The incidence of nephropathy in type 1 diabetic patients with proliferative retinopathy: a 10-year follow-up study.

Patients with type 1 diabetes mellitus and with proliferative retinopathy often have a concomitant diabetic nephropathy. However, in cross-sectional studies it has been shown that 35% of patients with proliferative retinopathy do not show signs of diabetic nephropathy. The aim of the present study was to examine the incidence of diabetic nephropathy in type 1 diabetic patients with proliferative retinopathy but without signs of nephropathy. To that end, out of 102 consecutive patients with proliferative retinopathy attending the University Hospital, Lund, in 1986, 24 patients did not show any clinical signs of nephropathy, and were followed for 10 years regarding the development of nephropathy. Their age was 36.7 +/- 9.8 years, age at onset 11.8 +/- 7.5 years, diabetes duration 25.7 +/- 6.9 years and duration of proliferative retinopathy 4.6 +/- 3.8 years (mean +/- S.D.). At entry, no patient had albuminuria (< 30 mg/l), and albumin creatinine clearance ratio was < 0.01 x 10(-3). During the 10-year follow-up period, two of the patients showed isolated higher peaks of elevated urinary albumin, but none of the 24 patients developed persistent microalbuminuria (> or = 30 mg/l). Two patients died before follow-up, but none of these had developed microalbuminuria at the time for death. Based on mean annual measurements, there were no increases in HbA1c, systolic and diastolic blood pressure, and serum creatinine levels. At entry, seven of the patients were treated with antihypertensive drugs and another three patients received such treatment during the study period. In conclusion, in a subgroup of patients with proliferative retinopathy, i.e. without clinical signs of diabetic nephropathy, no patient developed persistent microalbuminuria during a 10-year follow-up period. These results indicate further evidence for at least partly different pathogenic mechanisms behind diabetic retinopathy and nephropathy.