Definition & Overview
Endomicroscopy is the process of obtaining real-time, high-resolution images using devices known as endomicroscopes. The procedure, which is performed for the diagnosis and evaluation of different diseases and medical conditions, is also known as optical biopsy or fluorescence confocal microscopy. Various techniques can be used when performing this procedure some of which involve the use of laser technology to get optical sectioning, scanning a laser over the targeted tissue in a rapid fashion. The obtained images are then assembled to evaluate any abnormal growths or physiologic changes.
There are different types of endomicroscopes that are in use today. These include:
- Fibre bundle endomicroscopes - Typically used with endoscopes with flexible tips
- Distal scanning endomicroscopes - Obtain two-dimensional images from the tip of the imaging probe
- Confocal endomicroscopes - Have a lens and condenser with the same focal point. These integrate fluorescence and reflectance techniques in microscopy to obtain high-resolution two- or three-dimensional images. A fluorescent agent is introduced and different tissue characteristics are identified according to their reaction to the staining agent. The staining substance provides adequate contrast between different types of tissues and makes the imaging of microvasculature or blood vessels easier.
The use of endomicroscopy offers various benefits, which include eliminating the need for surgical procedures in evaluating tissues, enhanced tissue and cell classification, and providing real-time information, which helps in the decision-making among physicians.
Who Should Undergo and Expected Results
Endomicroscopy is indicated for those suffering from:
Barrett’s oesophagus - This condition results from the exposure of the oesophagus lining to gastric acid when the patient is suffering from recurring gastroesophageal reflux. There is a need to monitor this condition, as it can lead to oesophageal cancer. Its symptoms are chest pain, swallowing difficulty, vomiting blood, and bloody stools. In diagnosing the condition, physicians typically determines if dysplasia, or abnormal epithelial growth, has occurred in the oesophagus and the extent of the damage, if present.
Colorectal polyps – Patients with this condition need to have the abnormal growths examined. A polyp in the colon refers to a group of cells typically found in its lining. Older people and smokers have a higher risk of developing this condition, which is asymptomatic in its early stages but could lead to colorectal cancer later on.
Inflammatory bowel diseases - This group of diseases is caused by the chronic inflammation of the digestive tract. One type of this condition is ulcerative colitis, in which the patient experiences diarrhoea and abdominal pain. The stools are often loose and bloody. A related condition, Crohn’s disease, involves the entire gastrointestinal wall and leads to abdominal cramps and constipation. These conditions often adversely impact the patient’s quality of life. As such, they must be managed effectively as soon as possible. The procedure is also used to diagnose, monitor, and treat gastric lesions, both the precancerous and benign types. Changes brought about by a bacterial infection can also be identified with endomicroscopy. Additionally, this procedure can help classify metaplastic, dysplastic, and malignant cells.
Biliary or bile duct strictures – This condition is characterised by the narrowing of the bile duct and is caused by injuries or certain diseases like cancer or pancreatitis. Its symptoms include fever, chills, abdominal pain, jaundice, nausea, and vomiting.
Pancreatic cyst - Another application of endomicroscopy is the imaging of the pancreas. Patients diagnosed with pancreatic cysts can take advantage of this procedure for definitive diagnosis and monitoring. Symptoms of this condition include abdominal pain, palpable mass in the upper part of the abdomen, vomiting, and recurring nausea.
Recent advancements in endomicroscopy technology also allow the procedures to be used in examining other body parts such as the urinary tract, cervix, ovary, neck, and the lungs. Some physicians may recommend this procedure in cases where cancer or any diseases of these body parts are suspected.
Endomicroscopy is considered a safe and simple procedure for the diagnosis of diseases and evaluation of the state of internal body parts. It is typically performed in an outpatient setting and patients are allowed to go home afterwards. Patients have to make follow-ups visits to their doctor where the results of the procedure are discussed.
When compared to other endoscopic techniques, endomicroscopy provides more accurate and comprehensive results, which is crucial in making a definitive diagnosis.
How is the Procedure Performed?
The use of endomicroscopy for evaluating the gastrointestinal tract begins with the administration of anaesthetics. This could be in the topical form or injected intravenously. A fluorescent agent is also needed to facilitate visualisation.
The patient is made to lie on the left side and a mouth gag is placed to keep the oral cavity open. An endoscope is gently inserted into the mouth and pharynx, passed through the oesophagus and into the gastrointestinal tract. During this process, the endoscope transmits images to a monitor where a physician can perform an optical biopsy. One advanced method uses laser technology to focus on a specific, single point in the target tissue. Images from the tissue surface and beneath it are collected simultaneously without the need to physically dissect the tissue. Once complete, the endoscope is slowly retracted and taken out of the mouth.
Possible Risks and Complications
Although safe, the procedure can result in:
- Bleeding, if the endoscope injures the mucosal lining or damages a blood vessel
- Adverse reaction to anaesthesia and/or the staining or fluorescent agent
Nausea and vomiting
Pierce, M., D. Yu, and R. Richards-Kortum, High-resolution fiber-optic microendoscopy for in situ cellular imaging. Journal of visualized experiments : JoVE, 2011: p. 8-11.
Sharman MJ et al. The exogenous fluorophore, fluorescein, enables in vivo assessment of the gastrointestinal mucosa via confocal endomicroscopy: optimization of intravenous dosing in the dog model. Journal of Veterinary Pharmacology and Therapeutics, 2012. DOI: 10.1111/jvp.12031