Validation of inulin as a marker for glomerular filtration in preterm babies

Abstract

Comparisons between the clearance of inulin and that of other markers have led to the hypothesis that glomerular pore size is related to body size, and that inulin may not be freely filtered in some small mammals. Similar conclusions may be reached from data on estimated glomerular pore size in young children calculated from dextran clearances, but the serious limitations of such an approach are well documented. Studies of inulin handling in fetal lambs and rats by glomerula micropuncture have failed to confirm any restriction to filtration, but no direct evidence is available in man. We therefore used gel chromatography to assess whether or not higher molecular weight inulin accumulated in the plasma of very immature babies who were infused with inulin for several days.