Incidence of intra-abdominal injury after blunt abdominal trauma with negative CT scan: a systematic review and meta-analysis

Abstract

Background

Missed intra-abdominal injuries (IAI) after blunt abdominal trauma (BAT) with a negative CT scan are rare, but incidence estimates vary across populations and over time, leading to heterogeneous practices regarding observation and discharge. The aim of this study is to synthesize available evidence to estimate the incidence of IAI among patients with BAT and a negative CT scan and to examine how different characteristics influence this risk.

Methods

Systematic searches were conducted in MEDLINE, EMBASE, CENTRAL, and LILACS from inception to May 12, 2025, without language restrictions, and supplemented with WoS, trial registries and grey literature sources. Eligible studies included cohort, cross-sectional, case–control studies, or randomized trials evaluating patients of any age with BAT who underwent CT with negative findings for IAI. Emergent procedures and hemodynamic instability were exclusion criteria. Screening and study selection were performed independently by two reviewers. Duplicate and independent data extraction was conducted. Reporting followed PRISMA guidelines and quality was assessed using the Joanna Briggs Institute tool. Pooled incidences were estimated using random-effects meta-analysis. The primary outcome was the incidence of IAI in patients with negative CT scans, and subgroup and sensitivity analyses were performed to assess heterogeneity and robustness.

Results

Thirty-one studies comprising 27,342 patients were included. The pooled incidence of IAI after a negative CT was 0.34% (95% CI, 0.21–0.51%). Heterogeneity was substantial (I² = 62.8%) and largely explained by patient characteristics and CT technology. Subgroups with high-risk clinical features had a higher incidence (1.03%; 95% CI, 0.31–2.12%) than unselected trauma cohorts (0.22%; 95% CI, 0.12–0.35%, p = 0.01). Older CT technology showed a higher incidence (0.69%; 95% CI, 0.25–1.33%, compared with MDCT (0.26%; 95% CI 0.14–0.42%, p = 0.05). Sensitivity analyses with GLMM confirmed the robustness of our findings.

Conclusions

In patients with blunt abdominal trauma and a negative CT scan, the incidence of intra-abdominal injury is exceedingly low (0.34%). These findings provide robust, contemporary evidence to inform clinical decisions regarding the need for in-hospital observation and support consideration of early discharge in most patients, while recognizing that individuals with high-risk clinical features may warrant closer monitoring.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13017-026-00680-4.

Background

Blunt abdominal trauma (BAT) is frequently encountered in the Emergency Department (ED), with intra-abdominal injuries (IAI) occurring in about 8–15% of cases [1–3]. Computed Tomography (CT) scan is the standard of care for evaluating BAT in hemodynamically stable patients with abnormal examination findings or high-risk features [4, 5]. The diagnostic accuracy of CT scan for detecting IAI in hemodynamically stable patients is high, with sensitivity typically reported between 85 and 98% and specificity between 97 and 99% [3, 4, 6]. Among patients with an initial negative CT scan, most studies report a very low incidence of IAI (0–0.7%), [7–10] though a minority have observed higher rates (2.9–5.3%) [11, 12] with variation across populations and over time [8–10, 13–19]. Despite the overall low risk, clinical practice remains heterogeneous, with some centers discharging BAT patients soon after a negative CT, whereas others admit for prolonged observation times because of concern about rare missed injuries and the potential consequences of delayed treatment [7, 20, 21]

This systematic review and meta-analysis estimate the incidence of IAI among BAT patients with normal CT findings and examines how different population characteristics and imaging technology influence that risk, with the aim of informing decisions about the need for prolonged in-hospital observation in stable patients with negative CT findings.

Methods

This systematic review was conducted according to the Cochrane Handbook for Systematic Reviews [22] and reported according to the preferred reporting items for systematic review and meta-analysis (PRISMA) [23] included in eTable S1 (Supplement). The protocol for this review was registered in PROSPERO (CRD42024516800).

