When ideal positioning is impossible: can we limit pediatric gastric ultrasound to the supine semi-recumbent position?

This commentary uses the study by Cercueil et al. (1) as an opportunity to reexamine the role of preoperative gastric ultrasound in pediatric anesthesia. Instead of advocating for its universal adoption, the aim is to situate gastric ultrasound within a realistic clinical context by highlighting both the strengths of the semi‑recumbent approach and the limitations that constrain its use, including modest diagnostic accuracy, uncertain cutoffs for “at-risk” volumes, and variable feasibility in higher-risk patients. The central question is not whether gastric ultrasound can be performed but when, how, and in whom it meaningfully alters risk assessment and management.

Recently, Cercueil et al. (1) performed an important investigation that contributes to the growing body of literature on the utility of preoperative gastric ultrasound in pediatric patients. The authors conducted a prospective, observer-blinded, randomized case-control investigation that employed gastric ultrasound before and after ingestion of five specific volumes of water (from 0 to 2 mL/kg) in 90 healthy children aged 1–10 years. Anesthesiologists with expertise in gastric ultrasound performed the scans, with the patients in the supine 45° semi-recumbent and the right lateral decubitus (RLD) 45° semi-recumbent positions. The semi-recumbent position was chosen based on adult literature, which shows it to be highly sensitive and to have a negative predictive value for detecting high gastric fluid volumes (defined in previous studies as either >1.5 or >0.8 mL/kg) or an empty stomach (2-4). Considering that this position had not been examined in pediatric populations, this study additionally aimed to validate it.

Gastric content was evaluated through both qualitative assessment (i.e., categorizing the stomach as empty vs. non-empty) and quantitative estimation of residual volume. The latter employed a clinical algorithm similar to the one previously published by Bouvet et al. (4), alongside the mathematical model for gastric content calculation developed by Spencer et al. (5). Patients with a gastric volume >1.25 mL/kg were considered at risk of gastric content aspiration. The authors reported a sensitivity of 75% and a specificity of 85% for the qualitative assessment, and 86% and 78% when the algorithm was employed.

Among the notable strengths of the study by Cercueil et al. (1) are its rigorous methodological controls and careful blinding. The investigators eliminated variability in baseline residual gastric content by ensuring that all participants underwent a pre-scan to confirm an empty stomach before fluid ingestion. Furthermore, the study team precisely measured and recorded the volume consumed by each child, keeping the sonographers blinded to this information, thereby making the assessment of gastric content both objective and reproducible. This design provided a high degree of confidence in estimating sensitivity and specificity without relying on indirect assumptions or invasive validation approaches, such as gastric suctioning.

With advances in technology, increased familiarity, and lower costs, portable ultrasound has evolved from a tool used solely for regional anesthesia and central line placement to a versatile instrument for a variety of targeted, practical applications (6). Point-of-care ultrasound is now employed for focused assessment of the airway, lung, heart, and abdomen (6). In particular, gastric ultrasound to determine the patient’s fasting status appears to provide valuable information on the risk of pulmonary aspiration. Attempts to mitigate this risk often result in the last-minute cancellation of elective surgery when patients do not adhere to institutional fasting guidelines (7), delays in urgent procedures, or unacceptable extended fasting periods (8). More importantly, up to 78% of families do not understand the importance of perioperative fasting (9), which leads to as many as 13.5% of parents feeding their children before surgery, leaving them improperly fasted at the time of induction (10). Historically, the rationale for employing rapid sequence induction was that avoiding positive-pressure ventilation in patients with a full stomach would prevent gastric insufflation and subsequent regurgitation (11,12). However, emerging evidence suggests that gentle bag-mask ventilation with low pressures (10–12 cmH₂O) is unlikely to insufflate the stomach of pediatric patients (13). Pulmonary aspiration remains a rare event, occurring in fewer than 5 out of 10,000 cases, but it can lead to significant morbidity (14,15). When it does occur, it is generally not due to mask ventilation but rather to intrinsic pathology or delayed gastric emptying (16).

