ESPN 50th Annual Meeting

ESPN 2017


 
Evidence for "shrunken pore syndrome" in children
Emil den Bakker 1 Isabelle Hubeek 1 Joanna AE van Wijk 1 Reinoud JBJ Gemke 1 Arend Bökenkamp 1

1- VU MEDICAL CENTRE
 
Introduction:

Cystatin C (CysC), a LMW protein marker for kidney function, has been linked to mortality independently of kidney function in adults. Elevated levels of CysC compared to serum creatinine (Crea) may reflect diminished filtration of CysC due to a smaller size of glomerular pores - the “Shrunken Pore Syndrome” (SPS). In adult populations, around 8% fulfill the criteria of SPS. This study aims to compare the elimination characteristics of the LMW protein GFR markers CysC, beta-trace protein (BTP) and beta-2 microglobulin (B2M) with creatinine in children using a gold standard GFR measurement.

Material and methods:

Retrospective study of 459 inulin clearance (Cin) studies with simultaneous determination of Crea, CysC, BTP and B2M. Establishing eGFR equations in a subset of 153 of these studies. Analysis of the remaining 306 studies for the presence of SPS defined as eGFRLMW-P/eGFRCrea <0.6. Comparison of Cin, eGFRCrea and the three eGFRLMW-P in relation to the eGFRCysC/eGFRCrea ratio.

Results:

Cin, eGFRcreat and the three eGFRLMW-P gave comparable results as long as eGFRCysC/eGFRcreat was above 0.6. Beyond this point, eGFR decreased for CysC, BTP and B2M, while eGFRCrea increased. Of note, Cin did not change indicating that filtration of all three LMW markers was diminished compared to inulin while eGFRcreat overestimated GFR. Based on eGFRBTP SPS was observed in 5.6%, on eGFRCysC in 5.2% and on eGFRB2M in 4.2% of the patients.

Conclusions:

The proportion of children meeting the criteria of SPS is comparable to adults. In SPS patients, filtration of the three LMW-protein markers is impaired compared to inulin suggesting abnormal filtration rather than an extra-renal mechanism. At the same time, eGFRcreat is increased, most likely due to diminished creat synthesis. Taken together, these findings support a link between SPS and muscle wasting caused by retention of pro-inflammatory cytokines of similar size.