U.S. Department of Health and Human Services

Approximating Kidney Function through Urine Analysis

The levels in urine of genetic material from a type of kidney cell correlate with loss of kidney function, according to a recent study.  This finding offers the possibility of a new, non-invasive way to approximate the kidneys’ filtering ability and monitor the progression of chronic kidney disease.
 
The podocyte is a cell that is a component of the glomerulus, the fundamental filtering apparatus in the kidney.  It has been hypothesized that progressive loss of kidney function in many forms of kidney disease can be attributed, at least in part, to damage to the glomeruli and accompanying depletion of podocytes.  As podocytes are lost, traces of them may be detectable in the urine.  In the current study, investigators analyzed urine samples from over 350 adult and pediatric volunteers with kidney disease and compared them with urine samples from nearly 300 people without kidney disease.  They observed a nearly 80-fold increase in podocyte-derived genetic material in patients who had glomerular disease (based on a previous biopsy) and who had progressive kidney disease.  A second group of patients with Alport syndrome, a hereditary glomerular disease, found a 23-fold increase in podocyte-derived genetic material.  Interestingly, in people with autosomal dominant polycystic kidney disease, which does not feature glomerular injury, urine podocyte-derived genetic material was not increased.  These observations suggest that the presence of podocyte genetic material in the urine may be a marker for glomerular injury and may provide a window into glomerular function.
 
These findings support the hypothesis that podocyte depletion is an important element of some forms of progressive kidney disease.  Furthermore, measurement of urine levels of podocyte-derived genetic material may provide an easy, non-intrusive way to evaluate and monitor podocyte health in people with glomerular diseases.
 
Wickman L, Afshinnia F, Wang SQ, Yang Y, Wang F, Chowdhury M, Graham D, Hawkins J, Nishizono R, Tanzer M, Wiggins J, Escobar GA, Rovin B, Song P, Gipson D, Kershaw D, Wiggins RC. Urine podocyte mRNAs, proteinuria, and progression in human glomerular diseases.  J Am Soc Nephrol 24: 2081-2095, 2013.