Ultrasonographic thyroid nodular findings in Japanese children.
OBJECTIVE
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.


CONCLUSIONS
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.
Department of Clinical Laboratory Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan. taniguch@jichi.ac.jp.
Nobuyuki
N
Taniguchi
Department of Global Health, Medicine and Welfare, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan.
Naomi
N
Hayashida
Department of Environmental Internal Medicine, Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi, Japan.
Hiroki
H
Shimura
Department of Social Medicine, Hirosaki University Graduate School of Medicine, Aomori, Japan.
Noriyuki
N
Okubo
Department of Emergency and Disaster Medicine, Hirosaki University Graduate School of Medicine, Aomori, Japan.
Yasushi
Y
Asari
Department of Endocrinology and Metabolism, Hirosaki University Graduate School of Medicine, Aomori, Japan.
Takeshi
T
Nigawara
Department of Radiation Health Management, Fukushima Medical University, Fukushima, Japan.
Sanae
S
Midorikawa
Department of Clinical Laboratory Medicine, Jichi Medical University, 3311-1 Yakushiji, Shimotsuke, Tochigi, 329-0498, Japan.
Kazuhiko
K
Kotani
Department of Social Medicine, Hirosaki University Graduate School of Medicine, Aomori, Japan.
Shigeyuki
S
Nakaji
Department of Clinical Studies, Radiation Effects Research Foundation, Nagasaki, Japan.
Misa
M
Imaizumi
Department of Radiation Health Management, Fukushima Medical University, Fukushima, Japan.
Akira
A
Ohtsuru
The First Department of Medicine, Wakayama Medical University, Wakayama, Japan.
Takashi
T
Akamizu
Division of Endocrinology and Metabolism, Showa General Hospital, Tokyo, Japan.
Masafumi
M
Kitaoka
Department of Organ Regulator Surgery, Fukushima Medical University, Fukushima, Japan.
Shinichi
S
Suzuki
Department of Radiation Medical Sciences, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan.|Radiation Science Center for Fukushima Health Management Survey, Fukushima Medical University, Fukushima, Japan.
Shunichi
S
Yamashita
Department of Global Health, Medicine and Welfare, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan.
Noboru
N
Takamura
Children; Nodular thyroid lesion; Thyroid cyst; Thyroid nodule; Thyroid ultrasonography