Colorectal cancer (CRC) remains a significant global health concern, with surveillance colnoscopy playing a crucial role in improving survival rates after curative resection [12]. Studies have shown that over 50% of all metachronous CRCs are detected within 3 years of surgery [3]. Thus, early surveillance colonoscopy, which typically begins within the first year after surgery, is particularly important [4].

Withdrawal time (WT) is a critical factor in determining the colonoscopy quality. For standard screening colonoscopies, a minimum WT of 6 minutes is widely recommended, as it has been associated with higher adenoma detection rates (ADR) [5]. However, the optimal WT for postsurgical surveillance colonoscopy remains unclear, especially considering the altered colonic anatomy following resection. The colon-sidedness of right- and left-sided CRC exhibits distinct characteristics in terms of demographics, molecular features, and prognosis [6]. In addition to the different status of the remaining colon after surgery, the different nature of the polyps, including the smaller and sessile morphology found in the right-sided colon, may require more meticulous examination during colonoscopy [7].

This study aimed to investigate the optimal WT for initial surveillance colonoscopy after curative resection for CRC. The patients were categorized into 2 groups based on their surgical procedures: anterior/low anterior resection (AR/LAR) and right hemicolectomy (RHC). This approach considers the potential differences in the remaining colon length, characteristics, and impact of colon-sidedness on surveillance outcomes. The primary objective was to determine the optimal WT for each surgical group and to evaluate its impact on the ADR and advanced neoplasia detection rate (ANDR). By focusing on different surgical treatments, we aimed to provide tailored recommendations that could contribute to performing more effective surveillance colonoscopy in CRC, considering the anatomical and physiological changes resulting from different surgical procedures.

This study examined the optimal WT for the first surveillance colonoscopy following curative resection of both right- and left-sided CRC. ROC analysis revealed that the ideal WTs for the AR/LAR and RHC groups were 7 and 6 minutes, respectively. The cutoff values were evaluated using logistic regression models and were found to be appropriate for maintaining asatisfactory ADR and ANDR. Therefore, it is advisable to maintain a minimum WT of 6 minutes for initial surveillance colonoscopy following curative resection for CRC, even ifthe length of the colon is reduced after surgery. Furthermore, for patients who underwent AR or LAR, the minimum WT should be extended to 7 minutes.

WT during colonoscopy is crucial to the quality and efficacy of the procedure [8]. This refers to the time at which the colon is thoroughly examined and the endoscope is gradually withdrawn. This is important for detecting polyps and other abnormalities. A landmark study by Barclay et al. [5] demonstrated that endoscopists with a mean WT of ≥6 minutes had higher ADRs compared to those with shorter WTs. This finding was replicated in subsequent research, leading to the current recommendation of a minimum 6-minute WT for colonoscopies. Studies have shown that longer WTs are associated with a higher ADR and detection of precancerous lesions. Aziz et al. [9] performed a meta-analysis of 3 randomized controlled trials on the optimal WT during colonoscopy and reported that the 9-minute WT improved the ADR and adenoma per colonoscopy rate compared with the 6-minute WT. The authors recommended that a minimum 9-minute WT is required to improve colonoscopy quality. However, another prospective cohort study found that when WT was >8 minutes, the adenoma detection OR no longer changed significantly after a WT of >8.24 minutes [10]. The authors of this study acknowledged that although there is a direct correlation between the length of the WT and ADR, longer procedures would lead to increased patient discomfort and decreased colonoscopy efficiency. Therefore, determining the optimal WT is important to perform colonoscopies more efficiently.

The surveillance colonoscopy plays an essential part in enhancing the survival rates of patients with CRC following surgery [11]. Early surveillance colonoscopy within 3 years after surgery is advisable because the cumulative incidence of non-anastomotic recurrence during this period is reported to be approximately 53.7% of all non-anastomotic recurrences [3]. Furthermore, a study conducted using population-based data from the Netherlands Cancer Registry revealed that over 43% of all metachronous CRCs occurring within 3 years were classified as missed lesions prior to surgery [12]. The proportion of anastomotic CRCs that occurred within the first year following surgery was 1.7% of all anastomotic CRCs [3]. Therefore, it is generally recommended to conduct an initial surveillance colonoscopy within 1 year after surgery to clear metachronous and missed lesions during the perioperative period.

