The systematic searches returned a total of 731 citations. Following deduplication, 441 citations were identified. Of the 441 citations, 73 full manuscripts were identified as potentially eligible with a total of 17 RCTs meeting our eligibility criteria (n = 3,157 patients). Eleven studies were included in our meta-analysis as shown in our PRISMA flow diagram (Fig. 1).
Studies were published between 1996 and 2019, with sample sizes ranging from 32 to 516 participants. The mean age of participants was similar across studies ranging from 50.8 to 67.5 years old. Follow-up periods were highly variable ranging from 3 months to 3 years. Most studies were performed in China (5 studies, 19%), India (4 studies, 24%), Japan (3 studies, 18%), or other (5 studies [Iran, Hong Kong, Thailand, Netherlands, France], 29%). The proportion of male participants was higher than female participants in all studies except one. The incidence of AL ranged from 1.4 to 17%. The patient characteristics of the included studies are provided in Table 1.
Table 1 Characteristics of the included studies and participants studies Seven studies (41%) investigated stapled (vs. hand sewn) anastomosis, three studies (18%) investigated omentoplasty (vs. conventional stapled or hand-sewn anastomosis), three studies (18%) investigated early NG tube removal (postop day 1 or 2 days) or no NG tube (vs. conventional 7 to 10 days to NG tube removal), two studies (12%) that investigated subtotal gastric resection (vs. slender gastric tube) reconstruction, one study (6%) investigated valvuloplasty (vs. stapled anastomosis), and one study (6%) that compared end-to-end (vs. end-to-side) anastomosis. Sixteen studies (94%) used contrast to diagnose AL and six studies (35%) used additional endoscopy and/or chest tube or drain output. Seven studies (41%) administered medical management, three studies (18%) administered surgical management, and two studies (12%) administered endoscopic management for the treatment of AL. The length of stay in hospital postoperatively varied from 10.7 to 29.4 days. The study intervention characteristics are outlined in Table 2.
Table 2 Intervention characteristics of the included studies Primary outcome
Anastomotic leak
The pooled results for eleven meta-analyzed studies are summarized in Fig. 2 and the descriptive results for single RCT interventions are summarized in Additional file 1: Table S2. Esophagectomy patients that received stapled esophagogastric anastomosis demonstrated a similar risk of AL (RR: 0.92; 95% CI: 0.45, 1.87; I2 40.1%) compared to hand-sewn that was not significantly different (6 studies, n = 1454 patients). Esophagectomy patients that received omentoplasty had a 78% reduction in risk of AL (RR: 0.22; 95% CI: 0.10, 0.50; I2 0%) compared to hand-sewn or stapled anastomosis alone that was significant (3 studies, n = 611 patients). Esophagectomy patients with early NG tube removal (or no NG tube) demonstrated a 62% reduction in risk of AL (RR: 0.38; 95% CI: 0.02, 0.65; I2 0%) compared to prolonged NG tube removal that was significant (2 studies, n = 293 patients).
The pooled RR estimates for AL were subgrouped according to the site of esophagogastric anastomosis (Table 3). The pooled RR estimate for AL in the cervical esophagogastric anastomosis subgroup (2 studies, RR: 0.23; 95% CI: 0.069, 0.788; I2 0%) was not significantly different compared to the pooled RR for thoracic esophagogastric anastomosis subgroup (2 studies, RR: 0.19; 95% CI: 0.034, 1.032; I2 0%). The pooled RR estimates for AL were also subgrouped according to stapled or hand-sewn esophagogastric anastomosis (Additional file 1: Table S3). The RR estimate for AL in the stapled esophagogastric anastomosis subgroup (1 study, n = 194 patients, RR: 0.214; 95% CI: 0.064, 0.722) was not significantly different compared to the pooled RR estimate in the hand-sewn esophagogastric anastomosis subgroup (2 studies, n = 417 patients, RR: 0.264; 95% CI: 0.089, 0.789). Due to a lack of reporting of AL according to neoadjuvant therapy type (radiation and/or chemotherapy), it was not possible to perform this planned subgroup analysis.
