Background: Venous congestion remains a leading cause of potentially salvageable flap failure. Indocyanine green angiography (ICGA) provides real-time perfusion visualization, yet most applications emphasize arterial inflow. Quantitative analysis may enable earlier and more objective detection of venous compromise. This systematic review evaluates how quantitative ICGA has been used to assess venous outflow in free and pedicled flaps and summarizes its clinical utility. Methods: Following PRISMA 2020 guidelines, a search of PubMed, MEDLINE, Scopus, and Web of Science (2000–2025) was conducted to identify studies reporting quantitative ICGA parameters related to venous outflow in free or pedicled flaps assessed intra- or postoperatively. Two reviewers screened studies and extracted data on imaging systems, quantitative metrics, and outcomes; risk of bias was assessed using the Risk of Bias in Non-randomized Studies of Interventions (ROBINS-I) tool. Results were synthesized descriptively. Results: Nine studies encompassing 210 patients and 164 flaps were included. Quantitative ICGA was applied across breast, head and neck, perineal, and lower extremity reconstructions using SPY, Quest, and Zeiss platforms. Reported measures included ratio-based indices, time-to-maximum fluorescence, inflow and outflow slopes, and washout or clearance analyses. Abnormal trends, such as prolonged Tmax, flattened egress slopes, or delayed washout, correlated with venous congestion and postoperative necrosis. Heterogeneity in dosing, imaging timing, software platforms, and definitions of “outflow” precluded meta-analysis. Conclusions: Quantitative ICGA can reliably detect subclinical perfusion abnormalities and may influence intraoperative decision-making. Standardized protocols and validated venous outflow metrics are needed to establish reproducible thresholds and confirm its prognostic value in flap monitoring.
Valadez et al. (Mon,) studied this question.