Hyponatraemic seizure secondary to primary polydipsia following urological surgery

An 82-year-old man presented to the emergency department with delirium, vomiting and an initial hyponatraemia of 112 mmol/L the day after successful transurethral vaporisation of the prostate. He had a tonic-clonic seizure in the acute surgical unit and was managed subsequently in the intensive care unit with a controlled rate of hypertonic saline. Initial work-up for the cause of hyponatraemia revealed a low urine osmolality, suggestive of relative excess water intake. Detailed examination of the operation notes revealed no discrepancy between intraoperative irrigating fluid input and output. Careful collateral history revealed that the patient had drunk 8 L of water in the 24 hours following the operation, after taking advice to 'drink plenty of water' literally. This case highlights the importance of conveying specific advice to patient, the lower incidence of transurethral resection syndrome in resections using saline as an irrigation fluid and outlines the pathway for investigation and management for hyponatraemia.