Endocrine Abstracts (2017) 49 EP942 | DOI: 10.1530/endoabs.49.EP942

Characteristics and 1-year follow-up of patients with profound hyponatremia due to primary polydipsia - a multicentre prospective observational study

Clara Sailer1,3, Bettina Winzeler1,3, Nicole Nigro1, Isabelle Suter-Widmer1, Birsen Arici1, Martina Bally2, Philipp Schuetz2,3, Beat Mueller2,3 & Mirjam Christ-Crain1,3

1Endocrinology, Diabetology and Metabolism, University Basel, Basel, Switzerland; 2Division of Endocrinology, Diabetology and Metabolism, Medical University Clinic, Kantonsspital Aarau, Aarau, Switzerland; 3Department of Clinical Research, University Hospital Basel, Basel, Switzerland.

Introduction: Hyponatremia due to excessive fluid intake (i.e. primary polydipsia (PP)) is common. It may culminate in profound hyponatremia – carrying considerable risk of morbidity. However, data on patients with PP leading to hyponatremia is largely lacking. Herein, we describe the characteristics of polydipsic patients hospitalised with profound hyponatremia, and assess one-year outcomes.

Method: In this prospective observational study, we included 23 patients with an episode of profound hyponatremia (≤125 mmol/l) due to PP. Patients were classified into subgroups: psychogenic polydipsia (PsyP), dipsogenic polydipsia (DiP), and beer potomania (BP). Symptoms, laboratory findings, and factors contributing to hyponatremia (co-morbidities, medication, and liquid intake) were assessed. A 1-year follow-up was performed to evaluate recurrence of hyponatremia, re-admission rate, and mortality.

Results: Of the 23 patients (median age 56 years [IQR 50–65], 74% female) 7 had PsyP, 8 DiP, and 8 BP. Median serum sodium of all patients was 121 mmol/l (IQR 114–123), median urine osmolality 167 mmol/l (IQR 105–184), and median copeptin 3.6 mmol/l (IQR 1.9–5.5). Psychiatric diagnosis, particularly dependency disorder (43%) and depression (35%), were highly prevalent. Factors provoking hyponatremia were found in all patients (e.g. acute water load, medication, stress). During the follow-up period, 67% of patients were readmitted, 52% of these with re-hyponatremia, and three patients (38%) with BP died.

Conclusion: Patients with PP have a high prevalence of addictive and affective disorders. Given the high recurrence, re-hospitalisation, and mortality rate, careful monitoring and long-term follow-up including controls of serum sodium, education and behavioural therapy is needed.