Urine Retention Versus Post-obstructive Diuresis as a Potential Cause of Acute Hyponatremia: A Case Report.

Acute urine retention is a common urologic emergency that is frequently seen in the Emergency room (ER). Standard treatment includes placing a urinary catheter or a suprapubic catheter with outpatient urologic follow-up. Urine retention can cause complications, such as hyponatremia and post-obstructive diuresis. It is crucial to diagnose and manage these life-threatening complications appropriately. Herein, we present a case of urine retention-induced hyponatremia. The patient's urine sodium level and osmolality were consistent with the diagnosis of syndrome of inappropriate antidiuretic hormone (SIADH). In this patient, sodium autocorrection started after a urinary catheter placement. Hypotonic saline was administered to prevent rapid autocorrection. This type of hyponatremia is unique as autocorrection occurs after catheter placement; however, monitoring is needed to ensure fast autocorrection does not occur. Potential fast autocorrection is concerning in those patients. Treating those patients with hypertonic fluids or normal saline can exacerbate the fast autocorrection and lead to severe complications. Hypotonic fluid administration should be considered when developing rapid autocorrection.