Comparative insertion performance of three high-end colonoscopes: a post hoc analysis of a randomized controlled trial

Introduction

Colorectal cancer (CRC) is the fourth most prevalent form of cancer and the third leading cause of cancer-related deaths (1). Early detection and prompt treatment are paramount in reducing the mortality rate associated with CRC. Numerous studies have indicated the efficacy of colonoscopy in preventing CRC-related deaths (2). Screening colonoscopies reduce the percentage of CRC fatalities, similar to polypectomy. Nevertheless, several factors contribute to the potential of not identifying CRC during colonoscopies. Achieving thorough cecal intubation is pivotal during colonoscopy procedures to ensure comprehensive observation and effective control of CRC. Various factors affect cecal intubation, such as patients’ characteristics [e.g., body mass index (BMI), age, and sex], the expertise of the endoscopist, and the equipment used (3-5). Numerous endoscopic instrument companies have introduced a diverse range of endoscopes in recent years. These endoscopes have an array of functionalities, such as CO₂ insufflation (6), adjustable stiffness features (7,8), and jet water delivery systems (9), all of which aim to enhance insertion capabilities. Although the usefulness of each endoscopic function has been evaluated, the evaluations of each function were only an in-house comparison and not a comparison of endoscopes between companies. Therefore, the endoscopes of different companies have not yet been directly compared.

We previously performed a randomized, controlled trial on three different endoscopes and endoscopy systems to assess the diagnostic efficacy of colonoscopy image enhancement using the narrow banding image (NBI) International Colorectal Endoscopic (NICE) classification and the Japanese NBI Expert Team (JNET) classification (10). We not only gained insight into image enhancement but also collected a lot of data regarding the performance of endoscope insertion. Therefore, in the current study, we performed a post hoc analysis of data from our previous study, and specifically focused on comparing the insertion performance of each endoscope. This study aimed to determine any differentiating factors in the insertion efficacy among the various endoscope models.

Methods

Study design and setting

This analysis was conducted as a post hoc evaluation based on data obtained from a randomized controlled trial at a single center. The original trial enrolled patients undergoing endoscopic removal of colorectal neoplasms. Study management, including coordination, data acquisition, and trial oversight, was carried out by the Department of Gastroenterology and Hepatology, Yokohama City University Hospital.

Ethical considerations

The research adhered to the ethical principles outlined in the Declaration of Helsinki (11) and its subsequent amendments.

Participants

In the original trial, adult patients who visited our institution for endoscopic resection (ER) of colorectal neoplasms between April 2018 and December 2019 were prospectively enrolled. Eligibility criteria included: (I) age 20 years or older at the time of consent; (II) presence of colorectal tumors for which ER was indicated; and (III) agreement to participate in the research. All individuals meeting these criteria in the previous trial were reanalyzed in the present post hoc investigation.

Patients were excluded from the prior study under the following conditions: (I) lesions that could not be appropriately assessed using the NICE or JNET classification systems; or (II) cases deemed unsuitable for inclusion by the study investigators based on clinical judgment. In the current study, we excluded patients who underwent cecal insertion owing to colonic stenosis or those who underwent polypectomy before cecal insertion or post-colectomy.

Endoscopes

PCF-H290ZI with the EVIS LUCERA ELITE system (Olympus Medical Systems, Tokyo, Japan)

The PCF-H290ZI has an 11.7-mm outer diameter and 11.8-mm outer diameter insertion tube with 180° maximum angulation up, 180° down, and 160° right and left. This scope has three unique proprietary technologies comprising passive bending, high force transmission, and variable stiffness. These technologies work together to improve the ease of insertion and operator control, which may help to minimize the patient’s discomfort and enhance procedural efficiency.

EC-L600ZP7 with the LASEREO endoscopic system (Fujifilm, Tokyo, Japan)

The EC-L600ZP7 has an 11.7-mm outer diameter and 11.8-mm outer diameter insertion tube with 180° maximum angulation up, 180° down, and 160° right and left. This scope has three unique proprietary technologies comprising a flexibility adjuster, advanced force transmission, and adaptive bending. The ColoAssist Adjust features the flexibility adjuster with different levels of stiffness, as well as advanced force transmission and adaptive bending, which are expected to be helpful for maneuverability. The LASEREO endoscopic system and their scopes are only available in Japan, China, and some Asian countries.

