Endocrine Abstracts

This case pertains to a 58 year old female who attended hospital with right leg pain. Past medical history included metastatic uterine cancer (lung, bone, and brain), and bipolar disorder treated with sodium valproate and lithium. Prior to admission the patient lived at home with her husband, mobilised independently, and communicated with a mild expressive dysphasia secondary to brain metastases. The patient was admitted under orthopaedics and diagnosed with a pathological right femur fracture. During pre-operative assessment it was noted that the patient was acutely confused and drowsy with new onset tachycardia and shortness of breath. CTPA showed multiple PEs and increased burden of metastatic disease, chest XR showed nil focal, and CT head was similar to previous with some white matter oedema. The patient was treated clinically with antibiotics for pneumonia and treatment dose clexane. The patient continued to deteriorate overnight with decreased GCS and episodes of twitching (seizure activity) isolated to the upper limbs. EEG showed no status but mild encephalopathy. Neurology advised starting on leviteracetam and a course of dexamethasone. On day 4 of admission blood tests showed a sodium of 165 (previously within range). Fluid balance showed a 5 litre per 24 hours urine output with poor oral intake resulting in a deficit of approximately 4 litres per day. Urine and serum osmolalities were sent to the laboratory and treatment with intravenous fluids was commenced. A titration of dextrose, 0.18% saline, and normal saline were used variably over the next 11 days to return sodium levels to normal range. During this period the patient was taking 7-8 litres of fluid per day, initially intravenous and then orally, maintaining a positive fluid balance of approximately 1L per day. Urine osmolality=172 mOsm/kg Serum osmolality=327 mOsm/kg Endocrinology advised a trial of low dose desmopressin for long-term management of urine output. This reduced urine output to 2 l per day thus reducing the patient’s oral intake requirements. The patient had a successful surgery with IVC filter in situ 12 days post admission. It transpired that prior to admission the patient’s family had been assisting the patient in drinking 8 litres of water per day. At point of admission, an unintentional water-deprivation test revealed the underlying diagnosis of diabetes insipidus. The debate remains as to what the underlying pathology was. A) Nephrogenic diabetes insipidus secondary to lithium or B) neurogenic diabetes insipidus secondary to brain metastases?