From the surface to the single cell: Novel endoscopic approaches in inflammatory bowel disease

A spotlight on intestinal permeability and inflammatory bowel diseases

INTRODUCTION

The intestinal barrier is a multi-faced structure lining the surface of the intestinal mucosa of the GI tract. To exert its main functions as a physical and immunological defense barrier, several components of the intestinal barrier act in a concerted and cooperative manner.

AREAS COVERED

Herein, we first introduce to the basic organization of the intestinal barrier and then summarize different methods to assess barrier function in and ex vivo. Finally, we provide an in-depth overview of the relevance of intestinal barrier dysfunction in inflammatory bowel diseases.

EXPERT OPINION

In parallel to a more fundamental understanding of the intestinal barrier as a key component for intestinal integrity is the notion that intestinal barrier defects are associated with a variety of diseases such as inflammatory bowel diseases. Recent research has fueled and perpetuated the concept that barrier defects are critical components of disease development, disease behavior, and potentially also an area of therapeutic intervention in IBD patients. Although being far away from standard, new technologies can be used to easily assess barrier healing in IBD and to derive clinical consequences from these findings such as more accurate forecasting of future disease behavior or the identification of novel therapeutic targets.

Artificial Intelligence Enhances Studies on Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), which includes ulcerative colitis (UC) and Crohn’s disease (CD), is an idiopathic condition related to a dysregulated immune response to commensal intestinal microflora in a genetically susceptible host. As a global disease, the morbidity of IBD reached a rate of 84.3 per 100,000 persons and reflected a continued gradual upward trajectory. The medical cost of IBD is also notably extremely high. For example, in Europe, it has €3,500 in CD and €2,000 in UC per patient per year, respectively. In addition, taking into account the work productivity loss and the reduced quality of life, the indirect costs are incalculable. In modern times, the diagnosis of IBD is still a subjective judgment based on laboratory tests and medical images. Its early diagnosis and intervention is therefore a challenging goal and also the key to control its progression. Artificial intelligence (AI)-assisted diagnosis and prognosis prediction has proven effective in many fields including gastroenterology. In this study, support vector machines were utilized to distinguish the significant features in IBD. As a result, the reliability of IBD diagnosis due to its impressive performance in classifying and addressing region problems was improved. Convolutional neural networks are advanced image processing algorithms that are currently in existence. Digestive endoscopic images can therefore be better understood by automatically detecting and classifying lesions. This study aims to summarize AI application in the area of IBD, objectively evaluate the performance of these methods, and ultimately understand the algorithm–dataset combination in the studies.

Artificial intelligence in gastrointestinal endoscopy for inflammatory bowel disease: a systematic review and new horizons

INTRODUCTION

Since the advent of artificial intelligence (AI) in clinical studies, luminal gastrointestinal endoscopy has made great progress, especially in the detection and characterization of neoplastic and preneoplastic lesions. Several studies have recently shown the potential of AI-driven endoscopy for the investigation of inflammatory bowel disease (IBD). This systematic review provides an overview of the current position and future potential of AI in IBD endoscopy.

METHODS

A systematic search was carried out in PubMed and Scopus up to 2 December 2020 using the following search terms: artificial intelligence, machine learning, computer-aided, inflammatory bowel disease, ulcerative colitis (UC), Crohn's disease (CD). All studies on human digestive endoscopy were included. A qualitative analysis and a narrative description were performed for each selected record according to the Joanna Briggs Institute methodologies and the PRISMA statement.

RESULTS

Of 398 identified records, 18 were ultimately included. Two-thirds of these (12/18) were published in 2020 and most were cross-sectional studies (15/18). No relevant bias at the study level was reported, although the risk of publication bias across studies cannot be ruled out at this early stage. Eleven records dealt with UC, five with CD and two with both. Most of the AI systems involved convolutional neural network, random forest and deep neural network architecture. Most studies focused on capsule endoscopy readings in CD (n = 5) and on the AI-assisted assessment of mucosal activity in UC (n = 10) for automated endoscopic scoring or real-time prediction of histological disease.