In contrast to adults, evidence on the utility of gastric ultrasound in the pediatric population remains limited. Significant contributions have been made by Spencer et al. and Schmitz et al. (5,17), in which ultrasound-measured cross-sectional area correlates with gastric volumes measured in the RLD recumbent position by endoscopy aspiration [coefficient of determination (R²) =0.60] and magnetic resonance imaging (R² =0.62), respectively. Additionally, these studies showed that the RLD recumbent position provides the most effective window for assessing the gastric antrum. However, these groups’ sample sizes, methods of gastric volume measurement, and patient ages as well as, importantly, nil per os status of participants vary significantly.

Cercueil et al.’s (1) study is particularly interesting for its robust methodology and innovative design. Rather than employing techniques such as blind suctioning (18), endoscopic aspiration (5), or magnetic imaging (17) to measure residual gastric volume, the authors randomized the cohort into six groups receiving predetermined water volumes, thereby closely replicating real clinical scenarios. The study also has significant results that warrant a detailed discussion.

Because the primary intent of a gastric ultrasound is to exclude significant gastric residual volume, high sensitivity is crucial. In Cercueil et al.’s study (1), qualitative and quantitative methods show positive likelihood ratios of 5.06 and 3.88, respectively. Conversely, the negative likelihood ratios were 0.29 and 0.18, respectively. When the described clinical algorithm was used, the sensitivity was 86%, and the negative predictive value was 89%, yielding positive and negative likelihood ratios of 3.88 and 0.18, respectively. As a rule of thumb, positive likelihood >10 and negative likelihood <0.1 indicate a strong diagnostic test (1). Based on Cercueil et al.’s data, a gastric ultrasound would be useful only in the presence of high suspicion of a significant residual volume in the stomach (i.e., high pretest probability).

Although the point estimates of sensitivity and specificity were moderate to good, the relatively wide confidence intervals (with lower bounds near 60%) indicate limited precision and suggest that the true test performance could be meaningfully lower than the point estimates imply. Several factors may contribute to this result, including the employment of two different assessors and the age of the cohort. Cercueil et al.’s study relied on a previously developed predictive model (5) for pediatric gastric volume using ultrasound measurements and backward stepwise linear regression on seven candidate variables. Ultimately, Spencer et al. (5) in the original investigation identified RLD recumbent position antral cross-sectional area and age as the only independent predictors. The resulting model demonstrated good explanatory performance (R² =0.60), and RLD recumbent position antral area showed the strongest predictive contribution. However, contrary to an R² of 0.60 reported in investigations employing older children (median age 12 years) (5), the Spencer model in Cercueil et al.’s (1) study enrolled younger patients (median age 7 years), and showed correlation coefficient (r) of 0.67 (equivalent to an R² of 0.45), leaving 55% of the estimated gastric volume variance unexplained. This decline in the predictive power of the Spencer model underscores the even greater significance of qualitative assessment in younger populations.

It should also be noted that the study was conducted in healthy, cooperative children and did not include patients at increased risk of pulmonary aspiration, who constitute the population in whom preoperative gastric ultrasounds would be most clinically relevant. Although no single risk factor has been conclusively validated as predictive of aspiration in children (19), it is reasonable to assume that conditions such as trauma, neurologic impairment, sepsis, obesity, diabetes, and disorders affecting esophageal, gastric, or duodenal function are associated with altered gastric emptying and a higher probability of clinically significant residual gastric contents. In a recent investigation (20), up to 37% of children who underwent urgent orthopedic procedures had a gastric residual volume greater than 1.5 mL/kg, including 24% with solid or thick liquids at the time of the intervention. In this context, validating the semi‑recumbent position as an alternative scanning position in healthy children is an important methodological step, but further work will be needed to confirm that these findings extend to higher‑risk populations in whom relevant gastric content is more prevalent.

