CAN WE IDENTIFY GLOMERULAR HYPERFILTRATION IN PATIENTS WITH TYPE 2 DIABETES BY CLINICAL PARAMETERS?

Abstract

Objective: In the early state of renal involvement in patients with type 2 diabetes (T2DM), glomerular hyperfiltration is often found, preceding the onset of albuminuria, leading to a slow decline of kidney function and finally to end-stage kidney disease. Our study goal was to identify the patients with glomerular hyperfiltration by clinical parameters. Design and method: In this cross-sectional study, we analyzed 192 patients with T2DM in the early stage of the disease having a normal renal function estimated by the CKD-EPI formula (eGFR). In each patient we measured glomerular filtration rate (mGFR) and renal plasma flow (RPF) by applying the constant infusion input clearance technique with inulin and sodium p-aminohippurate (PAH). In our study population, glomerular hyperfiltration was defined as mGFR >= 142 ml/min (>= 75th percentile). We assessed clinical and renal hemodynamic parameters. We also analysed the changes in renal function after medication. Results: Of all the patients with glomerular hyperfiltration (n = 50), only 12 patients had also an eGFR above the 75th percentile (eGFR >= 100 ml/min/1.73m2) and only 6 showed a microalbuminuria. Patients with glomerular hyperfiltration had significantly lower BMI, uric acid as well as cystatin C levels. BP, HbA1c, fasting plasma glucose or diabetes duration were not different between the two groups. Patients with glomerular hyperfiltration had significantly higher renal plasma flow, consequently higher renal blood flow and filtration fraction as well as intraglomerular pressure. The resistance in the vas afferens was significantly lower and in the vas efferens significantly higher than in patients with mGFR < 75th percentile. The sensitivity analysis (using the 70th, 80th and 90th percentile) did show similar results. Of the 192 patients, 6 patients showed an increase and 7 patients a decrease by 20% in mGFR. One of the 13 patients had a concordant increase or decrease, respectively, by 20% on the eGFR corrected for the actual body surface area. Conclusions: The data suggest that patients in the early stage of T2DM with glomerular hyperfiltration and thereby at risk for diabetic kidney disease are not identifiable by routinely used clinical parameters.