Search strategy

Systematic searches were conducted in MEDLINE, EMBASE, CENTRAL, and LILACS from the date of inception to April 7th, 2024, with no language restrictions and no additional filters, and were updated on May 12th, 2025, using the same strategy. The database search was supplemented by a search in the Web of Science Complete Core Collection (including the Science Citation Index and the Conference Proceedings citation index), a search in the two main sources for trial registries (ClinicalTrials.gov and International Clinical Trials Registry Platform) and checking reference lists on studies included in the review. Relevant studies were identified through a search in Google Scholar and a search in Google to identify unpublished studies or relevant grey literature. Search terms included a combination of Medical Subject Headings (MeSH) terms and free text using permutations of the search terms “abdominal injury”, “blunt”, and “computed tomography” (eTable 2, Supplement).

Eligibility criteria

The review included prospective or retrospective cohort, cross-sectional, case–control studies, and randomized controlled trials. Case reports/series and animal studies were excluded. We included studies conducted in patients with BAT who underwent an initial abdominal CT scan, and the result was negative for IAI. Patients who required emergent procedures or who presented hemodynamic instability were excluded. IAI injuries were detected by additional abdominal imaging or surgical exploration. There were no restrictions on age, language, geographical location, year of publication, or publication status. The primary outcome was the incidence of intra-abdominal injury in patients with negative CT scan.

Screening, selection, and data extraction

Search results were imported into Covidence (Veritas Health Innovation, Melbourne, Australia; www.covidence.org) for management and de-duplication. Title and abstract screening were performed independently by two reviewers (LO, MCG). Potentially eligible records underwent independent full-text assessment and data extraction by LO and MCG. Discrepancies were resolved through discussion, or a third reviewer when needed (VZ). Multiple publications arising from the same population were merged to avoid bias [24]. Study authors were contacted if clarification was required. We extracted data using a pre-specified data extraction form, optimized after a pilot extraction (Supplement). Data extracted included the author, year of publication, total number of patients with negative CT scans, number of intra-abdominal injuries detected in patients with negative CT scans, and all relevant variables for the description of the included studies and for the subgroup analysis.

Assessment of methodological quality

Methodological quality was assessed by two independent reviewers (LO and JPA) using the Joanna Briggs Institute (JBI) Critical Appraisal Tool for meta-analysis of prevalence due to its high methodological rigor and completeness [25]. The JBI tool comprises nine domains described in more detail in eTable 3 (Supplement). Studies were rated as low, moderate, or high risk based on the number of items considered fulfilled and the extent to which departures from key domains could affect the validity of prevalence estimates [26]. Disagreements were resolved through consensus. The robvis tool was used to create the risk-of-bias plots [27].

Statistical analysis

We synthesized study data using a random-effects meta-analysis of proportions with the Freeman–Tukey double-arcsine transformation using a logit link and reported pooled incidences with 95% confidence intervals after inverse-variance (IV) back-transformation, recommended to avoid the harmonic-mean artifact [28, 29]. Between-study variance (τ²) was estimated by restricted maximum likelihood (REML). Heterogeneity was assessed by visual inspection of forest plots, τ², I², and 95% prediction intervals [30].

Pre-specified subgroup analyses evaluated potential sources of heterogeneity by CT technology (single slice/helical CT vs multi-detector computed tomography [MDCT]), study population (adults vs. children), and country income level (high- vs low- and middle-income). When CT scanner type was not explicitly reported, we assigned the predominant technology in use during the study period, provided that the year of patient enrollment allowed a reliable classification. Owing to variability in baseline inclusion criteria and its clinical relevance, we also performed a post-hoc comparison of studies enrolling high-risk populations versus general BAT cohorts. Studies were classified as high-risk if CT was obtained predominantly in patients who had an abnormal or equivocal abdominal examination, hematuria or a positive seat belt sign [3, 31]. In contrast, studies were classified as general-risk if CT was performed broadly in patients with BAT, including those with high-energy mechanisms of injury, regardless of abdominal examination findings, reflecting current practice.

