Comparative study of transabdominal ultrasound alone versus combined transabdominal and transvaginal ultrasound in gynecological acute abdomen

Introduction

Gynecological acute abdomen represents a critical clinical condition requiring prompt and accurate diagnosis to prevent serious complications. Among gynecologic causes, ectopic pregnancy remains one of the most frequently encountered emergencies in clinical practice (1), whereas corpus luteum and hemorrhagic ovarian cyst rupture are also recognized as important and increasingly reported causes of acute pelvic pain and hemoperitoneum in reproductive-age women (2). Ectopic pregnancy, occurring in approximately 1–2% of pregnancies, carries significant morbidity and mortality when undiagnosed or misdiagnosed. Delayed recognition may lead to tubal rupture, massive hemoperitoneum, and hemodynamic instability, particularly in atypical extra-tubal implantations that are more difficult to visualize (3). Early and reliable diagnosis is therefore essential for preventing catastrophic outcomes and preserving reproductive potential.

Diagnostic evaluation of suspected ectopic pregnancy and other gynecologic acute abdominal conditions relies on clinical assessment, serum beta-human chorionic gonadotropin (β-hCG) dynamics, and imaging. Integrating β-hCG changes with ultrasound findings improves diagnostic accuracy in ectopic pregnancy and pregnancy of unknown location (4). Ultrasound is widely accepted as the first-line imaging modality in acute pelvic pain because it is rapid, radiation-free, and readily accessible in emergency settings (5). Current recommendations emphasize pelvic ultrasound—including both transabdominal and transvaginal approaches with Doppler assessment—as the initial study when a gynecologic etiology is suspected (6). When ultrasound findings are inconclusive, magnetic resonance imaging or contrast-enhanced computed tomography may provide additional diagnostic clarification, particularly for extra-pelvic ectopic pregnancies or non-gynecologic causes of acute abdomen (3). Additionally, ultrasound detection of pelvic free fluid should prompt thorough assessment of both adnexae, as it may indicate hemorrhage from ruptured ectopic pregnancy or adnexal torsion (7).

Given the central role of ultrasound in gynecologic emergencies, understanding the complementary strengths of transabdominal and transvaginal techniques is crucial. Transabdominal ultrasound (TA-US) offers a wide field of view and is well suited for evaluating pelvic organs and intraperitoneal fluid. However, its sensitivity may be reduced by obesity, bowel gas, or deep pelvic lesions, limiting its ability to detect early ectopic pregnancies or small adnexal masses (8). Transvaginal ultrasound (TV-US) provides superior spatial resolution and is considered the modality of choice for evaluating first-trimester pregnancies and early ectopic gestations (7). It is also essential for characterizing adnexal pathology such as ovarian cysts, corpus luteum hemorrhage, and adnexal masses (5). In ovarian torsion, TV-US may show characteristic features such as ovarian enlargement and peripheral follicles, although Doppler flow assessment may be unreliable, occasionally resulting in false-negative findings (9). Given that TA-US and TV-US have complementary strengths, their combined use enhances diagnostic confidence and improves detection of ectopic pregnancy, corpus luteum rupture, and adnexal torsion (6). It has been reported that among patients with suspected ectopic pregnancy, the combination of TV-US and TA-US demonstrates a sensitivity of 85.00%, specificity of 90.00%, and accuracy of 93.75% for diagnosing ectopic pregnancy. This report revealed that the combined use of TV-US and TA-US can effectively reduce missed diagnoses and misdiagnoses in ectopic pregnancy, clearly display relevant sonographic features, and help determine the location of ectopic pregnancy (10).

However, existing studies have primarily focused on single disease entities, and there are variations in diagnostic thresholds and operator dependency across different studies, with a lack of systematic comparisons specifically for gynecological acute abdomen. Therefore, this study aims to evaluate and compare the diagnostic value of TA-US alone, TV-US alone, and their combined use in diagnosing gynecological acute abdomen. We present this article in accordance with the STARD reporting checklist (available at https://qims.amegroups.com/article/view/10.21037/qims-2026-0477/rc).

Methods

Ethical approval

The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Medical Ethics Committee of The First Affiliated Hospital, Fujian Medical University (No. 2023057). This study has applied for and been granted exemption from informed consent by the ethics committee.

