Perioperative alvimopan versus no alvimopan after elective minimally invasive colorectal resection within enhanced recovery pathways: a GRADE-assessed systematic review and meta-analysis.

This systematic review and meta-analysis were conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement and the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines. This review aimed to evaluate the comparative effectiveness of perioperative alvimopan versus no alvimopan after elective colorectal resection performed in the minimally invasive and enhanced recovery era. The review question, eligibility criteria, outcomes of interest, and analytical framework were specified before formal screening and data extraction. A comprehensive electronic literature search was performed in PubMed/MEDLINE, Embase, Scopus, Web of Science, and the Cochrane Library from database inception to the date of the final search 24th -March,2026. The search strategy combined controlled vocabulary and free-text terms related to alvimopan, colectomy, colorectal resection, laparoscopic surgery, minimally invasive surgery, enhanced recovery, and fast track pathways. The search syntax was tailored to the requirements of each database, and the complete database-specific search strings with the number of retrieved records are provided in Supplementary Table 1. In addition to the electronic search, the reference lists of relevant studies were manually reviewed to identify additional eligible records for inclusion. All retrieved citations were imported into Covidence for duplicate removal and screening workflow management (Supplementary Table 1). Studies were considered eligible if they met all of the following criteria: adult patients, elective colorectal resection, minimally invasive surgery only or a clearly extractable minimally invasive colorectal subgroup, and a clearly defined enhanced recovery, fast-track, or perioperative recovery pathway. Eligible studies were required to directly compare perioperative alvimopan with no alvimopan, placebo, or a historical/control pathway cohort without alvimopan. Only comparative study designs, including prospective and retrospective comparative studies, were included in this review. Studies also had to report at least one relevant postoperative outcome, including postoperative ileus, length of stay, time to bowel recovery, time to diet tolerance, complications, readmission, and cost or resource utilization. Only studies published in English were considered. These eligibility criteria were intentionally restrictive because the objective was to estimate the incremental value of alvimopan in the contemporary minimally invasive and enhanced recovery setting, rather than to reproduce older evidence from open surgery or non-standardized perioperative care. We recognized that this approach would narrow the eligible evidence base and potentially limit generalizability but considered this trade-off necessary to preserve clinical relevance to current colorectal ERP practice. Studies were excluded if they included open surgery only, mixed surgical populations without an extractable minimally invasive colorectal subgroup, emergency surgery, pediatric populations, non-comparative study designs, reviews, editorials, letters, conference abstracts without usable full data, or duplicate publications. Studies focusing primarily on stoma closure, non-resectional colorectal procedures, or populations outside the scope of elective colorectal resection were excluded. When overlapping cohorts were suspected, the most complete and methodologically informative study was selected for inclusion. Full-text exclusions were assigned according to the dominant reason for ineligibility, and a study-level list of excluded full-text reports with specific reasons was prepared to improve transparency. Two reviewers (W.M. and Z.S.) independently screened records in Covidence, first at the title and abstract level and then at the full-text level, with disagreements resolved through discussion with a third author (M. M. S.). Data were extracted independently using a standardized form and cross-checked before the final analyses. The extracted variables included study characteristics, country, study design, sample size, baseline patient demographics, indication for surgery, procedural details, and postoperative outcomes. The primary outcome was the incidence of postoperative ileus. The secondary outcomes were length of hospital stay and readmission rates. When studies reported outcomes in multiple formats, the most clinically relevant and quantitatively extractable datasets were selected for the synthesis. Authors were not contacted for further information. As all the included studies were comparative non-randomized studies, their methodological quality was assessed using the ROBINS-I tool. Two reviewers independently evaluated each study across the ROBINS-I domains, including bias due to confounding, participant selection, classification of interventions, deviations from intended interventions, missing data, outcome measurement and selection of reported results. Any discrepancies were resolved through discussion and consensus agreement. The final risk-of-bias judgments were incorporated into both the qualitative interpretation and certainty assessment of pooled evidence. Statistical analyses were performed using the Review Manager (RevMan). A random-effects model was used for all pooled analyses to account for the anticipated clinical and methodological heterogeneity across studies. For dichotomous outcomes, pooled effect estimates were calculated as risk ratios (RRs) with 95% confidence intervals (CIs) using the Mantel-Haenszel method. For continuous outcomes, pooled estimates were expressed as mean differences (MDs) with 95% CIs using the inverse variance method when the outcomes were reported on the same scale. Statistical heterogeneity was assessed using the I² statistic and Cochran’s test. Statistical significance was set at P  < 0.05. Where required, continuity correction was applied to the zero-event cells. Publication bias was not formally assessed because fewer than 10 studies were included in each pooled analysis, rendering funnel plot interpretation unreliable. Given anticipated clinical heterogeneity across studies, pooling was considered clinically meaningful only for outcomes that were reported across broadly comparable elective colorectal MIS/ERP cohorts. We used random-effects models to account for between-study variability and interpreted pooled estimates in conjunction with heterogeneity statistics, leave-one-out sensitivity analyses, subgroup analyses, and GRADE certainty ratings. Therefore, pooled estimates were not interpreted as uniform treatment effects across all colorectal procedures, but as summary estimates across related contemporary practice contexts. Sensitivity analysis was performed using a leave-one-out approach, in which each study was sequentially removed, and the pooled estimate was recalculated to assess the robustness of the overall findings. A prespecified clinical subgroup analysis was performed for the primary outcome according to the procedure scope, with studies categorized into segmental colectomy with primary anastomosis cohorts [ 1 , 3 ] and procedure-diverse colorectal surgery cohorts [ 2 , 6 ]. Kelley [ 4 ] was not included in the subgroup meta-analysis for the primary outcome because postoperative ileus event counts were not directly extractable. Given the small number of included studies and sparse event counts, subgroup analyses were considered exploratory and descriptive rather than definitive tests of effect modification. The certainty of the evidence for the main outcomes was assessed using the GRADE approach, considering the risk of bias, inconsistency, indirectness, imprecision, and publication bias. Publication bias was considered undetected and was not downgraded because fewer than 10 studies contributed to each pooled outcome, and the formal funnel plot assessment was uninformative.

