Reversible diabetic nephropathy is characterized by:
Microalbuminuria (<300 mg/day or <300mg/d) shows that diabetic nephropathy is reversible. Overt proteinuria ie >300mg/d is usually irreversible. 
The most common histological pattern in DM is Diffuse Glomerulosclerosis. 
The most typical histological pattern in DM is Kimmelstiel-Wilson lesion (nodular glomerulosclerosis).
Microalbuminuria
Macroalbuminuria
Kimmelstiel Wilson lesion
Diffuse glomerulosclerosis