Assessment of ICG fluorescence in identification and preservation of parathyroid glands in thyroid surgeries and correlation with postoperative parathormone and serum calcium levels

Introduction: Intraoperative parathyroid gland (PG) localization remains challenging during thyroid surgeries, contributing to postoperative hypocalcemia and hypoparathyroidism. This study assessed the efficacy of indocyanine green (ICG) fluorescence in identifying and preserving PGs during thyroid surgeries and its correlation with postoperative outcomes.

Materials and methods: This ambispective observational study included 57 patients undergoing thyroid surgeries using ICG and compared outcomes with 56 historical controls. ICG was administered intravenously in two 5 mg boluses. Parathyroid identification rates, fluorescence intensity, and postoperative calcium and parathormone levels were assessed. Fluorescence intensity was qualitatively scored on a 1-3 scale.

Results: ICG significantly improved PG identification (92.5% vs 69.3% with white light alone). Postoperative hypocalcemia occurred in 22.81% of ICG patients compared to 39.29% in controls (p = 0.045). Hypoparathyroidism rates were 10.53% and 32.14% respectively (p = 0.005). Higher fluorescence intensity (FI) correlated with lower risk of postoperative hypocalcemia (p = 0.026) and combined hypocalcemia and hypoparathyroidism (p = 0.046). Considering both FI 2 and 3 as positive yielded 100% sensitivity and 85.7% accuracy. When only FI 3 was considered positive, sensitivity was 78.4%, specificity was 50%, and accuracy was 69.4%.

Conclusion: ICG fluorescence is a safe and effective tool for enhancing PG identification and preservation in thyroid surgeries, significantly reducing postoperative hypocalcemia and hypoparathyroidism. It also helps in confirming the vascularity of the PGs post thyroidectomy. Fluorescence intensity of preserved PGs, rather than quantity, better predicts postoperative outcomes. These findings support the integration of ICG fluorescence imaging and the application of our methodology in thyroid surgeries to improve postoperative results.