General data

This study was a single-center, retrospective cross-sectional study. A total of 120 patients with suspected gynecological acute abdomen admitted to the Department of Ultrasound Medicine of The First Affiliated Hospital, Fujian Medical University from January 2023 to October 2024 were retrospectively analyzed, with ages ranging from 24 to 62 years and a mean age of 40.66±5.86 years. All eligible patients meeting the inclusion criteria were consecutively included without selective exclusion. According to the actual ultrasound examination methods received, patients were divided into three groups: TA-US group, TV-US group, and combined group, each comprising 40 cases. The predominant clinical manifestations included acute lower abdominal pain, some accompanied by amenorrhea, cyclic pelvic pain, fever, abdominal distension, and abnormal vaginal bleeding.

Inclusion criteria: (I) diagnosis initially based on ultrasonography and subsequently confirmed by surgery, laparoscopy, or histopathology; (II) complete and intact clinical records; (III) female patients with a marital history or prior sexual activity; (IV) voluntary participation with good compliance.

Exclusion criteria: (I) concomitant malignancies such as hepatic or pulmonary cancer; (II) pregnancy (confirmed intrauterine pregnancy) or lactation; (III) contraindications to ultrasound examinations; (IV) presence of congenital disorders or immunologic abnormalities; (V) history of secondary surgical intervention.

Methodology

Ultrasound examinations were performed by physicians from the Department of Ultrasound Medicine with more than 5 years of experience using a GE E8 color Doppler ultrasound system (GE Healthcare, USA).

• TA-US: a 3.5 MHz abdominal probe was used. For hemodynamically stable patients, 500–750 mL of warm water was given orally, while ultrasound equipment setup, patient positioning, and other preparations were completed simultaneously, allowing natural bladder filling during the time from water intake to the start of the examination. If patients could not tolerate oral intake or had contraindications (e.g., nausea and vomiting), a 16 Fr-Foley catheter was inserted via the urethra under strict aseptic technique, and 300–400 mL of normal saline was slowly instilled to achieve rapid bladder opacification. The pelvis was evaluated in transverse, longitudinal, and oblique planes using two-dimensional imaging to identify abnormal pelvic masses, free fluid, gestational sacs, or other pathological findings.
• TV-US: a 7.5-MHz endovaginal probe was utilized. Patients emptied their bladders and were placed in the lithotomy position. The probe was covered with a disposable sheath, and sterile coupling gel was applied. Multiplanar scanning was conducted to assess pelvic anatomy, including detection of pelvic fluid effusion, abnormal adnexal or uterine masses, rectouterine pouch changes, endometrial contour abnormalities, and atypical pelvic echoes. Color Doppler imaging was adopted to evaluate the vascularity of suspicious lesions (Table S1).

Observation indicators

Two or more diagnostic physicians from the ultrasound department with more than 5 years of experience (at least one holding the title of attending physician) independently reviewed the acquired ultrasound images using a double-blind method. In cases of disagreement, a consensus was reached through joint discussion. Comprehensive clinical diagnosis [including last menstrual period, intraoperative findings, laparoscopic examination results, laboratory test results (serum β-hCG levels, etc.), or postoperative pathological results] served as the reference standard for evaluating the diagnostic performance of TA-US, TV-US, and their combined application in detecting gynecological acute abdominal disorders, as well as for assessing their agreement with the final clinical diagnosis.

A true positive (TP) was defined as a positive finding on ultrasound consistent with the pathology-confirmed diagnosis. A false positive (FP) referred to positive sonographic results in any modality (TA-US, TV-US, or combined) while the gold standard indicated a negative outcome. A false negative (FN) indicated negative ultrasound findings that contradicted a positive pathological diagnosis. A true negative (TN) was recorded when all ultrasound assessments were negative and pathology confirmed the absence of gynecological acute abdominal disease. Diagnoses consistent with gynecologic acute abdomen were classified as positive; those unrelated to gynecologic causes were recorded as negative. Diagnostic performance was assessed using accuracy, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV): accuracy = (TP + TN)/total cases × 100%; sensitivity = TP/(TP + FN) × 100%; specificity = TN/(TN + FP) × 100%; PPV = TP/(TP + FP) × 100%; NPV = TN/(TN + FN) × 100%.

