In vivo confocal laser scanning chromo-endomicroscopy of colorectal neoplasia: changing the technological paradigm

Role of ultra-high definition endoscopy (endomicroscopy and endocytoscopy) and real-time histologic examination in inflammatory bowel disease: Scoping review

OBJECTIVES

Confocal laser endomicroscopy (CLE) and endocytoscopy (EC) are ultra-high definition (HD) imaging modalities that enable real-time histological assessment. Although existent for nearly two decades, their role in current clinical decision making in inflammatory bowel disease management is not well defined.

METHODS

We searched PubMed using keywords ("confocal" OR "CLE" OR "endocytoscopy") AND ("IBD" OR "inflammatory bowel" OR "Crohn*" OR "Crohn's" OR "colitis ulcerosa" OR "ulcerative colitis") between 2005 and March 2023. We identified 52 studies for detailed review.

RESULTS

Confocal laser endomicroscopy was useful in real-time assessment of histologic inflammation and dysplasia characterization in both ulcerative colitis (UC) and Crohn's disease. Although CLE was associated with higher per-biopsy yield for UC-associated neoplasia (UCAN), the benefit was offset by higher procedure time, frequent equipment failure, and conflicting results on incremental yield over chromoendoscopy. Assessment of barrier dysfunction by CLE did not correlate with disease/endoscopic activity but could predict major adverse outcomes. The implications of residual CLE abnormalities in endoscopic remission remain uncertain. Ex vivo binding of labeled biologics can help in predicting biologic response in UC. EC can discriminate mucosal inflammatory cells by morphology and allows assessment of histologic activity. EC combined with pit pattern was better than pit pattern alone for UCAN. Artificial intelligence-assisted EC in UCAN needs further study.

CONCLUSION

Ultra-HD imaging in inflammatory bowel disease can be useful in assessment of UCAN, barrier dysfunction, predicting histologic remission, and biologic response. Future controlled studies are warranted to define the role of these novel technologies in clinical decision making.

Diagnostic accuracy of probe-based confocal laser endomicroscopy and tissue sampling by endoscopic retrograde cholangiopancreatography in indeterminate biliary strictures: a meta‑analysis

Probe-based confocal laser endomicroscopy (pCLE), also known as optical biopsy, is a new endoscopic technique that provides real-time magnification of 1000 × microscopic tissue information to diagnose indeterminate biliary strictures. Tissue sampling by endoscopic retrograde cholangiopancreatography (ERCP) is routinely performed to evaluate indeterminate biliary strictures. To evaluate the accuracy of pCLE and tissue sampling by ERCP in the diagnosis of indeterminate biliary strictures, 18 articles were included from 2008 to 2021 through Embase, PubMed, Web of Science, and Cochrane library databases. The summary estimates for the pCLE diagnosis of indeterminate biliary strictures were: sensitivity 0.88 (95% confidence interval (CI), 0.84-0.91); specificity 0.79 (95% CI 0.74-0.83); and Diagnostic Odds Ratio (DOR) 24.63 (95% CI 15.76-38.48). The summary estimates for tissue sampling by ERCP diagnosis for indeterminate biliary strictures were: sensitivity 0.54 (95% CI 0.49-0.59); specificity 0.96 (95% CI 0.94-0.98); and DOR 11.31 (95% CI 3.90-32.82). The area under the sROC curve of pCLE diagnosis of indeterminate biliary strictures is 0.90 higher than 0.65 of tissue sampling by ERCP. The pCLE is a better approach than tissue sampling by ERCP for the diagnosis of indeterminate biliary strictures by providing real-time microscopic images of the bile ducts.

In Vivo and Ex Vivo Microscopy: Moving Toward the Integration of Optical Imaging Technologies Into Pathology Practice

The traditional surgical pathology assessment requires tissue to be removed from the patient, then processed, sectioned, stained, and interpreted by a pathologist using a light microscope. Today, an array of alternate optical imaging technologies allow tissue to be viewed at high resolution, in real time, without the need for processing, fixation, freezing, or staining. Optical imaging can be done in living patients without tissue removal, termed in vivo microscopy, or also in freshly excised tissue, termed ex vivo microscopy. Both in vivo and ex vivo microscopy have tremendous potential for clinical impact in a wide variety of applications. However, in order for these technologies to enter mainstream clinical care, an expert will be required to assess and interpret the imaging data. The optical images generated from these imaging techniques are often similar to the light microscopic images that pathologists already have expertise in interpreting. Other clinical specialists do not have this same expertise in microscopy, therefore, pathologists are a logical choice to step into the developing role of microscopic imaging expert. Here, we review the emerging technologies of in vivo and ex vivo microscopy in terms of the technical aspects and potential clinical applications. We also discuss why pathologists are essential to the successful clinical adoption of such technologies and the educational resources available to help them step into this emerging role.

