This study is a retrospective analysis, selecting patients with SDELs who underwent ER in our hospital (a high-volume institution that actively carries out endoscopic treatment) from January 2010 to September 2021. The selection criteria include: 1) duodenal lesions were found by upper gastrointestinal endoscopy; 2) upper gastrointestinal endoscopy, endoscopic ultrasonography or computed tomography confirmed that the lesions were limited to the mucosal layer or superficial submucosa layer; 3) patient signed and agreed for ER. Exclusion criteria include: 1) patients with incomplete information; 2) patients with contraindications of ER, such as coagulation dysfunction, cardiopulmonary insufficiency, etc; 3) patients with multiple lesions in the duodenum. The collected data include: basic information of the patient (gender, age, smoking, etc.), symptoms, characteristics of duodenal lesions (location, size, etc.), surgery and treatment situations (en bloc resection, R0 resection, positive margins, pathology results), postoperative complications (postoperative bleeding and postoperative perforation), and the patient’s background diseases. All patients have been fully informed and signed informed consent. This study was approved by the ethics review committee of the Second Xiangya Hospital of Central South University.

En bloc resection is defined as the lesion is completely removed, and there is no segmentation or partial resection. R0 resection is defined as: on the basis of complete resection of the lesion, no cancerous tissue and components are found on the horizontal and vertical edges. Postoperative bleeding is defined as: patient has hematemesis, melena, and unexplained hemoglobin drop more than 2g/dL after ER (8). Postoperative perforation is defined as: the patient had sudden abdominal pain after resection of the lesion, accompanied by retroperitoneal pneumatosis or free gas detected on abdominal computed tomography scan or radiographs (8, 9). Polyps are defined as: discrete abnormal tissue masses that protrude into the lumen of the digestive tract, and duodenal polyps include neoplastic and non-neoplastic lesions. The polyps mentioned in the histological results in this study refer to non-neoplastic polypoid lesions (10).

We choose specific ER method according to the size, location of the lesion and the results of biopsy. ESD is usually recommended for lesions larger than 2cm (11). If the results of biopsy tend to be non-neoplastic lesions or LGIN, EMR will be selected, otherwise ESD will be selected. For lesions larger than 2 cm and had technical difficulty to perform ESD, EPMR will be selected.

The instruments used for ER include single channel endoscope (GIFQ260J, GIF-H290; Olympus) with a transparent cap (D201-11802; Olympus), high-frequency generator (ICC 200, ICC 300, or VIO 200D; ERBE), argon plasma coagulation device (APC300; ERBE; Tübingen, Germany), carbon dioxide inflator (UCR; Olympus), thermal biopsy forceps (FD-1U-1; Olympus), injection needle (NM-4L-1; Olympus), snare (SD-221L-25, SD-230–20; Olympus) dual knife (KD650Q; Olympus), insulation-tip knife (KD-611L; Olympus), hybrid knife (ERBE; Tübingen, Germany) and hemostatic clips (HX-600-90, HX-600-135; Olympus). During EMR, 100 ml of normal saline, 1 ml of indigo rouge and 1 ml of adrenaline solution were injected into the submucosal layer, and then resect the lesion with a snare. ( Figure 1 ) If it was piecemeal resected the lesion with a snare, it was endoscopic piecemeal mucosal resection (EPMR). For ESD, dual/hybrid knife was used to mark around the lesion, followed by administration of a submucosal injection. After precutting the mucosa and submucosa, dual knife, hybrid knife or insulation-tip knife was used to dissect the lesion. Then, if the muscularis propria was unintentionally damaged or there was a risk of bleeding and perforation, the mucosal defect was closed with metal clip or metal clip together with endoloop. The resected lesions were embedded in paraffin and sectioned for pathological assessment ( Figure 2 ).

The data in this article will be statistically analyzed through SPSS 18.0. Among them, categorical variables will be expressed by frequency, and continuous variables will be expressed by mean ± standard deviation. For the screening of risk factors, first carry out univariate logistics regression analysis, and then incorporate statistically significant indicators into multivariate logistic regression. P<0.05 is considered statistically significant.

A total of 137 patients in our hospital from January 2010 to September 2021 were collected ( Figure 3 ), including 84 males and 53 females, with an average age of 52.92 ± 12.90 years, including 114 who underwent EMR, 19 who underwent ESD, and 4 who underwent EPMR. The main symptoms were abdominal pain (42.33%, 58/137), physical examination findings (27.00%, 37/137), and abdominal distension (21.90%, 30/137). 41 patients (29.93%) had concomitant diseases, of which hypertension (19.71%, 27/137) was the most common. A total of 36 people smoked (26.28%). ( Table 1 ). 54 patients (39.42%) completed preoperative biopsy, including 1 case (1.85%) of lymphoma, 5 cases (9.26%) of Low-grade intraepithelial neoplasia (LGIN), 7 cases (12.96%) of high-grade intraepithelial neoplasia (HGIN), 10 cases (18.52%) of polyps, 7 cases (12.96%) of inflammation, 4 cases (7.41%) of ectopic gastric mucosa and 20 cases (37.04%) of adenomas, of which 9 cases were complicated with LGIN and 3 cases were complicated with HGIN.

73 cases (53.28%) were located at the bulb, 39 cases (28.47%) were located at the descending portion, 24 cases (17.52%) were located at the junction of first and second portions, and 1 case (0.73%) were located at the horizontal section. The histology results showed that there were 59 cases (43.07%) of polyps, including 2 cases (1.46%) with ectopic gastric mucosa. There were 58 cases (42.34%) of adenoma, including 28 cases (20.44%) with LGIN and 2 cases (1.46%) with HGIN. There was 1 case (0.73%) of adenocarcinoma with HGIN. There were 10 cases (7.30%) of simple LGIN, 2 cases (1.46%) of simple HGIN and 7 cases (5.11%) of simple ectopic gastric mucosa. Among the patients who completed the biopsy, 40 cases (74.07%) had consistent postoperative histological results with the biopsy results, while the remaining 14 cases had inconsistent pre- and postoperative histological results. Among the 14 patients with inconsistent histological results, 7 cases (12.96%) had lighter histological results than the biopsy results and 7 cases (12.96%) had more serious histological results than the biopsy results. 131 cases (95.62%) underwent en bloc resection, 126 cases (91.97%) underwent R0 resection, and 5 cases (3.65%) had positive margin. Postoperative bleeding was 3 cases (2.19%) and no intraoperative or postoperative perforation to be found. A total of 72 cases (52.55%) used metal clips after ER ( Table 1 ).

Univariate logistic regression analysis was conducted on the risk factors of potential surgical complications. The results are shown in Table 2 . No statistically significant risk factors were found in the patients included in this research.

Univariate logistic regression analysis was performed on the risk factors of potential non-en bloc resection and non-R0 resection. The results are shown in Table 3 . We found that histology result of ectopic gastric mucosa was risk factor for non-en bloc resection (OR: 8.857, 95% CI: 1.378-56.915, P=0.022) and the lesion size ≥2 cm and histology result of HGIN were risk factors of non-R0 resection (OR: 12.606, 95% CI: 3.095-51.343, P < 0.001; OR: 9.111, 95% CI: 1.345-61.708, P=0.024). Further multivariate logistic regression analysis was performed on lesion size ≥2 cm and histology result of HGIN ( Table 4 .) The risk factors for non-R0 resection were lesion diameter ≥ 2cm (OR: 12.549, 95% CI: 2.950-53.379, P=0.001).