Authors: Seong-Jung Kim, Sung Noh Hong
Categories: Review, Balloon enteroscopy, Crohn disease, Inflammatory bowel diseases, Small bowel endoscopy
Source: Clinical Endoscopy
Doi: 10.5946/ce.2025.144
Authors: Seong-Jung Kim, Sung Noh Hong
Inflammatory bowel disease is classified into Crohn’s disease (CD) and ulcerative colitis. Ulcerative colitis involves only the colon, whereas CD is characterized by small bowel involvement, which is a hallmark feature. However, the small bowel is the final frontier of endoscopic evaluation; therefore, small bowel involvement is considered a significant medical challenge in the diagnosis and treatment of patients with CD. Endoscopic visualization and biopsy sampling of the small bowel are crucial for accurate diagnosis, effective monitoring, and management of complications of CD. Small bowel endoscopy enables the early detection of mucosal lesions, facilitates timely intervention for complications such as strictures or bleeding, and plays a critical role in reducing the need for surgical resection. Moreover, it enables targeted tissue acquisition and objective assessment of disease activity, both of which are crucial for optimal treatment planning and monitoring of therapeutic responses. Given these clinical advantages, small bowel endoscopy has become an indispensable tool in the comprehensive management of CD. This review summarizes the current role and evolving advances in small bowel endoscopy, with particular emphasis on its therapeutic applications—including enteroscopic balloon dilation, endoscopic hemostasis, and foreign body retrieval—and discusses future directions based on recent evidence and expert guidelines.
Endoscopy remains fundamental in the diagnosis and management of inflammatory bowel diseases (IBD), including ulcerative colitis (UC) and Crohn’s disease (CD).1 While colonic involvement is routinely assessed by ileocolonoscopy, CD often affects the small bowel, necessitating enteroscopic evaluation. Traditional ileocolonoscopy may miss proximal lesions beyond the terminal ileum, which are clinically relevant for early diagnosis, tight disease monitoring, and therapeutic endoscopy. Given that approximately one-third of patients with CD have inflammation limited to the small bowel, the importance of endoscopic evaluation of the small bowel in these cases cannot be overstated.2
This review summarizes the current role and recent advances in small bowel endoscopy, focusing on diagnostic and therapeutic applications in the management of CD, including enteroscopic balloon dilation (EBD), hemostasis, and foreign body retrieval.
According to the European Crohn’s and Colitis Organization and American Gastroenterological Association guidelines, advanced imaging modalities, such as computed tomography (CT) or magnetic resonance (MR) enterography, and small bowel endoscopy, such as video capsule endoscopy (VCE) or balloon-assisted enteroscopy (BAE), are recommended for the evaluation of suspected small bowel CD when initial ileocolonoscopy or imaging is inconclusive.3-5
CD is typically diagnosed by ileocolonoscopy. However, when inflammation is localized to the small bowel, visualization of the entire small bowel mucosa can be challenging. VCE offers the advantage of complete visualization of the small bowel and has demonstrated a high diagnostic yield, with strong positive and negative predictive values for the detection of small bowel CD.6,7 A meta-analysis showed that VCE demonstrated a higher diagnostic yield for the detection of small bowel CD lesions than CT enterography and results comparable to those of MR imaging-based techniques.6 A study comparing pan-enteric VCE with ileocolonoscopy in patients with active CD found that VCE had a higher diagnostic yield per-subject (83.3% vs 69.7%) and per-segment (40.6% vs 32.7%) than ileocolonoscopy (Fig. 1).8 These findings highlight the potential of VCE to improve the diagnosis and surveillance of small bowel CD.
However, unlike cross-sectional imaging modalities, VCE depends more on adequate bowel preparation for optimal mucosal visualization and diagnostic yield. Therefore, current guidelines recommend bowel cleansing before VCE.9-11 Although no standardized regimen has been universally established, polyethylene glycol (PEG)-based preparations are commonly used. Recent studies have shown that low-volume regimens, such as 1 L PEG combined with ascorbic acid, offer cleansing efficacy comparable to that of traditional 2 L PEG.12
VCE retention remains a potential concern, particularly in patients with stricturing CD. The risk of retention is higher in patients with known CD (13%) than in those with suspected CD (1.6%).13 A meta-analysis found overall retention rates of 3.32% in patients with CD, with higher rates in established CD (4.63%) than in those with suspected CD (2.35%).14 The risk of retention can be reduced by using patency capsules or CT/MR enterography before VCE in patients with established CD.14 However, several studies have highlighted the limited sensitivity of CT/MR enterography for detecting functional strictures. These modalities may overestimate or underestimate stricture severity, and their negative predictive value for capsule retention is suboptimal.15,16 Therefore, the patency capsule is considered a more reliable tool for evaluating small bowel patency before VCE in patients with suspected strictures.9-11 While most cases of VCE retention can be managed conservatively with medical therapy, surgical intervention may be required in selected cases.
