Comparing existing classifications of fistula-in-ano in 440 operated patients: Is it time for a new classification? A Retrospective Cohort Study

Int J Surg. 2017 Jun;42:34-40. doi: 10.1016/j.ijsu.2017.04.019. Epub 2017 Apr 13.


Background: Fistula-in-ano are classified so as to grade them according to increasing complexity which can help guide their management. The classifications used are Parks, St James Hospital University (SJHU) and Standard Practice Task Force (SPTF). Laying open (fistulotomy) of the fistula tract is the most commonly done procedure for fistula-in-ano and has high success rate. The lower grade fistulas are supposed to have low risk of incontinence when laid open and vice-versa. The objective of the study was to evaluate the efficacy of the existing classifications.

Materials & methods: 440 consecutive fistula-in-ano patients operated over four years were analyzed on the basis of preoperative MRI scan and operative findings. It was assessed whether the amenability to fistulotomy (measurement of fistula simplicity) correlated with the fistula-in-ano grades in different classifications.

Results: Out of 440 patients operated, 242 underwent fistulotomy whereas 198 underwent sphincter-sparing procedures for complex fistula. As per SJHU classification, the amenability to fistulotomy was 99.1% in Grade-I, 82.1% in Grade-II, 46.2% in Grade-III, 29.0% in Grade-IV and 5.4% in Grade-V. In Park's classification, the amenability to fistulotomy was 93.5% in Grade-I, 34.8% in Grade-II, 5.4% in Grade-III and 0% in Grade-IV. As per SPTF classification, 99.3% of simple and 32.1% of complex fistulas underwent fistulotomy. Even the higher grade fistula-in-ano in all three classifications had high rate of amenability to fistulotomy. Therefore none of the above classifications were accurate. A new classification is being proposed which divides fistula-in-ano in 5 grades in order of increasing complexity. Grade I & II are simple fistulas (fistulotomy be done conveniently) and Grade III-V are high complex fistulas (fistulotomy should not be attempted). The data was analyzed as per new classification and found it to be highly accurate.

Conclusions: None of the existing classifications accurately correlated between the grade and the complexity of fistula. A new classification is being proposed.

Keywords: Anal fistula; Classification; Fistula-in-ano; Fistulotomy; Parks; Treatment.

Publication types

  • Comparative Study

MeSH terms

  • Anal Canal
  • Cohort Studies
  • Digestive System Surgical Procedures
  • Fecal Incontinence / epidemiology
  • Female
  • Hospitals, University
  • Humans
  • Magnetic Resonance Imaging
  • Male
  • Organ Sparing Treatments
  • Postoperative Complications / epidemiology
  • Rectal Fistula / classification*
  • Rectal Fistula / diagnostic imaging
  • Rectal Fistula / surgery
  • Retrospective Studies
  • Risk Assessment
  • Severity of Illness Index
  • Treatment Outcome