The optimal WT for initial surveillance colonoscopy in patients with CRC should be determined, considering both the reduced colon length after resection and the time needed to detect all metachronous and missed lesions. Jung et al. [13] previously investigated the relationship between WT and ADR during surveillance colonoscopy after CRC surgery. The researchers found that a WT of ≥8 minutes had significantly higher ADRs compared to shorter WTs (49.1% vs. 32.2%, P < 0.001). The study concluded that thorough observation with 8–10 minutes of WT is necessary for optimal adenoma detection in postoperative surveillance colonoscopy, despite the shorter colon length due to surgery. They also identified a positive linear relationship between the WT and ADR, which is consistent with our results. In addition, they showed similar results to our study for average polyp sizes (Jung et al. [13], 6.0 mm; current study, 6.5 mm) and average ANDR (Jung et al. [13], 7.6%; current study, 8.0%). However, there are several differences. First, Jung et al.’s study [13] included multiple endoscopists (8), resulting in significant variability in average WT (6.4–10.9 minutes) and ADR (29.3%–50.6%). In contrast, our study included only 2 endoscopists, which contributed to data consistency and uniformity. Second, the optimal WT determined by ROC curve analysis in the study by Jung et al. [13] was 7.8 minutes, which was longer than that in our study. This difference could be attributed to the Jung group’s longer average WT of 8.1 minutes compared to our 7.3 minutes. Lastly, while Jung et al. [13] did not analyze WT according to the type of surgery, our study categorized all patients into 2 groups based on their surgical treatment: the AR/LAR and RHC groups. Patients who underwent AR/LAR or RHC were analyzed independently because of potential variations in the characteristics of the residual colon. Mostpatients with AR/LAR have the remaining colonlocated on the right side, whereas patients with RHC have the colon primarilyon the left side. The anatomical structures of the right- and left-sided colons differ, and the features of polyps that dominate the right side are distinct from those that dominate the left side [7]. Therefore, we separately evaluated the optimal WTs of patients with AR/LAR and RHC to identify differences in initial surveillance colonoscopy.

In our study, colonoscopy results differed between right- and left-sided CRC. The polypectomy detection rate and ADR in the AR/LAR group were higher than those in the RHC group (38.9% and 32.4% vs. 31.1% and 25.1%; P = 0.021 and P = 0.014, respectively). The mean WT (7.8 ± 3.1 minutes) and optimal WT (7.05 minutes) of the AR/LAR group were longer than those of the RHC group (6.4 ± 2.1 minutes and 6.05 minutes, respectively). Additionally, when each group was divided into subgroups based on the cutoff value of optimal WT (7.05 in the AR/LAR group and 6.05 in the RHC group), there was a significant difference in ANDR between subgroups within each group. In the AR/LAR group, the subgroup with a WT ≥7 minutes had an ANDR of 11.9%, which was twice as high as the subgroup with a WT <7 minutes (P = 0.001). Furthermore, within the RHC group, the incidence of ANDR in the subgroup with a WT ≥6 minutes was 10.2%, which was 4 times greater than the incidence in the subgroup with a WT <6 minutes (P = 0.004). Thus, to perform initial surveillance colonoscopy more efficiently, it is advisable to adhere to the optimal WTs according to the surgical treatments and consider other factors in patients with CRC.

The longer optimal WT and higher ADR in the AR/LAR group than those in the RHC group could be attributed to anatomical differences and surgical techniques. Central vessel ligation, a common technique for improving oncological outcomes, results in a considerably fixed range of resected colons for RHC, whereas surgeons have more flexibility in determining the extent of resection for AR/LAR. In addition, the length of the resected colon is generally longer for right-sided tumors than for left-sided tumors, potentially explaining the higher ADR and WT in the AR/LAR group [1415]. Moreover, right-sided polyps tend to be smaller and more sessile, making them harder to detect during colonoscopy, whereas left-sided polyps are generally larger and pedunculated [1617]. These anatomical differences necessitate careful examination to thoroughly detect and manage polyps in the right-sided colon, thereby contributing to the longer WT in the AR/LAR group. In addition, the right-sided colon is the largest part of the colon and has a saccular morphology with tangential trabecula [18]. This large diameter and distinct structure can pose challenges during colonoscopy, necessitating careful maneuvering to avoid complications. Right-sided polyp location has been reported as a significant risk factor for major complications, including bleeding and perforation, during colonoscopic polypectomy [19]. Thus, the larger diameter and specific anatomical features of the right colon increase the complexity and risks associated with polypectomy, resulting in a longer WT in the AR/LAR group.

In addition to WTs, several additional characteristics, such as advanced age, male sex, obesity, and insufficient bowel preparation, significantly affect the enhancement ofADR during colonoscopy [202122]. In our study, the effect of bowel preparation could not be evaluated because we excluded patients with “poor” and “inadequate” bowel preparation. BMI was not a significant factor in either the AR/LAR or RHC groups. However, older age and male sex were significantly associated with ADR in both groups. In the multivariate analysis, older age (≥75 years) was a significant factor in both groups. Male sex was found to have a significant association with higher ADR in the AR/LAR group but not in the RHC group. This difference may be attributed to the small number of patients in the RHC group.

This study has some limitations. First, the retrospective design of the study could have led to a bias in data selection between the AR/LAR and RHC groups. Second, because of the significant dependence on the technical expertise of endoscopists, it is essential to validate the findings of this study by integrating a greater number of endoscopists and collecting data from multiple centers. Third, the WT was calculated by excluding the time spent on polypectomy; however, it was impossible to exclude the time spent on suctioning the luminal fluid or contents. Thus, data from colonoscopies with “fair” bowel preparation may have influenced the analytical outcomes.

In conclusion, this study suggests that a minimum WT of 7 minutes for AR/LAR patients and 6 minutes for RHC patients are optimal for maintaining a satisfactory ADR and ANDR. These findings emphasize the importance of tailoring colonoscopy procedures based on the type of surgical resection performed, potentially leading to more effective detection of metachronous lesions and improved treatment outcomes for patients with CRC.