The systematic search identified 88 records across the selected electronic databases, with no additional references obtained from other sources (Fig.  1 ). After the removal of 22 duplicate records, including those identified through manual checking and Covidence, 66 studies underwent title and abstract screening, of which 57 were excluded from the review. Nine full-text reports were sought and successfully retrieved, and all were assessed for eligibility. Five comparative studies were included in the final qualitative and quantitative syntheses. Full-text exclusions were determined independently by two reviewers according to the predefined eligibility criteria. Studies were excluded at this stage when they lacked a direct alvimopan versus no-alvimopan comparator, did not report extractable outcomes relevant to the review question, used an ineligible study design, or included populations outside elective minimally invasive colorectal resection within an enhanced-recovery or comparable perioperative pathway. Disagreements regarding full-text eligibility were resolved through discussion and, when required, adjudication by a third reviewer. Fig. 1 PRISMA 2020 flow diagram of study identification, screening, eligibility assessment, and inclusion, with duplicate removal and screening workflow managed in Covidence PRISMA 2020 flow diagram of study identification, screening, eligibility assessment, and inclusion, with duplicate removal and screening workflow managed in Covidence The included evidence consisted of retrospective comparative studies conducted in the United States, all of which examined perioperative alvimopan within contemporary elective colorectal surgical practice (Table  1 ). Although the studies shared a broadly similar clinical framework centered on elective resection in minimally invasive and/or enhanced recovery settings, there were meaningful variations in cohort definition, operative scope, and exclusion strategy across studies. Outcome selection was not fully uniform, with length of stay and postoperative ileus emerging as the most consistently evaluated endpoints, while other studies additionally incorporated readmission, postoperative complications, recovery of bowel function, and hospitalization costs. Taken together, these study-level differences are important for contextualizing the clinical diversity of the evidence base and anticipating heterogeneity in pooled analyses. Table 1 Study characteristics of the included comparative studies evaluating perioperative alvimopan versus no alvimopan after elective colorectal resection in minimally invasive and/or enhanced-recovery settings Study Country Experimental group, n Control group, n Inclusion criteria Exclusion criteria Primary endpoints Secondary endpoints Itawi et al. 2011 [ 1 ] USA 101 64 Elective laparoscopic segmental colectomy with primary anastomosis within a perioperative recovery pathway Emergent/open procedures, non-segmental colectomy, stoma cases, multiple anastomoses, concomitant procedures, recent opioid use Length of stay: postoperative ileus Readmission; mortality Barletta et al. 2011 [ 2 ] USA 150 132 Elective colectomy managed within an enhanced recovery protocol Major surgical/medical complications; prolonged preoperative work-up Postoperative ileus; length of stay Readmission for delayed ileus Obokhare et al. 2011 [ 3 ] USA 100 100 Adults undergoing laparoscopic segmental colectomy with primary anastomosis in an accelerated care pathway Pregnancy, chronic opioid use, colonic inertia, multiple prior abdominal operations, planned stoma, ESRD Length of stay Postoperative ileus; readmission; complications Kelley et al. 2013 [ 4 ] USA 26 64 Adults undergoing minimally invasive colorectal surgery within a fast-track pathway Open conversion, protocol deviation, pregnancy, chronic opioid use, or contraindication to alvimopan Tolerating diet; return of gastrointestinal function; length of stay; readmission Hospital cost outcomes Keller et al. 2016 [ 6 ] USA 321 321 Elective laparoscopic colorectal resection within an enhanced recovery pathway Emergency surgery, age < 18 years, stoma closure, no resection, anorectal procedures, open conversion Length of stay; complications; readmission; cost Reoperation; mortality; operative outcomes; postoperative ileus Abbreviations : ERP enhanced recovery pathway, HALS hand-assisted laparoscopic surgery, PCA patient-controlled analgesia POI postoperative ileus, USA United States of America Study characteristics