Ultrasonographic thyroid nodular findings in Japanese children.

Purpose: The Fukushima Health Management Survey conducted after the accident at the Fukushima Nuclear Power Plant included thyroid ultrasound examinations for children aged ≤18 years at the time of the accident. The purpose of this study was to investigate the frequency of thyroid nodular lesions detected using high-quality ultrasonography in a general population of Japanese children, in whom such data have not been previously characterized.

Methods: The current study investigated 4,365 free-living children aged between 3 and 18 years in three Japanese prefectures (Aomori, Yamanashi and Nagasaki). The same ultrasonography equipment as that used in the Fukushima Survey was employed to observe thyroid nodular lesions. The following categories of findings were used-'A', further examinations are not necessary; 'B', the presence of thyroid nodules with a diameter of ≥5.1 mm or thyroid cysts with a diameter of ≥20.1 mm; and 'C', immediate further examinations are required. As a sub-category of 'A', 'A1' was defined as the absence of nodules or cysts, and 'A2' was defined as the presence of thyroid nodules with a diameter of ≤5.0 mm or thyroid cysts with a diameter of ≤20.0 mm.

Results: Overall, 4,321 (99 %) of the total participants were classified with a status of 'A' and 44 (1 %) were classified with a status of 'B'. No participants were classified with a status of 'C'. A total of 56.5 % of the total participants was classified with a status of 'A2'. Thyroid nodules were identified in 1.6 % of the total participants and thyroid cysts were identified in 56.9 % of the participants.

Conclusion: The current study provides data regarding the actual frequency of ultrasonographically detected thyroid nodular lesions among the Japanese children. These results would be useful for evaluating thyroid findings in Japanese children, although careful interpretation is required.