Abstract: FR-PO0881
Unbelted Post-Motor Vehicle Accident (MVA) Hyponatremia and Subsequent Polyuria: Is This Concurrent Post-Traumatic Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH) and Central Diabetes Insipidus?
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Case Reports - 1
October 23, 2026 | Location: Exhibit Hall A, Convention Center
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid, Electrolytes, and Acid-Base Disorders
- 1102 Fluid, Electrolyte, and Acid-Base Disorders: Clinical
Authors
- Onuigbo, Macaulay A., University of Vermont The Robert Larner MD College of Medicine, Burlington, Vermont, United States
- Bau, Kimberly, University of Vermont The Robert Larner MD College of Medicine, Burlington, Vermont, United States
Introduction
Post-traumatic SIADH with hyponatremia and post-traumatic central diabetes insipidus with polyuria are well described syndromes. We describe hyponatremia post-MVA compounded by polyuria. The mechanisms of these dueling syndromes are revisited.
Case Description
An 18-yo female after an unbelted single occupancy passenger MVA - hit a tree - had exploratory laparotomy for free abdominal fluid and endovascular repair of thoracic aorta transection on hospital day (HD) 1. She had mediastinal hematoma, lung contusions, liver lacerations, right upper kidney laceration, and multiple fractures. She had pelvic ring fixation of right femoral shaft fracture on HD 2. Non-contrast head CT was unremarkable. Nephrology was consulted on HD 11 for polyuria of 7-8 L/day, with worsening hyponatremia (Fig 1). Creatinine peaked at 1.09 mg/dL on HD 3 and then normalized (Fig 2). Sodium fell from 145 mmol/L to 129 mmol/L on HD 11. (Fig 1). Urine osmolality, 493 mOsm/kg, and urine sodium, 190.7 mmol/L, on HD 10, were consistent with SIADH. Plasma Copeptin was <2.8 pmol/L (<13.1) on Hospital Day 12.
The diagnosis was post-traumatic (TBI) and post-surgical SIADH causing hyponatremia and post-AKI osmotic diuresis with some elements of primary polydipsia to explain polyuria. Moderated fluid restriction of 2-2.5 L/day was instituted. Hyponatremia and polyuria both resolved (Fig 1).
Discussion
We describe concomitant sequential post-TBI and post-surgical SIADH with hyponatremia and superimposed post-AKI recovery osmotic diuresis (AKI recovery, IV fluids, and multiple iodinated contrast) after an unbelted MVA. The dueling mechanisms of these pathologic processes called for a moderated approach to fluid management with resolution of the problems in good time.
Acknowledgment
This abstract is dedicated to all the hard-working staff at the University of Vermont Medical Center, here in Burlington, VT, USA, including the faculty, the fellows, the nurses, the nursing assistants, the technicians, the residents and the medical students. This abstract is also dedicated to the patients we treat dilgently, every day.
Intake/Output and sodium levels
Creatinine trajectory