of the included comparative studies evaluating perioperative alvimopan versus no alvimopan after elective colorectal resection in minimally invasive and/or enhanced-recovery settings Abbreviations : ERP enhanced recovery pathway, HALS hand-assisted laparoscopic surgery, PCA patient-controlled analgesia POI postoperative ileus, USA United States of America The included studies evaluated broadly comparable adult populations who underwent elective colorectal surgery during the minimally invasive and enhanced recovery eras ( Table  2 ) . Across cohorts, the baseline demographic profiles were generally balanced between the alvimopan and control groups, particularly with respect to age, sex distribution, body habitus, and perioperative risk. The dominant clinical indications were colorectal neoplasia, diverticular disease, benign colorectal pathology, and inflammatory bowel disease, although the relative proportions of these diagnoses varied among the studies. The procedural composition was heterogeneous, ranging from segmental colectomy-predominant series to broader minimally invasive colorectal cohorts, which also included proctocolectomy, low anterior resection, and stoma-related procedures. This variability in case mix and operative scope should be considered when interpreting pooled postoperative outcomes and potential heterogeneity between studies. Table 2 Baseline patient demographics, clinical characteristics, indication profiles, and procedural details of the included studies were collected Study Sample size Age, y Sex distribution BMI / weight ASA / baseline risk status Previous abdominal surgery Primary indication/diagnosis Cancer-specific details Procedure type Operative approach/technique Itawi et al. 2011 [ 1 ] Alvimopan: 101; Control: 64 61.9 ± 14.5 vs. 62.9 ± 14.2 Female: 72 (61.0%) vs. 33 (52.0%) BMI: 28.3 ± 7.8 vs. 27.7 ± 4.65 kg/m² ASA score: 2.4 ± 0.48 vs. 2.4 ± 0.50 NR Neoplasm: 60 (60%) vs. 44 (69%); Diverticulitis: 38 (37%) vs. 19 (30%); Crohn’s disease: 2 (2%) vs. 0; Appendicitis: 1 (1%) vs. 0; A-V malformation: 0 vs. 1 (1%) Not separately reported beyond neoplasm Sigmoid colectomy: 41 (40%) vs. 26 (41%); Low anterior resection: 35 (35%) vs. 19 (30%); Right colectomy: 20 (20%) vs. 17 (27%); Left colectomy: 3 (3%) vs. 1 (1%); Transverse colectomy: 1 (1%) vs. 1 (1%) Straight laparoscopy: 91 (90%) vs. 55 (86%); HALS: 10 (10%) vs. 9 (14%) Barletta et al. 2011 [ 2 ] Open/HALS: Alvimopan 74, Control 75; LAP: Alvimopan 76, Control 57 Open/HALS: 62 ± 15 vs. 58 ± 16; LAP: 57 ± 16 vs. 58 ± 18 Male reported only. Open/HALS: 54% vs. 44%; LAP: 49% vs. 53% Weight. Open/HALS: 85 ± 23 vs. 81 ± 23 kg; LAP: 82 ± 18 vs. 86 ± 19 kg NR NR Open/HALS: cancer 37 (50%) vs. 32 (43%); benign mass 6 (8%) vs. 7 (9%); diverticular disease 14 (19%) vs. 12 (16%); IBD 6 (8%) vs. 14 (19%); rectal prolapse 6 (8%) vs. 4 (5%); fistula 1 (1%) vs. 3 (4%); constipation 2 (3%) vs. 0; other 2 (3%) vs. 3 (4%). LAP: cancer 22 (29%) vs. 22 (39%); benign mass 22 (29%) vs. 13 (23%); diverticular disease 26 (34%) vs. 18 (32%); IBD 2 (3%) vs. 2 (4%); rectal prolapse 2 (3%) vs. 2 (4%); constipation 2 (3%) vs. 0 Not separately reported beyond cancer diagnosis Baseline procedure profile was reported by the operative stratum rather than by individual colorectal resection subtypes Open/HALS cohort and LAP cohort analyzed separately Obokhare et al. 2011 [ 3 ] Alvimopan: 100; Control: 100 62 vs. 61 Female: 55 vs. 51; Male: 45 vs. 49 NR NR NR Crohn’s disease: 12% vs. 9%; Diverticulitis: 20% vs. 20%; Colon cancer: 61% vs. 68%; Other: 7% vs. 3% Colon cancer reported; no further histopathologic details provided Laparoscopic colectomy in all patients Laparoscopic colectomy cohort Kelley et al. 2013 [ 4 ] Alvimopan: 26; Control: 64 38.1 vs. 46.1 Female: 10 (38.4%) vs. 39 (43.3%) BMI: 23.4 (18.5 to 40.4) vs. 23.8 (16.2 to 36.2) kg/m² ASA 1 to 2: 25 (96.1%) vs. 57 (89.1%); ASA 3 to 4: 1 (3.8%) vs. 7 (10.9%) 19 (73.1%) vs. 37 (57.8%) Irritable bowel disease: 12 (46.2%) vs. 23 (35.9%); benign: 11 (42.3%) vs. 28 (43.8%); malignant: 3 (11.5%) vs. 13 (20.3%) Malignant indication reported; no tumor stage or histopathologic grading reported Proctocolectomy: 8 (30.8%) vs. 15 (23.4%); Segmental colectomy: 5 (19.2%) vs. 27 (42.2%); Subtotal colectomy: 4 (15.4%) vs. 6 (9.4%); Stoma procedure: 9 (34.6%) vs. 16 (25.0%) Minimally invasive colorectal surgery cohort Keller et al. 2016 [ 6 ] Alvimopan: 321; Control: 321 60.34 ± 13.39 vs. 59.04 ± 13.96 Female: 168 (52.3%) vs. 172 (53.4%); Male: 153 (47.7%) vs. 149 (46.6%) BMI: 27.36 ± 4.93 vs. 27.59 ± 5.16 kg/m² Median ASA: 2 (range 1 to 4) vs. 2 (range 1 to 4) 181 (56.4%) vs. 189 (58.9%) Colon cancer: 136 (42.2%) vs. 106 (33.0%); Diverticulitis: 70 (21.8%) vs. 73 (22.7%); Polyp: 82 (25.5%) vs. 83 (25.9%); Rectal cancer: 20 (6.2%) vs. 20 (6.2%); IBD: 8 (2.5%) vs. 17 (5.3%); Endometriosis: 2 (< 1.0%) vs. 13 (4.0%); Rectal prolapse: 3 (< 1.0%) vs. 9 (2.8%) Colon and rectal cancer reported separately; no tumor stage, grade, or nodal details reported Segmental colectomy: 190 (59.2%) vs. 182 (56.7%); Anterior proctosigmoidectomy: 104 (32.4%) vs. 108 (33.6%); Low anterior resection: 26 (8.1%) vs. 29 (9.0%); Total proctocolectomy: 1 vs. 2 Laparoscopic colorectal resection cohort Abbreviations : ASA American Society of Anesthesiologists, A-V arteriovenous, BMI body mass index, HALS hand-assisted laparoscopic surgery, IBD inflammatory bowel disease, LAP laparoscopic, NR not reported Baseline patient demographics, clinical characteristics, indication profiles, and procedural details of the included studies were collected Abbreviations : ASA American Society of Anesthesiologists, A-V arteriovenous, BMI body mass index, HALS hand-assisted laparoscopic surgery, IBD inflammatory bowel disease, LAP laparoscopic, NR not reported The ROBINS-I assessment showed a generally acceptable methodological profile across the included studies, with most domains judged as having either a low or moderate risk of bias (Supplementary Fig. 1; Supplementary Fig. 2). Low-risk judgments were consistently observed for the classification of interventions, deviations from intended interventions, and missing data, indicating that treatment allocation, perioperative management, and outcome availability were well described across studies. In contrast, bias due to confounding, bias due to selection of participants, and selection of reported results were uniformly rated as moderate, reflecting the retrospective non-randomized design of the included cohorts and the inherent risk of residual confounding and selective-reporting. Bias in the measurement of outcomes was low in most studies but moderate in a minority, resulting in some variability in this domain. Overall, the body of evidence was judged to be at moderate risk of bias, supporting a cautious but clinically meaningful interpretation of pooled findings. For the primary outcome, perioperative alvimopan was associated with a lower risk of postoperative ileus than no alvimopan in the primary pooled analysis (Fig.  2 ). Across the included studies contributing to this outcome, postoperative ileus occurred in 23 of 672 patients receiving alvimopan and 46 of 617 patients not receiving alvimopan (3.4% vs. 7.5%). The pooled effect estimate showed a borderline reduction in postoperative ileus with alvimopan (RR 0.43, 95% CI 0.18–0.99), with moderate-to-substantial heterogeneity (I² = 60%). Because the upper confidence interval approached the null and the overall effect was sensitive to removal of the most influential study, this finding should be interpreted cautiously. Fig. 2 Forest plot of postoperative ileus comparing perioperative alvimopan versus no alvimopan after elective colorectal resection Forest plot of postoperative ileus comparing perioperative alvimopan versus no alvimopan after elective colorectal resection For the secondary outcome of length of stay, the pooled analysis numerically favored alvimopan, with a mean difference of -0.63 days (95% CI -1.27 to 0.02) (Fig.  3 ). However, the result did not reach statistical significance because the confidence interval crossed the null value and the overall P-value was 0.06. Heterogeneity was considerable (I² = 87%), indicating substantial inconsistency across studies. Thus, the primary pooled analysis did not demonstrate a statistically significant reduction in length of stay with alvimopan, and any apparent LOS benefit should be interpreted cautiously in light of high heterogeneity. Fig. 3 Forest plot of the length of hospital stay comparing perioperative alvimopan versus no alvimopan after elective colorectal resection Forest plot of the length of hospital stay comparing perioperative alvimopan versus no alvimopan after elective colorectal resection For the secondary outcome of readmission, there was no significant difference between the alvimopan and no-alvimopan groups (Fig.  4 ). Readmission occurred in 21 of 698 patients receiving alvimopan and 23 of 681 patients not receiving alvimopan (3.0% vs. 3.4%). The pooled analysis yielded a risk ratio of 0.89 (95% CI 0.48–1.64), showing that alvimopan was not associated with a meaningful reduction in the risk of readmission after discharge. Unlike the other outcomes, heterogeneity was absent (I² = 0%), indicating highly consistent findings across the included studies. Overall, the available evidence does not support a significant effect of alvimopan on postoperative readmission. Fig. 4 Forest plot of readmission comparing perioperative alvimopan versus no alvimopan after elective colorectal resection Forest plot of readmission comparing perioperative alvimopan versus no alvimopan after elective colorectal resection Taken together, the pooled results showed that postoperative ileus was the only endpoint reaching statistical significance in the primary analysis, but this finding was borderline and sensitivity-dependent. In contrast, length of stay and readmission were not statistically significant in the primary pooled analyses, although length of stay showed a numerical trend favoring alvimopan. Heterogeneity was highest for length of stay, moderate for postoperative ileus, and absent for readmission. Overall, these findings suggest that the most consistent interpretation of the evidence is a possible ileus-specific signal rather than a reliable improvement across broader postoperative recovery outcomes. The leave-one-out sensitivity analysis demonstrated that the primary postoperative ileus finding was not robust to removal of the most influential study (Supplementary Table 2). Specifically, removal of Itawi et al. [ 1 ] reduced heterogeneity from 60% to 2%, but the pooled effect was no longer statistically significant. This indicates that the primary ileus result was directionally favorable but sensitivity-dependent, rather than a stable finding across all included studies. For length of hospital stay, removal of Kelley [ 4 ] reduced heterogeneity from 87% to 76% and shifted the pooled estimate to statistical significance, suggesting that this study contributed importantly to inconsistency in the continuous outcome analysis. Therefore, both the primary and secondary pooled estimates should be interpreted with caution, and the sensitivity analyses should be considered central to interpretation rather than confirmatory only. Subgroup analyses were considered exploratory because of the small number of included studies. In the primary outcome analysis, alvimopan was associated with a reduction in postoperative ileus within the segmental colectomy with primary anastomosis subgroup, whereas no statistically significant effect was observed in the procedure-diverse colorectal surgery subgroup (Supplementary Fig. 3). However, given the limited number of studies and events, these subgroup findings should be interpreted descriptively and should not be considered definitive evidence of effect modification. For length of hospital stay and readmission, neither subgroup demonstrated a statistically significant reduction, and there was no clear evidence of subgroup-dependent benefit (Supplementary Figs. 4 and 5). Overall, these subgroup findings suggest a possible stronger ileus-related signal in more clinically uniform colectomy cohorts, but this observation remains hypothesis-generating. The certainty of evidence was rated as very low for all three outcomes after the domain-based GRADE assessment (Supplementary Table 3). Downgrading was primarily driven by serious risk of bias because all included studies were retrospective non-randomized comparisons with potential residual confounding and selection bias. Inconsistency also contributed to downgrading, particularly for postoperative ileus and length of stay, where heterogeneity was moderate-to-substantial and effect estimates varied across studies. Imprecision further reduced certainty because confidence intervals were wide, event numbers were limited, and the secondary outcome confidence intervals crossed the line of no effect. For postoperative ileus, certainty was further tempered by sensitivity dependence, because removal of the most influential study eliminated statistical significance. Indirectness was not considered a major concern because the included populations and interventions were directly aligned with the review question, whereas publication bias was considered undetected. Overall, the very low certainty of evidence indicates that these findings should be interpreted as hypothesis-generating rather than definitive.

