**5. Conclusions**

*Endoscopy in Small Bowel Diseases*

accuracy of EUS alone compared to the final histology (ESD or surgical specimen) varies between 44% and 66% and tissue acquisition is important for a correct

*External invasion from a pancreatic head adenocarcinoma. (A) Endoscopic view: There are mucosal modifications visible (as opposed to 6A). (B) Echoendoscopic view confirms there is a pancreatic tumor. (C) EUS-FNA - foci of pancreatic ductal adenocarcinoma infiltrating submucosa of the duodenal wall (HE-5X).*

The sampling has to be performed using bite-to-bite biopsy followed by mucosal resection or submucosal resection in case of the lesions belonging to the second or third layers [11]. In case of the lesions originating from the fourth layer, the indication is for EUS-FNA or EUS–fine-needle biopsy (EUS-FNB) [23]. The unroofing method for sampling of fourth-layer lesions of gastric location was compared to EUS-FNB, but no difference for histologic core procurement was noted [24].

EUS sampling is preferred in case of lesions situated in the third or fourth layer,

However, the use of EUS-FNA, especially with 22-guage and 25-guage needles, gave a diagnostic rate of 60% in a meta-analysis of 978 patients [25]. The main limitation is difficulty in assessing the architecture of the lesion sampled and the mitotic index. No influence of SET size on the diagnostic rate of FNA was found in a retrospective study of 112 patients [26]. The use of a pro-core needle compared to FNA needles does not improve the diagnostic rate [27–30]. However, only one study included SETs from

because the risk of bleeding is usually low and seeding into the peritoneum is

**84**

diagnosis [20–22].

**Figure 7.**

avoided compared to percutaneous biopsy.

EUS is essential for evaluating duodenal lesions correctly and completely. EUS can identify if the lesion originates from the mucosa or the deeper layers of the duodenal wall, or if it is extrinsic. Other diagnostic methods lack the resolution to distinguish between them correctly. In addition, EUS can obtain tissue for histological analysis in all cases, as EGD-guided biopsies are not deep enough for SETs. Choice of treatment is also decided following EUS, as benign lesions do not need removal, potential malignant lesions (NETs, GISTs) can be followed or resected and malignant lesions can be resected endoscopically if EUS does not identify invasion of the deeper layers. Given all this, along with the complex surroundings of the duodenum, its thin walls and the difficult anatomical position for surgical interventions, EUS is crucial in lesions of the duodenal wall.