The positive diagnostic criteria for ectopic pregnancy by TA-US and TV-US were as follows—direct signs: a gestational sac-like structure detected in the adnexal area with visible embryo or primitive cardiac pulsation (highly specific); indirect signs: thickened endometrium without intrauterine gestational sac, mixed adnexal mass, free pelvic fluid (especially in the pouch of Douglas). The positive diagnostic criteria for corpus luteum rupture are—direct signs: cystic structure within the ovary (corpus luteum cyst) with a rupture opening, or heterogeneous echogenicity within the cyst (clot formation); indirect signs: irregular hypoechoic area around the cyst (hematoma), free pelvic fluid (usually less than in ectopic pregnancy), color Doppler showing peripheral blood flow signals around the cyst (corpus luteum blood flow characteristics), which may weaken or disappear after rupture. The above diagnostic criteria and protocols reference the guideline recommendations of the International Society of Ultrasound in Obstetrics and Gynecology and the European Society of Emergency Radiology (11,12).

Statistical analysis

Data processing was carried out with IBM SPSS Statistics, version 26.0 (IBM Corp., Armonk, NY, USA). Categorical data were expressed as rates or proportions and analyzed using the chi-square test. Continuous data were first tested for normality using the Shapiro-Wilk test. Normally distributed data were presented as mean ± standard deviation (X¯±s), and comparisons between two groups were performed using the independent samples t-test. Non-normally distributed data were presented as median and interquartile range [M (P25–P75)], and comparisons between two groups were performed using the Mann-Whitney U test. Consistency was evaluated using the Kappa test, with a Kappa value ≥0.75 indicating good consistency, suggesting that the diagnostic results are highly reliable and can serve as an important reference in clinical practice.

Results

Clinical comprehensive diagnosis

A total of 158 patients with suspected gynecological acute abdomen who underwent examination at the Ultrasound Department between January 2023 and October 2024 were initially screened from the database. After strict application of inclusion and exclusion criteria: 132 patients met the basic inclusion criteria; 7 were excluded due to incomplete data (e.g., missing ultrasound images, incomplete clinical records), and 5 were excluded due to exclusion criteria (2 cases of concurrent malignancy, 2 cases of intrauterine pregnancy, 1 case of ultrasound contraindication). Among the 120 patients evaluated for suspected gynecologic acute abdomen, 65 were ultimately diagnosed with ectopic pregnancy (54.17%) and 39 with corpus luteum rupture (32.50%). The remaining 16 cases (13.33%) included disorders such as endometriosis and degenerative changes of uterine fibroids.

Baseline characteristics

No differences were noted in baseline variables such as age, body mass index (BMI), medical history, or disease type among the three groups (P>0.05) (Table 1).

Detection rates across the three ultrasound approaches

Using TA-US, the detection rates for ectopic pregnancy and corpus luteum rupture were 69.57% (16/23) and 75.00% (9/12), respectively. TV-US achieved detection rates of 77.27% (17/22) and 83.33% (10/12). The combined modality showed higher performance, identifying all ectopic pregnancy cases (100.00%, 20/20) and 93.33% (14/15) of corpus luteum rupture cases. The improvement, particularly in the recognition of ectopic pregnancy, reached statistical significance (P<0.05) (Table 2).

Assessment between each diagnostic method with the comprehensive clinical diagnosis

For gynecologic acute abdomen overall, TA-US detected 70.00% (28/40) of cases, TV-US detected 77.50% (31/40), and the combined approach detected 95.00% (38/40). The combined examination demonstrated a significantly higher diagnostic yield than either single modality (χ²=8.498, P=0.014) and showed strong concordance with comprehensive clinical diagnostic outcomes (P<0.05) (Table 3).

Accuracy, sensitivity, specificity, PPV, and NPV of the three ultrasound approaches

The accuracy, sensitivity, specificity, PPV, and NPV of TA-US for diagnosing gynecological acute abdomen were 70.00%, 71.43%, 60.00%, 92.59%, and 23.08%, respectively; those of TV-US were 77.50%, 79.41%, 66.67%, 93.10%, and 36.36%, respectively; and those of the combined examination were 95.00%, 97.14%, 80.00%, 97.14%, and 80.00%, respectively. The accuracy and sensitivity of the combined examination were higher than those of TA-US or TV-US alone, and the NPV of combined examination was higher than that of TA-US alone. All differences were statistically significant (all P<0.05) (Table 4).