DISCUSSION

AI-assisted endoscopy in IBD is a rapidly evolving research field with promising technical results and additional benefits when tested in an experimental clinical scenario. External validation studies being conducted in large and prospective cohorts in real-life clinical scenarios will help confirm the added value of AI in assessing UC mucosal activity and in CD capsule reading.

PLAIN LANGUAGE SUMMARY

Artificial intelligence for inflammatory bowel disease endoscopy Artificial intelligence (AI) is a promising technology in many areas of medicine. In recent years, AI-assisted endoscopy has been introduced into several research fields, including inflammatory bowel disease (IBD) endoscopy, with promising applications that have the potential to revolutionize clinical practice and gastrointestinal endoscopy.We have performed the first systematic review of AI and its application in the field of IBD and endoscopy.A formal process of paper selection and analysis resulted in the assessment of 18 records. Most of these (12/18) were published in 2020 and were cross-sectional studies (15/18). No relevant biases were reported. All studies showed positive results concerning the novel technology evaluated, so the risk of publication bias cannot be ruled out at this early stage.Eleven records dealt with UC, five with CD and two with both. Most studies focused on capsule endoscopy reading in CD patients (n = 5) and on AI-assisted assessment of mucosal activity in UC patients (n = 10) for automated endoscopic scoring and real-time prediction of histological disease.We found that AI-assisted endoscopy in IBD is a rapidly growing research field. All studies indicated promising technical results. When tested in an experimental clinical scenario, AI-assisted endoscopy showed it could potentially improve the management of patients with IBD.Confirmatory evidence from real-life clinical scenarios should be obtained to verify the added value of AI-assisted IBD endoscopy in assessing UC mucosal activity and in CD capsule reading.

Advances in Imaging Modalities and Contrast Agents for the Early Diagnosis of Colorectal Cancer

Colorectal cancer is one of the most common gastrointestinal cancers worldwide. The mortality rate of colorectal cancer has declined by more than 20% due to the rapid development of early diagnostic techniques and effective treatment. At present, there are many diagnostic modalities available for the evaluation of colorectal cancer, such as the carcinoembryonic antigen test, the fecal occult blood test, endoscopy, X-ray barium meal, computed tomography, magnetic resonance imaging, and radionuclide examination. Sensitive and specific imaging modalities have played an increasingly important role in the diagnosis of colorectal cancer following the rapid development of novel contrast agents. This review discusses the applications and challenges of different imaging techniques and contrast agents applied to detect colorectal cancer, for the purpose of the early diagnosis and treatment of patients with colorectal cancer.

Advanced Endoscopic Imaging in Colonic Neoplasia

BACKGROUND

Endoscopic imaging is a rapidly evolving field with a constant influx of new concepts and technologies. Since the introduction of video endoscopy and subsequently high-definition imaging as the first revolutions in gastrointestinal endoscopy, several technologies of virtual chromoendoscopy have been developed and brought to the market in the past decade, which have shaped and revolutionized for a second time our approach to endoscopic imaging. In parallel to these developments, microscopic imaging technologies, such as endomicroscopy and endocytoscopy, allow us to examine single cells within the mucosa in real time, thereby enabling histological diagnoses during ongoing endoscopy.

SUMMARY

In this review, we provide an overview on the technical background of different technologies of advanced endoscopic imaging, and then review and discuss their role and applications for the diagnosis and management of colorectal neoplasms as well as limitations and challenges that exist despite all technological improvements.

KEY MESSAGES

Technologies of advanced endoscopic imaging have profound impact not only on our imaging capabilities, they are also about to fundamentally change our approach to managing lesions in the gastrointestinal tract: not every lesion found during colonoscopy has to be excised or sent for histopathologic evaluation. However, before this becomes widespread reality, major obstacles such as patient acceptance, adoption by less trained endoscopists, and also legal aspects need to carefully addressed. The development of computer-aided diagnosis and artificial intelligence algorithms hold the potential to overcome the obstacles associated with the concept of optical biopsy and will most likely fundamentally facilitate, shape, and change decision making in the management of colorectal lesions.

