Are Perineal and Luminal Fistulas Associated in Crohn's Disease? A Population-Based Study

Background & Aims: We aimed to determine the frequency of fistulizing Crohn's disease (CD) and the relationship between perineal and luminal fistulas. Methods: A population-based retrospective study was conducted by using the University of Manitoba Inflammatory Bowel Disease Research Registry. In 2003 there were 3192 IBD patients, 1595 had (CD), and 398 patients reported stricturing or fistulizing disease. Patients were interviewed and medical records were reviewed for phenotype assessment. Perineal fistulas were defined as those exiting in the perineum or fistulizing to sexual organs. Luminal fistulas were defined as arising from the bowel to organs other than the perineum. Results: The prevalence of fistulizing CD was at most 22.1%. Of the 398 patients, 280 CD patients were eligible for full phenotype verification. Of these, 50 patients had both perineal and luminal fistulas, 151 had only perineal fistulas, and 79 had only luminal fistulas. Odds ratio (OR) for likelihood of having luminal fistula disease if perineal disease was present was 5.02 (95% confidence interval [CI], 3.40-7.42; P < .0001). Fistula patients were more likely to be diagnosed younger; 20-29 years (OR, 1.37; 95% CI, 1.02-1.85; P = .048). Compared with luminal fistulas, perineal fistulas had a higher likelihood to have colonic (OR, 3.32; 95% CI, 1.59-6.90; P = .002) rather than isolated ileal involvement (OR, 0.39; 95% CI, 0.21-0.72; P = .004). The comparison of fistulizing CD to non-fistulizing disease revealed a predisposition to colonic (OR, 1.41; 95% CI, 1.04-1.90; P = .032), ileocolonic (OR, 2.49; 95% CI, 1.91-3.26; P < .001), and upper gastrointestinal (OR, 3.87; 95% CI, 1.93-7.74; P < .0001) disease versus isolated ileal involvement (OR, 0.25; 95% CI, 0.19-0.34; P < .0001). Conclusions: There is a lower prevalence of fistulizing CD in this population than previously published. Perineal and luminal fistula diseases are highly related to one another but typically have distinct clinical associations.