Case analysis

• Case 1: a 36-year-old woman presented with symptoms suggestive of ectopic pregnancy. Routine transabdominal early pregnancy color Doppler ultrasound showed no obvious gestational sac echo in the uterine cavity, thickened endometrium with heterogeneous echogenicity, and a small amount of pelvic fluid (Figure 1A,1B).
  

  Figure 1 Transabdominal ultrasound findings in a 36-year-old woman with ectopic pregnancy.
• Case 2: a 31-year-old woman was diagnosed with corpus luteum rupture. Transvaginal color Doppler imaging revealed a cystic lesion within the left ovary surrounded by clot formation, along with mild pelvic effusion, findings characteristic of hemorrhagic corpus luteum rupture (Figure 2A,2B).
  

  Figure 2 Transvaginal ultrasound findings in a 31-year-old woman with corpus luteum rupture.

Discussion

The diagnosis of gynecological acute abdomen is often difficult because its symptoms resemble other abdominal emergencies, underscoring the need for rapid and accurate imaging (13). Although TV-US is generally preferred for its superior visualization of pelvic structures, especially in early pregnancy and ectopic pregnancy assessment (7), both TA-US and TV-US have method-specific limitations. In this study, we compared the diagnostic value of the two modalities. The results showed that combined TA-US and TV-US were superior to either single method in terms of overall detection rate, accuracy, sensitivity, and NPV.

The results of this study showed that the combined TA-US and TV-US examination achieved higher detection rates for ectopic pregnancy and corpus luteum rupture than TA-US alone or TV-US alone. This indicated that the combined application of the two ultrasound methods achieved technical complementarity—TA-US provides a global overview, while TV-US provides local detail—thereby enhancing the detection capability for adnexal emergencies (14,15). The study by Zhang et al. also confirmed that the sensitivity of the combined examination for adnexal emergencies (84%) is higher than that of TA-US alone (72%) and TV-US alone (76%) (16), which is consistent with our findings.

In terms of overall detection rate, the combined TA-US and TV-US examination was also superior to either single method and showed higher consistency with the final clinical comprehensive diagnosis. This may be because the combined examination can simultaneously provide a global overview of the pelvis along with local details, thereby more comprehensively covering the imaging information upon which the clinical diagnosis is based, resulting in better concordance with the final clinical comprehensive judgment. Furthermore, in our study, the diagnostic accuracy of the combined examination was 95.00% with a sensitivity of 97.14%, both higher than those of TA-US and TV-US alone. This result is similar to the diagnostic study by Zhang et al., which showed that in patients with suspected ovarian cyst torsion, the combined TV-US and TA-US increases sensitivity to 84%, specificity to 72.2%, and area under the curve (AUC) to 0.781, with both accuracy and AUC significantly superior to TA-US alone (16), suggesting that combined examination can further improve diagnostic precision and provide important value for early diagnosis and treatment decision-making (16). Furthermore, Thom et al. confirmed the clinical value of the combined ultrasound strategy from another perspective. Their study found that among emergency early pregnancy patients in whom intrauterine pregnancy had been confirmed by TA-US, supplementary TV-US still identified 15 cases of subchorionic hematoma and 3 cases of ovarian cysts, among other additional pathologies, indicating that even when TA-US yields a positive result, transvaginal examination still has incremental diagnostic value (14). Notably, in our study, the PPV of TA-US, TV-US, and the combined examination were all relatively high, indicating that positive results have high confirmatory value, with the main differences being reflected in the ability to exclude disease. The NPV of TA-US alone was only 23.08%, implying an extremely high risk of missed diagnosis, whereas the NPV of the combined examination increased to 80.00%, significantly reducing the probability of missed diagnosis. Shibata et al. also noted in their review that relying solely on TA-US to exclude gynecological acute abdomen is an unreliable strategy, and recommended routinely supplementing with TV-US in patients with high clinical suspicion (17).

