【Introduction】
Colorectal cancer (CRC) is one of the most common and deadly malignant tumors worldwide. The primary principle of CRC treatment is to remove the tumor. Besides traditional open surgeries, minimally invasive surgeries, such as laparoscopic surgeries or robot-assisted surgeries, are also becoming increasingly popular, leading to significant changes in the surgical methods for CRC. It has been reported that compared with open surgeries, laparoscopic surgeries can achieve better short-term efficacy, and in terms of long-term oncological efficacy, they are comparable to open surgeries.

Source:Ohnuma S, Kanehara K, Sato Y, Ono T, Murakami M, Kajiwara T, Suzuki H, Karasawa H, Watanabe K, Kawamorita N, Ito A, Kamei T, Unno M. Prophylactic Ureteral Catheterization for Preventing Ureteral Injury in Colorectal Cancer Surgery. J Clin Med. 2025 Jun 11;14(12):4123. doi: 10.3390/jcm14124123. PMID: 40565869; PMCID: PMC12193882.


【Materials and Methods】
This study included 42 patients who underwent primary or locally recurrent colorectal cancer (CRC) surgery at Tohoku University in Japan. All these patients had previously received pelvic radiotherapy (PUC). This study excluded benign diseases such as Crohn's disease, ulcerative colitis, and diverticulitis, as well as other colorectal malignancies, gynecological tumors, and urinary system tumors except adenocarcinoma. Before the surgery, a consultation was held by the colorectal surgeons based on the patient's pelvic surgery history (including history of open surgery and pelvic radiotherapy), the proximity of the tumor to the ureter, pelvic inflammation, and morbid obesity, to select patients for preoperative ureteral catheterization. All patients underwent preoperative computed tomography (CT) examination to assess the CRC stage and urinary system condition, including the presence of hydronephrosis or ureteral dilation. Urine volume was monitored during and after the surgery, and renal function was evaluated on the 1st, 3rd, and 7th days after the surgery.


【Results】
（1）Basic information on the surgery and PUC
Surgical indications: The most common type is primary rectal cancer (33.3%), followed by local recurrence of rectal cancer (31.0%), colon cancer (28.6%), and local recurrence of colon cancer (7.1%).
Surgical approach: Abdominoperineal resection (35.7%), low anterior resection (21.4%), sigmoid colon resection (19.0%), tumor resection (16.7%) were the main methods; 4 patients underwent robot-assisted surgery (1 case of tumor resection, 2 cases of LAR, 1 case of APR).
Surgical approach: 38 cases (90.5%) underwent open surgery, and 4 cases (9.5%) underwent robot-assisted surgery.

（2）Details related to PUC
PUC indications (sorted by incidence): Previous open abdominal pelvic surgery history (47.6%), tumor adjacent to the ureter (26.2%), previous radiotherapy history (19.0%), pelvic inflammation (16.7%), morbid obesity (2.4%).
Catheter placement method: 60% (25 cases) of cases had bilateral catheter placement, 40% (17 cases) had unilateral catheter placement; among the unilateral placements, 14 cases were on the left side and 3 cases were on the right side.
Catheterization time: The median time for single-sided catheterization was 8 minutes (range: 4 - 21 minutes), and the median time for bilateral catheterization was 13 minutes (range: 5 - 27 minutes).

（3）Complications and the condition of ureteral injury
Intraoperative ureteral injury: Among the 42 patients who underwent PUC, no intraoperative ureteral injury was observed; in the 1,369 patients who did not receive PUC during the same period, 2 cases of ureteral injury occurred (incidence 0.15%), involving a patient with T4b stage appendiceal cancer and a patient with locally recurrent sigmoid colon cancer.
PUC-related complications: All were mild complications, with Clavien-Dindo classification ≤ 2. All resolved before discharge. Specifically: gross hematuria (14.3%), dysuria (12.0%), urinary tract infection (9.5%), hydronephrosis (2.4%). There was no PUC-related ureteral injury.


【Discussion】
The main cause of iatrogenic ureteral injury is the difficulty in identifying the ureter during the operation. Especially for patients with a history of pelvic surgery, local tumor recurrence, or tumors adjacent to the ureter, the ureter is prone to damage due to adhesions and disordered anatomical structure. PUC serves as an auxiliary identification method. It can help the surgeon clearly locate the ureter through stent imaging. Especially in robotic surgery (without tactile feedback), the fluorescent ureteral stent can enhance ureter visualization and further improve surgical safety.

In this study, the usage rate of PUC was 3.0%, mainly applied to high-risk populations, and no ureteral injury occurred during the operation. Compared with patients who did not use PUC (with an injury rate of 0.15%), it demonstrated its protective value. At the same time, the complications related to PUC were relatively mild and could subside before discharge. Compared with the serious consequences such as hydronephrosis and reoperation caused by ureteral injury, the benefits of PUC far outweigh the risks.

At present, the application of PUC still faces controversy: On one hand, some studies suggest that PUC cannot significantly reduce the incidence of ureteral injury and will prolong the operation time and increase medical costs; on the other hand, for complex surgical cases, the auxiliary identification role of PUC cannot be replaced. The European Association of Urology recommends that the decision on whether to use PUC should be made individually based on the patient's risk factors and the surgeon's experience.

Furthermore, the implementation of PUC currently relies heavily on urologists. If it is incorporated into the training of surgical residents, it can enhance the flexibility of surgical scheduling, shorten the total time for anesthesia and surgery, and is particularly suitable for emergency scenarios. At the same time, there are currently no-stent ureter identification technologies (such as indocyanine green injection, new fluorescent dyes) in the exploration stage, and in the future, they are expected to reduce PUC-related complications and optimize clinical application.

At the same time, this study also has certain limitations: Firstly, it is a single-center retrospective study with a small sample size (42 cases), and the overall incidence of ureteral injury is low, making it difficult to comprehensively evaluate the true efficacy of PUC; Secondly, it is a non-controlled study, and the implementation of PUC depends on the experience and preferences of surgeons, which may lead to selection bias; Thirdly, it did not explore the long-term impact of PUC on postoperative ureteral stricture, nor did it compare the advantages and disadvantages of PUC with other methods of ureteral identification.


【Conclusion】
Preventive ureteral catheterization (PUC) is a safe and effective method for preventing ureteral injury during colorectal cancer surgery. It is particularly suitable for high-risk groups such as those with a history of pelvic surgery, local recurrence of rectal cancer, or tumors adjacent to the ureter. It can precisely assist in identifying the ureter during the operation, avoiding irreversible damage, and the related complications are mild and controllable.

Although the indications of PUC have not yet reached a unified consensus and there are certain limitations, for complex and high-risk colorectal cancer surgeries, PUC remains a reliable strategy for protecting the ureter. In the future, through prospective multi-center studies, it is necessary to further standardize the clinical application of PUC, optimize the selection of applicable populations, and explore safer and more efficient alternative methods for identifying the ureter, in order to enhance the safety of colorectal cancer surgeries.