Advanced endoscopic imaging techniques
The cornerstone to successful treatment of early gastrointestinal neoplasia lies in lesion recognition and characterization. These next pages outline some of the key concepts which underpin in-vivo diagnosis in the oesophagus and colon.
Advanced diagnostic imaging in Barrett's Oesophagus
Advanced Diagnostic Imaging in Barrett's Oesophagus
Before any endoscopic treatment of Barrett's neoplasia can be performed it is vital to be able to confidently identify areas of dysplasia and intramucosal cancer with confidence.
Advanced endoscopic techniques include the use of high resolution endoscopy, spectral imaging and dye sprays. However, before any of these techniques are performed it is first important to clean the mucosa of any mucous or debris. In our unit we favour a mix of NAC with infacol. Furhermore, inflammation can look similar to dysplasia. Therefore this should be treated with acid suppression before advanced imaging is performed.
The following videos illustrate several key points in identifing neoplasia.
This first case demonstrates how subtle lesions can be difficult to see with white light. It also illustrates how spectral imaging in this case failed to identify the dysplastic changes. However, acetic acid dye spray made the area visible. It is important to appreciate that no single technique is 100% effective in identifying early neoplasia and that it is desirable to be skilled in the use of multiple techniques.
This next video demonstrates how residual dysplasia in patients who have undergone previous endoscopic mucosal resection can be very subtle and difficult to spot. Furthermore, multiple neo-squamous islands can make endoscopic assessment very difficult. Small squamous islands in Barrett's should not be mistaken for aceto-whitening of dysplasia. The key is to evaluate the area around the squamous islands in a very careful fashion as residual dysplasia is likely to be at the border of the neo-squamous patch.
Acetic acid can show subtle changes in surface patterns and abnormal vasculature, both of which can then be easily confirmed by spectral imaging techniques like FICE.
FICE can also highlight the abnormal tumour vessel patterns seen in dysplasia. The following video to the right demonstrates the same pathology seen with acetic acid in the previous video with FICE.
Sometimes a lesion can be macroscopically visible on white light but pose a significant diagnostic challenge.
In particular the decision as to whether a large lesion can be endoscopically resected is challenging. This next video demonstrates this.
Kudo pit patterns
In order to confidently resect large colonic lesions it is necessary to be able to make an in-vivo diagnosis. The most commonly used system is pit pattern interpretation as proposed by Professor Kudo.
Kudo pit patterns describe the surface characteristics of polyps. They should not be confused with the Paris classifications, which describe the morphological features of polyps. These patterns were orignally described using vital stains and zoom endoscopy. However, they can also be assessed using indigo carmine, which sits on the surface of lesions, highlighting the structures. Because indigo carmine does not bind to the polyp tissue, it can be washed off or reapplied as necessary during assessment and lesion resection.
Before making any assessment of surface patterns it is important to clean the lesion first. When doing this care should be taken not to traumatise the polyp. Once a lesion is inflammed or bleeding an accurate prediction of histology is very difficult.
Click to run through images
Electronic spectral imaging techniques, like Narrow Band imaging (NBI), fujinon intelligent color enhancement (FICE) and i-scan can also be used to predict polyp histology. However, these techniques work by enhancing vascular patterns. Therefore although the appearances are often similar to the kudo patterns it is not correct to describe a kudo pattern using these techniques. Specific classification systems have been developed for these tools.