ICG-Guided Flap / Graft Perfusion Assessment in Urethral Reconstruction
ICG-guided flap and graft perfusion assessment is an emerging intraoperative adjunct in urethral reconstruction. Indocyanine green near-infrared fluorescence angiography (ICG-FA) gives a real-time, semiquantitative reading of tissue perfusion that supplements visual and tactile assessment.[1] The evidence base is early but growing across adult urethroplasty, pediatric hypospadias repair and ureteral reconstruction.[2] An international Delphi consensus supports ICG angiography in plastic and reconstructive surgery.[2]
For ICG mechanism, FDA dosing limits, agent-specific contraindications and safety profile, camera hardware, broader GU applications (ureteral identification, lymphatic mapping, VUA, fistula localization), and adverse events, see the canonical Indocyanine Green (ICG) hub.
Applications in Urethral Reconstruction
1. Graft-bed assessment in substitution urethroplasty
Zhang 2024 described a protocol in three illustrative cases for intravenous ICG use in open urethral reconstruction with two imaging modes: a black-and-white qualitative brightness mode and a quantitative perfusion mode comparing the tissue of interest to a control area of similar tissue type.[1] In dorsal onlay buccal mucosal graft urethroplasty, graft-bed perfusion was compared to the proximal erectile bodies. A proposed perfusion cutoff of ≥ 60% of control correlated with the surgeon's clinical judgment of adequate graft-bed quality. Graft take depends on imbibition and inosculation from the recipient bed, so a poorly perfused bed is a concern.
2. Flap perfusion in perineal urethrostomy (Blandy flap)
In the same Zhang series, ICG was used to assess a Blandy flap during perineal urethrostomy both before and after mobilization. A flap-perfusion cutoff of ≥ 40% of control was proposed based on existing flap-reconstruction literature, with the goal of tailoring flap design to avoid ischemia and necrosis.[1]
3. Staged urethroplasty after failed hypospadias repair
In complex staged substitution urethroplasty after prior hypospadias repair, ICG facilitated a more limited excision and shorter graft inlay by objectively delineating well-perfused from poorly perfused tissue, preserving viable tissue that might otherwise have been excised on visual inspection alone.[1]
4. Onlay preputial-island-flap hypospadias repair
Paraboschi 2023 first described ICG-guided assessment of a preputial island flap during onlay urethroplasty in one 13-month-old with mid-shaft hypospadias. With EleVision IR (Medtronic) and ICG 0.15 mg/kg, favorable fluorescence was observed 80 seconds after injection and informed the proximal flap resection margin.[3] In a separate 14-patient first-stage proximal-hypospadias pilot, Raines et al. imaged preputial flaps after degloving, mobilization and inset; ICG changed one intraoperative decision, and five patients underwent second-stage repair with repeat ICG assessment.[8]
5. Neourethral coverage in TIP (tubularized incised plate) urethroplasty
Wang 2026 evaluated ICG-FA with the SPY Elite system in 14 boys undergoing primary TIP hypospadias repair, with a mean follow-up of 24 months. Perfusion was categorized as well perfused or poorly perfused based on grayscale fluorescence intensity:[4]
| Cohort | n | Ventral necrotic crust | Urethrocutaneous fistula |
|---|---|---|---|
| Well-perfused | 10 | 0% (1 glans dehiscence only) | 0% |
| Poorly perfused | 4 | 100% (ventral necrotic crust) | 75% (3/4) |
No ICG-related adverse events were observed in these 14 boys; the sample is too small to establish safety or outcome benefit.
6. Open ureteral reconstruction — instructive parallel
Hebert 2024 is an observational reconstructive parallel: a prospective single-surgeon series of 39 patients and 40 operations, 32/40 with radiation-induced etiology. ICG-NIFI changed intraoperative decisions in 63% of operations, and white-light and fluorescence assessments differed in 61% of ureters. Mean resected ureter length was 3.6 cm after fluorescence assessment versus 1.8 cm under white light. One stricture occurred among 57 anastomoses (1.8%) at median 23.4-month follow-up.[5] Outcomes use operation-, ureter- and anastomosis-level denominators; 1.8% is anastomosis-level.[5]
For the technique-page on this application, see Ureteroenteric Anastomotic Stricture Repair and the broader Upper Tract Reconstruction atlas.
