Abstract
Background:
When performing endoscopic ultrasound (EUS) using a miniature probe, filling the lumen with water is necessary. However, because of gravity and peristalsis, satisfactory images are often not obtained. Recently, it has been reported that injecting a viscous gel instead of water could facilitate EUS imaging.
Objectives:
To determine if EUS performed with rehydration jelly returned interpretable images when the standard method did not.
Design:
Prospective cohort study.
Methods:
EUS was first attempted in 50 patients using the conventional water-filling method; in cases where satisfactory images were not obtained, EUS was additionally performed using oral rehydration jelly (OS-1). Five endoscopists evaluated the obtained images, and their outcomes were examined.
Results:
Satisfactory images were not obtained in 34 cases when using the water-filling method. The images obtained using the jelly method were improved compared to the water-filling method in 29 cases, with a significant improvement in 18 cases. No complications were observed with the jelly method.
Conclusion:
For EUS, the jelly method will likely yield good images when satisfactory image quality cannot be obtained using the water-filling method.
Plain language summary
Endoscopic ultrasound (EUS) is a medical technique used to examine organs in the digestive system, such as the esophagus and stomach. For accurate imaging, water is usually injected to fill the space between the ultrasound probe and the tissue being examined. However, sometimes water doesn’t stay in place due to body movements or gravity, making it hard to get clear images. This study tested a new approach using an oral rehydration jelly, called OS-1, instead of water during EUS. The jelly is safe to eat and flows more slowly than water, helping it stay in place during the procedure. Fifty patients were included in this study. If the images taken with water were not clear enough, the jelly was then used. The quality of the images taken with jelly was judged by experts and compared to those taken with water. Results showed that the jelly method significantly improved image quality, especially in hard-to-see areas like the esophagus. It also caused no harmful side effects, and no cases of nausea or aspiration were observed with the jelly. In conclusion, using oral rehydration jelly instead of water can make EUS safer, faster, and more effective in certain cases, especially when water doesn’t work well.
Introduction
Among the endoscopic ultrasound (EUS) techniques, the probe method using a miniature probe is frequently employed to diagnose depth in determining treatment strategies for gastrointestinal cancers, evaluating the hemodynamics of esophageal varices, and assessing treatment effects after sclerotherapy. In the EUS probe method, filling the space between the lesion and the probe with water is necessary as a precondition. However, depending on the location of the lesion, there may be cases requiring the injection of a large amount of water due to gravity or peristalsis or instances where water retention does not occur. To overcome this issue, Yamada et al. 1 reported filling the duodenum with jelly instead of water for EUS. Esaki et al. compared EUS of superficial esophageal cancer using balloon-assisted water-filling and jelly-filling methods. They reported the superiority of the jelly method. 2 Conventional medical gels are highly viscous and require considerable force for injection through the forceps channel and dedicated tubes to prevent backflow. In addition, extracting the gel from the gastrointestinal tract post-observation requires time and effort.
Yano et al. 3 reported the use of OS-1 (Otsuka Pharmaceutical Factory, Tokushima, Japan), widely available as an oral rehydration agent, injected through the forceps channel of an endoscope for hemostasis in gastrointestinal bleeding, aiding in visual field confirmation and identification of the bleeding site. 2
Therefore, we investigated the safety and efficacy of oral rehydration jelly (OS-1) as an alternative to water for EUS preconditioning.
Subjects and methods
We recruited 50 consecutive patients who underwent EUS with a miniature probe for tumors of the esophagus, stomach, colon, and esophageal varices. All 50 consecutive patients were included without exclusion. The patients initially underwent EUS with conventional water filling. During the examination, the endoscopist evaluated the quality of the images on a 5-point scale: excellent, 5 points; good, 4 points; acceptable, 3 points; needs to improve, 2 points; and unacceptable, 1 point. If the endoscopist rated the images as 4 points or below, additional EUS with OS-1 was performed. Specifically, the probe was removed, the water in the gastrointestinal tract was aspirated, and OS-1 was injected through the forceps channel using a syringe. The probe was reinserted for EUS. To ensure consistency, we limited the volumes of water and jelly injected to 200 mL. OS-1 was drawn into a 50-mL syringe after pouring it into a separate container, ensuring no air was mixed in, and then injected through the forceps channel. In the esophagus, after injecting sufficient water to fill the upper part of the stomach, as much air as possible was aspirated from the stomach before injecting the necessary amount of water. Similarly, in the case of jelly, after injecting approximately 100 mL of jelly into the stomach, 35–50 mL of jelly was slowly injected into the esophagus for observation.
