シスプラチン使用後に著しい低ナトリウム血症をきたした1例

A case of hyponatremia after cisplatin administration

はじめに

　シスプラチンは，頭頸部癌治療でよく使用されるが，有害事象の1つに低ナトリウム血症がある。原因として，抗利尿ホルモン不適合分泌（syndrome of inappropriate secretion of antidiuretic hormone：SIADH）がよく知られているが，塩類喪失性腎症（renal salt-wasting syndrome：RSWS）という報告は少ない^1）。今回，シスプラチン3コース目施行後，意識障害にて発症したRSWSによる低ナトリウム血症をきたした症例を経験したため報告する。

　Hyponatremia is an adverse event associated with cisplatin administration. We report a case of hyponatremia secondary to renal salt-wasting syndrome（RSWS）that occurred after cisplatin administration.

　A 68-year-old woman was treated with chemoradiotherapy for carcinoma of the oropharynx. Two weeks after she received the third course of cisplatin, the patient experienced disturbance of consciousness, and the serum sodium level was 102 mEq/L. We diagnosed the patient with RSWS based on measurement of the fluid volume, urine output, time of onset, and fractional excretion of uric acid, and she was treated with sodium infusion, and mineralocorticoids. The patient's symptoms resolved on day 26 after the third course of cisplatin administration.