Urinary iodine excretion after using povidone iodine or chlorhexidine gluconate for topical disinfectant in patients undergoing thyroidectomy due to thyroid carcinoma: When to do radio active iodine therapy?

Background: Povidone Iodine (PI) is the most frequent antiseptic used as a topical disinfectant in surgery. It has been reported high transcutaneous iodine absorption due to topical PI usage, but there is a lack of data in periods of excess iodine depletion.

Materials and methods: This is a cross-sectional study designed to assess serial urinary iodine concentration (UIC) after topical administration of PI to evaluate the transcutaneous iodine absorption and the proper iodine depletion time for safe administration of Radio Active Iodine (RAI) therapy as ablative or adjuvant therapy.

Results: Thirty-seven patients with papillary thyroid carcinoma undergoing total thyroidectomy were assigned to the PI group (n = 20) or chlorhexidine gluconate (CHG) group (n = 17). In the PI group, the UIC levels rose to a maximum of 2 times in the 4^th week after administration and returned to pre-operative levels in the 8^th week after. In the CHG group, there was a decrease in UIC levels due to a low iodine diet (LID) with a significant P-value of 0.001, <0.001, and 0.001 in the 2^nd, 4^th, and 8^th weeks follow up respectively compared to the PI group. The urinary excretion of excess iodine lasts about 8 weeks after total thyroidectomy until iodine levels turn back to pre-operative values.

Conclusion: If the thyroidectomy was prepared with PI, RAI is better to be performed 6-8 weeks after surgery rather than the standard prescription of 4 weeks.