Colonoscopy is very useful for diagnosing and treating colorectal diseases. Bowel preparation with polyethylene glycol (PEG) or magnesium citrate has been widely performed and is considered to be safe, but it can sometimes cause severe electrolyte disturbances.
A 74-year-old man was admitted to our hospital for a planned colonoscopy. He had no history of neurological diseases. He was taking no medications. He was given oral administration of 1.8 L magnesium citrate. While he was waiting to undergo colonoscopy, he began to respond slowly and consciousness disorder developed. Brain computed tomography showed no abnormalities. Laboratory examination showed a serum sodium level of 119 mEq/L. He was diagnosed with severe symptomatic hyponatremia and treated with hypertonic saline infusion. Colonoscopy was cancelled. The next day, the sodium level increased to 127 mEq/L and his consciousness level recovered to normal. If a patient shows neurological disturbance at the time of colonoscopy, serum electrolytes should be checked and treatment should be started promptly.