Perfusion Thresholds
| Context | Proposed cutoff or observed perfusion | Source |
|---|---|---|
| Graft bed (dorsal onlay urethroplasty) | ≥ 60% of control | Zhang 2024[1] |
| Blandy flap (perineal urethrostomy) | ≥ 40% of control | Zhang 2024[1] |
| Perforator flap (rat model) | Day-0 mean perfusion across 278 measurements: ~27% for tissue that necrosed vs ~59% for tissue that survived | Monahan 2014[6] |
| Head and neck reconstruction | Observational studies used 20–50% fluorescence reductions from reference areas to flag impaired viability; cutoffs varied | Poen 2026[7] |
The 60% graft-bed value was proposed from surgeon judgment in case 1 and a small series to date; the 40% Blandy-flap value was proposed in case 2 using other flap literature.[1] Neither is a validated decision threshold for urethral reconstruction.[1] Standardization across camera systems, tissue types, and clinical contexts remains an open challenge.[7]
Practical Workflow
- Agent and imaging protocol. Use the ICG pharmacology hub for product-specific dosing, cumulative limits and hypersensitivity precautions. Document injection-to-image timing and camera distance; interpretation varies by system and tissue.[2]
- Hardware. SPY Elite (Stryker) and EleVision IR (Medtronic) have been used in published hypospadias repairs.[3][4]
- Repeatability. Short hepatic clearance allows repeat injections within a single procedure.
- Confounders. The Delphi panel identified vasopressor use, lower body temperature and ambient light as factors that may alter ICG assessment quality. Document these conditions when interpreting borderline readings.[2]
For full FDA-label dosing, agent-specific contraindications, anaphylaxis precautions, and camera-system technical detail, refer to the foundations ICG hub.
Where It Fits in Urethral Reconstruction
ICG-FA is an intraoperative quality-assurance adjunct to a reconstruction. It may be considered where tissue quality is uncertain and the cost of graft or flap failure is high:
- Failed prior hypospadias repair with a depleted, scarred urethral plate.
- Radiated or otherwise hostile graft beds in adult substitution urethroplasty.[1]
- Staged BMG repairs where conservative excision preserves usable tissue.
- Perineal urethrostomy / flap-based reconstruction with concern for apical ischemia.
- Pedicled preputial / fasciocutaneous flap design where margin viability is the failure-mode of interest.
Outcome benefit versus unguided reconstruction has not been shown in randomized urethral data. Preliminary evidence includes a Wang 2026 association in 14 boys after TIP repair (fistula in 0/10 well-perfused versus 3/4 poorly perfused at mean 24 months)[4] and a Hebert 2024 ureteral series (decisions changed in 63% of 40 operations; 1/57 anastomoses strictured at median 23.4 months).[5]
Limitations
- Urethroplasty-specific evidence is limited to case reports, small feasibility series, and one TIP cohort.
- Perfusion thresholds are not yet standardized across camera systems, tissue types, and clinical contexts.[7]
- Vasopressor use, lower body temperature and ambient light can alter fluorescence-perfusion assessment quality, according to a plastic-surgery Delphi panel.[2]
- The technology adds cost (camera systems, ICG dye) and requires familiarity with interpretation.
- Hypersensitivity screening must be product-specific; a nonspecific “iodine allergy” label is not an adequate substitute. See foundations ICG for full safety detail.
Videos
References
1. Zhang X, Lin JS, Raines A, et al. Semiquantitative tissue perfusion assessment using indocyanine green in complex open urethral reconstruction. Urology. 2024;185:e149-e151. doi:10.1016/j.urology.2023.11.032.
2. Schols RM, Dip F, Lo Menzo E, et al. Delphi survey of intercontinental experts to identify areas of consensus on the use of indocyanine green angiography for tissue perfusion assessment during plastic and reconstructive surgery. Surgery. 2022;172(6S):S46-S53. doi:10.1016/j.surg.2022.04.015.
3. Paraboschi I, Gnech M, Minoli DG, et al. Indocyanine green (ICG)-guided onlay preputial island flap urethroplasty for the single-stage repair of hypospadias in children: a case report. Int J Environ Res Public Health. 2023;20(13):6246. doi:10.3390/ijerph20136246.
4. Wang Y, Du G, Guo F, et al. Preliminary use of ICG-FA in predicting the blood perfusion of neourethra covering in TIP hypospadias repair. Urology. 2026;214:93-97. doi:10.1016/j.urology.2026.04.044.
5. Hebert KJ, Bearrick E, Anderson KT, Viers BR. High rates of discordant ureteral perfusion during open ureteral reconstruction with indocyanine green: does near-infrared fluorescence imaging change management or stricture outcomes? Urology. 2024;190:117-122. doi:10.1016/j.urology.2024.04.055.
6. Monahan J, Hwang BH, Kennedy JM, et al. Determination of a perfusion threshold in experimental perforator flap surgery using indocyanine green angiography. Ann Plast Surg. 2014;73(5):602-606. doi:10.1097/SAP.0b013e318276da2d.
7. Poen WAFM, Nijssen DJ, van 't Hof LWP, et al. The role of indocyanine green fluorescence angiography in head and neck reconstruction: a systematic review. J Craniomaxillofac Surg. 2026;54(6):104477. doi:10.1016/j.jcms.2026.104477.
8. Raines A, Fernandez N, Ahn J, et al. "Preputial pedicle flap ICG blood flow assessment during proximal hypospadias repair: Development of a standardized protocol." J Pediatr Urol. 2024;20(4):691.e1-691.e7. doi:10.1016/j.jpurol.2024.05.015