Prevalence of anal fistula in the United Kingdom

Abstract

BACKGROUND Anal fistula is a pathological connection between the anal canal and perianal skin, which most commonly develops from an infected anal crypt. While the majority of anal fistulas are idiopathic, they are also associated with Crohn’s disease (CD) and other inflammatory conditions. The prevalence of anal fistula is estimated to be 1-2 per 10000 patients, but population-based studies on anal fistula epidemiology are limited and outdated. AIM To assess the prevalence of anal fistula and relevant comorbidities, with and without CD in the United Kingdom and Europe. METHODS A retrospective population-representative observational cohort study was performed in The Health Improvement Network (THIN), a United Kingdom primary care database. Mid-year point prevalence of anal fistula was calculated on the first of July for each year between 2014 and 2017. Estimates were calculated for anal fistula overall and by CD status and standardized to the United Kingdom and European population. Prevalence of relevant comorbidities including lymphogranuloma venereum, hidradenitis suppurativa, anal presentation of sexually transmitted diseases, diabetes mellitus, and radiation in the pelvic area was reported. RESULTS The United Kingdom-standardized overall point prevalence of anal fistula was 1.80 (95%CI: 1.65-1.94) per 10000 patients in 2017, while the Europe standardized estimate was 1.83 (95%CI: 1.68-1.98) per 10000 patients. Both these standardized point prevalence estimates ranged from 1.89 to 2.36 between 2014-2016. The United Kingdom-standardized point prevalence of anal fistula without CD was 1.35 (95%CI: 1.23-1.48) per 10000 patients, while the Europe-standardized estimate was 1.39 (95%CI: 1.26-1.52) per 10000 patients. In contrast, the standardized point prevalence estimate of anal fistula with CD was lower for both United Kingdom and Europe (0.44; 95%CI United Kingdom: 0.37-0.52, 95%CI Europe: 0.37-0.51) per 10000 patients in 2017. In 2017, 19% of anal fistula patients without CD and 13% of anal fistula patients with CD had at least one relevant comorbidity. These results show that anal fistulas are infrequent in the general population. 24.5% of prevalent anal fistulas are associated with CD, but other potentially etiological comorbidities are rare. CONCLUSION This real-world evidence study estimated the United Kingdom-standardized prevalence of anal fistula was 1.80 per 10000 patients in 2017. Approximately 25% of cases may be associated with CD, while other comorbidities are rare.

Advances in the Treatment of Anal Fistula: A Mini-Review of Recent Five-Year Clinical Studies

“…A statistical analysis based on a large population database in the UK showed that the incidence of anal fistula is 1.69 cases per 10,000 individuals ( 2 ). This was also evidenced by other relevant studies ( 3 ). Patients with anal fistula are mainly adults between 30 and 40 years old, and the incidence rate of this condition in men is higher than that in women ( 4 ).…”

Efficacy and safety of ligation of intersphincteric fistula tract in the treatment of anal fistula

“…[ 1 , 2 ] An anal fistula commonly occurs in people with a history of anal abscesses, in a prevalence of 0.01% to 0.02% in Europe, [ 3 ] 0.018% in the United Kingdom. [ 4 ] Surgery is the only treatment for anal fistula, and there are many described surgical techniques against it, such as anal fistula incision, cutting seton. In conventional surgeries, the internal sphincter, external sphincter, and part of the superficial part should be cut, which is frequently followed by a long and complicated postoperative course.…”

Surgical treatment for cryptoglandular and Crohn’s perianal fistulas: Protocol of an umbrella review

“…Anal fistula, also named fistula-in-ano, is a benign anorectal disease characterized by abnormal inflammatory communication between the anal canal and the perianal skin caused by infection and injury of perianal region [ 1 ]. In Europe, the estimated incidence of anal fistula is 1.2–2.8 per 10000 people, with a peak incidence between the ages of 20 and 40 years [ 2 , 3 ]. In China, epidemiological studies show that anal fistula accounts for 1.67% to 3.60% of the incidence of anorectal diseases, with a ratio of male to female of 5–6: 1 [ 4 ].…”