Submucosal lesions of the duodenum refer to lesions below the epithelial layer of the duodenal mucosa, which are difficult to diagnose by conventional endoscopy. Miniprobe Endoscopic Ultrasonography (mEUS) has the advantages of flexible operation and clear display of the hierarchical structure of the gastrointestinal wall, and can distinguish the exact location of the lesion in the gastrointestinal wall, and with Fine Needle Aspiration (FNA) or transendoscopic The pathological diagnosis of submucosal lesions can be made with Fine Needle Aspiration (FNA) or transendoscopic mucosal resection techniques. We retrospectively analyzed 71 duodenal submucosal lesions examined by mEUS to investigate the diagnostic value of mEUS on duodenal submucosal lesions. 1. Subjects and methods 1. 1 Study subjects From May 2000 to July 2007, 69 patients, 43 males and 26 females, with an average age of 55 years (30-81 years) and a total of 71 lesions, underwent endoscopic ultrasound examination of submucosal lesions due to gastroscopic examination of duodenal augmentation lesions. Extramural compression and mucosal epithelial lesions (e.g., polyps, carcinomas, etc.) were not included in this study. 1, 2 Instruments and methods A PENTEX EG-3840T double-clamp channel electronic gastroscope, a PENTEX CGI-4000 electrocoagulation-water injection machine, and a FUJINON-SP-701 small probe ultrasound system with probe frequencies of 7.5 MHz, 12 MHz, and 20 MHz were applied. a routine upper gastrointestinal examination was first performed with the double-clamp channel gastroscope, and the augmentation site was clearly identified with a clamp channel All endoscopic and ultrasound images were recorded and/or captured by computer and saved in clear pictures. The echogenic nature of the mass was referenced to the third (hyperechoic) and fourth (hypoechoic) layers of the GI tract, and the imaging diagnosis was made based on the size of the lesion, the imaging features, and the layer of the tract wall from which it originated [1]. The diagnosis was made independently by 2 endoscopists reviewing the video and/or pictures of each lesion, and in case of disagreement, it was discussed and resolved with the assistance of a third physician. 2, Results Of 71 duodenal submucosal lesions, 48 (67.6%) were in the bulb and 23 (32.4%) in the descending segment. Cysts were the most common, 33 (46.5%), and mostly located in the bulb (27/33), others included 15 mesenchymal tumors (21.1%), 8 lipomas (11.3%), 2 mucinous adenomas (2.8%), 1 hemangioma (1.4%), 5 Brunner’s gland hyperplasia (7.1%), 4 paramecium (5.6%), 3 EUS uncharacterizable ( 4.2%), the type, distribution and ultrasound imaging characteristics of the lesions. 3. Discussion Endoscopy combined with tissue biopsy can lead to a clear diagnosis of many GI diseases (mainly superficial mucosal lesions), but endoscopy is often unable to make a diagnosis of lesions deep in the mucosa and below, and elevated GI lesions compressed by extra GI organs or lesions. mEUS can directly perform ultrasound scanning examination of suspected lesions and their surroundings under direct endoscopic vision, thus obtaining clear ultrasound images It is the best method for diagnosing submucosal lesions in the upper gastrointestinal tract [2, 3], as it accurately shows the hierarchical location of the lesion in the GI wall or in relation to the GI canal wall, and suggests the nature of the lesion based on its level of origin and imaging features such as the echogenic strength, homogeneity, margins and surrounding lymph nodes of the lesion. mEUS can usually clearly show the five-layered structure of the wall of the digestive tube, but due to the presence of Brunner’s glands, the 1-3-layered structure of the wall of the duodenal bulb mostly appears as a layer of strongly echogenic bands. We also found that for the duodenal bulb in clinical practice, mEUS often fails to clearly show the five-layered structure of the intestinal wall, in agreement with other reports [4]. Among the submucosal lesions of the duodenum in our group, the bulb accounted for 67.6%, and cysts were the most common among the submucosal lesions, accounting for 46.5% (33/71), while other more common ones were lipomas and mesenchymal tumors. The accuracy of mEUS diagnosis was 88.9% for nine submucosal lesions confirmed by pathology or cyst aspiration treatment. Cysts were most common in the duodenal bulb and were located in the submucosa. mEUS was specific for their diagnosis, but mucinous adenomas and some Brunner’s gland hyperplasia showed irregular cystic occupations on ultrasound imaging. 2 cases of descending mucinous adenomas and bulbous Brunner’s gland hyperplasia in our group were the above-mentioned manifestations, respectively, and attention should be paid to their differentiation. In addition, the ultrasound manifestation of submucosal hemangioma is also a well-defined anechoic occupancy, and it is often difficult to distinguish it from cyst by simple imaging manifestation. We performed endoscopic Doppler examination on a submucosal lesion suspected to be a hemangioma but could not be distinguished from cyst by mEUS examination [5], and the exact arterial flow signal was detected and diagnosed as aneurysm. Therefore, we believe that endoscopic Doppler examination, as a supplement to mEUS, may be meaningful for the differential diagnosis of submucosal hemangiomas and cysts and may avoid blind puncture or resection treatment, and its clinical value remains to be further investigated. Lipomas are located in the submucosal layer, and the sonographic features are dense hyperechoic occupancy with posterior echogenic attenuation seen in larger lesions, but a few lipomas are slightly hypoechoic and should be differentiated. Mesenchymal tumors are mostly located in the intrinsic muscular layer and are characterized by hypoechoic occupying lesions, often shuttle-shaped or elliptical in shape, which continue with the hypoechoic zone of the muscular layer. Malignant mesenchymal tumors are usually larger in size, with inhomogeneous internal hypoechogenicity, focal hyperechoic spots, “broken wall sign”, and enlarged lymph nodes around the lesion, but mEUS is not reliable for the differential diagnosis of benign and malignant [6], and larger benign tumors can have similar changes. In our group, one larger mesenchymal tumor was pathologically diagnosed as benign after surgery, while in 10 other patients with mEUS-diagnosed mesenchymal tumors, the tumors were not resected due to their small size, and two of them did not show tumor growth on review after 1 year. In the other 10 cases of mesenchymal tumors diagnosed by mEUS, the tumors were not resected because they were small, and in 2 cases, the tumors did not grow after 1 year. In conclusion, small probe endoscopic ultrasonography has a greater diagnostic value for submucosal lesions of the duodenum, and the corresponding treatment modality can be correctly selected according to the mEUS results.