Three-dimensional endoanal ultrasound for diagnosis of perianal fistulas: Reliable and objective technique

Table 1 Gynecological history and past perianal surgery

	n = 70 (n females = 19)	%
Females with vaginal deliveries	9	47.3
Episiotomy	4	21.0
Hysterectomy	2	10.5
Perianal abscesses drained	42	60.0
Seton	22	31.4
Fistulotomy	6	8.6
Fistulectomy	3	4.3
LIS	7	10.0
Hemorroidectomy	3	4.3
Rectal mucosal advancement flap	3	4.3

LIS: Lateral internal sphincterotomy.

Table 2 Results of fistula evaluation in 70 patients n (%)

	PE	2D-EAUS	3D-EAUS	Surgery
IO identified	3 (75.7)	67 (95.7)	67 (95.7)	67 (95.7)
Primary tract
Intersphincteric	19 (27.1)	14 (20)	10 (14.3)	13 (18.6)
Transsphincteric
Low	22 (31.4)	25 (35.7)	34 (48.6)	33 (47.1)
High	19 (27.1)	30 (42.9)	25 (35.7)	24 (34.3)
Unclassified	10 (14.3)	1 (1.4)	1 (1.4)	0 (0)
Secondary tract	6 (8.6)	15 (21.4)	16 (22.9)	11 (15.7)
Adjacent abscesses	12 (17.1)	17 (24.3)	19 (27.1)	8 (11.4)

2D-EAUS: Two dimensional endoanal ultrasound; 3D-EAUS: Three dimensional endoanal ultrasound; IO: Internal opening; PE: Physical examination.

Table 3 Concordance grade and k coefficient (k) between intraoperative findings and the different diagnostic techniques used

	PE		2D-EAUS		3D-EAUS
	Concordance	k	Concordance	k	Concordance	k
IO identified	51/70 (72.8%)	1	68/70 (97.1%)	1	68/70 (97.1%)	1
Primary tract	37/70 (52.9%)	0.33	55/70 (78.6%)	0.67	58/70 (82.8%)	0.75
Secondary tract	61/70 (87.1%)	0.44	64/70 (91.4%)	0.66	65/70 (92.8%)	0.60
Adjacent abscesses	58/70 (82.8%)	0.30	61/70 (87.1%)	0.57	60/70 (85.7%)	0.54

¹P > 0.05. k < 0: No agreement; k = 0: Concordance due to chance; k = 0-0.19: Insignificant; k = 0.2-0.39: Low; k = 0.4-0.59: Moderate; k = 0.6-0.79: good; k = 0.8-0.1: Very good. 2D-EAUS: Two dimensional endoanal ultrasound; 3D-EAUS: Three dimensional endoanal ultrasound; IO: Internal opening; PE: Physical examination.

Table 4 Efficacy parameters in relation to surgery for the different diagnostic techniques: Sensitivity, specificity, positive predictive value and negative predictive value

		S	SP	PPV	NPV
IO identified (%)	PE	76	33	96	6
	2D-EAUS	98	66	98	66
	3D-EAUS	98	66	98	66
Primary tract (%)
Intersphincteric	PE	69	82	47	92
	2D-EAUS	77	93	71	95
	3D-EAUS	22	98	90	93
Transsphincteric
Low	PE	45	81	68	67
	2D-EAUS	67	92	88	75
	3D-EAUS	85	84	82	86
High	PE	38	87	68	78
	2D-EAUS	64	76	70	70
	3D-EAUS	88	91	84	93
Secondary tract (%)	PE	40	97	67	91
	2D-EAUS	90	90	60	98
	3D-EAUS	90	88	56	98

2D-EAUS: Two-dimensional endoanal ultrasound; 3D-EAUS: Three-dimensional endoanal ultrasound; PE: Physical examination; IO: Internal opening; S: Sensitivity; SP: Specificity; PPV: Positive predictive value; NPV: Negative predictive value.

Table 5 Results of receiver operatives characteristic curves for the diagnosis of transsphinteric fistulas

		Area under curve	95%CI	P value
Low transsphincteric fistula	PE	0.608	0.474-0.742	0.120
	2D-EAUS	0.819	0.714-0.924	0.0001
	3D-EAUS	0.829	0.724-0.934	0.0001
High transsphincteric fistula	PE	0.672	0.541-0.803	0.019
	2D-EAUS	0.842	0.745-0.939	0.0001
	3D-EAUS	0.910	0.835-0.985	0.0001

2D-EAUS: Two-dimensional endoanal ultrasound; 3D-EAUS: Three-dimensional endoanal ultrasound; PE: Physical examination.