Pre-defined sensitivity analyses were conducted by re-estimating the pooled incidence fitting a generalized linear mixed model (GLMM), a leave-one-out meta-analysis and excluding studies at high risk of bias to assess the robustness of our results.

To explore potential publication bias we constructed funnel plots using study sample size as a measure of accuracy in the y-axis instead of the inverse SE, since conventional funnel plots have been shown to be inaccurate for meta-analyses of proportions, with misleading asymmetry even in the absence of publication bias, especially with low proportion outcomes [32–34]. Visual inspection of the funnel plot was complemented by arcsine-Thompson regression-based tests for proportion outcomes [34, 35]. Analyses were performed using Stata 19.5 [36] and R (PersystMA WebApp tool) [37]. The GRADE approach was used to assess the certainty of evidence and results displayed using GRADEpro GDT [38–40].

Results

A total of 14,881 records were identified through database searches, of which 4419 were duplicates and removed. After screening 10,464 records, 152 full-text articles were assessed for eligibility, resulting in 31 studies included in the review (Fig. 1) [41]. Reasons for the exclusion of full text studies are described in the Supplemental Material (eTable 4, Supplement).

Fig. 1.

PRISMA flow diagram of search results and study selection

Characteristics of included studies

The review included 31 studies conducted between 1983 and 2024, across Europe, [42] Asia, [12, 43–45] South America, [46] and with most originating from North America, with two studies from Canada [47, 48], and twenty-three studies from the United States. The vast majority were cohort studies (16 prospective and 14 retrospective) and there was one randomized clinical trial (Table 1) [11]. Study settings were predominantly Level I trauma hospitals (28 studies), and the majority were single-center (27studies) with a few multicenter studies [8, 16, 19, 49]. Twenty-three cohorts enrolled adults, 7 included children, [8, 42, 47, 50–53] and one included both, [54] reflecting mixed age populations seen in trauma care.

Table 1.

