Renal dysfunction is fairly common in people with diabetes. Approximately 25% to 40% of patients with Type 1 diabetes ultimately develop diabetic nephropathy (DN), whilst the corresponding figures for Type 2 diabetes are in 5% to 15% although some studies show that the figure may go as high as 40% even in this category of patients. Diabetic nephropathy (DN) progresses through about five predictable stages. Progression through these five stages is rather predictable because the onset of DM 1 can be identified, and most patients are free from age-related medical problems. The time line for Type 2 patients is not too clear as the onset can be quite insiduos and some patients progress through the stages very rapidly.

The five stages are:
Stage 1 (very early diabetes) Increased demand upon the kidneys is indicated by an above-normal glomerular filtration rate (GFR).

Stage 2 (developing diabetes) The GFR remains elevated or has returned to normal, but glomerular damage has progressed to significant microalbuminuria (small but above-normal level of the protein albumin in the urine). Patients in stage 2 excrete more than 30 mg of albumin in the urine over a 24-hour period. Significant microalbuminuria will progress to end-stage renal disease (ESRD). Therefore, all diabetes patients should be screened for microalbuminuria on a routine basis.

Stage 3 (overt, or dipstick-positive diabetes) Glomerular damage has progressed to clinical albuminuria. The urine is "dipstick positive," containing more than 300 mg of albumin in a 24-hour period. Hypertension (high blood pressure) typically develops during stage 3.

Stage 4 (late-stage diabetes) Glomerular damage continues, with increasing amounts of protein albumin in the urine. The kidney's filtering ability has begun to decline steadily, and the levels of blood urea and serum creatinine have begun to increase. The glomerular filtration rate (GFR) decreases about 10% annually. Almost all patients have hypertension at stage 4.

Stage 5 (end-stage renal disease, ESRD) GFR has fallen to approximately 10 milliliters per minute (<10 mL/min) and renal replacement therapy (i.e., hemodialysis, peritoneal dialysis, kidney transplantation) is needed.

Why is renal dysfunction so common in patients with diabetes? Poor glycemic control, hypertension, dyslipidemias are the major predisposing factors to renal dysfunction in a person with diabetes. Genetics also play an important role: Patients who have one or two deletions of the angiotensin-converting enzyme (ACE) gene, a defect in the sodium proton pump, or a family history of hypertension are at increased risk for progression to diabetic nephropathy. However in such patients renal dysfunction does not occur until diabetes develops; the worse and more prolonged the hyperglycemia, the greater the risk of diabetic nephropathy.

Whilst some people feel that renal dysfunction is a part and parcel of the diabetic scene and will invariably occur with time, it is also widely accepted that we can do quite a bit to delay the onset. In spite of this, if renal dysfunction does occur, early diagnosis and certain specific treatments can, if not reverse, at least slow down the rate of progression of the renal dysfunction so that it reaches its end stage at a very late age.

So how are we to avoid or the least delay the onset and rate of progression of renal dysfunction?