High-resolution direct magnetic resonance imaging fistulography with hydrogen peroxide for diagnosing anorectal fistula: A preliminary retrospective study

Table 1 Clinical characteristics of patients with fistula-in-ano (n = 60)

Clinical characteristic	Cases, n	Percentage (%)
Age (years)
Median	38.5 (20-65)
Distribution
≤ 45	45	75
> 45	15	25
Sex
Male	57	95
Female	3	5
Symptoms
Discharge in the vicinity of perianal fistula	60	100
Localized pain	54	90
History of treatment
None	24	38.09
Medication	9	14.28
Previous perianal abscess surgery	18	28.57
Previous fistula-in-ano surgery	12	19.04

Table 2 Magnetic resonance imaging protocol.

Sequences	TR (millisecond)	TE (millisecond)	Slice thickness (mm)	Slice spacing (mm)	FOV (mm)	NSA	Voxel size (mm3)
Low-spatial-resolution MRI protocol
Sagittal T2WI TSE	3000	100	7	1.5	250 × 350	1	0.87 × 1.16 × 7
Oblique axial T2WI TSE	3361	80	6	1	300 × 400	1	1.1 × 1.39 × 6
Oblique coronal T2WI TSE	3000	100	4	0.4	250 × 250	1	0.87 × 1.16 × 4
Oblique axial/coronal T1WI-TSE	520	10	6	1	300 × 400	1	1 × 1.15 × 6
High-resolution direct HPMRI fistulography protocol
Oblique axial/coronal 3D-T2WI-FSE	2000	244	2	-1	200 × 200	2	1 × 1 × 2
Oblique axial/coronal T1WI-mDIXON-TFE	6.4	2.1	3	-1.5	200 × 200	1	1 × 1 × 3
Oblique axial/coronal T1WI-mDIXON-TFE (postcontrast)	6.4	2.1	3	-1.5	200 × 200	1	1 × 1 × 3

FOV: Field of view; HP: Hydrogen peroxide; MRI: Magnetic resonance imaging; TE: Echo time; TR: Repetition time; TSE: Turbo spin echo; NSA: Number of signal averages.

Table 3 Methods for recurrent and complex fistula-in-ano in 60 patients

Type of fistula	Physical examination	Conventional ultrasound (TPUS)	Low-spatial-resolution MRI	HPMRI fistulography	Surgery
Intersphincteric	27	63	78	84	90
Transphincteric	9	36	42	48	54
Extrasphincteric	0	0	0	9	9
Suprasphincteric	0	0	0	9	9
Internal opening	72	99	120	147	153
Perianal abscess	18	36	45	54	54

HP: Hydrogen peroxide; MRI: Magnetic resonance imaging; TPUS: Trans-perineal ultrasonography.

Table 4 Comparison of findings from different methods used for fistula-in-ano

Observational indicator	Evaluation methods	True positive	False positive	False negative	Sensitivity	Specificity	Positive predictive value	Negative predictive value	Surgical outcome
Internal opening	Physical examination	72	36	81	47.06 (72/153)	63.64 (63/99)	66.67 (72/108)	43.75 (63/144)	153
	TPUS	99	27	54	64.71 (99/153)	72.73 (72/99)	78.57 (99/126)	57.14 (72/126)	153
	Low-spatial-resolution MRI	120	12	33	78.43 (120/153)	87.88 (87/99)	90.91 (120/132)	72.50 (87/120)	153
	High-resolution direct HPMRI fistulography	147	9	6	96.08 (147/153)	90.91 (90/99)	94.23 (147/156)	90.91 (90/96)	153
Fistula track	Physical examination	36	27	126	22.22 (36/162)	66.67 (54/81)	57.14 (36/63)	30.00 (54/180)	162
	TPUS	99	18	63	61.11 (99/162)	77.78 (63/81)	84.62 (99/117)	50.00 (63/126)	162
	Low-spatial-resolution MRI	120	9	42	74.07 (120/162)	88.89 (72/81)	93.02 (120/129)	63.16 (72/114)	162
	High-resolution direct HPMRI fistulography	150	6	12	92.59 (150/162)	92.59 (75/81)	96.15 (150/156)	86.21 (75/87)	162
Abscess	Physical examination	18	36	36	33.33 (18/54)	76.47 (117/153)	33.33 (18/54)	76.47 (117/153)	54
	TPUS	136	27	18	66.67 (36/54)	82.35 (126/153)	57.14 (36/63)	87.50 (126/144)	54
	Low-spatial-resolution MRI	45	9	9	83.33 (45/54)	94.12 (144/153)	83.33 (45/54)	94.12 (144/153)	54
	High-resolution direct HPMRI fistulography	54	6	0	100 (54/54)	96.08 (147/153)	90.00 (54/60)	100 (147/147)	54

HP: Hydrogen peroxide; MRI: Magnetic resonance imaging; TPUS: Trans-perineal ultrasonography.

Table 5 Interobserver agreement across diagnostic modalities for detecting fistula-in-ano features

Observational indicator	Diagnostic modality	Kappa value	95%CI	Interpretation
Internal openings	Physical examination	0.48	0.40-0.56	Fair agreement
	TPUS	0.63	0.55-0.71	Moderate agreement
	Low-spatial-resolution MRI	0.78	0.71-0.85	Substantial agreement
	High-resolution HPMRI	0.89	0.83-0.95	Almost perfect agreement
Fistula tracks	Physical examination	0.41	0.34-0.48	Fair agreement
	TPUS	0.57	0.50-0.64	Moderate agreement
	Low-spatial-resolution MRI	0.74	0.68-0.80	Substantial agreement
	High-resolution HPMRI	0.85	0.79-0.91	Almost perfect agreement
Perianal abscess	Physical examination	0.33	0.25-0.41	Fair agreement
	TPUS	0.45	0.37-0.53	Moderate agreement
	Low-spatial-resolution MRI	0.69	0.62-0.76	Substantial agreement
	High-resolution HPMRI	0.8	0.74-0.86	Almost perfect agreement

HP: Hydrogen peroxide; MRI: Magnetic resonance imaging; TPUS: Trans-perineal ultrasonography.