Background: Choosing an optimal reconstruction method is pivotal for patients with gastric cancer undergoing distal gastrectomy. The uncut Roux-en-Y reconstruction, a variant of the conventional Roux-en-Y approach (or variant of the Billroth II reconstruction), employs uncut devices to occlude the afferent loop of the jejunum. This modification is designed to mitigate postgastrectomy syndrome and enhance long-term functional outcomes. However, the comparative benefits and potential harms of this approach compared to other reconstruction techniques remain a topic of debate., Objectives: To assess the benefits and harms of uncut Roux-en-Y reconstruction after distal gastrectomy in patients with gastric cancer., Search Methods: We searched CENTRAL, PubMed, Embase, WanFang Data, China National Knowledge Infrastructure, and clinical trial registries for published and unpublished trials up to November 2023. We also manually reviewed references from relevant systematic reviews identified by our search. We did not impose any language restrictions., Selection Criteria: We included randomised controlled trials (RCTs) and quasi-RCTs comparing uncut Roux-en-Y reconstruction versus other reconstructions after distal gastrectomy for gastric cancer. The comparison groups encompassed other reconstructions such as Billroth I, Billroth II (with or without Braun anastomosis), and Roux-en-Y reconstruction., Data Collection and Analysis: We used standard Cochrane methodological procedures. The critical outcomes included health-related quality of life at least six months after surgery, major postoperative complications within 30 days after surgery according to the Clavien-Dindo Classification (grades III to V), anastomotic leakage within 30 days, changes in body weight (kg) at least six months after surgery, and incidence of bile reflux, remnant gastritis, and oesophagitis at least six months after surgery. We used the GRADE approach to evaluate the certainty of the evidence., Main Results: We identified eight trials, including 1167 participants, which contributed data to our meta-analyses. These trials were exclusively conducted in East Asian countries, predominantly in China. The studies varied in the types of uncut devices used, ranging from 2- to 6-row linear staplers to suture lines. The follow-up periods for long-term outcomes spanned from 3 months to 42 months, with most studies focusing on a 6- to 12-month range. We rated the certainty of evidence from low to very low. Uncut Roux-en-Y reconstruction versus Billroth II reconstruction In the realm of surgical complications, very low-certainty evidence suggests that uncut Roux-en-Y reconstruction compared with Billroth II reconstruction may make little to no difference to major postoperative complications (risk ratio (RR) 0.98, 95% confidence interval (CI) 0.24 to 4.05; I² = 0%; risk difference (RD) 0.00, 95% CI -0.04 to 0.04; I² = 0%; 2 studies, 282 participants; very low-certainty evidence) and incidence of anastomotic leakage (RR 0.64, 95% CI 0.29 to 1.44; I² not applicable; RD -0.00, 95% CI -0.03 to 0.02; I² = 32%; 3 studies, 615 participants; very low-certainty evidence). We are very uncertain about these results. Focusing on long-term outcomes, low- to very low-certainty evidence suggests that uncut Roux-en-Y reconstruction compared with Billroth II reconstruction may make little to no difference to changes in body weight (mean difference (MD) 0.04 kg, 95% CI -0.84 to 0.92 kg; I² = 0%; 2 studies, 233 participants; low-certainty evidence), may reduce the incidence of bile reflux into the remnant stomach (RR 0.67, 95% CI 0.55 to 0.83; RD -0.29, 95% CI -0.43 to -0.16; number needed to treat for an additional beneficial outcome (NNTB) 4, 95% CI 3 to 7; 1 study, 141 participants; low-certainty evidence), and may have little or no effect on the incidence of remnant gastritis (RR 0.27, 95% CI 0.01 to 5.06; I 2 = 78%; RD -0.15, 95% CI -0.23 to -0.07; I 2 = 0%; NNTB 7, 95% CI 5 to 15; 2 studies, 265 participants; very low-certainty evidence). No studies reported on quality of life or the incidence of oesophagitis. Uncut Roux-en-Y reconstruction versus Roux-en-Y reconstruction In the realm of surgical complications, very low-certainty evidence suggests that uncut Roux-en-Y reconstruction compared with Roux-en-Y reconstruction may make little to no difference to major postoperative complications (RR 4.74, 95% CI 0.23 to 97.08; I² not applicable; RD 0.01, 95% CI -0.02 to 0.04; I² = 0%; 2 studies, 256 participants; very low-certainty evidence) and incidence of anastomotic leakage (RR 0.34, 95% CI 0.05 to 2.08; I² = 0%; RD -0.02, 95% CI -0.06 to 0.02; I² = 0%; 2 studies, 213 participants; very low-certainty evidence). We are very uncertain about these results. Focusing on long-term outcomes, very low-certainty evidence suggests that uncut Roux-en-Y reconstruction compared with Roux-en-Y reconstruction may increase the incidence of bile reflux into the remnant stomach (RR 10.74, 95% CI 3.52 to 32.76; RD 0.57, 95% CI 0.43 to 0.71; NNT for an additional harmful outcome (NNTH) 2, 95% CI 2 to 3; 1 study, 108 participants; very low-certainty evidence) and may make little to no difference to the incidence of remnant gastritis (RR 1.18, 95% CI 0.69 to 2.01; I² = 60%; RD 0.03, 95% CI -0.03 to 0.08; I² = 0%; 3 studies, 361 participants; very low-certainty evidence) and incidence of oesophagitis (RR 0.82, 95% CI 0.53 to 1.26; I² = 0%; RD -0.02, 95% CI -0.07 to 0.03; I² = 0%; 3 studies, 361 participants; very low-certainty evidence). We are very uncertain about these results. Data were insufficient to assess the impact on quality of life and changes in body weight., Authors' Conclusions: Given the predominance of low- to very low-certainty evidence, this Cochrane review faces challenges in providing definitive clinical guidance. We found the majority of critical outcomes may be comparable between the uncut Roux-en-Y reconstruction and other methods, but we are very uncertain about most of these results. Nevertheless, it indicates that uncut Roux-en-Y reconstruction may reduce the incidence of bile reflux compared to Billroth-II reconstruction, albeit with low certainty. In contrast, compared to Roux-en-Y reconstruction, uncut Roux-en-Y may increase bile reflux incidence, based on very low-certainty evidence. To strengthen the evidence base, further rigorous and long-term trials are needed. Additionally, these studies should explore variations in surgical procedures, particularly regarding uncut devices and methods to prevent recanalisation. Future research may potentially alter the conclusions of this review., (Copyright © 2024 The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.)