In order to evaluate the renal lesion and the clinical picture in diabetics with microalbuminuria the urinary albumin excretion rate (AER) was assessed and renal biopsy was performed in nonproteinuric (Albustix-negative) diabetics. The following results were obtained.
The resting AER was 6.6±3.8 (mean±SD)μg/min and 21.0±24.8μg/min in 20 healthy controls and 59 non-proteinuric diabetics, respectively. In diabetics, normal (<15 μg/min) and elevated (≥15 μg/min) AER was found in 40 cases (Group A) and 19 cases (Group B) respectively. Group B had longer duration of diabetes, higher systolic blood pressure and a higher incidence of retinopathy than group A.
AER after exercise using an Ergometer was measured in 14 healthy controls and 19 diabetics of group A. No significant differences were found as far as duration of diabetes, HbA₁, GFR, max. systolic blood pressure and incidence of retinopathy were concerned. The kidney was similarly damaged in 10 subjects with normal AER and 9 with AER elevated by exercise.
Renal biopsy was performed in 13 subjects in group A, 7 in group B and 5 with persistent proteinuria (group C). The glomerular diffuse lesion (Gellman's classification) was grade O, I or II in group A; II or III in B, and III or IV in C. The glomerular nodular lesion was grade O in A, O or I in B, and I or II in C. Arteriolar hyalinosis (Takazakura's classification) was graded as O or I in A, II or III in B, and III in C.
From these results, it was concluded that 1) diabetics with microalbuminuria had an advanced renal lesion which had the possibility of progress easily into persistent proteinuria and 2) determination of AER induced by exercise is not an adequate method to discriminate the more lerb renal lesion than that in diabetics with microalbuminuria.