In such cases, BAE, including double-balloon and single-balloon enteroscopies, may serve diagnostic and therapeutic purposes. BAE enables intubation of the small intestine beyond the scope of conventional endoscopy. Depending on the route of insertion, BAE can access up to 240 cm beyond the ligament of Treitz via the oral route and approximately 140 cm from the ileocecal valve via the anal route.17 Combined oral and anal approaches may achieve near total enteroscopy in selected cases, with reported total enteroscopy rates ranging from 40% to 80% depending on the operator’s experience and clinical indication.10 BAE offers direct mucosal visualization and biopsy capability, enabling the confirmation of initial diagnosis by identifying characteristic endoscopic features; differentiation of CD from mimics such as intestinal tuberculosis, Behçet’s disease, and nonsteroidal anti-inflammatory drug-induced enteropathy; accurate assessment of disease location, extent, and activity; and detection of complications including strictures, fistulas, bleeding, and neoplasia.3,5,9,11,18,19 Endoscopic findings in CD include aphthous ulcers, longitudinal ulcerations, cobblestone appearance, and skip lesions. Conversely, segmental circular ulcers with patulous ileocecal valves and absence of cobblestoning may suggest intestinal tuberculosis.20 BAE is useful when radiologic imaging is inconclusive or when histologic confirmation is required. Compared with radiographic studies or VCE alone, BAE provides superior specificity for differentiating between inflammatory, infectious, and neoplastic conditions. In a multicenter study, BAE provided a definitive diagnosis in approximately 65% of such cases and enabled therapeutic intervention in up to 30% of the patients.21 As such, accurate phenotyping and guiding appropriate treatment selection are integral for small bowel CD.
Recent advances in artificial intelligence (AI) have demonstrated promising results in VCE by enhancing the detection of ulcers, erosions, and bleeding lesions while significantly reducing reading time. A meta-analysis reported pooled sensitivity and specificity values of 0.95 and 0.94 for ulcer detection and 0.98 and 0.99 for bleeding, respectively.22 In a large-scale study conducted in China, an AI model trained on over 13 million images achieved better diagnostic sensitivity than that of conventional readings by gastroenterologists and reduced interpretation time from 96.6 minutes to 5.9 minutes.23 A recent study developed a convolutional neural network model that detected protruding lesions in the small bowel with an accuracy of 97.3%. This proof-of-concept study demonstrated the potential utility of AI in device-assisted enteroscopy, suggesting that AI also supports therapeutic decision-making, such as determining the need for surgical intervention.24 AI has shown increasing potential in the diagnostic and therapeutic management of CD.25-28 In the diagnostic field, convolutional neural networks applied to VCE have demonstrated excellent performance in detecting CD-specific lesions. For instance, one study reported a sensitivity and specificity of 95.7% and 99.8%, respectively, for the detection of ulcers using AI.25 Additionally, AI models have been developed to quantify disease activity by correlating with established indices such as the Lewis score and capsule endoscopy Crohn’s disease activity index, offering objective and reproducible assessments.29 Beyond diagnostics, AI has also been applied in treatment decision support. A machine learning model using week-8 laboratory data predicted long-term remission in patients with CD treated with ustekinumab, achieving an area under the receiver operating characteristic curve of 0.78 (95% confidence interval, 0.69–0.87). These findings support the role of AI in identifying likely non-responders early in the treatment course to avoid ineffective biologic use.30 However, the integration of AI into real-time therapeutic endoscopy, such as balloon dilation, hemostasis, or stricturotomy, remains investigational, with no clinical trials demonstrating direct procedural support. Although international guidelines acknowledge the potential adjunctive role of AI in VCE, they emphasize the need for further clinical validation in real-world settings before AI can be routinely applied for the diagnostic evaluation of CD.10
