The aim of this study is to evaluate whether a new test using mannitol infusion can diagnose the cause of polyuria-polydipsia syndrome as accurately as the current standard test (hypertonic saline infusion) and to compare which test patients prefer. The goal is to identify a simpler and more patient-friendly diagnostic approach.
Age ≥ 18 years
Hypotonic polyuria/polydipsia syndrome defined as polyuria >40ml/kg body weight/24h and polydipsia >3l/24h; and urine osmolality <800mOsm/L or known AVP-D based on accepted criteria
Polyuria/polydipsia secondary to diabetes mellitus, hypercalcemia, or hypokalemia
Diagnosis of AVP-R (Copeptin > 21.4 pmol/L)
Evidence of acute illness
Epilepsy requiring treatment