Structured magnetic resonance imaging and endoanal ultrasound anal fistulas reporting template (SMART): An interdisciplinary Delphi consensus

Table 4 Shortcomings in the Parks classification reported by the panelists[22]

	Shortcomings in the Parks classification
1	The Parks classification does not categorize fistulas based on the increasing severity[22]. Transsphincteric fistulas are considered more complex than intersphincteric fistulas. However, a low linear transsphincteric fistula involving ≤ 30% of the external sphincter (Parks grade II) is simpler than a high intersphincteric horseshoe fistula with a high rectal opening (Parks grade I). Therefore, the classification does not grade fistulas according to the complexity
2	The Parks classification does not provide any recommendations for the management of fistulas.
3	The Parks classification was not validated by MRI/EAUS as these investigations were not available at the time of its introduction[22]. The 25% of suprasphincteric or extrasphincteric fistulas in the original cohort is not consistent with the literature and it could be due to the absence of preoperative imaging[22]
4	Parks grade IV is assigned to the extrasphincteric fistulas. However, by using MRI/EAUS, it has been shown that extrasphincteric fistulas are extremely rare[3,4]
5	The Parks classification does not consider many characteristics of the fistula such as the presence of an abscess, horseshoe extension, anterior location in a female or patients comorbidities like Crohn’s disease, previous irradiation, weakened sphincter due to previous operations or obstetrical anal sphincter injury[22]

EAUS: Endoanal ultrasound; MRI: Magnetic resonance imaging.