This review is strengthened by its methodological rigor, including adherence to the PRISMA 2020 and MOOSE guidelines, independent dual-reviewer screening and data extraction, ROBINS-I quality assessment, random-effects analytic framework, and unique incorporation of prespecified leave-one-out sensitivity analyses, subgroup analyses stratified by operative scope, and formal GRADE certainty assessment, collectively establishing this as the most structured synthesis to date on this focused clinical question. However, this study has several important limitations. All included studies were retrospective and observational, creating a risk of residual confounding and confounding by indication; patients selected to receive alvimopan may have differed systematically from controls in ways that were not fully captured in the source studies. The number of eligible studies was small, and all were conducted in the United States, limiting generalizability to other healthcare systems with different ERP structures, discharge thresholds, medication costs, and readmission practices. Recent real-world colorectal practice data also reinforce that perioperative decision-making and procedural pathways vary substantially across centers, supporting caution when generalizing pooled observational recovery outcomes across institutions [ 27 , 28 ]. Clinical heterogeneity was also substantial. Included cohorts varied by operative scope, indication for surgery, inclusion of benign and malignant disease, proportion of stoma-related procedures, and ERP maturity. Definitions of postoperative ileus and reporting of recovery milestones were not uniform, and granular ERP elements such as early feeding, mobilization, opioid route and dose, epidural use, and multimodal analgesia were inconsistently reported. These limitations restricted the ability to perform meaningful patient-level or protocol-level subgroup analyses. Publication bias could not be formally assessed because fewer than 10 studies contributed to each pooled outcome. Finally, the certainty of evidence was very low across outcomes, primarily because of risk of bias, inconsistency, and imprecision; therefore, the pooled estimates should be considered hypothesis-generating rather than definitive.

In this meta-analysis of comparative studies conducted in the minimally invasive and enhanced recovery era, perioperative alvimopan was associated with a borderline reduction in postoperative ileus in the primary pooled analysis, whereas its effects on length of stay and readmission did not reach statistical significance. However, the postoperative ileus finding was sensitivity-dependent and supported by very low-certainty retrospective evidence, limiting the strength of clinical inference. These findings are directionally consistent with the individual study-level signals observed in the included laparoscopic and minimally invasive colorectal cohorts, although the magnitude of the benefit varied appreciably across the studies [ 1 – 5 ]. Broader contemporary observational studies outside our pooled dataset have similarly suggested benefits for bowel recovery and hospital utilization following bowel resection; however, their populations, operative approaches, and perioperative pathways were considerably more heterogeneous than the narrowly defined cohorts incorporated in the present review [ 6 – 8 ]. The most clinically relevant signal in this study was the directionally favorable association between alvimopan and reduced postoperative ileus. This finding is biologically plausible, but it should be interpreted cautiously because the pooled estimate was borderline, heterogeneity was moderate-to-substantial, and statistical significance was lost after removal of the most influential study. Alvimopan selectively antagonizes peripheral mu-opioid receptors within the gastrointestinal tract, thereby attenuating opioid-mediated gut dysmotility without reversing central analgesia. In the context of colorectal surgery, where early enteral feeding, opioid minimization, and early mobilization are the cardinal pillars of enhanced recovery, this mechanistic profile is particularly relevant [ 9 , 10 ]. Therefore, the pooled results support the premise that alvimopan may confer incremental clinical value in selected settings, particularly when the endpoint of interest is postoperative ileus rather than broader composite recovery metrics. The present findings should also be interpreted in relation to the earlier multicenter U.S. trial evidence that supported alvimopan’s efficacy in bowel resection. Those trials provided important proof of pharmacologic efficacy, but they were conducted largely in an earlier perioperative era with greater representation of open surgery, different opioid exposure patterns, and less mature enhanced recovery implementation than contemporary minimally invasive colorectal practice. In addition, industry sponsorship in pivotal drug trials increases the need for careful interpretation of effect size, endpoint selection, and applicability to routine practice. The current focused synthesis does not negate the earlier trial evidence, but suggests that the magnitude and consistency of benefit may be attenuated when alvimopan is evaluated within modern MIS/ERP pathways. The absence of a statistically significant effect on the length of stay in the primary pooled analysis warrants careful and nuanced interpretation. Length of stay is not a pure pharmacological outcome; it is fundamentally shaped by institutional discharge culture, pathway maturity, prevailing social circumstances, surgeon preference, and institutional thresholds for a safe discharge. This multifactorial nature likely explains why several individual constituent studies suggested shorter hospitalization with alvimopan, yet the pooled effect failed to attain statistical significance until a sensitivity analysis was performed [ 11 – 14 ]. The leave-one-out analysis demonstrated that removal of Kelley [ 4 ] shifted the pooled estimate toward significance, indicating that small-study effects, procedural heterogeneity, and differences in outcome reporting contributed to instability in the continuous outcome estimate. The influence of Kelley [ 4 ] may also reflect differences in procedural composition, because this study included a substantial proportion of stoma procedures, which may have different baseline bowel function, postoperative diet advancement, discharge criteria, and recovery trajectories compared with segmental colectomy with primary anastomosis. Accordingly, alvimopan may still reduce hospitalization duration in selected institutional settings, but the consistency and reproducibility of this effect appear substantially lower than that for the primary endpoint of postoperative ileus. Clinical and operational heterogeneity across included studies also likely contributed to variability in the pooled estimates. Postoperative ileus was not uniformly defined across studies and may have reflected a clinical diagnosis, delayed return of bowel function, diet intolerance, nasogastric tube requirement, or prolonged hospitalization related to gastrointestinal recovery. Similarly, specific ERP elements were not consistently granular across