EC-760ZP with the ELUXEO endoscopic system (Fujifilm)

The EC-760ZP has an 11.7-mm outer diameter and 11.8-mm outer diameter insertion tube with 180° maximum angulation up, 180° down, and 160° right and left. This scope has three unique proprietary technologies comprising a flexibility adjuster, advanced force transmission, and adaptive bending. The ColoAssist Adjust features the flexibility adjuster with different levels of stiffness, as well as advanced force transmission and adaptive bending, which are expected to be helpful for maneuverability. The ELUXEO endoscopic system is available in North America and European Union (EU) countries.

The key specifications of the three colonoscopes are summarized in Table 1 to facilitate comparison of their design and features.

Endoscopic procedure

Bowel cleansing began one day prior to the colonoscopy. Patients were advised to follow a low-residue diet and were prescribed 5 mg of oral sodium picosulfate on the evening before the examination. On the day of the procedure, 1,500 mL of polyethylene glycol solution was administered. In cases where stool clarity was deemed insufficient, an additional 500 mL of polyethylene glycol was provided to achieve adequate bowel preparation.

Cecal intubation was confirmed by visual identification of both the appendiceal orifice and the ileocecal valve. The duration of insertion was recorded using a stopwatch. All procedures were performed using an endoscopic cap attached to the tip of the colonoscope, in accordance with standard practice at our institution. Water-immersion colonoscopy was not routinely performed in our institution during the study period, and information regarding its use was not collected in the original dataset. To reduce procedural variability, all colonoscopies were conducted by expert endoscopists, each of whom had completed over 500 prior procedures.

Outcomes

The primary outcome was the cecal insertion time (CIT) and cecal insertion rate for each endoscope. Secondary endpoints were factors related to a rapid intubation and difficulty of cecal intubation. The secondary outcome, “difficulty of cecal intubation”, was operationally defined as prolonged CIT. Risk factors for prolonged CIT as an exploratory analysis were analyzed using logistic regression, and significant predictors were considered indicative of increased intubation difficulty. We analyzed the CIT and several factors that were previously reported as risk factors for difficulty in cecal insertion, such as ages, sex, and BMI (12,13).

Randomization

In the original randomized controlled trial, patient information was submitted by the investigators to a central registration unit via fax. Once eligibility was confirmed, a computerized randomization system assigned each patient to one of three endoscopy groups: PCF-H290ZI, EC-L600ZP7, or EC-760ZP. Following assignment, colonoscopic examinations were performed using the designated endoscope for each patient (10).

Statistical analysis

Quantitative variables are described as means or medians, accompanied by standard deviations or interquartile ranges (IQRs), respectively. Categorical variables are expressed as counts and percentages. For comparisons involving categorical data, either the Chi-squared test or Fisher’s exact test was employed, depending on the distribution. Continuous variables were tested for normality using the Shapiro-Wilk test. Variables with a normal distribution were analyzed using one-way analysis of variance (ANOVA) for comparisons among three groups and the t-test for two-group comparisons. Non-normally distributed data were evaluated using the Kruskal-Wallis test for three-group comparisons and the Mann-Whitney U test for two-group comparisons. Statistical significance was set at P<0.05. To identify risk factors associated with insert outcome, such as incomplete colonoscopy or prolonged insertion time, we performed logistic regression analysis. Candidate risk factors included patient-related variables (e.g., age, sex, BMI) and scope type. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. All analyses were performed using SPSS software, version 29.0.0.0 (SPSS Inc., Cary, NC, USA).

Results

Selection of patients

In the previous trial, from April 2018 to December 2019, 1,579 patients underwent polypectomy. After checking the eligibility and informed consent for the study, 230 patients were enrolled. The reasons for not being included were that 1,221 patients could not be registered because of a lack of medical resources (endoscopist or endoscope procedure) and 128 patients did not want to participate in the study. The remaining 230 patients were randomized and 78 were assigned to the PCF-H290ZI with EVIS LUCERA ELITE group, 76 to the EC-L600ZP7 with LASEREO group, and 76 to the EC-760ZP with ELUXEO group. Two participants who did not undergo cecal intubation because of colon stenosis by CRC were excluded from the analysis. Seventeen participants who underwent polypectomy without cecal intubation were excluded from the analysis. Five participants were post-colectomy and also excluded from the analysis. The remaining 206 participants, including 70 who had the PCF-H290ZI used, 69 who had the EC-L600ZP7 used, and 67 who had the EC-760ZP used, were included in the final analysis. No complications related to the procedure were observed in any of the groups. A study flow chart is shown in Figure 1.

