free water clearance 2020-05-28T14:54:46Z CMO:0003418 PMID:23955305 In the physiology of the kidney, free water clearance is the volume of blood plasma that is cleared of solute-free water per unit time. A free water clearance of zero means the kidney is producing urine isotonic with respect to the plasma. Values greater than zero for free water clearance imply that the kidney is producing dilute urine through the excretion of solute-free water. slaulede renal water clearance clinical_measurement_ontology kidney physiological measurement