Abstract
Background/Aim: In minimally invasive colorectal surgery, ureteral and urethral injuries are uncommon, but they can have serious complications leading to significant postoperative morbidity. Fluorescent catheters have recently been introduced to improve the intraoperative visibility of urological organs. However, clinical reports on their use remain limited. This study aimed to evaluate the feasibility and clinical outcomes of fluorescent ureteral and urethral catheters to prevent urological injuries during laparoscopic, robot-assisted, and transanal total mesorectal excision colorectal surgeries.
Patients and Methods: This retrospective observational study included 13 consecutive patients who underwent minimally invasive colorectal surgery with fluorescent catheter placement at the Hokkaido University Hospital between September 2023 and January 2025. The catheters were visualized using various near-infrared ray imaging systems. The primary endpoint was the occurrence of intraoperative ureteral or urethral injuries; the secondary endpoint was intraoperative visibility of the ureter/urethra.
Results: Nine patients received ureteral catheter, two received urethral catheter, and two received both ureteral and urethral catheters for pelvic exenteration. All ureters were clearly identified intraoperatively and no ureteral injuries occurred. In the two urethral catheter cases performed for urethral preservation, the catheter was not directly visible from the surgical field during transanal total mesorectal excision, suggesting a lack of proximity, and urethral preservation was achieved. In the two pelvic exenteration cases, both the ureters and urethral were visualized and intentionally resected without inadvertent injury.
Conclusion: Fluorescent catheterization is a feasible, safe, and practical technique for enhancing intraoperative identification of urological structures in high-risk colorectal surgery. Its use may help reduce the risk of inadvertent injury, particularly in anatomically complex and minimally invasive procedures.
Introduction
With the increasing adoption of laparoscopic and robot-assisted techniques in colorectal surgery, the risk of iatrogenic injury to the adjacent urological organs, particularly the ureter and urethra, remains a significant concern. Such injuries are associated with considerable postoperative morbidity and may require complex reconstructive interventions (1).
Ureteral injury reportedly occurs in approximately 0.5% of colorectal procedures (2), with a higher incidence in laparoscopic surgery than in open surgery. High-risk scenarios, such as locally advanced tumors, dense pelvic adhesions, or previous pelvic surgery, can increase the likelihood of injury two- to three-fold (3). While prophylactic ureteral stenting has been routinely used in open surgery, traditional catheters often lack sufficient visibility in minimally invasive procedures, where tactile feedback is limited (4).
In recent years, transanal total mesorectal excision (TaTME) has gained popularity as an innovative surgical approach for treating lower rectal cancer. Although this technique offers improved visualization and access in confined pelvic anatomy, it carries unique risks including urethral injury (5). The reported incidence of urethral injury in TaTME ranges from 0.1% to 0.8% (6, 7), and prevention remains a major intraoperative challenge, as no reliable visualization methods currently exists.
To address these limitations, near-infrared ray (NIR) fluorescent ureteral and urethral catheters have been developed to provide real-time visualization of urological structures (8-12). These catheters emit fluorescence under NIR imaging, allowing surgeons to identify and preserve critical anatomy without relying on palpation. But despite their promise, clinical evidence of their utility remains limited. To date, only one report has described the use of fluorescent urethral catheter (11), and the application of fluorescent ureteral catheter in robot-assisted colorectal surgery is poorly documented (12).
Therefore, this study aimed to evaluate the clinical utility of fluorescent ureteral and urethral catheters in preventing urological injuries during complex colorectal procedures, particularly in high-risk, minimally invasive settings.
Patients and Methods
Study design and patients. We conducted a retrospective observational study according to the STROBE guidelines. This study was approved by the Human Research Ethics Committee of Hokkaido University Hospital (approval number: 019-0351), and was conducted in accordance with the tenets of the 1964 Declaration of Helsinki and its later amendments. The requirement for informed consent was waived because of the retrospective nature of this study.
Consecutive patients who underwent minimally invasive surgery using fluorescent ureteral or urethral catheters between September 2023 and January 2025 were included. Indications for fluorescent ureteral catheter included bulky intra-abdominal tumors, locally advanced colorectal cancer with suspected retroperitoneal infiltration, severe inflammation (e.g., abscess), and a history of pelvic surgery. Indications for fluorescent urethral catheter were categorized into two clinical settings: 1) lower anterior rectal wall tumors and TaTME procedures, where the catheter assists in urethral preservation, and 2) pelvic exenteration, where the urethra is intentionally transected.
Study outcomes. The primary outcomes were the occurrence of intraoperative ureteral and urethral injuries. The secondary outcomes were intraoperative visibility of the ureter/urethra, technical feasibility, and safety of catheter use.