Figure 1 Flow diagram of the patients and colonoscopy devices used in this study. BLI, blue light imaging; LED, light emitting diode; NBI, narrow band imaging; TCS, total colonoscopy.

Patients’ characteristics

The clinical characteristics of the patients are shown in Table 2. There was no significant difference in the patients’ characteristics between the PCF-H290ZI with EVIS LUCERA ELITE, EC-L600ZP7 with LASEREO, and EC-760ZP with ELUXEO groups.

Comparison of the insertion ability of each endoscope

The cecal insertion rate and CIT of each scope are shown in Table 3. The insertion rate in each scope was 100%. The median overall CIT was 327 (IQR, 227–514.5, 95% confident interval: 95% CI: 363.8–425.5) seconds. The median CIT in PCF-H290ZI was 370 (IQR, 240–514, 95% CI: 355.6–487.3) seconds, in EC-L600ZP7 was 356 (IQR, 224–551.5, 95% CI: 362.3–493.9) seconds, EC-760ZP was 306 (IQR, 228–439, 95% CI: 310.7–392.4) seconds. There was no significant difference in the insertion rate or CIT by expert endoscopists between each type of endoscope.

Risk factors related to a longer CIT

Following prior studies that operationalized insertion difficulty by prolonged cecal intubation time, we defined difficult cecal intubation as CIT ≥600 seconds and examined risk factors for difficult insertion; this approach is consistent with reports that used similar thresholds. When we compared the standard CIT (CIT <600 seconds) group (n=176) with the longer CIT (CIT ≥600 seconds) group (n=30), the univariate analysis showed that an age older than 75 years was associated with longer CIT (OR 2.40, 95% CI: 1.096–5.275, P=0.02). Compared with standard BMI (18.5≤ BMI <25 kg/m²), low BMI (BMI <18.5 kg/m²; OR 3.57, 95% CI: 1.16–10.97, P=0.005) and high BMI (BMI ≥25 kg/m²; OR 3.60, 95% CI: 1.49–8.70, P=0.005) were associated with longer CIT, respectively (Table 4).

Discussion

To the best of our knowledge, this is the first study to compare the insertion performance of these three endoscopes using data derived from a randomized controlled trial. We directly compared the insertion ability of the PCF-H290ZI with the EVIS LUCERA ELITE system, the EC-L600ZP7 with the LASEREO system, and the EC-760ZP with the ELUXEO system by expert endoscopists and found that there was no significant difference in the insertion ability between the different scopes. The CIT in older patients, with underweight and overweight patients were significantly longer than that in those who were younger and had a standard body shape, regardless of the endoscope used.

Several reports have shown that an older age is a risk factor for difficulty of cecal insertion (12,13). In older patients, this issue might be due to inadequate compliance and a tortuous colon. In addition, the length of the colon increases with age, which may be associated with difficulty and a high incomplete rate of this procedure (14). In this study, an age older than 75 years was a risk factor for a longer CIT. Previous reports on this issue were published in approximately 2000, but the difficulty of cecal insertion with an older age has not changed using recently developed endoscopes. Therefore, an older age still appears to be risk factor for a longer CIT. Endoscopists should recognize the effect of age on colonoscopy and perform colonoscopic insertion carefully.

In this study, a low BMI was a risk factor for a longer CIT using recently developed endoscopes. Several reports have shown that a low BMI is also a risk factor for difficulty of cecal insertion (5,15-17). Patients with a low BMI have a sigmoid colon that is more redundant or difficult to navigate to next lumen (4). One possible explanation for this finding may be that a lower amount of fat provides resistance to a colonoscope and thus helps to decrease sigmoid mobility. However, high BMI also appeared as a risk factor for longer CIT in our cohort, likely reflecting unmeasured factors specific to therapeutic colonoscopy—such as hidden tumor‑related characteristics or other residual confounders—as well as technical limitations in applying abdominal pressure or repositioning in patients with higher adiposity.

