The emerging concept of chronic kidney disease without clinical proteinuria in diabetic patients.

The natural history of diabetic nephropathy was defined in the 1980s on the basis of longitudinal studies undertaken in patients with type 1 and type 2 diabetes. However, an increasing number of studies have indicated that certain diabetic patients do not present with the same evolution as was then defined: for example, some often have significant initial deterioration of glomerular filtration rate whereas, in others, microalbuminuria is reduced spontaneously. Chronic kidney disease (CKD) may be accompanied, rather than preceded, by macroalbuminuria, or it may develop in patients with microalbuminuria or even in those with albuminuria levels that revert to normal. CKD can also develop in patients whose albuminuria levels remain normal. Progression to macroalbuminuria is, in fact, less frequent than regression to normoalbuminuria or no change in microalbuminuria status in diabetic patients with microalbuminuria, especially in type 1 diabetes. Some experience progressive deterioration of renal function due to diabetes without developing significant proteinuria: this is seen fairly frequently and can affect 50% of patients with renal insufficiency. Such cases are more often older patients treated with renin-angiotensin system blockers who usually have a history of cardiovascular disease. Evolution to end-stage renal disease is slower in this subgroup of patients, although histological analyses may show surprisingly advanced glomerular lesions. The main parameters of surveillance remain regular monitoring of glycaemia, and control of blood pressure and the evolution of initial albuminuria levels. Nevertheless, why some patients exhibit conventional diabetic nephropathy while others have slower declines in renal function associated with normal albuminuria levels or microalbuminuria is unclear. It is hoped that the new pathological classification of diabetic nephropathy will help in our understanding of these discrepancies.