Endoscopic intervention using small bowel endoscopy has emerged as a critical strategy in managing the complications of CD, particularly strictures and bleeding. Although biologics have been introduced to reduce inflammation, structural interventions are still often necessary.5,10,11 EBD remains the first-line treatment for short fibrotic strictures. In patients with bleeding in the small bowel, small bowel endoscopy plays a pivotal role in the diagnosis and organ-preserving treatment.10,19 Foreign body removal using enteroscopy, especially for retained VCE, can be effectively and safely performed by combining EBD of strictures with retrieval devices, thereby avoiding the need for surgical intervention.31
BAE-assisted EBD is a minimally invasive, bowel-preserving procedure that has proven effective in managing fibrostenotic CD.32,33 It is most appropriate for short (≤4 cm), non-angulated, and accessible strictures that lack deep ulcerations or associated fistulas.11,34,35
Traditionally, EBD for Crohn’s strictures was performed with colonoscopy and applied to colonic or ileocolonic anastomotic strictures, with technical success rates ranging from 79% to 100% and clinical improvement of up to 90%.32,33 However, most strictures in patients with CD occur in the small bowel rather than in the colon. Nevertheless, for small bowel Crohn’s strictures, which are more technically challenging, BAE-assisted EBD has shown promising results, with long-term surgery-free survival exceeding 70% in some cohorts.36 Recent prospective cohort study involving 139 patients with CD and 219 small bowel strictures reported cumulative 1-, 3-, and 5-year surgery-free rates of 86.7%, 80.4%, and 76.6%, respectively.35 The long-term outcome of BAE-assisted EBD may depend on the endoscopic morphologic classification of the stricture, with web-like strictures having a favorable prognosis and spindle-shaped strictures having a poor prognosis. The cumulative surgery-free rates of EBD were 96.3%, 91.0%, and 73.3% at 1 year; 96.3%, 84.9%, and 63.0% at 3 years; and 96.3%, 78.3%, and 63.0% at 5 years for web-like, ulcerated, and spindle-shaped strictures, respectively.35
However, up to 50% of patients require repeat dilation within 2 years.37 Risk factors for restenosis include the presence of an ulcer at the site of stricture, even small and shallow ulcerations, involvement of long segments, and pre-stenotic dilation.38 In patients with ulcerated strictures, initiating or switching biologics after EBD may help avoid surgery.35 To reduce the recurrence of stricture, step-up therapy with biologics such as anti-tumor necrosis factor agents following EBD has been shown to lower surgery rates significantly.4
BAE-assisted EBD is considered a relatively safe and effective modality. According to recent multicenter data and guideline-based reviews, the overall complication rate of EBD ranges from 4% to 10%, with major adverse events such as perforation occurring in approximately 1.8% and bleeding in 1.4% of cases.33,39 In a recent study, the major complication rate of EBD was 2.7% (4/150) in the per-patient analysis and 1.7% (4/235) in the per-procedure analysis.35 Minor complications such as transient abdominal pain or minor bleeding not requiring intervention are more common but generally self-limiting.
EBD involves the use of a controlled radial expansion balloon catheter, which is delivered over a guidewire through the working channel of the enteroscope and positioned across the stricture. The balloon is then gradually inflated, typically to a target diameter of 12 to 15 mm, and maintained for 30 seconds to 2 minutes, depending on the tightness and characteristics of the stricture.11 This diameter is generally sufficient to relieve obstructive symptoms while minimizing the risk of adverse events, such as bleeding or perforation.40-42 Multiple sessions of dilation are often required, especially in cases of recurrent or residual strictures, although the precise number of repeat procedures is determined based on symptom recurrence and endoscopic findings. Before dilation, it is critical to ensure that the stricture is primarily fibrotic without active ulceration, as this significantly affects the safety and efficacy of the procedure (Fig. 2).11
For strictures refractory to EBD, endoscopic stricturotomy (ESt) is emerging as a valuable alternative.43 ESt involves a radial or linear incision of the stricture using an electrosurgical knife and has demonstrated comparable or superior outcomes to EBD, with a lower risk of deep perforation but a higher risk of bleeding. In cases of short, fibrotic, or anastomotic strictures, particularly those that are refractory to balloon dilation or located at anatomically challenging sites, such as the ileocecal valve, ESt may be preferred over endoscopic balloon dilation because of its superior efficacy and ability to achieve a more durable luminal opening.11,33 A comparative summary of EBD and ESt, including their efficacy, adverse events, and clinical indications, is presented in Table 1.