In this study no significant difference in cecal insertion rate or CIT was observed between each type of endoscope. Each endoscopy provider that we investigated in this study developed various technologies. An example of this technology is that CO₂ use rather than air insufflation during the colonoscopy procedure reduces abdominal pain in the patients (6). Additionally, a colonoscope with variable stiffness is associated with a higher chance of achieving cecal intubation and with fewer position changes (8), and water jet use leads to a shorter cecal intubation time (9). These technologies are evolving daily, and each endoscope production company has developed a variety of new endoscopes with a high level of technology. Recently developed endoscopes have excellent performance. Although detailed mechanical properties such as elastic modulus were not available, the three endoscopes compared in this study share similar design concepts aimed at facilitating insertion, including comparable shaft flexibility, tip angulation range, and outer diameter. These similarities may explain why insertion times did not differ significantly among the devices. Our hypothesis is that, in procedures performed by expert endoscopists, these advanced scopes provide equivalent insertion performance because their design differences are minimized by operator skill. Future studies should incorporate objective measurements of scope flexibility and torque transmission to further clarify these relationships. In this study, there was no difference in the cecal intubation rate or time between the different endoscopes.

Therefore, endoscopists are likely to focus on improving the diagnostic ability or equipment of image-enhanced endoscopies (IEEs) or artificial intelligence (AI) to support the detection and diagnosis of lesions. Recently, each endoscope company launched various IEEs, such as NBI (18), blue light imaging (BLI) (19), linked color imaging (20) flexible spectral imaging color enhancement (21) and i-Scan (22). We previously compared the diagnostic accuracy between NBI, Laser-BLI, and LED-BLI, and showed that Laser-BLI and LED-BLI had high diagnostic accuracy and noninferiority to NBI (9). Other IEEs also have high detection and diagnostic abilities, and their abilities are improving daily (23). Further new technologies and new products are expected. Regarding AI, several endoscopy companies are developing AI endoscopy for detecting cancer, identifying the depth of cancer invasion, predicting the pathological diagnosis, and predicting Helicobacter pylori infection and inflammatory bowel disease (24). In the future, endoscopists will select endoscopes based not only on their insertion performance, but also on their diagnostic ability, AI, and other accessory functions.

There are several limitations to this study. First, this study was a post hoc analysis in single-center. Therefore, the study endpoints, cecum insertion rate, and CIT were not planned at the time of designing the study. Furthermore, study participants were relatively small. Consequently, the study may have lacked power. Second, because this study is a post hoc analysis, several procedure-related factors such as bowel preparation, use of anti-spastic agents, history of abdominal surgery, application of abdominal pressure, and patient position changes were not systematically recorded and were missing for most cases. For this reason, our analyses focused on variables that were consistently collected. While the primary findings remained generally robust across alternative model specifications, the absence of these procedure-related factors remains an important limitation and may contribute to unmeasured confounding. Third, many endoscopes have been recently developed worldwide, but we were only able to compare three endoscopes in this study. Further studies are required to compare the various endoscopes. Fourth, all endoscopists in this study were experts, which likely reduced variability in insertion time among the three endoscopes. If trainees had performed the procedures, differences in insertion performance might have been more pronounced. Further analysis is required to establish whether these results can be applied to trainees. Finally, all patients in this study were recruited for polypectomy, not for colonoscopy screening. However, there have been few studied that directly compared the insertion ability of each scope in the randomized, controlled trial setting, which is a strength of this study.

Conclusions

This study suggests that the insertion ability of the PCF-H290ZI with the EVIS LUCERA ELITE system, the EC-L600ZP7 with the LASEREO system, and the EC-760ZP with the ELUXEO system by expert endoscopists is similar. An age older than 75 years and a low BMI are risk factors for a longer CIT, regardless of the endoscope used. These findings are significant because they provide evidence from a randomized controlled trial dataset, supporting the comparable performance of three advanced endoscopy systems in routine clinical practice. While the results are most applicable to settings with experienced endoscopists, caution should be exercised when generalizing to less experienced operators or different patient populations. Future research should evaluate these endoscopes in diverse clinical environments, include anatomical and procedural factors, and assess whether emerging technologies can further reduce insertion time and improve patient comfort.

Acknowledgments

The authors thank the staff of the participating institutions for their support in recruiting eligible patients and the patients who participated in this study. We thank Ellen Knapp, PhD, from Edanz (https://jp.edanz.com/ac) for editing a draft of this manuscript.

Footnote

Peer Review File: Available at https://ales.amegroups.com/article/view/10.21037/ales-25-33/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://ales.amegroups.com/article/view/10.21037/ales-25-33/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.

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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