Although the ileocecal area is the most common site (80–95 %) of intestinal BD involvement, it can affect any site of gastrointestinal tract, from oral cavity to anus [3, 5]. The locations of ulcers in intestinal BD are depicted in Fig. 3.3. Esophageal involvement is quite uncommon (less than 5 %), and it usually involves the middle part of the esophagus (Fig. 3.4) [3]. Moreover, the stomach is the least frequently involved part of the gastrointestinal tract (Fig. 3.5). Usually, the number of ulcers is one (60–65 %) or several (Fig. 3.5); however, diffuse involvement can occasionally be present. Although the size of ulcer can vary from small to large size, patients with intestinal BD usually have relatively large ulcers (70–80 % of patient have more than 1 cm-sized ulcers). When the ulcer was small, it appears like an aphthous lesion or small well-demarcated circular or oval-shaped ulcer with normal adjacent mucosa (Fig. 3.6). As the size of ulcer increase, deeply penetrating ulcer which is “typical” to intestinal BD is formed; however, the ulcer shape is maintained with circular or oval shape with discrete, elevated margin, and the ulcer base is covered with whitish, thick exudate (Fig. 3.7). These intestinal BD ulcers can cause clinical complications such as bleeding (Fig. 3.8) or perforation. Meanwhile, irregular-shaped ulcers can present in patients with intestinal BD (Fig. 3.9). As mentioned above, ulcer type has a prognostic implication for patients with intestinal BD, and intestinal BD ulcers showing large, well-demarcated nodular margins, deeply penetrating feature, are known as a “volcano-type” ulcer (Fig. 3.10), and patients having these type ulcers show less favorable response to medical treatment, a more frequent requirement for surgery, and more frequent relapse [6, 7]. Ileocecal valve deformity can be seen due to shrinkage of adjacent mucosa by inflammatory or scaring change (Fig. 3.11). In addition, luminal stricture can be seen in active stage (Fig. 3.12). Various findings of healing of ulcerative lesions after medical therapy are presented in Fig. 3.13. During the disease course of intestinal BD, a substantial number of patients eventually undergo bowel resective surgery due to complications or medically refractory diseases. After surgery, intriguingly, most recurrences occur at the anastomotic site or within the vicinity of the site (Fig. 3.14).