Magnification endoscopy with optical chromoendoscopy shows strong correlation with histologic inflammation in patients with inflammatory bowel disease

Background and study aims  Apart from mucosal healing as an established treatment goal in inflammatory bowel diseases (IBD), recent evidence suggests that histologic healing may become another key prognostic parameter in IBD patients. We aimed to evaluate whether magnification endoscopy with optical chromoendoscopy can accurately assess histologic inflammation in IBD patients. Patients and methods  In this prospective study, 82 patients with IBD (30 UC, 52 CD) were included. In all patients, magnification endoscopy in conjunction with optical chromoendoscopy was performed and rated on a novel magnification endoscopy score by three independent endoscopists. Targeted biopsies of the imaged areas were obtained and results were compared against two histological scores in UC (Robarts Histopathology Index, RHI; Nancy Histology Index, NHI) and one score in CD (modified Riley index, mRI). Moreover, interobserver agreement was calculated. Results  Magnification endoscopy showed strong correlation with histopathologic scoring in both UC (RHI: r = 0.83, NHI: r = 0.78, P  < 0.05) and CD (mRI: r = 0.74, P  < 0.05) with high accuracy, sensitivity, and specificity. Further, 25 % of patients with mucosal healing on standard endoscopy showed signs of microinflammation on magnification endoscopy with optical chromoendoscopy, while none of the patients with mucosal and vascular healing under magnification endoscopy with optical chromoendoscopy exhibited microscopic inflammation. Interobserver agreement for grading intestinal inflammation by magnification endoscopy with optical chromoendoscopy was substantial (κ > 0.7). Conclusion  Magnification endoscopy in combination with optical chromoendoscopy shows strong correlation with histologic inflammation in patients with IBD. This approach has potential to reduce physical biopsies for monitoring of inflammatory activity in patients with IBD during colonoscopy.

Molecular imaging within the lower gastrointestinal tract: From feasibility to future

Molecular imaging is based on the labelling of defined molecular targets through the utilization of fluorescently linked probes and their subsequent detection with high-resolution endoscopic devices, thereby enabling visualization of single molecules including receptors. Whereas early studies have used molecular imaging for improved visualization and detection of early dysplasia and cancer as well as for assessing intestinal inflammation and inflammation-associated cancer within the gastrointestinal (GI) tract, more recent studies have impressively demonstrated that molecular imaging can also be used to characterize and visualize the molecular fingerprint of cancer and inflammation in vivo and in real time. With this, molecular imaging can be used to guide expression-tailored individualized therapy. With the rapid expansion and diversification of the repertoire of biological agents utilized in inflammatory bowel disease and cancer, this approach is gaining increasing attention. Within this review, we first summarize the technical components commonly used for molecular imaging and then review preclinical and clinical studies and evolving clinical applications on molecular imaging within the lower GI tract. Molecular imaging has the potential to significantly change endoscopic diagnosis and subsequent targeted therapy of gastrointestinal cancer and chronic gastrointestinal diseases.

Imaging of Mucosal Inflammation: Current Technological Developments, Clinical Implications, and Future Perspectives

In recent years, various technological developments markedly improved imaging of mucosal inflammation in patients with inflammatory bowel diseases. Although technological developments such as high-definition-, chromo-, and autofluorescence-endoscopy led to a more precise and detailed assessment of mucosal inflammation during wide-field endoscopy, probe-based and stationary confocal laser microscopy enabled in vivo real-time microscopic imaging of mucosal surfaces within the gastrointestinal tract. Through the use of fluorochromes with specificity against a defined molecular target combined with endoscopic techniques that allow ultrastructural resolution, molecular imaging enables in vivo visualization of single molecules or receptors during endoscopy. Molecular imaging has therefore greatly expanded the clinical utility and applications of modern innovative endoscopy, which include the diagnosis, surveillance, and treatment of disease as well as the prediction of the therapeutic response of individual patients. Furthermore, non-invasive imaging techniques such as computed tomography, magnetic resonance imaging, scintigraphy, and ultrasound provide helpful information as supplement to invasive endoscopic procedures. In this review, we provide an overview on the current status of advanced imaging technologies for the clinical non-invasive and endoscopic evaluation of mucosal inflammation. Furthermore, the value of novel methods such as multiphoton microscopy, optoacoustics, and optical coherence tomography and their possible future implementation into clinical diagnosis and evaluation of mucosal inflammation will be discussed.