Characteristic of included studies

Study ID	County	Study design	Recruitment dates	# Centers/Trauma level	Age group	Population	Mean Age	Male (%)	ISS (median)	CT scan type
Maix_1985	United States	Prospective cohort	Jan–Jun 1984	1 center/Level 1 Trauma	Mixed	Patients with BAT and CT token for signs of hypovolemia, equivocal abdominal physical findings, were unevaluable due to intracranial injury or intoxicants, or had sustained high-deceleration injury	35	81.0%	NA	Single-slice axial Conventional CT scan
Fabian_1986	United States	Prospective cohort	Apr 1984–Feb1985	1 center/Level 1 Trauma	Adult	Stable BAT patients and CT taken for either equivocal abdominal examinations or examinations rendered unreliable by either impaired sensorium or spinal cord injury	31	72.0%	20	Single-slice axial Conventional CT scan
Pevec_1991	United states	Prospective cohort	Jun 1983–Dec 1987	1 center/Level I Trauma	Adult	Patients with BAT and CT taken for equivocal abdominal exam, decreased level consciousness, pelvic trauma, Spinal injury, hematuria	35	72.0%	NA	Single-slice axial Conventional CT scan
Sriussadapom_1993	Thailand	Retrospective cohort	May 1991–Sep 1992	1 center/ Level 1 Trauma	Adult	Patients with multisystem injuries in whom abdominal physical examination was considered unreliable or difficult, particularly In the presence of associated major pelvic fracture, or In whom retroperitoneal organ Injuries were suspected. All pts had equivocal abdominal signs at examination	29.7	84.0%	12.5	Single-slice axial Conventional CT scan
Meyer_1993	United States	Prospective cohort	Not reported	1 center/Level 1 Trauma	Pediatric	Patients with BAT and indication for DPL. No description of indications of DPL	5.8	70.0%	NA	Single-slice axial Conventional CT scan
Sherck_1994	United States	Retrospective cohort	Sep 1988–Feb 1994	2 centers/ Level 1 Trauma	Adult	Patients with BTA and CT scan taken for equivocal signs or symptoms of abdominal injury, and in those whose abdomens cannot be evaluated adequately because of abdominal mental status	30.6%	69.2%	13a	Single-slice axial Conventional CT scan
Graham_1996	Canada	Retrospective cohort	Jan1987 Dec1994	1 center/Laval 1 Trauma	Pediatric	Children with BATand CT during initial evaluation. No description for indication of CT	7.36	NA	NA	NA
Brasel_1996	United States	Retrospective cohort	Jul 1991–Jun 1995	1 center/Level 1 Trauma	Adult	All ptswlth BATand ISS < 15,andCT scan taken. The most common Indication for obtaining an abdomlnaL CT scan was pain/tenderness followed by mechanism alone	31.5	67.0%	9.6b	Helical CT
Ruess_1997	United States	Prospective cohort	Jan 1983–Jan 1993	1 center/ Level 1 Trauma	Pediatric	Children 1 month to ≤ 18 years and were presumed on clinical grounds to have injury to abdominal tenderness/hematuria or both	7	63.0%	NA	Single-slice axial Conventional CT scan
Richards_1998	United States	Prospective cohort	Apr 1995–Oct 1995	1 center/Level 1 Trauma	Adult	Patients receiving CT in the emergency department (ED) for BAT. Most patients with abdominal tenderness/hematuria or both	34	55.0%	8.9a	Helical CT
Jhirad_1998	Canada	Prospective cohort	Feb 1996–Jan 1997	1 center/Terciary-level care facility	Adult	Patients with BATand CTscan taken for suspected of having significant blunt abdominal trauma but without an obvious indication for laparotomy (abdominal exam, hematuria, hypotension, pelvic ring injuries, unreliable exam)	40	67.0%	16a	Single-slice axial Conventional CT scan
Livingston_1998	United States	Prospective cohort	Apr1995–Jan 1996	4 centers /Level 1 Trauma	Adult	All pts older than 16 years who sustained blunt abdominal Injury	36.1	68.0*	9.9	Helical CT
