Persisting glomerular hyperfiltration in short-term diabetic children without microalbuminuria.

The renal function in a group of diabetic children (n=29;age;4-17 yr; IDDM duration: 1,5-13 yr) was studied with a 3 year interval. At the first evaluation glomerular filtration rate (GFR) as assessed by inulin clearance was significantly increased compared to control values (167 +/- 32 vs. 124 +/- 18 ml/min/1.73 m2; pl less than 0.01). Eighteen out of 29 children exhibited a glomerular hyperfiltration (GFR greater than 160). Three years later mean GFR was identical (169 +/- 25 ml/min/1.73 m2) and 16 children were hyperfiltrating. Among them, 11 have had a persisting glomerular hyperfiltration over the 3-year period. Renal plasma flow (RPF) was positively correlated to GFR (r=0.7; p less than 0.01) and remained elevated at both evaluations (794 +/- 163 and 812 +/- 157 ml/min/1.73 m2, p greater than 0.01 vs, control values). When the children were separated into 3 groups according to IDDM duration no significant differences were observed in the results for GFR and RPF, Mean urinary albumin excretion was comparable at the 3-year interval, and not significantly different from the control values (5.2 +/- 3.7 and 8.2 +/- 6.6 respectively vs. 8.65 +/- 4 microgram/min). None of the children demonstrated a persistent microalbuminuria. This study reveals a high proportion of diabetic children with a persisting glomerular hyperfiltration, without any other symptom of incipiens nephropathy, If elevated GFR plays an important role in the development of diabetic nephropathy, this study emphasizes the value of regular evaluation of renal function in diabetic children.