The Risk of Inflammatory Bowel Disease in Subjects Presenting with Perianal Abscess: Findings from the THIN Database

Background: Perianal abscess [PA] is associated with inflammatory bowel disease [IBD]. The incidence of IBD after a diagnosis of PA and potential predictors of a future diagnosis of IBD are unknown. Methods: The Health Improvement Network [THIN] is a primary care database representative of the UK population. Incident cases of PA were identified between 1995 and 2017. Subjects with PA were matched to controls within the same general practice. The primary outcome was a subsequent diagnosis of Crohn's Disease [CD] or ulcerative colitis [UC]. A Cox regression model was used to assess potential predictors of a new diagnosis of CD or UC following PA. Results: The risk of CD was higher in the PA cohort compared with controls; adjusted hazard ratio [HR] 7.51 (95% confidence interval [CI] 4.86-11.62), p < 0.0001. The risk of UC was also higher in the PA cohort compared with controls; adjusted HR 2.03 [1.38-2.99], p < 0.0001. Anaemia in men (HR 2.82 [1.34-5.92], p = 0.002), and use of antidiarrhoeal medications (HR 2.70 [1.71-4.25], p < 0.0001) were associated with an increased risk of CD following PA. Anaemia in men (HR 2.58 [1.09-6.07], p = 0.03), diarrhoea (HR 2.18 [1.23-3.85], p = 0.007), and use of anti-diarrhoeal medication (HR 2.27 [1.19-4.30], p = 0.012) were associated with an increased risk of UC following PA. Conclusion: Subjects with PA are at an increased risk of subsequent diagnosis of CD and UC. Clinicians should strongly consider investigation for IBD in young patients presenting with diarrhoea and anaemia [in males] following PA. Future research should discern appropriate screening strategies for this high-risk cohort.