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Indocyanine Green (ICG)

Indocyanine green (ICG) is a tricarbocyanine near-infrared (NIR) fluorescent dye that binds rapidly to plasma proteins after IV injection and is cleared almost exclusively by hepatic excretion into bile — with a plasma half-life of 3–4 minutes. When excited by 750–800 nm light, ICG emits at 830 nm — a wavelength that is invisible to the naked eye but visualized by dedicated NIR imaging systems (Firefly, SPY, Rubina, PINPOINT). This combination — rapid plasma binding, rapid clearance, biliary excretion, and NIR emission through several millimeters of tissue — makes ICG the dominant intraoperative fluorophore in GU reconstruction.[1][2]

Pharmacology​

PropertyValue
ClassTricarbocyanine NIR fluorescent dye
Molecular weight775 Da
Plasma half-life3–4 minutes
Protein binding>95% (plasma proteins, primarily albumin)
DistributionPredominantly intravascular initially; fluorescence is not a direct quantitative measure of tissue viability
ClearanceHepatic — excreted into bile; no renal or urinary excretion
Peak excitation~800 nm
Peak emission~830 nm
FDA approvalCurrent IC-GREEN label includes vessels, blood flow and tissue perfusion; retrograde urinary instillation and GU sentinel mapping remain off-label

Why the pharmacology matters​

  • Rapid plasma half-life means you can give multiple doses per case as anatomy evolves
  • No urinary excretion — ICG given IV does not appear in urine; this is the critical distinction from indigo carmine / methylene blue and is why IV ICG is not useful for ureteral visualization from within the urinary tract. IV ICG can still be used for ureter visualization by assessing perfusion of exposed adventitial vessels, but not for visualization of the urinary column itself
  • Biliary excretion — ICG can faintly highlight the biliary tree, which is rarely clinically relevant in GU work but worth knowing

Dosing​

IV perfusion dosing — current US IC-GREEN label​

For an adult image sequence, 1.25–5 mg IV, followed immediately by a 10 mL saline flush. For extremity perfusion through skin, the adult range is 3.75–10 mg. Additional sequences may be obtained during the procedure, without exceeding 2 mg/kg total. This is a ceiling, not a target or a fixed repeat-every-5-minutes protocol. Reconstitute the 25 mg vial with 10 mL Sterile Water for Injection (2.5 mg/mL); other vial presentations have their own instructions. Use within 6 hours and discard unused solution. Use an imaging device authorized for the intended ICG application.[5]

Direct urinary instillation and lymphatic mapping​

Retrograde intraureteral or intravesical ICG is off-label. Concentration, volume and catheter handling should follow a defined specialist protocol; published case-series recipes are not interchangeable with the IV label. Penile/prostate lymphatic mapping also must not borrow a generic injection recipe from the separately labeled cervical/uterine cancer indication. Do not force injection against resistance.

Hypersensitivity and iodide​

The January 2026 US IC-GREEN label contraindicates use in patients with hypersensitivity to indocyanine green. It does not list shellfish allergy or a nonspecific “iodine allergy” as that contraindication. Clarify the actual prior drug and reaction, check the specific product label, and obtain allergy/anesthesia input when needed. Anaphylaxis, including fatal reactions, has occurred: monitor every patient and have resuscitation personnel and equipment available. Sodium iodide in IC-GREEN can interfere with thyroid radioiodine uptake for at least one week.[5]

GU Reconstruction Applications​

1. Perfusion assessment​

The original and highest-yield urologic application. IV ICG highlights the arterial perfusion of any tissue — ureteral stump viability, bowel mesentery before urinary diversion, bladder flap vascularity, phalloplasty flap perfusion, omental pedicle viability.

  • Ureter after reimplantation — helps assess perfusion of the distal segment after dissection
  • Ileal conduit before anastomosis — helps assess bowel-segment perfusion
  • Kidney perfusion during partial nephrectomy — helps assess residual parenchymal perfusion after clamp release; an imaging adjunct rather than an isolated indication for tissue excision[3]
  • Bladder flap for Boari — helps assess perfusion of the flap before tubularization
  • Omental flap — may supplement visual assessment of pedicle perfusion after mobilization
  • Bowel anastomosis in urinary diversion — early identification of poorly perfused anastomotic segments

2. Ureteral identification​

Two distinct techniques — IV vs. intraureteral:

Intraureteral ICG (retrograde):

  • Ureteral catheter placed cystoscopically; instillation proceeds retrograde according to the local protocol
  • The urinary column within the ureter fluoresces under NIR imaging
  • An adjunct for intraoperative ureter localization during robotic pelvic surgery
  • Particularly valuable in fibrotic / reoperative / malignant fields where ureter is hard to identify by dissection alone

IV ICG for ureter:

