Phenotype of Inflammatory Bowel Disease at Diagnosis in the Netherlands: A Population-based Inception Cohort Study (the Delta Cohort)

Background:To describe the clinical characteristics of inflammatory bowel disease (IBD) at diagnosis in The Netherlands at the population level in the era of biologics.Methods:All patients with newly diagnosed IBD (diagnosis made between January 1, 2006 and January 1, 2007) followed in 9 general hospitals in the southwest of the Netherlands were included in this population-based inception cohort study.Results:A total of 413 patients were enrolled, of which 201 Crohn's disease (CD) (48.7%), 188 ulcerative colitis (UC) (45.5%), and 24 IBD unclassified (5.8%), with a median age of 38 years (range, 14-95). Seventy-eight patients with CD (38.8%) had ileocolonic disease and 73 patients (36.3%) had pure colonic disease. In 8 patients (4.0%), the upper gastrointestinal tract was involved. Nineteen patients with CD (9.5%) had perianal disease. Thirty-nine patients with CD (19.4%) had stricturing phenotype. Of the patients with UC and IBDU, 39 (18.4%) suffered from pancolitis and 61 (29%) from proctitis. Severe endoscopic lesions at diagnosis were seen in 119 patients (28.8%, 68 CD, 49 UC, and 2 IBDU), whereas 98 patients (23.7%) had severe histological disease activity. Thirteen patients (3.1%, 10 CD and 3 UC) had extraintestinal manifestations at diagnosis. Twenty-three patients (5.6%, 20 CD and 3 UC) had fistula at diagnosis.Conclusions:In this cohort, 31% of the patients with CD had complicated disease at diagnosis, 39% had ileocolonic disease, 9.5% had perianal disease, and in 4% the upper gastrointestinal tract was involved. Most patients with UC suffered from left-sided colitis (51%). Severe endoscopic lesions were reported in 34% of the patients with CD and 26% of the patients with UC. Three percent of the patients with IBD had extraintestinal manifestations.