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

Table 1 Panelist characteristics (n = 95 experts)

Characteristics
Gender, n (%)	Males: 24 (25.3)
	Females: 71 (74.7)
Age, mean ± SD, yr	49.7 ± 10.5
Region, n (%)	Europe: 63 (66.3); Asia: 20 (21.0); North America: 4 (4.2); South America: 3 (3.1); Africa: 3 (3.1); Australia: 2 (2.1)
Scientific societies	Asian Pacific Federation of Coloproctology, Emirates Society of Colon and Rectal Surgery, European Federation for Ultrasound in Medicine and Biology, European Society for Magnetic Resonance in Medicine and Biology, European Society of Colo-Proctology, French National Society of Coloproctology, International Society of Coloproctology, International Society of Treatment of Anorectal Disorders, Italian Society of Medical and Interventional Radiology Foundation, Italian Society of Colorectal Surgery, Polish Club of Coloproctology
Type of hospital, n (%)	Academic/university: 64 (67.3)
	Public regional: 12 (12.6)
	Private: 16 (16.8)
	Other: 3 (3.1)
Duration of medical practice, mean ± SD, yr	20.0 ± 10.7
Specialty, n (%)	Colorectal surgeons: 69 (72.6)
	Radiologists: 23 (24.2)
	Anatomists: 2 (2.1)
	Gastroenterologists: 1 (1)
No. of EAUS/MRI assessment for anal fistulas, n (%)	10/mo: 23 (24.2); 10–20/mo: 31 (32.6); 20–30/mo: 15 (15.8)
	> 30/mo: 23 (24.2); Not applicable: 3 (3.1)

EAUS: Endoanal ultrasound; MRI: Magnetic resonance imaging.

Table 2 Questionnaire for the Delphi process

	Questionnaire
Question #1	Is the Park’s classification optimal to be reported by MRI/EAUS for the characterization of the primary tract?
Question #2	Should the Park’s classification be modified or supplemented?
Question #3	Is the location of the primary tract on a clock dial optimal to be reported by MRI/EAUS, or should it be modified?
Question #4	Is the height of the primary tract properly described (≤ 30% and > 30%)?
Question #5	Is the inclusion of the diameter of the fistula in the template correct or should be modified?
Question #6	Should a fistula tract angle be added to the template?
Question #7	Are secondary tracts precisely defined: Number, location, and type?
Question #8	Are internal opening items, such as number, location on a clock dial, and patency complete or require completion?
Question #9	Is information on associated abscess, such as location according to the Corman classification, accurate?
Question #10	Is it sufficient to report sphincter integrity, location of damage, and percentage of sphincter involved?
Question #11	Is the graphic presentation of the fistula included in a template appropriate or it should be modified?
Question #12	Should a video describing the fistula details (if permitted by the rules) supplement the template of the fistula?
Question #13	Does the template include all the most relevant findings for the treatment decisions or other additional elements of the fistula should be included in the template?
Question #14	The following definitions are relevant for examiners describing anal fistulas by MRI and EAUS. Do you accept them in their current form, or do they require modification or addition? In the latter case, please suggest a correction

EAUS: Endoanal ultrasound; MRI: Magnetic resonance imaging.

Table 3 Results of the Delphi process

Statement	Percentage of agreement	Median (IQR) of answers	No. of round in which agreement was achieved
#1	89.5	10 (9-10)	2
#2	81.0	10 (8-10)	3
#3	93.7	10 (10-10)	3
#4	91.5	10 (9-10)	3
#5	80.0	10 (8-10)	3
#6	75.8	9 (8-10)	No consensus
#7	97.9	10 (9-10)	2
#8	95.8	10 (10-10)	1
#9	96.8	10 (9-10)	2
#10	95.8	10 (10-10)	1
#11	94.7	10 (9-10)	2
#12	66.3	10 (7-10)	No consensus
#13	96.81	-	2
#14	87.41	-	2

¹In statements 13 and 14 panelists could choose one of two answers: yes or not. The percentage of “yes” responses is given.

