Long-term retinal, renal and cardiovascular outcomes in diabetic chronic kidney disease without proteinuria.

BACKGROUND Patients with diabetes mellitus (DM) with chronic kidney disease (CKD) often have no proteinuria. METHODS To compare the characteristics that differ between DM + CKD patients with and without proteinuria, we conducted a cross-sectional study followed by surveillance over a decade for 'hard' cardiovascular, renal and retinal outcomes. Groups were stratified by presence (n = 129) and absence (n = 284) of DM. Each stratum had three groups: no CKD, CKD without proteinuria and CKD with proteinuria. RESULTS Compared to DM + CKD + proteinuria patients, those with DM + CKD but without proteinuria had similar clinical characteristics including estimated glomerular filtration rate. However, they had lower 24-h ambulatory systolic and diastolic blood pressure. Crude all-cause mortality rates per 1000 patient-years in the nondiabetic group with no CKD, CKD with no proteinuria and CKD with overt proteinuria were 29.3, 68.5 and 111.1, respectively. Respective rates in the diabetic group were 50.1, 105.7 and 136.8. Diabetes increased the risk of coronary (P = 0.01) and end-stage renal disease (ESRD) events (P = 0.05) even after multivariate adjustments. Proteinuria aggravated the risk of cardiovascular events, ESRD, death and time to first of these events similarly among diabetics with CKD compared to nondiabetics with CKD. Diabetic patients with CKD but no overt proteinuria were much more likely than nondiabetics to progress to overt proteinuria [adjusted hazard ratio 5.28 (95% confidence interval 1.64-17.02), P < 0.01). CKD was a risk factor for prevalent retinopathy and proteinuria was a risk factor for incident diabetic retinopathy. CONCLUSIONS To protect sight, those with proteinuria and DM need regular retinal examinations. Since diabetic CKD patients without proteinuria are more likely to develop overt proteinuria, close follow-up and risk factor management among these patients appear to be more important than among nondiabetic patients with CKD and no proteinuria.