It is also worth noting that the RLD position is not always feasible, leading the anesthesiologist to rely on the gastric ultrasound in the supine position, which has been shown to have limited value. For instance, the RLD position can be achieved in less than 50% of cases when lower-body extremity fractures are present, whereas visualization of the antrum in the supine position may be inconclusive in a substantial proportion of patients (20), particularly in the context of pain, distress, comorbidities, or recent intake of solids and liquids, all of which can increase intragastric air and impair image quality. Cercueil et al. (1) did not report positioning issues, likely because the cohort was healthy [American Society of Anesthesiologists-physical status (ASA-PS) 1, aged 1–10 years] and compliant with the examination. In daily practice, however, barriers such as acute abdominal pain and lower extremity fractures remind us of the limited generalizability of these results.

Finally, it should be noted that Cercueil et al. (1) used a threshold of 1.25 mL/kg to define gastric volume at risk, a criterion observed in approximately 1-5.7% of fasted pediatric patients undergoing elective surgery (5,18,21). However, other studies employed a more conservative threshold of 0.8 mL/kg, based on a primate model showing increased severity of pneumonitis and higher mortality when this volume of acidified gastric content was instilled into the trachea (22). Hence, the 1.25 mL/kg threshold is essentially distribution‑based, corresponding to approximately the 95th percentile of gastric volumes in fasted children, rather than being derived from outcome data on aspiration risk. This makes it statistically convenient but clinically somewhat arbitrary.

Further semi-quantitative assessments can be performed using the Perlas Grading System, which stratifies risk based on assessments of the contents of the RLD and supine recumbent positions (23). Using a modified Perlas Grading System, Gagey et al. modified their induction technique in 47% of urgent or emergency pediatric cases (24) and avoided rapid sequence induction in over 85% of patients presenting for pyloromyotomy (25). With a risk threshold of more than 0.8 mL/kg of gastric volume, visualization of a grade 1 or 2 antrum exhibited 94% sensitivity, 83% specificity, 85% positive predictive value, and 93% negative predictive value in distinguishing high-risk from low-risk cases.

Cercueil et al.’s (1) data and the current literature confirm important limitations in the use of gastric ultrasound in children. First, the 45° semi-recumbent supine approach is insufficient for rapid, reliable screening. Any information needs to be validated in the RDL position, either recumbent or semi-recumbent, although this is not always feasible (20). Second, using clinical algorithms seems to improve performance but still does not achieve the level of certainty for decision-making in high-stakes settings. Third, the qualitative assessment has some clinical utility in confirming whether the stomach is empty, but not in identifying patients at risk of aspiration.

Thus, there is no convincing evidence to support the routine use of gastric ultrasound in children to assess gastric residual volume. As noted above, clinically significant pulmonary aspiration after standard anesthesia induction is rare. Finally, competency in gastric ultrasound likely entails a considerable learning curve that has not yet been quantified and may hinder the use of this technique among inexperienced anesthesiologists.

These factors have relegated gastric ultrasound to a marginal role in anesthesia practice. Despite these limitations, gastric ultrasound should not be dismissed entirely. The technique has genuine potential, albeit likely in specific niches rather than as a universal tool. Even if it struggles at the individual level, ultrasound remains valuable for understanding population-level patterns. These include gastric emptying kinetics, comparisons of feed types, and the development of age-based models.

The 2022 European Society of Anaesthesiology and Intensive Care (ESAIC) guidelines on perioperative fasting in children suggested that gastric ultrasound may be used in children undergoing elective surgery when fasting instructions have not been adhered to, and in emergency surgery (19). It is worth noting that these current clinical guidelines recommend qualitative grading for its simplicity.

