Severe Hypercalcemia due to Drowning in an Onsen (Hot Spring)

Hypercalcemia is generally caused by primary hyperparathyroidism, malignancies, and drugs. Herein, we report a case of severe hypercalcemia due to drowning in hot springs. A 55-year-old woman was found floating in a public bath at a hotel and was admitted to a nearby hospital. The patient was intubated because of hypoxia and shock, and noradrenaline was titrated. Computed tomography revealed bilateral aspiration pneumonia. Blood tests revealed hypercalcemia (serum total calcium [Ca]: 18.7 mg/dL). Hyperparathyroidism, malignancy, and drug-related factors were ruled out as the causes of hypercalcemia. In addition, the public bath in which the patient drowned contained high concentrations of Ca. We concluded that the reason for hypercalcemia was accidental ingestion of the hot spring water containing a high concentration of Ca through the gastrointestinal tract. In the case of drowning and hypercalcemia, the cause may be clarified by examining the components that were accidentally swallowed.