Surveillance strategies for colitis-associated cancer: state of the art and future perspectives

Colitis-associated cancer (CAC) represents a concrete risk of morbidity and mortality in patients with long lasting inflammatory bowel diseases. Surveillance colonoscopy is a rapidly evolving research field with profound changes from the traditional approach based on scheduled controls and random biopsy protocols. Areas covered: A literature search was performed using PubMed/Embase to review the latest evidence supporting the need for surveillance colonoscopy. By focusing on the most promising recent advances in this field, we provide a state-of-the-art overview of the current gold standards for the diagnosis and management of colitis-associated dysplasia. Expert commentary: Evidence-based and emerging data have questioned the efficacy and effectiveness of both standard surveillance colonoscopy and random biopsy protocols. The latest guidelines endorse early initiation of surveillance programs, risk-profiling assessment of colonoscopy intervals and standardized use of advanced imaging modalities to detect early dysplasia. Current trends clearly reveal increased attention to direct visualization and endoscopic management of visible dysplastic lesions, even in patients with longstanding colitis. Emerging technological advances in gastrointestinal endoscopy are expected to change the endoscopic surveillance protocols in the near future.

Advanced imaging in colonoscopy: contemporary approach to dysplasia surveillance in inflammatory bowel disease

Inflammatory bowel disease (IBD) (ulcerative colitis (UC) and Crohn's disease (CD)) is a chronic relapsing/remitting condition characterised by intestinal inflammation. One of the main concerns in patients with longstanding ulcerative and Crohn's colitis is development of colonic dysplasia and colorectal cancer (CRC), a risk higher than that of the general population. Colonoscopy surveillance programmes have been developed by major societies worldwide to improve early dysplasia detection and treatment, thus preventing progression to colorectal cancer. Colonoscopy is an imperfect tool as lesions can be missed, an issue even more relevant to colitic patients, where mucosal inspection and lesion recognition may prove challenging. Extensive research has been undertaken on performance improvement in this area while technical advances in optical imaging, such as high-definition, have made their way into modern endoscopy units. Techniques and technologies available to enhance optical diagnosis of dysplasia in inflammatory bowel disease are reviewed in this paper, focusing on those that are realistic, widely available and feasible for everyday practice.

From bench to bedside: molecular imaging in inflammatory bowel diseases

PURPOSE OF REVIEW

Standard structural imaging procedures such as endoscopy, ultrasonography, or MRI are an integral part of the rational management of patients with inflammatory bowel diseases (IBDs). There is nevertheless the need for further refined imaging approaches that are able to overcome the limitations of currently used formats. The advent of molecular imaging modalities that allow real-time visualization of cellular processes not only in the preclinical setting but also in clinical trials has demonstrated its ability to improve current therapeutic strategies. The purpose of this review is to present and discuss advancements in the field of molecular imaging approaches in the IBD field.

RECENT FINDINGS

Recent preclinical and clinical studies have addressed the applicability of molecular imaging for improving the differentiation between benign and malignant mucosal alterations, increasing the detection of dysplastic intestinal lesions, and predicting individual responses to biological therapies.

SUMMARY

Molecular imaging in IBD represents an exciting and evolving field that has the potential to impact on current diagnostic and therapeutic algorithms in the treatment of IBD patients by analyzing and visualizing the molecular mechanisms that drive mucosal inflammation. It might enable us to base individualized therapeutic decisions on preceded molecular level analysis by suitable imaging modalities.