Assessing validity of existing fistula-in-ano classifications in a cohort of 848 operated and MRI-assessed anal fistula patients - Cohort study

Aim/background: The commonly used fistula-in-ano classifications, Park or St. James's University hospital(SJUH), neither grade fistulas as per their severity nor guide regarding their management. A new classification(NC), published in 2017, proposed to classify fistulas as per their severity and also guided in its management. The early grades (NC grade I & II) were simple fistulas and were amenable to fistulotomy whereas higher grades (NC grade III-V) were complex fistulas and were not amenable to fistulotomy. Methods: Lower grades of all the three classifications were classified as simple (Parks: I, SJUH:I-II, NC:I-II) whereas higher grades were classified as complex (Parks: II-IV, SJUH: III-V, NC: III-V) fistulas. Fistulotomy should be possible in simple fistulas but not in complex fistulas. This was analysed for all these classifications. The long-term follow-up of continence was done by an objective scoring system (Vaizey's scores). Results: The SJUH & Parks classifications categorized 504/828 fistulas as 'complex' which was quite inaccurate as 42.7%(215/504) of these fistulas were safely amenable to fistulotomy. On the other hand, the New classification (NC) classified 282/828 fistulas as 'complex' which was very accurate as 99% (279/282) of these were actually complex and were not amenable to fistulotomy. The change in the preoperative and the postoperative continence scores in the patients who underwent fistulotomy, as per these classifications, Parks & SJUH vs NC, was 0.064 +/- 0.62 and 0.089 +/- 0.85 respectively and was not significantly different(p = 0.80, Mann-Whitney U test). Conclusions: The New classification(NC) seems better than the existing classifications for grading the disease as well as in guiding the management of the disease.