.7%) had transsphincteric fistula, 11 (21.6%) had intersphincteric, 4 (7.8%) had superficial and only 2 (3.9%) had suprasphincteric fistula. Out of all 15 (29.4%) were high fistula-in-ano while the remaining 36 (70.6%) were low.

Discussion
Majority of tracts were transsphincteric. This is in contrast to Parks original observation where intersphincteric type made the majority. Superficial fistulae accounted for 7.8%, which were not described in Parks original study. Parks and SJUH classification have not considered the length of external anal sphincter involvement in their classifications, which is crucial in surgical decision making. In our study, 29.4% were high fistula-in-ano.

Conclusion
Majority was transsphincteric and this contradicts Parks and SJUH classification. High fistula-in-ano comprises 29.4%, where treatment modality has major implications. Parks and SJUH classification do not take this into account and the need for a new classification is stressed upon.