One important question that remains unanswered is which gastric volume cutoff should be considered clinically relevant in children. Since pulmonary aspiration is rare, even in “high-risk” settings, it is unlikely that a single, empirically derived milliliter-per-kilogram threshold will be directly validated against aspiration events. Therefore, future studies will likely need to combine physiological reasoning, observational data on residual volumes across different risk groups, and expert consensus to define practical cutoffs that balance sensitivity, specificity, and acceptable risk tolerance in various clinical contexts. An important next step would be to reanalyze datasets, such as that of Cercueil et al. (1), to determine which gastric volume cutoffs maximize sensitivity, specificity, and predictive values across clinically relevant ranges. These analyses would enable clinicians to use semi-recumbent gastric ultrasounds to more confidently answer specific questions, such as whether the gastric volume is highly likely to be above or below a specific value. This information can then be integrated along with comorbidities, the type and urgency of surgery, airway assessment, and overall risk tolerance. Although the gastric volume cutoff of the test may be more or less conservative regarding aspiration risk, making clinical decisions with higher predictive value may prove superior to those based on a likely arbitrary cutoff value of 1.25 mL/kg.

The Cercueil et al. (1) study also serves as a reminder of the challenges associated with translating adult data to pediatric settings, as well as the importance of conducting rigorous investigations before broadly adopting tools that, at first glance, may seem effective and straightforward to implement. When appropriately considered, gastric ultrasound constitutes a valuable clinical tool. It serves as a perioperative resource that can swiftly assist with risk stratification and guide anesthesiologists in selected cases. Therefore, it should be employed as one component of the decision-making toolkit prior to anesthesia. Future studies must address the ‘real-world’ feasibility of these algorithms in uncooperative children or those with habitus that preclude clear antral visualization, factors notably absent in Cercueil’s cohort.

Acknowledgments

The authors used DeepL Write Pro and Grammarly solely to improve readability and English grammar. All content and interpretations are the authors’ own, and the authors take full responsibility for the final manuscript.

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Translational Pediatrics. The article has undergone external peer review.

Peer Review File: Available at https://tp.amegroups.com/article/view/10.21037/tp-2026-1-0062/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://tp.amegroups.com/article/view/10.21037/tp-2026-1-0062/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.

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/.

