Endocrine Abstracts

Background: Arginine vasopressin disorder (previously diabetes insipidus (DI)) can be distinguished clinically into a relative deficiency of, or resistance to anti-diuretic hormone. Lithium is the mainstay of therapy for patients with bipolar affective disorder (BPAD), 40% of whom will go on to develop arginine vasopressin resistance (previously nephrogenic DI). We present a challenging case of an elderly gentleman receiving long-term lithium therapy who developed a hyperosmolar, hypernatremia with significant polyuria.

Case report: An 81 year-old man presented to the Emergency Department with dyspnoea and cough. He was treated for pneumonia with IV antibiotics. He had a background of COPD, laryngectomy for previous laryngeal cancer and BPAD taking 800 mg of Lithium Carbonate daily. As his pneumonia improved, he exhibited persistent low mood, oppositional behaviour towards staff and frequently declined oral intake. On Day 12 of admission his sodium acutely rose from 152 mmol/l to 161 mmol/l. His Corrected Ca2+ was > 2.7 mmol/l. His urea and creatinine were also acutely elevated and serum osmolality was 351mOsm/kg (275-295mOsm/kg). He was clinically dehydrated on hydration assessment. Fluid balance assessment revealed a polyuria of >4L in 24 hours, with a urine osmolality of 543mOsm/kg (<800mOsm/kg). He was treated with 2L of 5% dextrose. His lithium was held and serum lithium levels were shown to be 0.47 mmol/l (NR 0.6-1.0 mmol/l) two days later. Psychiatry reviewed remotely and advised cessation of lithium until biochemistry normalised. Desmopressin 0.1 mg PO was then administered. Over several days his sodium levels normalised and polyuria resolved. Although his mood remained an issue, he was discharged home on day 19 with plans to closely monitor.

Conclusion: This case not only highlights the complexities of lithium induced AVR but also the compounding systemic challenges of managing such cases in a regional model-three hospital, without psychiatry services and with extended wait times for specialised tests.