Increased kidney size,glomerular filtration rate and renal plasma flow in short-term insulin-dependent diabetics

Summary Glomerular filtration rate (GFR), renal plasma flow (RPF) and kidney volume were measured in thirteen male subjects (mean age 30 years) with short-term insulin-dependent diabetes (mean duration of disease 2.4 years) and fourteen normal male subjects (mean age 29 years). GFR and RPF were measured by constant infusion technique using I¹²⁵-iothalamate and ¹³¹I-hippuran. Kidney size was determined by means of ultrasound. GFR, RPF and kidney volume were increased in the diabetic patients compared to the normal controls, 144 versus 113 ml/ min×1.73m² (p<0.0005), 627 versus 523 ml/ min×1.73 m² (p<0.0025) and 278 versus 224 ml/ 1.73 m² (p<0.0005) respectively. Combining results from diabetic patients and controls revealed a positive correlation between kidney size and GFR (r= 0.70, p<0.001) and between kidney size and RPF (r=0.61, p<0.001). Within the groups kidney size and RPF correlated significantly in the diabetics (p< 0.01) and the same was found for kidney size and GFR (0.025< p<0.05), while no correlations were found in the normal group. GFR and RPF correlated in the diabetics when evaluated separately (r=0.81, p<0.001) and in the controls (r=0.73, p<0.001). The previous and present data suggest that the mechanisms of the elevated GFR in insulin-dependent diabetics are enhanced RPF, increased transglomerular hydrostatic pressure gradient and increased glomerular ultrafiltration coefficient. The increased kidney size is probably the main cause of the above alterations in the GFR determinants.