MON-242 A Hidden Thirst: Unmasking of Central Diabetes Insipidus

Abstract

Introduction:Central diabetes insipidus (CDI) is a common pathology following traumatic brain injury, intracranial operations, medication use, and some infections. This case highlights how CDI can be unmasked when access to free water is restricted.Case Description:A 50 yo AAM with history of Down syndrome, hydrocephalus with ventriculo-atrial shunt, and seizure disorder treated with phenytoin, was brought in from home after three back-to-back seizures. EMS was called and intubated the patient in the field. Medical history was significant for ventriculo-peritonal shunt placed shortly after birth with revisions in 2011 and 2016. Revision in 2016 was complicated by infection with klebsiella pneumoniae. He was admitted to NSICU. Shunt evaluation showed no abnormality or obstruction. Lab work on admission at 5 am was significant for low potassium and sodium was normal. Patient was stabilized and extubated later that day. Repeat labs, at 4 pm, showed a sodium of 155 mEq/L with a normal potassium. Urine output was reviewed and significant for greater than 400 cc’s per hour for at least 2 hours. Urine osmoles (264 mOsm/kg, n 50-1200) and serum osmoles (314 mOsm/kg, n 280-295) were consistent with diabetes insipidus (DI). His IV fluid intake during this time was 3 liters bolused on admission followed by continuous fluids at 125 cc’s per hour. On review of systems, patient admitted to polydipsia and polyuria throughout the day for last several years. He reported urinating 2-3 times at night. During an admission 3 years prior for ventriculo-peritoneal shunt revision, serum sodium had risen to 159 mEq/L following his surgery and returned to normal prior to discharge. MRI pituitary during admission was negative for pituitary abnormality. To treat as well as differentiate central versus nephrogenic DI, desmopressin 1mcg IV was given. The patient was allowed to drink to thirst. Urine osmolarity increased from 159 mOsm/kg to 494 mOsm/kg after 2 hours and serum sodium slowly trended down. His urine output and thirst decreased with continued administration of desmopressin. He was discharged on a maintenance dose of 0.1 mg desmopressin twice a day. On follow up in clinic, his sodium has been maintained between 140-145.Discussion:This patient with CDI was compensating with large fluid intake daily as an outpatient for at least three years. His risk factors included phenytoin use as well as previous VP shunt occlusion complicated by infection which has been reported to contribute to CDI in other case reports. This case highlighted how CDI can be unmasked when a patient loses access to free water such as with altered mental status or intubation for surgery.