Catheter type and imaging systems. The Near-Infrared Ray Catheter (NIRCTM) fluorescent ureteral and urethral catheters (Cardinal Health Inc., Tokyo, Japan) were used. Each catheter was inserted after induction of general anesthesia and prior to surgery. The fluorescent ureteral catheter was placed by an urologist, while the fluorescent urethral catheter was inserted by an operating room nurse. No special techniques other than those used for standard catheters were required for fluorescent catheter insertion. NIR visualization on the abdominal side was performed using VISERA ELITE II (Olympus, Tokyo, Japan), IMAGE1 STM and IMAGE1 STM Rubina® (KARL STORZ SE, Tuttlingen, Germany), 1688 AIM 4 K (Stryker, Kalamazoo, MI, USA), and da Vinci Xi® Firefly® mode (Intuitive Surgical Inc., Sunnyvale, CA, USA). The transanal side was visualized using the 1688 AIM 4 K system.
Data collection. We collected data on age, sex, underlying disease, surgical approach, surgical procedure, type of NIR imaging system used, intraoperative findings, occurrence of ureteral or urethral injury, and pathological findings, and postoperative course. Intraoperative NIR findings were reviewed using surgical video recordings routinely obtained for clinical documentation.
Results
Thirteen patients were included in the study. Of these, nine patients underwent fluorescent ureteral catheter placement, two underwent fluorescent urethral catheter placement, and two received both ureteral and urethral catheters during pelvic exenteration.
Fluorescent ureteral catheter cases are summarized in Table I. Among the 11 ureteral catheter cases, five surgeries were performed laparoscopically and six robotically. The indications included bulky tumor (one case), severe inflammation (two cases), locally advanced cancer (three cases), and a history of pelvic surgery (five cases). Unilateral catheter placement was performed in five cases and bilateral placement in six. Catheter insertion was successful in all cases, with fluoroscopic guidance required in three to adjust positioning. The median insertion time was 16.5 min (range=5-52 min). In all cases, the ureters were clearly visualized using NIR imaging and fluorescent overlay modes (Figure 1). No intraoperative ureteral injuries, including inadvertent damage, were observed. Postoperatively, hematuria occurred in eight cases but resolved spontaneously without intervention.
Summary of patients with fluorescent ureteral catheter.
Visualization of fluorescent ureteral catheter using near-infrared ray imaging (upper row) and fluorescent overlay modes (bottom row).
Fluorescent urethral catheter cases are summarized in Table II. The four urethral catheter cases involved robot-assisted abdominoperineal and intersphincteric rectal resections with TaTME (two cases) and pelvic exenteration (two cases). In the two urethral preservation cases, NIR visualization enabled safe dissection and ensured appropriate margins for the tumors involving the lower rectal wall (Figure 2). In the two pelvic exenteration cases, the urethras were visualized and intentionally resected (Figure 3). Neither intraoperative urethral (including inadvertent) nor rectal injuries were observed, and postoperative courses were uneventful. In the urethral preservation cases, the pathological circumferential resection margin (CRM) measured at 3.5 mm in Case 1 and 5.0 mm in Case 2.
Summary of patients with fluorescent urethral catheter.
Intraoperative near-infrared ray visualization using the overlay mode of the 1688 AIM 4K system during a transanal total mesorectal excision (TaTME) procedure. The white arrow indicates light capture on the ventral side. The fluorescent urethral catheter is not visible in the dissection of the rectourethralis muscle, suggesting that the urethra was not in close proximity to the surgical dissection plane—illustrating the “non-visualized” concept.
In a case involving urethral transection, the fluorescent urethral catheter was clearly visualized near the surgical field from both the ventral and anal sides—illustrating the “visualized” concept. Representative ventral-side images include the white light view (upper-left photo) and the Firefly® mode view (upper-right photo) using the da Vinci Xi®. Representative anal-side images include the white light view (bottom-left photo) and the overlay mode view (bottom-right photo) using the 1688 AIM 4K system.
Discussion
This study demonstrated the utility of fluorescent ureteral and urethral catheters in enhancing the intraoperative decision-making process during colorectal surgery. The ureters were clearly visualized using NIR imaging, enabling their safe preservation. In urethra transaction cases, the fluorescent urethral catheter allowed clear identification of the urethra and its intentional resection without inadvertent injury. Conversely, in the urethra preservation cases, the urethra was not visible in the operative field, indicating a lack of proximity to the surgical plane and allowing confident preservation. Notably, no special insertion technique is required for either catheter, making this approach both practical and easily applicable in routine clinical practice.