Sievars_1999	United States	Retrospective cohort	Jun 1996–Jun 1998	1 cantor/Level 1 Trauma	Pediatric	Children {≤ 14 vo) iwth BAT with or without abdominal tenderness. IndlcatlonsforCTnot described	6	68.0%	8.6a	Helical CT
Malhotra_2000	United States	Retrospective cohort	Aug 1995–Dec 1998	1 center/Level 1 Trauma	Adult	Patients with BATand CTscan	NA	NA	NA	Helical CT
Pal_2002	United States	Retrospective cohort	Jan 1991 –Dec2000	1 center/Level II Trauma	Adult	Patients with BATand glasgow < 11	36	59.0%	15a	Helical CT
Al-Salamah_2002	Saudi Arabia	Retrospective cohort	Jan 2000 –Dec 2001	1 center/Terciary-level care -facility	Adult	Patientswlth BAT and CTscan taken for equivocal or unreliable exam or spinal cord injury	23	79.0%	NA	Helical CT
Stuhlfaut_2004	United States	Retrospective cohort	Oct 2001–Sep 2003	1 center/Level 1 Trauma	Adult	Patients with BAT and CT in first 24 h. CT in patients suspected of having abdominal injury due to blunt trauma	39.8	70.7%	NA	MDCT4-32 slices
Allen_20D4	United States	Prospective cohort	Jul 2000–Nov 2001	Level 1 Trauma	Adult	abdomen and pelvis as pa rt of the cllnlcaL assessment, whose mechanism of Injury or clinical assessment whose mechanism of injury or clinical examination is suspicious for intra abnormality	35.1	50.0%	25.6a	Helical CT
Kumar_2005	India	Prospective cohort	Aug 2002–Mar 2004	1 centerr/Level II Trauma	Adult	Patientswlth BAT and clinical suspicion of Intra-abdominal Injury, Haemodynamically stable patient, Multi-trauma patients or a positive ultrasonography study	NA	79.0%	NA	Helical CT
Sallm_2006	United States	Prospective cohort	Jan 2004–Jun 2005	1 center/Level 1 Trauma	Adult	Adults with BAT with normalexamand high energy mechanism of Injury	37	70.0%	NA	Helical CT
Awasthi_2008	United States	Prospective cohort	Mar 2001–May 2004	1 center /Laval 1 Trauma	Pediatric	Patients younger than 18 years of age undergoing Initial abdomlnaL CT scanning In the ED alter blunt abdormnal trauma were eligible enrollment	9.6	60.0%	NA	MDCT4-32 slices
Gonzalez_2001	United States	Prospective randomized study	Feb 1999–Jul 2000	1 center/Level 1 Trauma	Adult	Patients with BAT and suspected abdominalinjury, Glasgow < 13	34.1	66.0%	NA	MDCT4-32 slices
Holmes_2012	United States	Prospective cohort	Not reported	Level 1 Trauma	Adult	Adults with BATand negative CT scan	39	66.0%	NA	MDCT4-32 slices
Kerrey_2013	United States	Prospective cohort	Jan 2007–Jan 2010	20 centers	Pediatric	ChlldrensiByo with BATand. Normal CTscan. CTSCAN were ordered for physicians concerned of abdominal trauma at each institution	11.5	NA	NA	NA
Benjamin_2013	United States	Retrospective cohort	Jan 2013–Dec 2013	1 center/Level 1 Trauma	Adult	Adults with BATand negative CTscan	NA	NA	5a	NA
Hefny_2015	United Arab Emirates	Retrospective cohort	Oct 2010–Dec 2013	1 center /Secondary-level care facility	Adult	Adult ptswlth CTscan and BAT	24	86.0%	18.8a	MDCT264 slices
Braungart_2017	United Kingdom	Retrospective cohort	Jan2014–Dec2014	1 center/Level 1 Trauma	Pediatric	Children < 16yo BATand CTscan. Indications for CTscan not reported	11	60.0%	9	NA
Barmparas_2018	United States	Retrospective cohort	Jan2014–Dec2016	1 center/Level 1 Trauma	Adult	Patients victims olMVA with Seatbatt sign and Negative CT	39.8	55.0%	4	MDCT ≥ 64 slices
Ben|amln_2018	United States	Prospective cohort	Nov 2014–May 2015	1 center/Level 1 Trauma	Adult	Patients > 14 years old BATand negative CTscan	39	70.4%	9	NA
Delaplain_2022	United States	Prospective cohort	Aug 2020–Oct 2021	9 centers /Level 1 trauma centers	Adult	Patients a IB years with BATand Seat belt Sign with negative CTscan	36	51.0%	14	NA
Zarama_2024	Colombia	Retrospective cohort	Jan 2021–Dec 2022	1 center/Level 1 Trauma	Adult	Patientswlth BATand negative CTscan	33	74.2%	5	MDCT ≥ 64 slices

