# Fluorescence-guided ureter mapping in colorectal surgery: a systematic review of intraureteral ICG and emerging renal fluorophores

## TL;DR

This paper reviews how fluorescence imaging using dyes like ICG can help surgeons better see the ureters during colorectal surgery, reducing injury risks.

## Contribution

The study systematically evaluates the effectiveness of ICG and new fluorophores for ureter identification in colorectal surgery.

## Key findings

- ICG fluorescence achieved ureter visualization rates of 95.3% to 100% with no major complications.
- Cystoscopy for ICG administration added 7 to 29 minutes to procedure time.
- Emerging renally excreted fluorophores may eliminate the need for ureteral catheterization.

## Abstract

Ureteral injury is a severe complication in colorectal surgery, with an incidence up to 2.5%. Despite meticulous surgical technique, intraoperative ureter identification can be challenging, particularly in cases involving prior operations or extensive inflammation. Indocyanine green (ICG) fluorescence imaging has emerged as a promising adjunct to enhance ureter visualization. In parallel, novel fluorophores with renal excretion properties (e.g., CW800-CA, ZW800-1) are undergoing investigation to avoid routine ureteral catheterization. This systematic review evaluates the efficacy, safety, and clinical impact of ICG-based and emerging fluorescence approaches for ureter identification in colorectal surgery.

A systematic literature search was performed in PubMed and Embase, up to March 2025, following PRISMA 2020 guidelines. Studies assessing intraoperative ureter identification via ICG fluorescence or other near-infrared fluorophores during adult colorectal surgery were included. Exclusion criteria comprised pediatric populations, non-colorectal procedures, reviews, editorials, and animal experiments. Primary outcomes were ureter visualization rate and intraoperative ureteral injury rate, while secondary outcomes included procedure-related complications, operative time, adverse effects, and preliminary cost data.

Ten studies comprising 716 patients undergoing colorectal surgery with ICG fluorescence imaging were analyzed. Ureter visualization rates ranged from 95.3% to 100%, with most studies reporting a rate of 100%. No ICG-related complications were documented. ICG administration was primarily via cystoscopy with intra-ureteral injection or ureteral catheterization, predominantly in laparoscopic and robot-assisted procedures. Mean duration of the cystoscopy varied from 7 to 29 min. Improved intraoperative ureter identification compared with conventional visualization was reported in available comparative studies.

ICG fluorescence imaging safely and effectively enhances intraoperative ureter visualization during colorectal surgery, potentially reducing the risk of ureteral injuries. However, the need for routine ureteral catheterization prolongs procedure duration. Emerging renally excreted fluorophores may eliminate the need for catheterization and should be prioritized in future clinical trials.

PROSPERO [CRD420250653992].

Infographic explaining fluorescence-guided ureter mapping with indocyanine green, highlighting over 95 percent visualization, no major complications, 716 patients, rare minor cystoscopy-related events, procedure duration of seven to twenty-nine minutes, catheter-based dye delivery, passive urinary tract accumulation, and the need for multicenter randomized trials, standardized protocols, and cost-effectiveness analyses.