To evaluate the quality of cold snare resection specimens of duodenal mucosa tissue in patients undergoing an upper gastrointestinal interventional endoscopy in order to improve the processing of histological samples and its assessment in general and for future duodenal ablation studies.

The duodenum plays an important role in metabolic health. There is evidence that the duodenal mucosa undergoes certain histological changes in the development of features of the metabolic syndrome and ultimately type 2 diabetes (T2D). To date, it is not known exactly what type of histological changes the duodenal mucosa undergoes in T2D, so elucidating these changes may lead to a better understanding and potentially new treatment options for metabolic syndrome and T2D.

The assessment of histological changes in tissue obtained from duodenal biopsies has proven to be very difficult due to the lack of orientation in the histological slides obtained. The investigators have learned that duodenal biopsies are too small and superficial to reliably assess histological changes in the duodenal mucosa and submucosa. Currently, the investigators are taking small cold snare resections from the duodenum to try to fully assess the duodenal (sub)mucosa. However, the investigators still have problems with the orientation of these resections. When slides are made, the specimens are curled, cut tangentially and artefacts occurr. As a result, it is still not possible to make a proper assessment of the duodenal (sub)mucosa.

Therefore, the investigators aim to optimise the process of obtaining, storing, processing and staining the duodenal mucosal tissue samples from cold snare resections. The investigators plan to optimise this process in patients who have already undergone upper gastrointestinal interventional endoscopy, including ablation therapy, endoscopic submucosal dissection (ESD) or endoscopic mucosal resection (EMR) for Barrett's neoplasia and squamous cell carcinoma of the oesophagus or small gastric neoplasia, or oesophageal dilatations, as the endoscopist performing DMR in the Netherlands also specialises in these endoscopic treatments. By studying the process of obtaining duodenal mucosal tissue samples in this specific patient population, there is no need to expose other patients to an upper gastrointestinal endoscopy with the associated propofol sedation.

Inclusion Criteria:

• Already scheduled to undergo an upper gastrointestinal interventional endoscopy
• Endoscopy under deep sedation (propofol) in Amsterdam UMC

Exclusion Criteria:

• Previous GI surgery that could affect the ability to reach the duodenum via endoscopy, such as Bilroth 2, Roux-en-Y gastric bypass, or other similar procedures or condition
• History of duodenal inflammatory diseases including Crohn's Disease and Celiac Disease