Polyuria in adults. A diagnostic approach based on pathophysiology

Polyuria is a common clinical condition characterized by a urine output that is inappropriately high (more than 3 liters in 24 hours) for the patient's blood pressure and plasma sodium levels. From a pathophysiological point of view, it is classified into two types: polyuria due to a greater excretion of solutes (urine osmolality >300 mOsm/L) or due to an inability to increase solute concentration (urine osmolality <150 mOsm/L). Sometimes both mechanisms can coexist (urine osmolality 150-300 mOsm/L). Polyuria is a diagnostic challenge and its propertreatment requires an evaluation of the medical record, determination of urine osmolality, estimation of free water clearance, use of water deprivation tests in aqueous polyuria, andmeasurement of electrolytes in blood and urine in the case of osmotic polyuria. (c) 2021 Elsevier Espana, S.L.U. and Sociedad Espanola de Medicina Interna (SEMI). All rights reserved.