Objective To investigate the clinical efficacy of jejunal interposed single-tract and doubletract reconstruction after proximal gastrectomy for Siewert type Ⅱ and Ⅲ adenocarcinoma of the esophagogastric junction (AEG).Methods The prospective study was conducted.The clinicopathological data of 108 patients with Siewert type Ⅱ and Ⅲ AEG who were admitted to the Affiliated Tumor Hospital of Shanxi Medical University between August 2013 and November 2016 were collected.All the patients underwent proximal gastrectomy and were allocated into the 2 groups by random number table,including patients using single-tract jejunal interposition reconstruction in the single-tract group and patients using double-tract jejunal interposition reconstruction in the double-tract group.Digestive tract reconstruction:after end-to-side anastomosis between distal jejunum and esophagus and side-to-side anastomosis between posterior wall of the gastric remnant and jejunum,single-tract jejunal reconstruction was done through ligating jejunum at 3 cm below the anastomotic stoma,and then side-to-side anastomosis between proximal jejunum and jejunum was performed in the single-tract group.Patients in the double-tract group used the same digestive tract reconstruction,but jejunum was not ligated.The postoperative pathological examinations showed that patients with positive lymph nodes or tumor invading all layers of gastric wall underwent chemotherapy.Observation indicators:(1) intra-and post-operative situations;(2) follow-up situations.Follow-up using telephone interview was performed to detect postoperative complication,gastrointestinal function and body mass index (BMI) up to November 2017.Measurement data with normal distribution were represented as-x± s and comparison between groups was analyzed using t test.Measurement data with skewed distribution were described as M (range),and comparison between groups was analyzed using the nonparametric test.Repeated measurement data were analyzed by the repeated measures ANOVA.Comparisons of count data were done using chi-square test.Ordinal data were analyzed by the Kruskal Wallis H test.Results One hundred and eight patients were screened for eligibility,including 55 in the single-tract group and 53 in the double-tract group.(1) Intra-and post-operative situations:total operation time,digestive tract reconstruction time,volume of intraoperative blood loss,time to initial anal exsufflation,postoperative complications,cases with gastroesophageal reflux,intestinal obstruction and Visick grading ＞ Ⅱ and duration of postoperative hospital stay were respectively (145±26) minutes,(30±6) minutes,(181±37) mL,(53± 16) hours,1,1,1,(10.0±2.4) days in the singletract group and (139±29)minutes,(26±3)minutes,(176±31)mL,(50±17) hours,3,0,3,(9.4±l.4)days in the double-tract group,with no statistically significant difference between groups (t =0.725,0.219,0.162,-0.576,x2 =2.960,5.830,t =-0.993,P＞0.05).Four patients with gastroesophageal reflux received motilium and omeprazole therapy for 2 weeks,and were improved by symptomatic treatment such as increasing the solid food intake.One patient in the single-tract group had internal hernia-induced intestinal obstruction and was cured by reoperation.There was no anastomotic leakage,bleeding,infection,dumping syndrome and gallstone between groups.Of 108 patients,71 underwent 6-cycle SOX chemotherapy,including 67 with perigastric lymph node metastasis and 4 with tumor invading all layers of gastric wall.(2) Follow-up situations:108 patients were followed up for 12.0-48.0 months,with a median time of 28.6 months.During the follow-up,bowel sound in the double-tract group and single-tract group was 8 times / minute (range,5-12 times / minute) and 3 times /minute (range,2-5 times/ minute),with a statistically significant difference between groups (Z=-0.692,P＜0.05).The single food intake,serum gastrin level,ratio of serum pepsinogen Ⅰ and Ⅱ levels and BMI from preoperation to postoperative 12 months were from (1 117± 129)mL to (817± 127)mL,from (12±5)pmol/L to (41±13) pmol/L,from 11.3±2.8 to 5.1±2.2,(65±7)kg to (63±5) kg in the single-tract group and from (1 095±118)mL to (783±80)mL,from (10±4)pmol/L to (40±10)pmol/L,from 12.4±2.9 to 4.2±1.3,from (63±6) kg to (58±6)kg in the double-tract group,respectively,with no statistically significant difference in single food intake,serum gastrin level and ratio of serum pepsinogen Ⅰ and Ⅱ levels between groups (F =0.468,0.108,0.161,P＞0.05).There was a statistically significant difference in changing trend of BMI between groups (F=24.930,P＜0.05).Conclusion Jejunal interposed single-tract and double-tract reconstruction after proximal gastrectomy for Siewert type Ⅱ and Ⅲ AEG have the same surgical safety and don't affect secretion function of gastric remnant,but there are frequent bowel sounds and obvious weight loss.