Recurrent Severe Hyponatremia Following Polyethylene Glycol Electrolyte Lavage Solution with Ascorbic Acid in a Patient with Undiagnosed Syndrome of Inappropriate Antidiuretic Hormone Secretion.

BACKGROUND Colonoscopy is the criterion standard for identifying colorectal cancer; however, adequate bowel preparation is required to achieve an effective evaluation of the colonic mucosa. Polyethylene glycol electrolyte lavage solution (PEG-ELS) is widely used for bowel cleansing because of its nonreactive and water-soluble composition and limited absorption in the digestive system. PEG-ELS with ascorbic acid (PEG-ELS/Asc) is effective because of its high osmolality, but it can cause rapid changes in the water content of the body. CASE REPORT A 79-year-old man ingested 2000 mL of PEG-ELS/Asc and was instructed to drink 1000 mL of free water to cleanse the bowel before colonoscopy. After completing bowel preparation, stupor and generalized tonic-clonic seizures developed. His serum sodium level was 119 mmol/L. Brain images revealed chronic ischemic changes and age-related brain atrophy; however, no active or acute changes were observed. Laboratory analyses indicated syndrome of inappropriate antidiuretic hormone secretion. Symptoms recurred during 2 separate events, and PEG-ELS/Asc was identified as the trigger of those symptoms. The patient's former physician indicated that PEG-ELS without Asc was used for bowel preparation before the previous colonoscopy, and that obvious symptoms suggestive of hyponatremia were not observed. CONCLUSIONS We observed reproducible and serious hyponatremia attributable to colonoscopy preparation. PEG-ELS/Asc triggered significant alterations in blood osmolality. Recurrence following PEG-ELS/Asc was confirmed on 2 separate occasions. Such reproducible cases underscore the importance of risk management and adequate bowel preparation for elderly patients.