References

1. Cercueil E, Henriet A, Barbe C, et al. Diagnostic accuracy of qualitative gastric ultrasound assessment for detecting high gastric fluid volume in children: a prospective randomised study. Anaesthesia 2025;80:636-44. [Crossref] [PubMed]
2. Bouvet L, Miquel A, Chassard D, et al. Could a single standardized ultrasonographic measurement of antral area be of interest for assessing gastric contents? A preliminary report. Eur J Anaesthesiol 2009;26:1015-9.
3. Bouvet L, Cordoval J, Barnoud S, et al. Diagnostic performance of qualitative ultrasound assessment for the interpretation of point-of-care gastric ultrasound to detect high gastric fluid volume: A prospective randomized crossover study. J Clin Anesth 2022;81:110919. [Crossref] [PubMed]
4. Bouvet L, Desgranges FP, Barnoud S, et al. Diagnostic accuracy of a simple qualitative ultrasound assessment for the diagnosis of empty stomach in the adult: A supplementary analysis of a prospective observer-blind randomized crossover study. Acta Anaesthesiol Scand 2023;67:1202-9. [Crossref] [PubMed]
5. Spencer AO, Walker AM, Yeung AK, et al. Ultrasound assessment of gastric volume in the fasted pediatric patient undergoing upper gastrointestinal endoscopy: development of a predictive model using endoscopically suctioned volumes. Paediatr Anaesth 2015;25:301-8. [Crossref] [PubMed]
6. Adler AC, Matisoff AJ, DiNardo JA, et al. Point-of-care ultrasound in pediatric anesthesia: perioperative considerations. Curr Opin Anaesthesiol 2020;33:343-53. [Crossref] [PubMed]
7. Lima LACN, Brown K, Sbrocchi AM, et al. A retrospective audit of same day cancellations in a Canadian tertiary paediatric hospital post implementation of a structured preoperative evaluation clinic. Eur J Anaesthesiol 2023;40:377-80. [Crossref] [PubMed]
8. Frykholm P, Modiri AR, Klaucane A, et al. Impact of liberal preoperative clear fluid fasting regimens on the risk of pulmonary aspiration in children (EUROFAST): an international prospective cohort study. Br J Anaesth 2025;135:141-7. [Crossref] [PubMed]
9. Walker H, Thorn C, Omundsen M. Patients' understanding of pre-operative fasting. Anaesth Intensive Care 2006;34:358-61. [Crossref] [PubMed]
10. Cantellow S, Lightfoot J, Bould H, et al. Parents' understanding of and compliance with fasting instruction for pediatric day case surgery. Paediatr Anaesth 2012;22:897-900. [Crossref] [PubMed]
11. Engelhardt T. Rapid sequence induction has no use in pediatric anesthesia. Paediatr Anaesth 2015;25:5-8. [Crossref] [PubMed]
12. Cools E, Habre W. Rapid sequence induction in Paediatric Anaesthesia: A narrative review. Trends in Anaesthesia and Critical Care 2023;49:101215.
13. Neuhaus D, Schmitz A, Gerber A, et al. Controlled rapid sequence induction and intubation - an analysis of 1001 children. Paediatr Anaesth 2013;23:734-40. [Crossref] [PubMed]
14. Pfaff KE, Tumin D, Miller R, et al. Perioperative aspiration events in children: A report from the Wake Up Safe Collaborative. Paediatr Anaesth 2020;30:660-6. [Crossref] [PubMed]
15. Andersson H, Zarén B, Frykholm P. Low incidence of pulmonary aspiration in children allowed intake of clear fluids until called to the operating suite. Paediatr Anaesth 2015;25:770-7. [Crossref] [PubMed]
16. Newton R, Hack H. Place of rapid sequence induction in paediatric anaesthesia. BJA Education 2016;16:120-3.
17. Schmitz A, Schmidt AR, Buehler PK, et al. Gastric ultrasound as a preoperative bedside test for residual gastric contents volume in children. Paediatr Anaesth 2016;26:1157-64. [Crossref] [PubMed]
18. Cook-Sather SD, Liacouras CA, Previte JP, et al. Gastric fluid measurement by blind aspiration in paediatric patients: a gastroscopic evaluation. Can J Anaesth 1997;44:168-72. [Crossref] [PubMed]
19. Frykholm P, Disma N, Andersson H, et al. Pre-operative fasting in children: A guideline from the European Society of Anaesthesiology and Intensive Care. Eur J Anaesthesiol 2022;39:4-25. [Crossref] [PubMed]
20. Evain JN, Durand Z, Dilworth K, et al. Assessing gastric contents in children before general anesthesia for acute extremity fracture: An ultrasound observational cohort study. J Clin Anesth 2022;77:110598. [Crossref] [PubMed]
21. Bouvet L, Bellier N, Gagey-Riegel AC, et al. Ultrasound assessment of the prevalence of increased gastric contents and volume in elective pediatric patients: A prospective cohort study. Paediatr Anaesth 2018;28:906-13. [Crossref] [PubMed]
22. Raidoo DM, Rocke DA, Brock-Utne JG, et al. Critical volume for pulmonary acid aspiration: reappraisal in a primate model. Br J Anaesth 1990;65:248-50. [Crossref] [PubMed]
23. Perlas A, Davis L, Khan M, et al. Gastric sonography in the fasted surgical patient: a prospective descriptive study. Anesth Analg 2011;113:93-7. [Crossref] [PubMed]
24. Gagey AC, de Queiroz Siqueira M, Monard C, et al. The effect of pre-operative gastric ultrasound examination on the choice of general anaesthetic induction technique for non-elective paediatric surgery. A prospective cohort study. Anaesthesia 2018;73:304-12.
25. Gagey AC, de Queiroz Siqueira M, Desgranges FP, et al. Ultrasound assessment of the gastric contents for the guidance of the anaesthetic strategy in infants with hypertrophic pyloric stenosis: a prospective cohort study. Br J Anaesth 2016;116:649-54. [Crossref] [PubMed]