Since up to 90 % of patients with SB CD have terminal ileal involvement [55], IC is considered to be the first choice of endoscopic investigation to help establish a diagnosis of CD [6]. In cases where IC is not attainable or remains inconclusive [56, 57] and there is no clinical evidence to support the presence of obstructive disease, SBCE may be considered for the assessment of the SB mucosa; otherwise CTE or MRE should be the investigation of choice [2, 12]. The clinical value of any SBCE findings and its cost-effectiveness would be enhanced by careful patient selection with application of pre-test probability criteria [41–48] and avoidance of potential confounding factors e.g. recent NSAID use [12, 28, 49, 50].

In the presence of known CD, further assessment of the SB is frequently warranted for staging of disease activity in the presence of symptoms regardless of IC findings [6, 12]. In this setting, cross-sectional radiological imaging in the form of CTE or MRE takes precedence since these would facilitate the identification of stricturing and or transmural/extramural disease activity and associated complications while also allowing enhanced anatomical mapping of disease extent and distribution [2, 6, 12] (Figs. 10.2 and 10.3). The use of SBCE may still be warranted if cross-sectional imaging in patients with known CD remains inconclusive, if there are ongoing symptoms, and/or if any additional findings may influence patient management [24, 37]. However, clinicians should be mindful of the higher risk of CR in this setting. Ensuring functional SB patency by the use of a PC is considered mandatory if SBCE is to be undertaken in patients with known CD [2, 12].

Assessment of CD severity as a guide to management can usually be undertaken by dedicated SB cross-sectional imaging, however, three retrospective studies have also demonstrated the potential usefulness of SBCE in this regard [58–60]. Another retrospective study of patients with known CD (n = 108) by Flamant et al. [61] focused on the clinical importance of jejunal disease detected by SBCE. This study from France demonstrated the presence of jejunal lesions in 56 % of patients (17 % of these had solitary jejunal disease) and found that jejunal disease was independently associated with a higher risk of relapse, suggesting the underlying presence of a more aggressive CD phenotype. In another retrospective study from France (n = 71; 3 month follow-up) lesion severity as assessed by SBCE led to an adjustment of medical management in 54 % of patients. The role of SBCE for the assessment of mucosal healing is also being assessed [62, 63], albeit this indication has not yet been recommended for use in routine clinical practice. More objective disease activity indices such as the Capsule Endoscopy Crohn’s Disease Activity Index (CECDAI) (Niv score) or Lewis score may help to standardize reporting of disease activity identified at SBCE in clinical trials and clinical practice [64, 65].

In the setting of IBDU, although the supportive evidence is scant and mainly relates to the findings of one retrospective study (n = 120) [66] and three small prospective studies [67–69], mucosal lesions compatible with SB CD have been reported in 17–70 % of patients with previously unclassified disease [66, 67, 69]. Within the appropriate clinical context, SBCE therefore may be a useful modality to assist reclassification and may lead to modification of disease management strategies in patients with this condition [2, 12, 70]. The role of SBCE in UC remains limited but it may be useful in patients who manifest atypical symptoms and in those with unexplained iron deficiency [2, 12, 71]. Usefulness of SBCE in the preoperative assessment of patients undergoing ileal pouch-anal anastomosis (IPAA) surgery was investigated prospectively by Murrell et al. in a longitudinal study of 68 patients [72]. At 12 months follow-up, the results of this study showed no significant correlation between preoperative SBCE findings and IPAA outcome. Pre-IPAA assessment by SBCE therefore appears to be of limited value and is currently not recommended in day-to-day clinical practice [2, 12].

A key meta-analysis from the Mayo clinic by Pasha et al. (11 studies, including 9 that compared yield of inflammatory lesions) confirmed that DBE and SBCE had similar diagnostic yields [53]. This was also demonstrated by another meta-analysis (including eight studies) [54], which showed that the yields of bi-directional DBE and SBCE were similar. For diagnostic and assessment purposes, DAE is usually reserved for cases where other less-invasive investigations remain inconclusive or where histopathological corroboration (to rule out infection or malignancy) is deemed to be essential [2, 12, 104]. When DAE is clinically indicated, correlation with other imaging modalities allows for “targeting” of suspect lesions and may enhance its diagnostic yield and clinical effectiveness [76, 80, 91, 103]. Direct evaluation of SB mucosal lesions is also useful for the diagnostic process and the presence of mesenteric border SB ulceration has been shown to be highly suggestive of underlying CD [81] (Fig. 10.4). A small pediatric study (n = 20) from the Netherlands, which compared the findings of SBE with ultrasound (+ Doppler) and MRE, found that SBE facilitated definitive diagnosis of active CD in 14/20 patients (70 %) and suggested that earlier use of DAE may expedite the diagnostic process [85]. DAE may also be useful in the guidance of medical management by direct endoscopic assessment of disease activity [78, 93, 96, 105]. In a retrospective study of 40 patients with established CD, Mensink et al. [96] showed that DBE identified active SB disease in 24 (60 %) patients and as a result, management was altered in 75 % of those with positive findings. These results were confirmed by another prospective longitudinal study performed by the same investigators in another 50 patients with known CD. In this second study, the findings at DBE had a direct impact on the medical management of 38 % of patients, 88 % of whom remained in remission with a significantly improved Crohn’s disease activity index (CDAI) at 12 months of follow-up [93].