Intestinal BD most commonly manifests in the terminal ileal and cecal regions (80–95%), but it can affect any part of the gastrointestinal tract, from the oral cavity to the anus. Multiple ulcerations tend to show localized distribution in the ileocecal area, whereas multisegmental or diffuse distributions of lesions are relatively uncommon [11]. Rectal and anal lesions are rare in intestinal BD patients [3, 18–20]. The distribution pattern of lesions is characterized into localized single, localized multiple, multisegmental, and diffuse appearance with the rates being 67%, 27%, 2%, and 4% in order of frequency, respectively [11].

The typical endoscopic findings are focal, segmental mucosal inflammation and punched-out fissuring-type or aphthoid ulcers in the ileocecal area (Table 9.1). Ulcers are deep, and tend to be round or ovoid. The presence of five or fewer intestinal or focal ulcers is a common endoscopic feature of intestinal BD. The majority of patients have only a single or a few ulcers (60–65%); however, multiple ulcers can also be present (Fig. 9.2). Ulcer sizes vary from small to large. When the ulcer is small, it appears aphthoid; that is, having a small, well-demarcated circular or ovoid shape (Fig. 9.3). The smaller ulcers have a similar appearance to the oral aphthoid ulcers of BD patients (Fig. 9.4). Small, well-demarcated circular or oval ulcers with normal adjacent mucosa are commonly presented. Larger ulcers typically seen in intestinal BD are usually oval or round. In particular, an ulcer with large, well-demarcated nodular margins and deep penetration is known as a volcano-type ulcer (Fig. 9.5). Ulcers with converging folds in this lesion can be regarded as chronic lesions. Owing to the elevated surrounding mucosa, this lesion can be misdiagnosed as ulcerofungating cancer; however, in contrast to a malignant ulcer, the margin in a volcano-type ulcer is clear, and no mucosa friability is noted. Volcano-type ulcers accompany fibrosis, and patients with these ulcers are less responsive to medical treatments and more frequently require surgery [21]. In large ulcer cases, the ulcer’s margin is commonly discrete and clear, and the surrounding mucosa appears normal. A thick, whitish exudate is often observed at the ulcer’s base (Fig. 9.6). Marginal elevation or erythema is also seen in intestinal BD patients. Longitudinal ulcers are rarely seen. As mentioned earlier, ulcerations of intestinal BD can be present at any site along the gastrointestinal tract. Therefore, when gastrointestinal ulcers with typical BD features are observed in patients with compatible clinical backgrounds, intestinal BD-related ulcerations should be suspected. The stomach is the least frequently involved part of the gastrointestinal tract (<5%), while esophageal involvement is diverse and nonspecific. The lesions are generally seen in the middle of the esophagus, although diffuse esophagitis and stenosis have also been reported (Fig. 9.7), Punched-out ulcers are sometimes seen in the perianal area (Fig. 9.8).

As a result of inflammation or scarring after ulcer healing, the adjacent mucosa may shrink, resulting in ileocecal valve deformity and scars. Luminal stricture can also follow during the healing process. The major endoscopic aspects of patients with intestinal BD and healed lesions with medical therapy are presented in Fig. 9.9.

The prevalent intestinal BD ulcer characteristics can be summarized as an oval or round shape and punched-out, deep, discrete ulcerations, mainly present in the ileocecal area. Another disease entity, simple ulcer syndrome, has also been characterized by deep, discrete ulcerations with a punched-out, round or oval appearance in the ileocecal region. The ulcer characteristics are similar to that of intestinal BD, but do not otherwise clinically fulfill the criteria for BD (Fig. 9.10) [22]. In fact, simple ulcer syndrome shows macroscopic and microscopic similarities to intestinal BD. As a result, some authors have proposed that intestinal BD and simple ulcer syndrome could be considered the same disease entity [23]. Whether these two diseases are actually the same disease or separate disease entities, however, is still controversial. Both diseases may present with a simple ulcer at the onset, followed by the systemic manifestations of BD. For this reason, simple ulcer syndrome and intestinal BD could be variations on the same disease spectrum [24]. On the other hand, at some points during its clinical course, simple ulcer is typically confined to the ileocecal area, while intestinal BD generally presents multiple ulcerations at any point along the gastrointestinal tract during the entire clinical course (unless it is an atypical presentation). Moreover, it is rare for simple ulcer to definitively progress into intestinal BD, making it more difficult to see both diseases as part of the same spectrum. Although these controversies exist, it might be appropriate, based on the observation that the treatment, progress, and recurrence of these diseases are similar, to clinically categorize the two diseases as components of the same entity. The recent diagnostic guideline suggests that simple ulcer syndrome corresponds to suspected-type intestinal BD [25].