Urine Osmolarity Predicts the Body Weight-Reduction Response to Tolvaptan in Chronic Kidney Disease Patients: A Retrospective, Observational Study

Abstract

Background/Aims: Tolvaptan, a vasopressin V2 receptor antagonist, promotes the excretion of electrolyte-free water. Patients with heart failure or liver cirrhosis, whose urine osmolarity is high due to increased vasopressin, show a good response to tolvaptan; however, it remains dubious whether tolvaptan is also effective in patients with low urine osmolarity due to decreased renal function. The aim of this study was to investigate whether urine osmolarity predicts the effect of tolvaptan in patients with decreased renal function. Methods: In this retrospective, observational study, 17 overhydrated chronic kidney disease patients with heart failure or liver cirrhosis who were admitted to Osaka University Hospital were included. They were treated with sodium-excreting diuretics first, and then tolvaptan was added. The clinically relevant parameters were evaluated before and after the use of tolvaptan, and they, including urine osmolarity before use of tolvaptan, were compared between the responder group and the non-responder group. The definition of responder was based on the decrease of body weight by ≥5% in one week, which is a more rigorous indicator of the effectiveness of tolvaptan than the increase in urine output. Results: The parameter that showed a significant difference between the responder and non-responder groups was urine osmolarity before the use of tolvaptan. The cut-off point derived from the receiver operating characteristic (ROC) curve analysis was 279 mOsm/kg H₂O, with sensitivity of 0.86 and specificity of 0.80. Conclusions: In patients with decreased renal function, urine osmolarity before the use of tolvaptan predicted the effectiveness of diuretics in terms of body weight reduction.