According to a global consensus, interventional IBD endoscopy, including ESt, stent placement, and intralesional therapies, should be considered before surgery in selected patients.31 Temporary self-expanding metal stents, including lumen-apposing metal stents, are also being investigated for refractory strictures, particularly in patients unfit for surgery; however, migration and adverse events remain limitations.44
Endoscopic hemostasis plays a critical role in the management of acute lower gastrointestinal bleeding. Gastrointestinal bleeding complications in patients with IBD are often related to deep ulceration or post-procedure bleeding.45 Acute severe lower gastrointestinal bleeding in CD is uncommon but is a diagnostic and therapeutic challenge. A retrospective study involving 70 patients with CD reported that the cumulative probabilities of bleeding after CD diagnosis were 1.7%, 3.6%, 6.5%, and 10.3% after 1, 5, 10, and 20 years, respectively.46 Rebleeding is common, but treatment with infliximab has been shown to reduce recurrence.
VCE can help localize the focus of small bowel bleeding before intervention.10,19 In CD, bleeding is often subtle and chronic but may occasionally present as overt hemorrhage requiring urgent endoscopic therapy. Endoscopic hemostatic techniques include thermal coagulation, argon plasma coagulation (APC), hemoclipping, and epinephrine injection. Among these, hemoclips and APC are commonly used in the small bowel via BAE.10 Endoscopic clipping is an effective method for achieving hemostasis in small bowel bleeding associated with CD, particularly when the bleeding source is focal and clearly identified. Using BAE, clips can be applied directly to the lesion to provide mechanical compression without inducing thermal injury, making it a safe option, even for inflamed or ulcerated mucosa.47 APC is another useful modality, particularly for diffuse or oozing bleeding, such as that seen in angiodysplasia or extensive mucosal inflammation. Given the risk of deep thermal injury in CD, particularly in areas with transmural inflammation, APC should be performed with caution. In such cases, combination therapies such as submucosal injection of saline or epinephrine before coagulation may improve safety by creating a protective cushion and enhancing the efficacy of the procedure.47
VCE retention is a recognized complication in patients with CD, especially in the presence of strictures or severe mucosal inflammation. BAE is the method of choice for the safe and effective retrieval of retained capsules.45 Clinical outcomes from large cohort studies and meta-analyses have consistently shown high technical success rates with BAE in retrieving retained VCE, with success rates ranging from 85% to 100%.48 Immediate retrieval is advised to mitigate risks such as bowel obstruction, ulceration, or perforation, all of which can result in severe clinical consequences. In many cases, BAE can be used to retrieve the capsule and perform concurrent balloon dilation of the stricture, if appropriate. Surgical removal is reserved for cases in which endoscopic retrieval fails or when the capsule is impacted within a complex or fibrotic stricture not amenable to dilation.49
Undiagnosed strictures predominantly cause the retention of VCE; hence, to avoid VCE retention, preprocedural evaluation using imaging modalities such as CT or MR enterography is crucial.15,50 The use of patency capsules has also become a standard preventive measure to minimize retention risks, providing reassurance regarding small bowel patency before VCE administration.48
As the therapeutic objectives of CD shift toward mucosal healing, early intervention, and personalized care, small bowel endoscopy has become increasingly integral to comprehensively managing IBD. While procedural challenges such as stricture-related retention or incomplete examination remain, the clinical benefits justify a broader implementation. Small bowel endoscopy plays a pivotal role in diagnosis and therapeutic intervention, supporting the evolution of treat-to-target paradigms. Future directions include enhancing diagnostic precision through standardized scoring systems and AI, optimizing patient selection using risk-based strategies, and expanding therapeutic applications, such as EBD and stricturotomy, to reduce reliance on surgery. The integration of AI-assisted interpretation and the development of platforms that combine diagnostic and therapeutic functions will further enable individualized, minimally invasive, and proactive disease management.