MO006: Identifying the Main Predictors of Urine Output in Autosomal Dominant Polycystic Kidney Disease (ADPKD) Patients taking Tolvaptan

Abstract

Abstract BACKGROUND AND AIMS Tolvaptan (TVP) blocks vasopressin V2 receptors causing severe polyuria. Few works have analyzed factors associated with urine output in autosomal dominant polycystic kidney disease (ADPKD) patients taking TVP. METHOD We selected 24 h urine samples from ADPKD patients treated with TVP. Urine osmolality/creatinine ratio was used as estimator of urine daily osmolar load. RESULTS We included 122 urine samples from 54 patients. After TVP, urine output doubled with a parallel reduction in solutes in urine with parallel reduction in urine solute concentration. However, when they were expressed as urine solute/creatinine ratios, no significant changes were observed. Daily osmolar load and osmolality/creatinine ratio did not change significantly. Before TVP, urine output was positively correlated with body weight and urine osmolality/creatinine ratio and negatively with estimated glomerular filtration rate (eGFR), urine morning osmolality and 24 h urine calculated osmolality. After TVP, urine output was positively correlated with body weight, eGFR and negatively with age. There was a poor correlation with urine calculated osmolality. We built a predictor model using general linear modeling, and we found that urine output was related to lower age, higher body weight, higher eGFR and greater doses of TVP. When body weight was removed, urine output was also related to male sex and higher daily osmolar excretion. CONCLUSION Patients taking TVP will undergo an increase about twice in urine production from baseline. Greater doses of TVP cause a progressive increase in urine output independent of renal function. GFR and specially age and body weight are the most important predictors of future urine output in patients taking TVP.