ESPN 50th Annual Meeting

ESPN 2017

Urinary potassium to urinary potassium plus sodium ratio can accurately identify hypovolaemia in nephrotic syndrome
WERNER KEENSWIJK Ann Raes 1 Johan Vande Walle 1

1- Ghent University
2- Ghent University

Background: Acute Kidney injury (AKI) as a complication of idiopathic nephrotic syndrome is uncommon. However, evidence exists pointing to a decrease of GFR in a subgroup of nephrotic children, likely secondary to hypovolaemia.

Aim: To validate the use of urinary potassium to the sum of urinary potassium plus sodium ratio (UK/UK+UNa) as an indicator of  hypovolaemia in nephrotic syndrome enabling detection of those patients who will benefit from administration of albumin.

Material and methods:

 Methods: We prospectively studied 44 nephrotic children before and after administration of a water loading test and compared different parameters to a control group (36 children). Renal perfusion and glomerular permeability were assessed by measuring clearance of para-aminohippurate and inulin. Vaso-active hormones (plasma renin activity, aldosteron) and urinary sodium and potassium were also measured. 


 Results: Subjects were grouped into low, normal, and high GFR groups based on reference values obtained from the control group. In the low GFR group hypovolaemia was seen as demonstrated by significantly lower renal plasma flow (p= 0.01), filtration fraction (p=0.01) and higher UK/UK+UNa (p=0.03) ratio. In addition, non significant higher plasma renin activity (p=0.11) and aldosteron (p=0.09) were also seen in the low GFR group compared to high GFR and normal GFR groups.  



Conclusion: A subgroup of patients in nephrotic syndrome has a decrease in glomerular filtration, apparently related to functional hypovolaemia which can be detected by an elevated  urinary potassium to urinary potassium plus sodium ratio (> 0.5-0.6). In the clinical setting, this group will most likely benefit from albumin administration.