The images obtained using both the water-filling and jelly methods were evaluated by five experienced specialists from the Japan Gastroenterological Endoscopy Society using the same 5-point scale. The image was provided in a concealed state regarding how it was captured (Figures 1 and 2). Interobserver agreement among the five raters was assessed using Fleiss’ kappa coefficient (κ) for each method. Based on the Landis and Koch criteria, κ values of <0.20, 0.21–0.40, 0.41–0.60, 0.61–0.80, and >0.81 were interpreted as slight, fair, moderate, substantial, and almost perfect agreement, respectively.
Patient selection. For the 34 cases in which satisfactory images could not be obtained using the water-filling method alone, EUS with the jelly method was added. Excluding the five cases with image evaluations of four points or more using the water-filling method, evaluations for all 29 cases improved, with significant improvement noted in 18 cases.
Comparison of images obtained using water filling and jelly methods.
The cases with evaluation scores of less than 4 points in the water-filling method were compared using the Wilcoxon signed-rank test to evaluate and compare the average scores between the water-filling method and the jelly method. In addition to hypothesis testing, we calculated the effect size (r = Z/√N) and conducted a post hoc power analysis using the observed Z value and sample size to evaluate the adequacy of the study power. We also investigated the time elapsed from the start of the jelly injection to the start of the observation and any complications during the examination in this study.
This trial was registered with UMIN000028168, reviewed by the Clinical Research Review Committee of Kanazawa University, and conducted after obtaining approval. Furthermore, informed consent was obtained from all patients before conducting the examinations. All patients received a written explanation of the study and provided written informed consent before participation.
The reporting of this study conforms to the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) statement. 4
Results
The 50 patients had tumors in the following locations: 18 in the esophagus, 29 in the stomach, 1 in the duodenum, and 2 in the colon. Among the esophageal cases, 8 were evaluated for esophageal varices, while the other 42 cases were evaluated for the depth of tumor invasion. Of the 50 patients, 34 (68%) underwent the jelly method; 14 cases in the esophagus (77.8%), 19 in the stomach (65.5%), and 1 in the colon (50%; Table 1). Five specialists evaluated the 34 cases on a scale of 5 points. Five cases were excluded, as the evaluation score of the water method exceeded 4 points, resulting in an evaluation of 29 cases. When all 68 evaluations (water-filling and jelly methods combined) were analyzed, the overall Fleiss’ kappa coefficient was κ = 0.268, indicating fair agreement.
Target cases and rate of transition to jelly method.
There were no cases in which the average score decreased with the jelly method, and the scores significantly improved (Figure 3, p < 0.001, Wilcoxon signed-rank test). The Wilcoxon signed-rank test revealed a significant improvement in image quality scores with the jelly method compared with the water-filling method (W = 1.5, p < 0.001), with a large effect size (r = 0.82). The post hoc power analysis (α = 0.05, two-tailed) indicated very high power (1−β ≈ 0.997).
Image quality scores. When 29 cases where satisfactory images could not be obtained using the water-filling method were transitioned to the jelly method, the image quality evaluation significantly improved in all cases (p < 0.001; Wilcoxon signed-rank test).
Eleven cases showed an improvement of one point or more, while 18 showed an improvement of two points or more. The median time required for jelly injection was 60 s (25–72 s).
Vomiting occurred during one case of esophageal examination using the water method, and no vomiting was observed in any of the cases using the jelly method. No adverse events with both water and jelly methods, such as abdominal pain, nausea, or diarrhea, were observed after the examination.
Discussion
During EUS, it is necessary to fill the space between the observed lesion and the probe with water. However, depending on its location in the gastrointestinal tract and peristalsis, there may be a need to inject a large amount of water, or water may not be retained due to gravity. Moreover, the presence of residual debris, mucus, or bubbles mixed in the water can hinder observations, leading to time-consuming procedures or unsatisfactory imaging. Water retention is particularly challenging in narrow lumens, such as the esophagus. Although methods exist for closing the esophageal opening with a soft balloon to prevent reflux and facilitate water filling, they require specialized equipment, incur high costs, and pose risks of complexity, vomiting, or aspiration.