In Vivo Rectal Mucosal Barrier Function Imaging in a Large-Animal Model by Using Confocal Endomicroscopy: Implications for Injury Assessment and Use in HIV Prevention Studies

Injury occurring on the surface of the rectal mucosal lining that causes defects in barrier function may result in increased risk for transmission of infection by HIV and other pathogens. Such injury could occur from microbicidal or other topical agents, mechanical trauma during consensual or nonconsensual intercourse, or inflammatory conditions. Tools for evaluation of rectal mucosal barrier function for assessing the mucosa under these conditions are lacking, particularly those that can provide in vivo structural and functional barrier integrity assessment and are adaptable to longitudinal imaging. We investigated confocal endomicroscopy (CE) as a means for in vivo imaging of the rectal epithelial barrier in the ovine model following spatially confined injury to the surface at a controlled site using a topical application of the microbicide test agent benzalkonium chloride. Topical and intravenous (i.v.) fluorescent probes were used with CE to provide subcellular resolution imaging of the mucosal surface and assessment of barrier function loss. A 3-point CE grading system based on cellular structure integrity and leakage of dye through the mucosa showed significant differences in score between untreated (1.19 ± 0.53) and treated (2.55 ± 0.75) tissue (P < 0.0001). Histological grading confirmed findings of barrier compromise. The results indicate that CE is an effective means for detecting epithelial injury and barrier loss following localized trauma in a large-animal model. CE is promising for real-time rectal mucosal evaluation after injury or trauma or topical application of emerging biomedical prevention strategies designed to combat HIV.

Topical injury evaluation of the murine colorectal mucosa using confocal endomicrosopy: a valuable method for assessing mucosal injuries associated with risk of pathogen transmission

BACKGROUND

Concern regarding the effect of epithelial damage to the colorectal surface and possible impact on sexually transmitted infection transmission prompts the need for methods to evaluate the mucosal microscopic surface in preclinical studies examining such injury. This includes determining the effect of topical HIV prevention products on mucosal barrier integrity. In vivo imaging with high-resolution endomicroscopy could reveal defects in the mucosal barrier resulting from injury/surface trauma.

METHODS

Confocal endomicroscopy was investigated to assess the ability to image surface injury resulting from topical application of a chemical used in lubricants and microbial products. Mice treated with a 50 μL rectal dose of 0.2% benzalkonium chloride solution, 1% benzalkonium chloride or phosphate-buffered saline control for 20 min were imaged in vivo using confocal endomicroscopy for assessment of epithelial disruption. Following imaging, mice were sacrificed and rectal tissue evaluated by histology. Confocal images were graded based on degree of disruption to crypt and epithelial microstructure. Histology was graded based on percent of epithelial disruption observed in stained sections. Confocal image features were confirmed by high-resolution two-photon microscopy.

RESULTS

Based on quantitative grading of in vivo confocal endomicroscopy images, disruption at the microscopic scale was observed following treatment with benzalkonium chloride, with increased injury occurring with higher dose. Epithelial disruption at the lumen surface, evident between crypts and alteration in crypt structure on the luminal side were observed in confocal endomicroscopy and confirmed by histology.

CONCLUSIONS

High-resolution imaging by confocal endomicroscopy can be used as a noninvasive tool for rapid visual assessment of rectal epithelial integrity following surface injury, potentially providing valuable indication of epithelial injury or trauma.

Advances in diagnostic and therapeutic colonoscopy

PURPOSE OF REVIEW

We review current studies on endoscopic and technologic advances for the detection and treatment of colorectal neoplasia.

RECENT FINDINGS

Improvements in adenoma detection have been shown to be possible with the use of high definition white light as well as water-related methods such as water exchange. Use of cap assist colonoscopy, when combined with water-related methods, has recently been shown to also improve the detection of adenomas. Narrow band imaging and confocal laser endomicroscopy may have an advantage of offering endoscopists the ability to make an 'optical diagnosis' with the possibility of discarding nonadenomatous tissue. Furthermore, educational interventions aimed at improving adenoma detection may have lasting effects on endoscopists' adenoma detection rates. Lastly, endoscopic mucosal resection and endoscopic submucosal dissection are being applied for the treatment of large colorectal polyps, obviating the need for surgery in most instances. However, further studies are needed to establish the optimal methods for polyp resection.

SUMMARY

Advances in endoscopic technology are being shown to enhance the detection of early cancers and precancerous lesions. However, these tools may be supplementary to a high-quality colonoscopy using excellent techniques, factors that are now being implemented in training programs.