BAT Blunt Abdominal Trauma, ISS Injury Severity Score, CT computed, ED Emergency Department, DPL Diagnostic Peritoneal Lavage, NA Not Available, MSCT Multidetector Computed Tomography

^aMean ISS

^bMean trauma score

Population demographics showed a male predominance across studies (50–86%) with adult mean ages between 30 and 40 years and a pediatric mean age around 6–12 years. Injury severity (ISS) medians, when available, ranged from 4 to 26. Across studies, most common mechanism of injury was motor-vehicle accidents (median 58%; range 31.6–100%; n = 23), followed by falls (14.6%; 0–34%; n = 20) and pedestrian injuries (12.8%; 0–40%; n = 18).

Indications for CT varied across institutions and over time. Earlier studies imaged more selective populations (abdominal tenderness, equivocal/unreliable exam, altered sensorium, hematuria, seat belt sign), whereas more recent cohorts usually adopted broader CT protocols, scanning most patients with high-energy mechanisms regardless of abdominal findings.

CT technology progressed over time from single-slice conventional scanners to helical and then MDCT systems (≥ 64 slices), reflecting advances in imaging across the study period. Additional imaging information with CT parameters and contrast administration is summarized in eTable 5 of the Supplement.

Risk of bias assessment

Six studies were judged to be at low risk of bias, eight moderate, and nineteen high. High ratings were driven mainly by sample sizes below the prespecified precision threshold; because the expected prevalence is extremely low, adequate precision required very large cohorts (Supplement). Less common limitations included retrospective designs, incompletely described recruitment methods, and limited or unreported statistical analyses with many studies reporting primarily descriptive results without confidence intervals. In contrast, missed intra-abdominal injuries were consistently identified using standardized CT protocols interpreted by qualified radiologists or intra-operative findings, although follow-up time was not described in most studies. The risk of bias plot and summary table is presented in eFigures 1 and 2 (Supplement).

Main findings

Across 31 studies comprising 27,342 patients with blunt abdominal trauma and a negative CT, the pooled incidence of intra-abdominal injury was 0.34% (95% CI 0.21–0.51%), with a 95% prediction interval of 0.0–1.06%. Study estimates ranged from 0% to 12.5%, though the vast majority were below 0.5% (Fig. 2). Between-study heterogeneity was moderate (I² = 62.8%, Q(30) = 98.3, τ² = 0.00). Visual examination of the forest plot, arranged chronologically by year of publication, suggested a temporal trend with higher incidences primarily observed in small, older single-center cohorts, while more recent and larger studies consistently reported incidences from 0 to 0.5%.

Fig. 2.

Forest plot of all included studies

Investigation of heterogeneity and subgroup analyses

Subgroup analyses explored potential sources of heterogeneity by age group (adult only vs pediatric only), CT technology (single slice or helical CT vs MDCT), baseline population risk (high vs overall risk) and country income classification (high vs low/middle income), and are depicted in Fig. 3.

Fig. 3.

Subgroup analysis forest plot

When stratified by age, the pooled incidence of intra-abdominal injury was 0.26% (95% CI 0.15–0.39%) among studies including only adults (23, n = 20,974) compared with 0.88% (95% CI 0.00–2.87%) among studies including only pediatric patients (7, n = 6,306). Although the point estimate was higher in children, the difference between subgroups was not statistically significant (p = 0.14).

By CT modality, studies using single-slice or helical scanners which included (n = 15,768) reported a higher pooled incidence (0.69%, 95% CI 0.25–1.33%) than those using MDCT (n = 11,574) that reported a very low pooled incidence of 0.26% (95% CI 0.14–0.42%), with borderline statistical significance (p = 0.05), suggesting that scanner generation potentially accounts, at least partially, for the observed variability across studies. Analyses stratified by country income classification did not reveal meaningful differences between studies conducted in high-income countries (n = 26,684) compared to studies conducted in low/middle income countries (n = 658), although only 3 studies with only several hundred patients were conducted in low-income countries.

Finally, when studies were grouped according to baseline risk of the enrolled population, we observed a higher incidence of IAI in cohorts restricted to patients with high-risk features (1.03%, 95% CI 0.31–2.12%; n = 4,361), compared with unselected BAT populations (0.22%, 95% CI 0.12–0.35%; n = 22,981). This difference was statistically significant (p = 0.01), indicating that patient selection criteria represent an important source of heterogeneity. Separate Forest plots for each subgroup analyses are included in eFigures 3, 4, 5 and 6 in the Supplement.

