Introduction Laparoscopic gastrectomy (LG) is a complicated procedure with a long learning curve. This study was performed to investigate the usefulness of our stepwise training program for LG for improving the quality of the surgery. Methods The stepwise training method comprised the following four steps: (1) basic training using a dry box and checking by mentors; (2) advanced training, including the use of animals and cadavers; (3) clinical experience, including standardization and preoperative three‐dimensional simulation; and (4) self‐assessment and feedback. In total, 153 patients who underwent curative gastrectomy for gastric cancer were included in this study. Results The operative time gradually decreased for both laparoscopic distal gastrectomy (LDG) (2013, 395 minutes; 2017, 278 minutes; P < .001; ρ = −0.68) and laparoscopic total gastrectomy (LTG) (2013, 476 minutes; 2017, 319 minutes; P < .001; ρ = −0.56). The blood loss volume gradually decreased for both LDG (2013, 43.0 mL; 2017, 18.6 mL; P < .005; ρ = −0.30) and LTG (2013, 143.8 mL; 2017, 13.5 mL; P < .005; ρ = −0.41). Conclusions Our stepwise training program contributes to reduce operation time and blood loss in LG.

Background Heterotopic pancreas (HP) is a rare disease commonly found incidentally on imaging studies, at endoscopy or at autopsy and can be associated with abdominal pain, vomiting, heart burn, gastric outlet obstruction, and even dysphagia in very rare cases. Heinrich’s classified HP into three groups, types1–3, with Heinrich’s type 3 HP the rarest and difficult to diagnose properly because it has only pancreatic ducts but has no islet and acini. The aim of this study is to report a case of gastric outlet obstruction caused by type 3 HP with gastroduodenal invagination with reference to the literature and diagnosed finally by immuno-histochemical analysis. Case presentation The case presented is a 40-year-old male presenting with vomiting and abdominal pain. Computed tomography (CT) revealed a cystic mass in the upper abdomen and he was referred to the Tokushima University. Gastric fiber showed that the pedunculated mass originated from the stomach. An open distal gastrectomy was performed. Pathologically, there was small glands proliferation in the sub-mucosal (SM) layer which was membrane and cytoplasm (MUC)1 positive and muscle proliferation. Results This finding revealed the tumor as HP. Postoperative course was uneventful and the patient was discharged 12 days after surgery. The patient has remained well 12 months after surgery. Conclusions HP should be considered in the differential diagnosis of SM tumors with gastroduodenal invagination even if this is a rare symptom.

584 Background: Clinical and molecular characteristics are different between Right-side and left-sided colorectal cancer (CRC). The aim of this study was to clarify the significance of the correlation of the Sidedness of CRC and tumor immunity. Methods: A total of 116 patients who underwent curative colectomy for stage II/III CRC were included in this study. The expression of PD-1, PD-L1, FoxP3, TGF-b, and IDO was examined by immunohistochemistry and the relationship of sidedness to several prognostic factors was examined. Results: In clinicopathological factors, there were no significant difference between right sided and left sided CRC except for differentiation. Regarding tumor immunity, there were no significant difference in PD-1 and IDO expression. However, Fox P3 (right side 72% vs. left side 59%) and TGFβ (right side 72% vs. left side 57%) tended to be highly expressed in right side(p < 0.1). PDL1 was significantly highly expressed in right side(right side 65% vs. left side 35%, p < 0.05). In OS and DFS, the patients with right sided tumor tended to have poor prognosis compared with left side (p < 0.1). The PD-L1 positive patients of right-sided tumor had poor prognosis (p < 0.05). Conclusions: Sidedness is associated with tumor immunity in colorectal cancer.

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511 Background: The best method of venous thromboembolism (VTE) prevention after surgery for colorectal cancer remains unclear. It is reported that about 20-40% of high-risk patients were diagnosed as DVT and 2-4% was diagnosed as PE and its mortality rate is 0.5-1.0%. The aim of this study is to evaluate the incidence of postoperative VTE patients with colorectal adenocarcinoma and to evaluate the efficacy of VTE preventive strategy. Methods: A total of 264 patients who had undergone curative surgical resection for colorectal cancer at Tokushima University Hospital were included in this study (n = 264 colon: rectum = 1:0.57). All patients were measured D-dimer preoperatively. When D-dimer was ≥ 1.1, lower extremities ultrasonography (US) was performed. All patients were treated with Heparin (10,000U/24h) continuously intravenous injection from the day of surgery, and administered Enoxaparin (2,000U/24h) subcutaneous injection after 24h of the operation. Results: In all 264 patients, 74 (28%) were D-dimer ≥ 1.1 and 16 (6%) diagnosed VTE in US (proximal:distal type n = 6:1). 239 (91%) were treated with postoperative anticoagulant therapy. 2 developed perioperative VTE (symptomatic: asymptomatic = 1:1) and after discharge 12 developed postoperative VTE and mortality rate of VTE was 0%. Univariate analysis indicated that obesity (BMI ≥ 25), hyperlipidemia and preoperative PE were risk factors for deep venous thrombosis (DVT) (p < 0.0001, 0.014, 0.0135, respectively) and multivariate analysis revealed that obesity was an independent risk factor for postoperative DVT (p < 0.0001). Conclusions: Obesity (BMI ≥ 25) was independent risk factor for postoperative VTE. Our preventive protocol including screening using D-dimer and lower extremities US and treatment with Enoxaparin is considered as effective for prevention of postoperative VTE.