  • IV injection does not fill the ureter (no urinary excretion)
  • However, the ureter's adventitial vessels fluoresce transiently after IV dose, outlining the ureter's course
  • Less reliable than intraureteral but useful when retrograde access is impractical
  • See also pudexacianinium (ASP-5354) — an investigational IV NIR agent that is excreted into urine

3. Lymphatic mapping​

  • Pelvic lymph node dissection during radical prostatectomy, cystectomy (within functional-urology scope where it overlaps)
  • Sentinel node mapping in penile cancer (outside primary WARWIKI scope but referenced for completeness)
  • Intradermal / peritumoral ICG injection → lymphatic channels fluoresce → sentinel node identification

4. Vesicourethral / bladder-neck identification (robotic)​

  • Y-V plasty for refractory bladder neck contracture — Firefly ICG visualization of the residual bladder neck in the scarred post-prostatectomy field is a defining technique-enabler. See Y-V plasty.[4]
  • Vesicourethral anastomotic stenosis repair — similar rationale

5. Penile reconstruction​

  • Perfusion assessment after Peyronie's degloving
  • Phalloplasty flap assessment — RFFF, ALT, SCIP perfusion
  • Penile shaft coverage flap viability

6. Fistula localization (emerging)​

Experimental use of intravesical ICG for VVF localization in selected cases; methylene blue remains standard.

NIR Imaging Hardware​

ICG fluorescence requires dedicated imaging:

SystemPlatformWorkflow
FireflyIntuitive da Vinci (Si, Xi, X, SP, 5)Toggle between white-light and NIR modes at the console
SPY / Luna-IRStryker (open + laparoscopic)Handheld NIR imager for open cases
PINPOINTNovadaq/StrykerLaparoscopic NIR video system
IMAGE1 S RubinaKarl StorzLaparoscopic NIR with side-by-side display
Visera Elite IIIOlympusLaparoscopic NIR

Firefly dominance in robotic reconstruction means ICG is overwhelmingly associated with da Vinci workflows in urology. Open and laparoscopic cases rely on SPY or Rubina.

Technique Pearls​

  • Give the bolus at the right moment — 15–45 seconds from injection to target tissue fluorescence. Coordinate with anesthesia so the bolus is given just before the assessment rather than 5 minutes ahead
  • Don't dose too early in the case — ICG clears in 3–4 minutes; if given before the tissue is fully mobilized, the fluorescence will have washed out
  • Track cumulative dose and residual background fluorescence; fluorescence intensity depends on dose, timing, camera settings and tissue conditions
  • Intraureteral retrograde dosing is more reliable than IV for ureteral course visualization
  • Firefly auto-gain can over-brighten adjacent tissues — toggle the NIR view intermittently to recalibrate
  • Clarify prior dye reactions; alternative dyes have their own risks and pudexacianinium remains investigational

Adverse Events​

ICG has an excellent safety profile over 65+ years of clinical use:

  • Anaphylaxis — potentially fatal; postmarketing reports do not provide a reliable incidence or establish shellfish allergy as a predictor[5]
  • Mild reactions — nausea, flushing; rare
  • Predominantly hepatic clearance — does not require urinary excretion for perfusion imaging; this does not mean risk-free in CKD
  • ICG is not a gadolinium contrast agent; apply its own label and hypersensitivity precautions

Interpretation and cost​

ICG highlights fluorescence associated with delivery and tissue uptake; it does not by itself prove durable anastomotic viability or exclude ischemia. Standardized thresholds and improvement in clinical outcomes remain procedure-specific questions. Acquisition prices vary by product and contract; the imaging system and workflow contribute to total cost.

See Also​

References​

1. Alander JT, Kaartinen I, Laakso A, et al. A review of indocyanine green fluorescent imaging in surgery. Int J Biomed Imaging. 2012;2012:940585. doi:10.1155/2012/940585

2. Reinhart MB, Huntington CR, Blair LJ, Heniford BT, Augenstein VA. Indocyanine green: historical context, current applications, and future considerations. Surg Innov. 2016;23(2):166–75. doi:10.1177/1553350615604053

3. Yang YK, Hsieh ML, Chen SY, Liu CY, Lin PH, Kan HC, Pang ST, Yu KJ. Clinical benefits of indocyanine green fluorescence in robot-assisted partial nephrectomy. Cancers (Basel). 2022;14(12):3032. doi:10.3390/cancers14123032

4. Granieri MA, Weinberg AC, Sun JY, Stifelman MD, Zhao LC. Robotic Y-V plasty for recalcitrant bladder neck contracture. Urology. 2018;117:163–165. doi:10.1016/j.urology.2018.04.017

5. IC-GREEN. US prescribing information, revised January 2026. DailyMed.