Pre-incisional, trans-isthmic injection of indocyanine green for lymph node mapping during the transoral endoscopic thyroidectomy vestibular approach.

Indocyanine green (ICG) is a useful tracer for lymph node mapping and retrieval. However, during endoscopic surgery, it is challenging to administer ICG into the thyroid without spillage. We developed a simple technique of delivering ICG, thereby preventing leakage. Patients who underwent the transoral endoscopic thyroidectomy were retrospectively reviewed. In 20 patients, who constituted the ICG group, 0.1 mL ICG was injected into the peri-tumoral space under ultrasound guidance, soon after the patients received general anesthesia. Patients with papillary thyroid carcinoma who did not receive the ICG injection comprised the control group (n = 43). The location, size, and number of harvested lymph nodes were recorded in conjunction with parathyroid-related parameters. No ICG spillage occurred in the ICG group, and 76 ICG-stained lymph nodes were detected in the pretracheal (57.9%), paratracheal (25.0%), and prelaryngeal regions (17.1%). The ICG group demonstrated a significantly higher number of total (5.3 vs 2.1) and metastatic (1.5 vs 0.6) lymph nodes, a larger metastatic deposit in the positive node (3.5 mm vs 1.6 mm), and a higher rate of pathologically node-positive disease (70.0% vs 27.9%) than did the control group. The postoperative calcium level (7.8 mg/dL vs 7.2 mg/dL) was also higher in the ICG group. Pre-incisional, trans-isthmic injection of ICG under ultrasound guidance is a simple technique to prevent the leakage of ICG. Under fluorescence imaging, an adequate number of lymph nodes can be harvested for examination, which may assist in intraoperative decision-making.