reports, including early feeding protocols, early mobilization targets, perioperative fluid management, use of intravenous versus oral opioids, epidural analgesia, and multimodal opioid-sparing strategies. These differences are important because alvimopan’s marginal benefit is likely greatest when opioid-mediated gastrointestinal dysmotility is a dominant driver of delayed recovery, and smaller when mature ERP pathways have already minimized opioid exposure and accelerated bowel recovery. The readmission analysis was neutral and demonstrated high consistency across all constituent studies. This finding is clinically plausible because readmission is a distal outcome influenced by a broad spectrum of postoperative events extending beyond transient gastrointestinal dysmotility, including surgical site infection, dehydration, uncontrolled pain, ileus recurrence, patient frailty, and pathway-specific post-discharge follow-up practices. Recent comprehensive reviews of postoperative ileus prevention and management have similarly emphasized that improvements in bowel recovery do not consistently translate into measurable reductions in broader postoperative healthcare utilization metrics, particularly when baseline institutional readmission rates are low [ 15 , 16 ]. In essence, alvimopan appears more likely to influence immediate gastrointestinal recovery than later care transitions and post-discharge outcomes. Subgroup analyses provided exploratory clinical context but should not be interpreted as definitive evidence of effect modification. The most favorable subgroup signal for postoperative ileus was observed in the more clinically uniform segmental colectomy with primary anastomosis cohort, whereas the magnitude of benefit was considerably less apparent in the procedure-diverse colorectal surgery cohort. Although these findings are clinically plausible, they are limited by the small number of included studies and sparse outcome events. Greater operative homogeneity within the segmental colectomy series likely reduces background variability in postoperative recovery trajectories, thereby allowing the pharmacological effects of alvimopan to emerge with greater clarity. This interpretation aligns with data from other minimally invasive and matched observational analyses, demonstrating that the benefit of alvimopan is most discernible when both pathway elements and operative populations are relatively standardized [ 17 – 19 ]. These subgroup findings collectively support further study of selective, rather than indiscriminate, alvimopan use, but they should not be treated as confirmatory evidence. Another important source of clinical heterogeneity was the inclusion of both benign and malignant colorectal disease. These populations may differ in baseline nutritional status, inflammatory burden, operative complexity, extent of resection, neoadjuvant treatment exposure, and discharge planning. Although all included studies addressed elective colorectal resection in a minimally invasive or enhanced recovery context, the mixture of benign and malignant indications may have introduced residual confounding that could not be resolved with study-level aggregate data. Future studies should report outcomes separately by indication where possible, particularly for postoperative ileus and length of stay. These results must also be interpreted within the broader framework of modern enhanced recovery principles. Enhanced recovery itself substantially mitigates the risk of ileus through early enteral nutrition, multimodal opioid-sparing analgesia, perioperative fluid optimization, and structured early mobilization, and these evidence-based pathway elements may collectively diminish the measurable marginal pharmacological benefit attributable to any single adjunct agent [ 20 – 25 ]. Therefore, the operative question has evolved beyond whether alvimopan is effective in isolation to whether it confers clinically meaningful incremental value above and beyond an already optimized perioperative pathway. The present results suggest that such incremental value may exist for postoperative ileus in selected settings; however, this benefit is not uniform across all recovery endpoints and is not sufficiently robust to justify assuming a universal therapeutic advantage across all minimally invasive colorectal surgery indications. Cost-effectiveness remains uncertain and context-dependent. Although some included and related studies suggest potential cost savings when alvimopan reduces ileus or shortens hospitalization, these estimates are highly sensitive to drug acquisition cost, baseline ileus incidence, institutional length-of-stay practices, payer structure, readmission penalties, and ERP maturity. Therefore, the present meta-analysis cannot define a universal cost-benefit threshold. Instead, cost considerations should be evaluated locally, particularly in centers where baseline postoperative ileus rates remain high despite ERP implementation or where delayed gastrointestinal recovery is a major driver of prolonged hospitalization. According to the formal GRADE assessment, the overall certainty of the evidence was judged to be very low across all outcomes. All included studies were observational in design, and the ROBINS-I evaluation identified predominantly low-to moderate-domain-level concerns rather than genuinely low-risk evidence-based. The downgrading was driven by the risk of bias, inconsistency, and imprecision of the studies. This assessment does not invalidate the observed association with postoperative ileus; however, it mandates that the pooled estimate be interpreted as hypothesis-generating and hypothesis-supporting rather than definitive or practice-changing. The sensitivity analysis reinforces this interpretive caution: the removal of Itawi [ 1 ] markedly attenuated heterogeneity for postoperative ileus but simultaneously rendered the pooled effect non-significant, confirming that the primary result, while directionally favorable, lacked complete statistical significance. From a practical clinical standpoint, these data support a nuanced and individualized approach to treatment rather than routine pathway-level use. In minimally invasive colorectal surgery performed within enhanced recovery frameworks, alvimopan may be most clinically justifiable when the primary therapeutic objective is to reduce the risk of postoperative ileus, particularly in more standardized segmental colectomy populations or in patients at higher baseline ileus risk. This interpretation is also consistent with broader minimally invasive colorectal literature showing that outcomes are strongly shaped by patient age, operative complexity, and case selection, reinforcing that postoperative recovery cannot be attributed to a single perioperative adjunct alone [ 26 ]. Its routine universal application solely to reduce readmission rates or guarantee reduced hospitalization duration is less robustly supported by current evidence. Therefore, clinical decision-making should be individualized according to the patient’s baseline ileus risk profile, operative complexity, anticipated postoperative opioid exposure, institutional pathway maturity, and local cost-effectiveness considerations.