Based on the above findings, the following clinical recommendations are proposed for reference. First, for women of reproductive age with high clinical suspicion of gynecological acute abdomen, if the initial TA-US result is negative, caution should be exercised in excluding the diagnosis of acute abdomen, and supplementary TV-US should be considered. The low NPV of TA-US in this study suggests that relying solely on a negative TA-US result carries a certain risk of missed diagnosis. Second, the combined examination demonstrated high diagnostic efficacy in this study and may be considered as one of the preferred protocols for ultrasound evaluation of gynecological acute abdomen. Third, the PPV of all three examination methods was relatively high, indicating that positive results have good confirmatory reference value; however, the NPV varied considerably, and caution is advised in interpreting negative results. Fourth, for patients at high risk of ectopic pregnancy (e.g., women who conceived through assisted reproductive technology or those with an intrauterine device in situ), even if TA-US shows an intrauterine pregnancy, TV-US may be considered at the clinician’s discretion to help exclude the possibility of a heterotopic pregnancy. Fifth, ultrasound reports are recommended to include detailed descriptions of adnexal findings, in order to provide more comprehensive imaging evidence for clinical decision-making.

However, this study has the following limitations. First, as a retrospective study, it may be subject to selection bias and information bias. Second, the relatively limited sample size may have affected the statistical power of subgroup analyses; the small number of cases for certain disease entities made stratified analysis difficult. Third, the case composition of this study was dominated by ectopic pregnancy and corpus luteum rupture. This disease spectrum was determined by the inclusion criteria. Therefore, this study reflects the characteristics of a high-risk population with high clinical suspicion of gynecological acute abdomen and eventual confirmed diagnosis, rather than all emergency department patients presenting with acute abdominal pain. In the real emergency setting, the etiologies of acute abdominal pain are more diverse; thus, the conclusions of this study should be cautiously extrapolated to specific populations with high clinical suspicion, rather than all patients with abdominal pain. Fourth, ultrasound examination carries a degree of subjectivity, and this study did not evaluate inter-operator agreement, which may affect the reproducibility of the results. Fifth, the actual impact of combined examination on clinical decision-making (e.g., timing of surgery, adjustment of treatment plans) and patient outcomes was not explored.

To address these limitations, future research can be improved in the following aspects. First, a prospective design is recommended, with strict adherence to sample size estimation and clinical trial registration requirements, to enhance the scientific rigor and level of evidence. Second, the sample size should be expanded and more disease entities included to comprehensively evaluate the diagnostic efficacy of combined ultrasound across different types of gynecological acute abdomen. Third, future studies should integrate multidimensional clinical symptom variables (e.g., pain characteristics, volume of bleeding, β-hCG levels) with sonographic features to develop clinical-imaging composite diagnostic models. Fourth, a multidisciplinary collaboration mechanism between radiology and gynecology is recommended, with regular case discussions and imaging-pathology correlation analyses to further validate and optimize the diagnostic concordance of ultrasound in gynecological acute abdomen. Fifth, inter-operator agreement studies for ultrasound, as well as health economic evaluations of the impact of combined ultrasound on clinical decision-making and patient outcomes, could be conducted to provide more robust evidence for clinical implementation.

Conclusions

In summary, this study revealed that combined TA-US and TV-US improved the diagnostic accuracy, sensitivity, and NPV for gynecological acute abdomen, with particularly evident advantages in detecting ectopic pregnancy and corpus luteum rupture. The NPV of the combined examination was higher than that of TA-US alone, suggesting that for patients with high clinical suspicion of gynecological acute abdomen, a negative TA-US result alone should not be used as a basis for exclusion, and routine supplementary TV-US is recommended. The combined examination strategy should be adopted as the recommended protocol for ultrasound diagnosis of gynecological acute abdomen.

Acknowledgments

None.

Footnote

Reporting Checklist: The authors have completed the STARD reporting checklist. Available at https://qims.amegroups.com/article/view/10.21037/qims-2026-0477/rc

Data Sharing Statement: Available at https://qims.amegroups.com/article/view/10.21037/qims-2026-0477/dss

Funding: None.

Conflicts of Interest: Both authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-2026-0477/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki and its subsequent amendments. The study was approved by the Medical Ethics Committee of The First Affiliated Hospital, Fujian Medical University (No. 2023057). This study has applied for and been granted exemption from informed consent by the ethics committee.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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