Sensitivity analyses

In sensitivity analysis using a generalized linear mixed model (GLMM), the pooled incidence of intra-abdominal injury after a negative CT was estimated at 0.30% with a 95% CI ranging from 0.16 to 0.57% (eFigure 7 in the Supplement). This was consistent with the main analysis based on the Freeman–Tukey transformation and inverse-variance method, which yielded a nearly identical pooled incidence. Sequential omission of each study in the leave-one-out meta-analysis did not significantly alter the summary incidence of intra-abdominal injury after a negative CT scan, with pooled estimates remaining consistent around 0.3% (95% CI range across models: 0.20–0.55%), and no single study exerted a disproportionate influence on the results (eFigure 8 in the Supplement). Finally, after the exclusion of studies judged to be at high risk of bias, the analysis (including 24,308 patients) yielded a pooled incidence of 0.21% (95% CI 0.12–0.33%), (eFigure 9 in the Supplement). Overall, the similarity of pooled estimates across all statistical models supports the robustness of the findings (Table 2).

Table 2.

Sensitivity analyses: pooled incidence of IAI in patients with negative CT scan

Model	Pooled incidence (95% CI)
Primary analysis (FTT + REML)	0.34% (0.21–0.51%)
GLMMa	0.30% (0.16–0.57%)
Excluding high ROB studies	0.21% (0.12–0.33%)
Leave-one-out	0.29–0.38% (NA)b

^aRandom intercept logistic regression with logit transformation

Visual inspection of the funnel plot suggested greater dispersion among smaller studies, with larger cohorts clustering near the pooled estimate and several small studies reporting higher incidences (eFigure 10 in the Supplement). The arcsine–Thompson regression test was significant (p < 0.001), consistent with possible small-study effects.

According to the GRADE assessment, the certainty of evidence was rated as low. Evidence was downgraded primarily due to risk of bias. In contrast, inconsistency, indirectness, and imprecision were not considered serious concerns, as results across most studies were highly consistent, populations and settings were well aligned with the review question, and confidence intervals around the pooled estimate were narrow. (eTable 6 of the Supplement).

Discussion

This systematic review synthesized 31 studies (n = 27,342) evaluating the incidence of IAI after a negative abdominal CT in BAT. The pooled incidence was extremely low, 0.34% (95% CI, 0.21–0.51%), equivalent to 3 IAIs per 1,000 negative CTs. Between-study heterogeneity was substantial overall (I² = 62.8%) but largely explained by differences in baseline population risk and CT technology. Studies that primarily enrolled patients with high-risk features had an estimated incidence of 1.03% (95%CI 0.31 to 2.12%) compared with 0.22% (95% CI 0.01 to 0.19%) in broader blunt-trauma populations that reflect a more contemporary approach (p = 0.01). Similarly, studies using older CT scan technology (single-slice or helical scanners) had a higher pooled incidence (0.69%; 95% CI 0.25 to 1.33%) versus 0.26% in more recent studies using MDCT (95% CI 0.14 to 0.42%); with borderline statistical significance (p = 0.05). Given the evolution in imaging performance, this source of heterogeneity was expected and reinforces the relevance of the consistently low incidence observed in contemporary studies. No statistically significant difference was found between adult-only and pediatric-only studies (p = 0.14) or country income level (p = 0.65), although the interpretability of the latter is limited to the scarcity of studies in low/middle income countries.

A previous meta-analysis published in 2010, including three prospective pediatric cohorts (n = 2,596) reported an incidence of IAI of only 0.19% after a negative CT, with a negative predictive value of 99.8%, which is consistent with our results. While reassuring, those findings were limited by the older CT technology of the time, smaller study sizes, and the exclusive focus on children [55, 56]. Previous research in adults has been limited to individual observational studies, many of which are retrospective, with several studies reporting heterogeneous results.

Notably, our meta-analysis expands the evidence for the safety of a negative CT after blunt abdominal trauma by including > 27,000 adults and children across 31 studies with contemporary data that reflect the routine use of modern MDCT, standardized imaging protocols, and broader CT application in trauma pathways, yielding estimates directly relevant to current practice and confirming that missed intra-abdominal injury after a negative CT in adults is exceedingly low. These findings support early discharge for most hemodynamically stable patients with blunt trauma after a negative CT, aligning with evolving practice in many trauma centers.