Ureteral injury is a serious complication, particularly in laparoscopic colorectal surgery, where its incidence is higher than that in open procedures (2, 3). The risk increases several-fold in cases involving bulky tumors, locally advanced cancers, severe inflammation, or prior pelvic surgery (3). Although prophylactic catheterization is often employed in such cases, conventional catheters have limited utility due to the lack of tactile feedback in minimally invasive surgery (4). In recent years, the development of fluorescence-guided navigation surgery has been remarkable (13). NIRCTM fluorescent ureteral catheters, introduced around 2020, utilize NIR imaging without heat emission and help overcome these limitations (8). In our nine high-risk cases, including four robotic-assisted surgeries, fluorescent ureteral catheters enabled reliable visualization of the ureters, facilitating safe dissection without injury. Moreover, fluorescent ureteral catheters provided consistent fluorescence across various NIR platforms, including VISERA ELITE II, IMAGE1 STM and IMAGE1 STM Rubina®, 1688 AIM 4 K, and da Vinci Xi® Firefly® system. Catheters are easily inserted by urologists using standard techniques and require no specialized training or equipment, making them practical for routine clinical use. To the best of our knowledge, reports on the use of fluorescent ureteral catheters in robot-assisted colorectal surgery are limited (12). These findings support their routine implementation in complex pelvic procedures, especially in minimally invasive settings.
The fluorescent urethral catheter proved useful in two distinct clinical settings: urethral preservation and urethral transection. In the urethral preservation cases performed with robot-assisted surgery with TaTME, the catheter was not directly visualized in the operative field. Its absence suggested a lack of proximity, allowing confident preservation. NIR light can penetrate biological tissues to a depth of approximately 5-10 mm (14), while the anatomical distance between the rectum and membranous urethra ranges from 0.2 to 2.3 cm (15). A previous study reported that, among 11 cases using fluorescent urethral catheter, fluorescence was detected in only one case (9.1%), yet a median CRM of 7 mm was achieved (11). In our cases, no intraoperative urethral or rectal injuries occurred, and pathological evaluation confirmed appropriate CRM in both anterior rectal wall tumors. These findings support the concept that a “non-visualized” catheter can still help secure oncologic margins while avoiding unnecessary proximity to the urethra. By contrast, in the urethral transection cases, the fluorescent urethral catheter was clearly visualized near the surgical field with NIR imaging, facilitating intentional resection of the urethra without inadvertent damage. This complementary “visualized” application demonstrates its value when urethral transection is planned. Importantly, these findings are consistent with prior reports citing urethral injury rates of 0.1–0.8% in TaTME, depending on study design and surgical experience (6, 7), and highlight the relevance of this technique in anterior rectal wall lesions where the urethra lies close to the dissection plane (5). To our knowledge, only one prior report has described the clinical application of a fluorescent urethral catheter in TaTME (11). Our results suggest that both visualized and non-visualized applications may contribute to oncologic safety while reducing the risk of iatrogenic urethral injury in high-risk pelvic surgery.
This study has some limitations, including its small sample size and retrospective design. Nonetheless, this study provides preliminary evidence supporting the feasibility and safety of fluorescent ureteral and urethral catheters in challenging colorectal surgeries. Further prospective studies with larger cohorts are warranted to validate these findings and evaluate their impact on oncologic outcomes and complication rates in high-risk pelvic surgery.
Conclusion
In conclusion, fluorescent ureteral and urethral catheters improve the visualization of urological structures and help prevent injury during high-risk minimally invasive colorectal surgery. This may offer a valuable strategy to avoid injuries caused by unrecognized anatomical structures.
Acknowledgements
The Authors would like to thank the Department of Urology, Hokkaido University Hospital, for their assistance with ureteral catheter placement, and the operating room staff for their support with urethral catheter placement.
Footnotes
Authors’ Contributions
KI, NI, YY, TY, YO, KS, CI, and SS, contributed to the surgery and perioperative management. KI drafted the manuscript. KI and YY reviewed the surgical videos and selected the representative intraoperative images. NI and AT supervised this study. All the Authors have read and approved the final version of the manuscript.
Conflicts of Interest
The Authors declare no conflicts of interest in relation to this article.
Funding
This report did not receive any grant or financial support.
Artificial Intelligence (AI) Disclosure
During the preparation of this manuscript, a large language model (ChatGPT 5, OpenAI) was used solely for language editing and stylistic improvements of the selected paragraphs. No sections involving the generation, analysis, or interpretation of research data were produced using generative AI. All the scientific content was created and verified by the authors. Furthermore, no figures or visual data were generated or modified using generative AI or machine learning–based image enhancement tools.
- Received October 9, 2025.
- Revision received October 25, 2025.
- Accepted October 27, 2025.
- Copyright © 2026 The Author(s). Published by the International Institute of Anticancer Research.
This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY-NC-ND) 4.0 international license (https://creativecommons.org/licenses/by-nc-nd/4.0).
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