Prevalence of anal fistula in the United Kingdom

Table 2 Prevalence of anal fistula without Crohn’s disease

		2014	2015	2016	2017
Prevalence of AF, n		891	726	514	437
Prevalence of AF, n/10000 patients		1.83	1.72	1.44	1.38
Gender	Female, n (%)	365 (43.7)	288 (44.6)	197 (44.4)	180 (44.9)
Age	0-19, n (%)	53 (5.9)	29 (4.0)	24 (4.7)	21 (4.8)
	20-39, n (%)	314 (35.2)	249 (34.3)	162 (31.5)	137 (31.4)
	40-59, n (%)	344 (38.6)	320 (44.1)	230 (39.5)	197 (45.1)
	60-79, n (%)	147 (16.5)	112 (15.4)	112 (21.8)	70 (16.0)
	80+, n (%)	33 (3.7)	16 (2.2)	13 (2.5)	12 (2.7)
Standardization to
	UK (95%CI)	1.80 (1.68-1.92)	1.69 (1.57-1.81)	1.41 (1.29-1.53)	1.35 (1.23-1.48)
	EU (95%CI)	1.84 (1.72-1.97)	1.73 (1.60-1.85)	1.45 (1.32-1.58)	1.39 (1.26-1.52)
Direct AF Read codes1
Prevalence of Direct AF, n		586	466	347	265
Prevalence of Direct AF, n/10000 patients		1.20	1.10	0.97	0.84
Standardization to
	UK (95%CI)	1.18 (1.09-1.28)	1.09 (0.99-1.19)	0.96 (0.86-1.06)	0.83 (0.73-0.92)
	EU (95%CI)	1.21 (1.11-1.31)	1.11 (1.01-1.21)	0.98 (0.87-1.08)	0.84 (0.74-0.94)
Most commonly used Read codes:
Anal fissure and fistula, n		360	245	186	139
Fistula-in-ano, n		250	224	167	141
Indirect AF Read codes2
Prevalence of Indirect AF, n		391	324	214	199
Prevalence of Indirect AF, n/10000 patients		0.80	0.77	0.60	0.63
Standardization to
	UK (95%CI)	0.79 (0.71-0.87)	0.75 (0.67-0.83)	0.60 (0.58-0.50)	0.61 (0.52-0.69)
	EU (95%CI)	0.81 (0.73-0.89)	0.77 (0.69-0.86)	0.61 (0.53-0.69)	0.63 (0.54-0.72)
Most commonly used Read codes:
Anal fistula operations, n		135	98	65	69
Laying open of anal fistula NEC, n		106	87	59	41
Excision of fistula in ano, n		94	74	61	55

AF: Anal fistula; n: Number; CI: Confidence interval; UK: United Kingdom; EU: European Union; NEC: Not elsewhere classified;

¹Direct codes: Read codes directly identifying anal fistula (e.g. anal fissure and fistula, and fistula-in-ano);

²Indirect codes: Read codes identifying procedures or surgeries related specific to anal fistulas (e.g., excision of fistula in ano, and anal fistula operations); One patient can have multiple Direct and Indirect anal fistula codes.