In minimally invasive colorectal surgery within enhanced recovery care, perioperative alvimopan was associated with a borderline, sensitivity-dependent reduction in postoperative ileus, while effects on length of stay and readmission were inconsistent or neutral. Because all included evidence was retrospective and the certainty of evidence was very low, these findings should be considered hypothesis-supporting rather than definitive. Current evidence is insufficient to support routine pathway-level use of alvimopan across all minimally invasive colorectal resections. Its use may be reasonable in selected settings where postoperative ileus prevention is a priority, baseline ileus risk is high, and local cost-benefit considerations support treatment.

Postoperative ileus (POI) is a clinically significant and economically burdensome complication that can occur following elective colorectal resection. It is characterized by transient but debilitating impairment of gastrointestinal (GI) motility, manifesting as nausea, vomiting, abdominal distension, failure to pass flatus, and intolerance to oral intake. The pathophysiology of POI is multifactorial, encompassing neurogenic inhibitory reflexes triggered by surgical bowel manipulation, systemic inflammatory cascades, and critically, peripheral µ-opioid receptor-mediated suppression of enteric motility induced by postoperative opioid analgesia. POI prolongs hospitalization, escalates costs, and increases the risk of readmission, collectively imposing a substantial burden on healthcare systems worldwide [ 1 , 2 ]. Alvimopan is an oral, peripherally acting µ-opioid receptor antagonist that selectively counteracts the enteric effects of opioids without compromising central analgesia, representing a rational pharmacological strategy for the treatment of opioid-mediated POI. Its FDA approval was based on pivotal phase III randomized controlled trials demonstrating accelerated GI recovery and reduced hospital length of stay (LOS), primarily in open bowel resection under traditional perioperative care. However, the translational validity of these findings to contemporary surgical practice has been increasingly challenged by two parallel paradigm shifts: the widespread adoption of minimally invasive surgery (MIS) and the implementation of Enhanced Recovery Pathways (ERPs). Both inherently attenuate the opioid-dependent pathophysiological substrate upon which alvimopan exerts its primary mechanism of action, raising substantive questions about its incremental benefits in these optimized contexts [ 3 , 4 ]. In parallel, increasing standardization of minimally invasive colorectal techniques may independently reduce tissue trauma, opioid exposure, and recovery variability, further complicating extrapolation from older open-surgery trials to contemporary laparoscopic practice [ 5 ]. The existing comparative literature addressing alvimopan in the MIS-ERP era is heterogeneous and yields conflicting conclusions. While some institutional studies have demonstrated significant reductions in POI and LOS with alvimopan following laparoscopic colectomy [ 1 , 3 , 6 , 7 ], others have reported no measurable benefits in LOS, readmission, or total costs in rigorously implemented ERP settings [ 2 , 4 , 5 ]. Large population-level analyses have revealed inconsistent outcomes across institutions [ 8 ]. A prior systematic review and meta-analysis examining alvimopan after open abdominal surgery supported its benefit in that setting [ 9 ], yet the most comprehensive surgical review to date acknowledged persistent uncertainty regarding its efficacy specifically within minimally invasive and ERP-based colorectal surgery, without being able to conduct a formal quantitative synthesis [ 10 ]. Prior reviews have evaluated alvimopan across broader abdominal surgery populations and perioperative contexts, but uncertainty remains regarding its incremental value specifically in elective minimally invasive colorectal resection performed within enhanced recovery pathways [ 9 , 10 ]. Therefore, the present review was designed to provide a focused quantitative synthesis of perioperative alvimopan versus no alvimopan in this contemporary clinical setting. Clinically, we framed alvimopan not as a universal enhanced recovery component, but as a potential selective adjunct for postoperative ileus prevention, while also evaluating whether any ileus-related benefit translated into broader recovery outcomes such as length of stay and readmission [ 1 – 5 ].

Supplementary Material 1. Supplementary Material 1. Supplementary Material 2. Supplementary Material 2. Supplementary Material 3. Supplementary Material 3.