IQR: Interquartile range.

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.

Table 5 Classifications of anal fistulas

	Parks classification[22]	Garg classification[11,12]	St. James University Hospital classification[36]
Grade I	Intersphincteric	Low trans-sphincteric/low or high intersphincteric: Single tract	Intersphincteric linear
Grade II	Transsphincteric	Low trans-sphincteric/low or high intersphincteric: Multiple tracts, horseshoe or associated abscess	Intersphincteric with extension/s or associated abscess
Grade III	Suprasphincteric	IIIA: High trans-sphincteric: Single tract; IIIB: (1) Anterior fistula in a female or any lower; (2) Grade I or II fistula with associated comorbidities1	Trans-sphincteric linear
Grade IV	Extrasphincteric	High trans-sphincteric: Multiple tracts, horseshoe or associated abscess	Trans-sphincteric with extension/s or associated abscess
Grade V		Suprasphincteric or supralevator or extrasphincteric or RIFIL fistula	Supralevator and translevator extension

¹Comorbidities: Crohn’s disease, existing sphincter injury/weakness or post-radiation Low fistula involves ≤ 1/3 and high fistula involves > 1/3 of the sphincters.

RIFIL: Roof of ischiorectal fossa inside levator.

Table 6 Definitions of anal fistulas

Terms	Definitions
Primary fistula	Main fistulous tract with the internal opening at the dentate line (occasionally the internal opening can be lower or higher than the dentate line)
Single fistula	Fistula without branching (extensions/ramifications)
Multiple fistulas	More than one primary fistula with their corresponding internal openings
Branching fistula	Fistula with branches (extensions/ramifications)
Low fistula[12,25]	Fistula that involves ≤ 1/3 of the external anal sphincter
High fistula[12,25]	Fistula that involves > 1/3 of the external anal sphincter
Simple fistula[12,25]	Low intersphincteric or low transsphincteric primary fistula (Garg grades I/II)[11,12] at low risk of incontinence or recurrence
Complex fistula[12,25]	High inter- or trans-sphincteric, suprasphincteric, extrasphincteric fistula (Garg grades III–V)[11,12], ano/rectovaginal fistula, any fistula in Crohn’s disease, a fistula postradiotherapy, anterior fistula in a female, recurrent fistula, fistulas with multiple tracts, pre-existing sphincter injuries at high risk of postoperative incontinence or recurrence

Table 7 Imaging reporting for anal fistulas

Ref.	Approach	Imaging modalities	Institutions	Methodology	N	Evidence-based
Tuncyurek et al[7], 2019	Multidisciplinary (RAD & CRS)	MRI	Single center	Institutional meeting	3	No
Ho et al[6], 2019	Multidisciplinary (RAD & CRS)	MRI	Single center	Institutional meeting	ns	No
Halligan et al[8], 2020	Monodisciplinary (RAD)	MRI, CT, EAUS	Multicenter	Delphi process	13	Yes (139 articles)
Sudoł-Szopińska et al[1], 2021	Multidisciplinary (RAD & CRS)	MRI	Multicenter	Online survey	5	No
Garg et al[9], 2022	Multidisciplinary (RAD & CRS)	MRI	Single center	Institutional meeting	4	No
Iqbal et al[5], 2022	Multidisciplinary (RAD, GASTR, CRS)	MRI	Multicenter	Online survey	14	Yes (26 articles)
SMART, 2024 (current paper)	Multidisciplinary (RAD, GASTR, CRS, ANAT)	MRI, EAUS	Multicenter	Delphi process	95	Yes (151 articles)

RAD: Radiologist; CRS: Colorectal surgeon; MRI: Magnetic resonance imaging; CT: Computed tomography; EAUS: Endoanal ultrasound; ns: Not stated; ANAT: Anatomist; GASTR: Gastroenterologist.