Table 3 Risk ratios for anastomotic leak for omentoplasty intervention (subgroup by cervical or thoracic approach) Secondary outcomes
Anastomotic stricture
Esophagectomy patients that received stapled esophagogastric anastomosis had a twofold increased risk of stricture (RR: 2.11; 95% CI: 1.36, 3.26; I2 35.0%) compared to hand-sewn (6 studies, n = 1380 patients). Esophagectomy patients that received omentoplasty had an 8% lower risk of stricture (RR: 0.92; 95% CI: 0.33, 2.57; I2 65.1%) that was not significantly different compared to conventional anastomosis (3 studies, n = 613 patients). The pooled results are summarized in Fig. 3.
Mortality rate
Esophagectomy patients that received stapled esophagogastric anastomosis had no statistically significant difference in risk of mortality (RR: 1.22; 95% CI: 0.75, 1.98; I2 0%) compared to hand-sewn esophagogastric anastomosis (6 studies, n = 1363 patients). Esophagectomy patients that received omentoplasty had a 20% lower risk of mortality (RR: 0.80; 95% CI: 0.32, 2.0; I2 0%) compared to conventional anastomosis (3 studies, n = 736 patients). Esophagectomy patients with early NG tube removal (or no NG tube) demonstrated no statistically significant difference in risk of mortality (RR: 0.90; 95% CI: 0.317, 2.55; I2 0%) compared to prolonged NG tube removal (2 studies, n = 190 patients). The pooled results are summarized in Fig. 4.
Length of stay
The pooled weighted mean difference (WMD) for length of stay in hospital postoperatively was determined based on statistical comparison of the mean (± SD) length of stay reported for intervention and control groups among the included studies. Esophagectomy patients that received stapled anastomosis had a 1.1-day longer length of stay in hospital [95% CI: − 0.01, 2.2; I2 0%] compared to hand-sewn anastomosis that was not significantly different (2 studies, n = 606 patients). Esophagectomy patients that received omentoplasty had a 2.1-day shorter length of stay in hospital (WMD: − 2.1; 95% CI: − 3.6, − 0.6; I2 0%) that was statistically significant compared to stapled or hand-sewn anastomosis alone (2 studies, n = 417 patients). Esophagectomy patients with early NG tube removal (or no NG tube) had a 3.2-day shorter length of stay in hospital (WMD: -3.2; 95% CI: − 6.5, 0.2; I2 0%) compared to prolonged NG tube removal that was not significantly different (2 studies, n = 111 patients). Mistry et al. 2012 was excluded from the pooled WMD estimate as only median (IQR) was reported for length of stay; early NG tube removal (or no NG tube) and prolonged NG tube removal groups each had a median length of stay of 12 days with similar variability of 9–17 and 10–17 days, respectively (P = 0.18) [17].
Risk of bias
Seven (64%) meta-analyzed studies did not report whether the allocation of participants was concealed. Nine (82%) meta-analyzed studies lacked any details surrounding blinding of outcome assessment was blinded. Ten (91%) meta-analyzed studies lacked reporting of outcome assessment blinding. The risk of bias across studies is summarized in Fig. 5 (Individual study risk of bias is summarized in Additional file 1: Table S4).
Grade
There was a high quality of evidence for AL in the omentoplasty intervention. The unclear risk of bias in omentoplasty studies was due to the lack of allocation concealment in one study decreased the quality of evidence by one level. The large magnitude of effect in the omentoplasty studies increased the quality of evidence by one level. There was a moderate quality of evidence for AL in the early NG tube removal (or no NG tube) intervention. The high risk of bias due to both the lack of randomization and allocation concealment in all studies decreased the quality of evidence by two levels. The large magnitude of effect increased the quality of evidence by one level. There was a very low quality of evidence for AL in the stapled anastomosis intervention. The high risk of bias due to both the lack of randomization and allocation concealment in nearly all studies decreased the quality of evidence by two levels. The imprecision of the measure of effect due to the lack of statistical significance reduced the quality of evidence by one level. The moderate level of heterogeneity in the pooled estimate decreased the quality of evidence by one level. The evidence profile is summarized according to intervention type in Table 4 (GRADE summarized in Additional file 1: Table S5).
Table 4 Summary of findings (11 meta-analyzed studies)