Demographic characteristics of the CD study population based on the Montreal classification [27].

<p>For each variable, the number of patients included is given.</p>1<p>Disease behaviour was defined according to the Montreal classification <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108503#pone.0108503-Silverberg1" target="_blank">[27]</a>. The stricturing disease phenotype was defined as the presence of stenoses without penetrating disease. The diagnosis of stenoses was made surgically, endoscopically, or radiologically (using MR enteroclysis).</p>2<p>The clinical course of CD was furthermore defined as “aggressive” in CD patients with a stricturing and/or penetrating disease behaviour and/or when CD-related surgery became necessary.</p>3<p>Immunosuppressive agents included azathioprine, 6-mercaptopurine, methotrexate, infliximab, and/or adalimumab.</p>4<p>Only surgery related to CD-specific problems (e.g., ileocecal resection, fistulectomy, colectomy, and ileostomy) was included.</p><p>Demographic characteristics of the CD study population based on the Montreal classification <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0108503#pone.0108503-Silverberg1" target="_blank">[27]</a>.