HYPERFILTRATION IN PATIENTS WITH TYPE-I DIABETES-MELLITUS - A PREVALENCE STUDY

Aim: An increase in glomerular filtration rate (GFR) and renal plasma flow (EFPR) may be considered as prognostic factors for the progressio n of diabetic nephropathy; however the real predicting value of hyperf iltration in the development of incipient and overt nephropathy is as yet unknown. We have examined the prevalence of hyperfiltration in a p opulation of normotensive adult IDDM patients and the possible effect of long-term metabolic control on glomerular hemodynamics. Materials a nd methods: We measured GFR and ERPF values in 177 normotensive, normo albuminuric insulin-dependent diabetic patients and in 30 healthy subj ects by single bolus intravenous injection of 1 mu Cu/kg [Cr-51]-EDTA and 0.2 mu C/kg [I-125]-Hippuran intravenously. We have correlated the GFR values with parameters of metabolic control over the last 3 years and with age, sex, and duration of diabetes. Results: Patients with a GFR greater than the 95 degrees percentile value of controls (135 ml/ min/1,73 m(2)) were defined as hyperfiltering. They represented the 55 .9% (99/177) of our population. We found a strong correlation between GFR and ERPF (p <0.001), and between GFR and average HbA(1c) levels (p = 0.016) in multiple regression analysis, with age, sex, ERPF, and av erage HbA(1c) levels entered as variables (r(2) = 0.45). There appeare d to be no correlation with the duration of the disease. Conclusions: Long-term hyperglycemia provides a significant contribution in GFR and a poor metabolic control is predictive of overt nephropathy. In this study hyperfiltration does not appear to be the major factor of diabet ic nephropathy. A follow-up of these patients is necessary to clarify the role of hyperfiltration in the development of overt nephropathy in diabetes.