Most importantly, subgroup analyses showed that while the baseline risk for most blunt trauma patients is minimal, certain subgroups, particularly those with clinically “high-risk features” like abdominal tenderness, equivocal physical exam, seat-belt sign, etc. although still low, demonstrate higher rates of IAI despite negative CT findings. These findings highlight the need for an individualized approach with tailored monitoring in select higher-risk groups.

This review has several strengths. The comprehensive search strategy is likely to have captured all relevant studies, and the inclusion of a large number of studies and patients provides greater precision in the summary estimates. The inclusion of studies from diverse geographic settings enhances the generalizability of the findings. Moreover, the results from pre-specified sensitivity analyses, including GLMM models, leave-one-out analyses, and exclusion of high–risk-of-bias studies, yielded estimates consistent with the primary analysis, supporting the robustness of our conclusions.

There are also several limitations. Substantial heterogeneity was observed (I² = 68%), which is expected in prevalence meta-analyses, but we performed a thorough evaluation of clinically relevant sources of variability. Subgroup analyses were based on study-level rather than individual patient data, so findings reflect between-study comparisons and must be interpreted cautiously, as differences may be due to unmeasured factors rather than true subgroup effects [57, 58]. Funnel plot asymmetry suggested small-study effects, however asymmetry in meta-analyses of proportions can also reflect clinical or methodological heterogeneity, so this should be interpreted cautiously [32]. If small-study effect is present, the pooled estimate may overestimate the true incidence. Finally, subgroup analysis by baseline risk (high-risk features vs. broad blunt-trauma populations), although post hoc, was clinically meaningful and improved the applicability of the findings.

Our findings provide the most comprehensive and contemporary evidence to date on the incidence of intra-abdominal injury after a negative CT scan in blunt abdominal trauma. The extremely low risk observed across more than 27,000 patients, particularly in studies using modern MDCT, supports the safety of early discharge in most hemodynamically stable blunt abdominal trauma patients with an initial negative CT scan.

The very low incidence observed across > 27,000 patients, particularly in cohorts imaged with contemporary MDCT, suggests that early discharge may be reasonable for most hemodynamically stable patients with blunt abdominal trauma after a negative initial CT, provided no other concerning clinical features are present. At the same time, the slightly higher incidence in subgroups with high-risk clinical features underscores the importance of individualized assessment.

Conclusion

In patients with blunt abdominal trauma and a negative CT scan, the incidence of intra-abdominal injury is exceedingly low (0.34%). These findings provide robust, contemporary evidence to inform clinical decisions regarding the need for in-hospital observation and support consideration of early discharge in most patients, while recognizing that individuals with high-risk clinical features may warrant closer monitoring.

Abbreviations

BAT

Blunt abdominal trauma

CI

Confidence intervals

CT

Computed tomography

ED

Emergency department

FTT

Freeman–Tukey transformation

GLMM

Generalized linear mixed models

IAI

Intra-abdominal injuries(IAI)

JBI

Joanna Briggs Institute

MDCT

Multi-detector computed tomography

REML

Restricted maximum likelihood

Author contributions

V.Z., L.J.O., and M.C.G. conceived and designed the study. L.J.O., M.C., and J.P.A.I reviewed the literature and conducted the data extraction. V.Z. performed the statistical analysis, and L.J.O., M.C., and J.P.A.I quality assessment. V.Z. drafted the manuscript draft, while L.J.O., M.C., and J.P.A. participated in the editing and revision process. All authors reviewed and approved the final manuscript.

Funding

The authors did not receive funding from any organization for the submitted work.

Data availability

The datasets used and/or analysed during the current study are available from the corresponding author on reasonable request.

Declarations

Ethics approval and consent to participate

Ethical approval was waived as the study involved analysis of previously published data and did not include any new collection of human or animal data.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.