Classification criteria for advanced adenomas of the colon by using probe-based confocal laser endomicroscopy: a preliminary study

BACKGROUND

Probe-based confocal laser endomicroscopy may allow a strategy of "diagnose, resect, and discard" for small nonadvanced adenomas, but there are concerns about discarding polyps with advanced histology.

OBJECTIVE

The aim of this study was to evaluate the potential use of probe-based confocal laser endomicroscopy to aid in distinguishing low-grade from advanced colon adenomas.

DESIGN

Six observers, blinded to histopathology, scored 5 adenoma features and an overall diagnosis and confidence level for the diagnosis.

SETTING

This study was conducted at single, tertiary care referral center.

PATIENTS

Patients undergoing screening and surveillance colonoscopies and for whom an adenomatous polyp was removed were included.

INTERVENTIONS

A sample of 27 advanced adenomas and 120 nonadvanced adenomas were used in the study. An initial classification system was created with 10 advanced and 10 nonadvanced adenomas. The remaining 127 adenomas were scored by each observer in the validation portion of the study.

MAIN OUTCOME MEASURES

The primary outcome measured was the accurate classification of advanced and nonadvanced adenomas.

RESULTS

Overall, across all 6 observers, the sensitivity in correctly classifying advanced adenomas was 43%, the negative predictive value was 89%, the specificity was 71%, and the positive predictive value was 19%. No single feature or combination of features as seen with probe-based confocal laser endomicroscopy consistently identified advanced adenomas.

LIMITATIONS

Classification criteria were developed subjectively, and there was limited observer experience with probe-based confocal laser endomicroscopy use.

CONCLUSIONS

Our initial attempt at creating classification criteria for probe-based confocal laser endomicroscopy did not consistently distinguish advanced from nonadvanced adenomas and, therefore, is not useful in applying a "diagnose, resect, and discard" strategy. However, further refinement of our probe-based confocal laser endomicroscopy classification scheme in future studies has potential to accurately detect advanced histology in colorectal polyps.

Ex vivo confocal imaging with contrast agents for the detection of oral potentially malignant lesions

OBJECTIVES

We investigated the potential use of real-time confocal microscopy in the non-invasive detection of occult oral potentially malignant lesions. Our objectives were to select the best fluorescence contrast agent for cellular morphology enhancement, to build an atlas of confocal microscopic images of normal human oral mucosa, and to determine the accuracy of confocal microscopy to recognize oral high-grade dysplasia lesions on live human tissue.

MATERIALS AND METHODS

Five clinically used fluorescent contrast agents were tested in vitro on cultured human cells and validated ex vivo on human oral mucosa. Images acquired ex vivo from normal and diseased human oral biopsies with bench-top fluorescent confocal microscope were compared to conventional histology. Image analyzer software was used as an adjunct tool to objectively compare high-grade dysplasia versus low-grade dysplasia and normal epithelium.

RESULTS

Acriflavine Hydrochloride provided the best cellular contrast by preferentially staining the nuclei of the epithelium. Using topical application of Acriflavine Hydrochloride followed by confocal microscopy, we could define morphological characteristics of each cellular layer of the normal human oral mucosa, building an atlas of histology-like images. Applying this technique to diseased oral tissue specimen, we were also able to accurately diagnose the presence of high-grade dysplasia through the increased cellularity and changes in nuclear morphological features. Objective measurement of cellular density by quantitative image analysis was a strong discriminant to differentiate between high-grade dysplasia and low-grade dysplasia lesions.

CONCLUSIONS

Pending clinical investigation, real-time confocal microscopy may become a useful adjunct to detect precancerous lesions that are at high risk of cancer progression, direct biopsy and delineate excision margins.

In vivo intraoperative confocal microscopy for real-time histopathological imaging of brain tumors

OBJECT

Frozen-section analysis is the current standard for the intraoperative diagnosis of brain tumors. Intraoperative confocal microscopy is an emerging technology with the potential to visualize tumor histopathological features and cell morphology in real time. The authors report their findings using this new intraoperative technology in vivo with sodium fluorescein contrast during the course of 50 microsurgical tumor resections.

METHODS

Eighty-eight regions were visualized with confocal microscopy, and corresponding biopsy samples were examined with routine neuropathological analysis. The tumors studied included meningiomas, schwannomas, gliomas of various grades, and a hemangioblastoma. The confocal microscopic features of each tumor and of various artifacts inherent to the technology were documented. A pathologist working in a blinded fashion reviewed a subset of the images in a further evaluation of the usefulness of the device as a diagnostic tool.

