Sweet and Salty: Diabetic Ketoacidosis in a Patient With Nephrogenic Diabetes Insipidus

The co-existence of nephrogenic diabetes insipidus (NDI) with diabetes mellitus (DM) in a patient that presents in diabetic ketoacidosis (DKA) is rare and, to our knowledge, has not been described even in case reports. We report the case of a 16-year-old male with known NDI who presented to the pediatric emergency department (ED) for one day with generalized weakness and decreased appetite, found to be in moderate DKA from new-onset DM. The initial management of his dehydration and hyperosmolar state presented a unique challenge. Fluid resuscitation with isotonic fluids in a patient with NDI poses a risk of worsening hypernatremia, which can lead to seizures and death. However, the use of hypotonic fluids has the potential to lower serum osmolality too quickly, which can result in cerebral edema. Nephrology, endocrinology, and the pediatric intensive care unit (PICU) consultants were notified of this patient, and a discussion was coordinated between sub-specialists to determine the appropriate fluid resuscitation. The patient was allowed to drink free water in addition to receiving intravenous fluids (IVF) of dextrose 5% with 0.2% sodium chloride at a rate of one-and-a-half maintenance (150 mL/hr) in the ED prior to transfer to the PICU where insulin infusion was initiated. This case report provides guidance to inpatient providers on the management of patients with co-existent NDI and DM in DKA, a rare combination that requires thoughtful and urgent management.