ICG fluorescence imaging in sentinel lymph node identification: toward a standardized protocol in paediatric renal...

Adequate lymph node sampling is essential for accurate staging and treatment planning in Wilms tumour. Both SIOP and COG protocols recommend sampling more than six lymph nodes. However, median retrieval rates remain low in both open and minimally invasive approaches. This study aimed to assess the feasibility, safety, and efficacy of intraoperative indocyanine green (ICG) fluorescence imaging for sentinel lymph node (SLN) identification in paediatric renal tumours and to contribute to the standardization of dosage and timing protocols.

A two-centre prospective study (2023-2025) was conducted in Wrocław and Gdańsk involving 20 paediatric patients undergoing nephron-sparing surgery (n = 14) or nephrectomy (n = 6) for renal tumours with ambiguous lymphatic drainage. ICG (0.2 ml of a 5 mg/ml solution) was injected into four sites of healthy renal parenchyma, 1-2 cm from the tumour margin, after kidney exposure and before vascular pedicle preparation. Near-infrared (NIR) imaging (Stryker) was used to visualise lymphatic drainage and sentinel nodes.

Twenty children were included (median age 3 years, IQR 1.75-5.00). The median number of lymph nodes retrieved was 4 (IQR 3-6), with a median of 3 fluorescent nodes (IQR 1.5-4.5). Sentinel lymph node visualisation was successful in six cases (one benign renal cyst and five nephroblastomas) and failed in chromophobe carcinoma and renal cell carcinoma. No ICG-related adverse events were observed. The number of lymph nodes retrieved did not differ significantly between nephron-sparing surgery and nephrectomy; however, a higher number of fluorescent nodes was observed in the nephron-sparing group (median 3.5 vs. 1.0; p = 0.0757). Compared with historical controls, the ICG-guided cohort demonstrated a significantly higher lymph node yield (median 4.0 vs. 3.0; p = 0.00468). Operative time was significantly longer in the ICG group (median 130.5 min [IQR 114.5-145.0] vs. 109.5 min [IQR 91.0-112.5]; p = 0.00513), likely reflecting the initial learning curve associated with adoption of the technique.

ICG fluorescence imaging is a promising adjunct for SLN mapping in paediatric renal tumours. Standardisation of injection protocols is required to improve reproducibility. The technique is safe, feasible, and may improve staging accuracy while reducing the need for repeat surgeries.