I. Diagnostic criteria (1) A definite history of diabetes mellitus. (2)Urinary albumin excretion rate (UAER): If the UAER is between 20-200µg/min (28.8-288mg/24h) for three consecutive urine tests within 3 months and other causes of increased UAER can be excluded, early diabetic nephropathy can be diagnosed. (3) Persistent proteinuria: urine protein >0.5g/24h for more than 2 consecutive times, and can exclude other causes of increased urine protein, can be diagnosed as clinical stage diabetic nephropathy. Clinically, diabetic nephropathy should be considered in all diabetic patients with abnormally high urinary albumin excretion rate and urinary protein quantification, or with edema, hypertension, renal function impairment, or with diabetic retinopathy. Attention should also be paid to exclude urinary tract infections and a variety of primary and secondary renal diseases as well as heart failure and hypertensive disease as causes of increased urinary albumin excretion rate and urinary protein. Stage I: Increased glomerular filtration rate, increased kidney volume, no albumin in urine, no pathological histological damage. Renal blood flow, glomerular capillary perfusion and internal pressure are increased, and its initial changes are reversible. Phase II: Normal albuminuria phase. The urinary albumin excretion rate (UAER) is normal, the GBM is thickened, the thylakoid matrix is increased, and the GFR is mostly higher than normal. Stage III: Early diabetic nephropathy. Urinary albumin excretion rate (UAER) is 20-200µg/min or 30-300mg/24h, GBM is thickened, thylakoid matrix is increased, glomerular nodular and diffuse lesions and small arterial glassy lesions appear, and glomerular wasting begins. Stage IV: Clinical diabetic nephropathy or overt diabetic nephropathy. UAER persists at 200µg/min or urine protein >0. 5g/24h, blood pressure is increased, edema appears. Glomerular wasting is evident and GFR begins to decline. Stage V: end-stage renal failure. gfr