Yamada et al. 1 performed duodenal EUS using a jelly substance instead of water. Esaki et al. compared the EUS of superficial esophageal cancer using a balloon-assisted water-filling method and a jelly-filling method and reported the superiority of the jelly method. However, medical lubricating jelly has high viscosity, requiring a strong force for injection through the forceps channel, dedicated tubes to prevent reflux, and time-consuming aspiration and retrieval of jelly residues after post-observation. 2
Yano et al. 3 reported the utility of OS-1, widely available as an oral rehydration agent, for gastrointestinal endoscopy in patients with gastrointestinal bleeding in the esophagus, small intestine, and colon. OS-1 has lower viscosity than conventional medical gels, requires less force for syringe aspiration and injection through the forceps channel, and shows minimal leakage around the forceps channel. Furthermore, as it is a commercially available food product, it is inherently safe for human use, and unlike conventional gels, it does not require aspiration or retrieval after examination.
The improvement observed with the jelly method over the water method may be attributed to the viscosity of the jelly, which allows it to remain between the observation site and the probe, enhancing the clarity of the gastrointestinal wall layers by jelly advancement and reducing mucosal and bubble interference, thereby decreasing noise. In cases where water retention is challenging, such as lesions in the gastric fornix or air inflow from the pylorus being blocked by jelly, good gastric wall expansion is ensured, and clear observation of the gastric wall layers is facilitated. Jelly reflux beyond the pyloric ring into the duodenum was not observed during the examination.
Furthermore, in esophageal lesions, water often flows quickly into the stomach owing to peristalsis, making it difficult with the water method to have sufficient time for imaging, even with additional water injections. However, when using the jelly method, the jelly remains in the esophagus and is less likely to flow into the stomach, allowing for relaxed observations and imaging. There were no cases of aspiration due to reflux. The results of this study indicate that if satisfactory images cannot be obtained with conventional water-filling during EUS, promptly aspirating water and injecting jelly for observation may provide good images safely and quickly. Although the image evaluations by five expert endoscopists showed only a fair level of interobserver agreement (Fleiss’ κ = 0.268), the generally consistent trend toward improvement with the jelly method still suggests that the findings are informative and clinically meaningful.
Furthermore, beyond its diagnostic role, the jelly method may have potential applications in therapeutic EUS procedures. As OS-1 can maintain a stable acoustic window, it may facilitate complex interventions requiring precise visualization, such as EUS-guided biliary drainage or gastrointestinal anastomosis creation. These therapeutic procedures demand optimal imaging stability to ensure the efficacy and safety of the intervention. Although our study was limited to diagnostic examinations, the physical properties of the jelly suggest that it may improve visualization and technical success in a therapeutic context. This hypothesis is supported by a recent comprehensive review that discussed the role of therapeutic EUS in managing malignant double obstruction (biliary and gastric outlet), 5 and emphasized the importance of establishing a secure echoendoscopic window for procedural success. Future prospective studies are warranted to evaluate whether the jelly method could expand the clinical utility of probes in therapeutic EUS.
Recently, a jelly for endoscopy, VISCOCLEAR, has been introduced as a medical device. Unlike OS-1, VISCOCLEAR does not contain electrolytes, allowing it to be used with monopolar high-frequency treatment devices during endoscopic procedures. However, as the viscosity is similar, VISCOCLEAR is expected to be similarly useful as OS-1.
In this study, we adopted a clinically appropriate method in which we switched to the jelly method only in patients for whom satisfactory images could not be obtained using the water-filling method, which may have introduced a selection bias. Furthermore, the number of patients was limited, and comparisons between organs or sites could not be made. In the future, with an increased number of patients, we plan to investigate and identify the organs or sites where the jelly method is useful. In particular, even within the stomach, the utility of the jelly method may differ according to the subregion (upper, middle, and lower). However, owing to the small number of patients included in this study, no statistically significant differences were observed. If useful organs or sites for the jelly method are identified, using the jelly method from the beginning to examine these sites is expected to shorten the time.
This study has several limitations. First, it was conducted at a single center with a relatively small number of patients, which may limit the generalizability of our findings. Second, the endoscopists were not blinded to the use of the jelly method, which may have introduced an observer bias. Finally, subgroup analyses according to organ or lesion location (e.g., esophagus, stomach, duodenum, colon, or gastric subregions) were not feasible; thus, the results should be interpreted with caution.