RESULTS

Overall, intraoperative confocal imaging correlated surprisingly well with corresponding traditional histological findings, including the identification of many pathognomonic cytoarchitectural features of various brain tumors. In the blinded study, 26 (92.9%) of 28 lesions were diagnosed correctly.

CONCLUSIONS

Further study will be necessary for better definition of the role of intraoperative confocal microscopy as a routine adjunct for intraoperative brain tumor diagnosis.

Telepathology and optical biopsy

The ability to obtain information about the structure of tissue without taking a sample for pathology has opened the way for new diagnostic techniques. The present paper reviews all currently available techniques capable of producing an optical biopsy, with or without morphological images. Most of these techniques are carried out by physicians who are not specialized in pathology and therefore not trained to interpret the results as a pathologist would. In these cases, the use of telepathology or distant consultation techniques is essential.

Confocal laser endomicroscopy in the "in vivo" histological diagnosis of the gastrointestinal tract

Recent technological advances in miniaturization have allowed for a confocal scanning microscope to be integrated into a conventional flexible endoscope, or into trans-endoscopic probes, a technique now known as confocal endomicroscopy or confocal laser endomicroscopy. This newly-developed technology has enabled endoscopists to collect real-time in vivo histological images or "virtual biopsies" of the gastrointestinal mucosa during endoscopy, and has stimulated significant interest in the application of this technique in clinical gastroenterology. This review aims to evaluate the current data on the technical aspects and the utility of this new technology in clinical gastroenterology and its potential impact in the future, particularly in the screening or surveillance of gastrointestinal neoplasia.

Endoscopic mucosal resection for early colorectal neoplasia: pathologic basis, procedures, and outcomes

Open access endoscopy and screening programs enable detection and removal of an increased number of colon polyps in the early stages of neoplastic transformation. Unfortunately, polyps larger than 3 cm, involving more than one-third of circumference or two haustral folds, or with a flat/depressed morphology are more challenging to remove with standard polypectomy techniques. Endoscopic mucosal resection potentiates the removal, in a minimally invasive way, of certain colonic lesions that would otherwise require surgical or ablative treatment. Because the plane of resection during endoscopic mucosal resection is typically the middle to deep submucosal layer, compared with standard polypectomy, which normally provides resection at a mucosal level, endoscopic mucosal resection offers the advantage of providing en bloc resection specimens for histopathologic analysis. Indications to perform endoscopic mucosal resection are adenoma and small, well-differentiated carcinoma, confined to the mucosa or with minimal invasion to submucosa, and without any invasion to lymphatic channels or vessels. The most frequently reported major complications, such as perforation (0-5%) and bleeding (0.5-6%), may be controlled by endoscopic methods and rarely require surgical treatment. Follow-up postendoscopic mucosal resection is essential because of the risk of neoplastic recurrence.

Medical decision analysis for the management of unifocal, flat, low-grade dysplasia in ulcerative colitis

BACKGROUND

Management of unifocal, flat, low-grade dysplasia (LGD) in ulcerative colitis (UC) remains controversial.

OBJECTIVE

To compare the relative costs and effectiveness of immediate colectomy and enhanced colonoscopic surveillance for the management of LGD.

DESIGN AND SETTING

Medical decision analysis by using state-transition Markov models. Transition probabilities and health utilities were derived from the literature, and costs were derived from national hospital data sets and Medicare and/or Medicaid reimbursement schedules.

PATIENTS

Two simulated cohorts of 10,000 patients with longstanding UC who were newly diagnosed with unifocal, flat LGD on initial surveillance colonoscopy.

INTERVENTIONS

Immediate colectomy or enhanced surveillance (repeated colonoscopy at 3, 6, and 12 months, and then annually).

MAIN OUTCOME MEASUREMENTS

Costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios.

RESULTS

Immediate colectomy dominated over enhanced surveillance and yielded higher QALYs (20.1 vs 19.9 years) and lower costs ($75,900 vs $83,900). These findings were robust to variations in model parameters, with immediate colectomy remaining dominant in 90% of simulations in sensitivity analysis. Varying postcolectomy health utility outside the range in the probabilistic sensitivity analysis rendered enhanced surveillance cost effective. When the health utility was below 0.77, the incremental cost-effectiveness ratio was $50,000 per QALY.

LIMITATIONS

Data based on observational studies and analyses rely on model assumptions.

CONCLUSIONS

Our analysis showed that immediate colectomy was preferable to enhanced surveillance. Health preference toward the postcolectomy state is, however, an influential factor. This decision analysis model provides a conceptual framework for physicians and patients to understand the relative benefits and costs of both interventions.