Diabetic Nephropathy

What Should I Know About Diabetic Nephropathy?

Diabetes can cause swelling and scarring of the glomeruli (the filtering units of the kidneys) and is one of the most important causes of kidney failure. A large percentage of people with diabetes (depending on certain risk factors) will develop diabetic nephropathy and a significant number of them will go on to require dialysis within two decades.

Knowing the Risk Factors

Not everyone with diabetes gets diabetic nephropathy but those that do often develop it within 10-20 years. The risk is roughly equal for both Type 1 and Type 2 diabetes. Risks factors include uncontrolled diabetes, high blood pressure, having family members with diabetic kidney disease, older age, being African American or Hispanic, and tobacco use.

Natural History of Diabetic Nephropathy

Diabetic nephropathy typically starts with a small amount of protein in the urine (or proteinuria) within 10-15 years after the onset of diabetes. Over time, the protein loss increases and high blood pressure develops. Continued scarring leads to kidney failure as seen by an elevated creatinine and eventually the kidneys fail completely and dialysis is required.

Making the Diagnosis

The first clue to a diagnosis is looking for protein in the urine. If protein is found in the urine of a diabetic, the most likely diagnosis is diabetic nephropathy. To be sure, you need to do a kidney biopsy. However, one is not usually performed because the risk usually outweighs the benefit. If a careful review of the medical history as well certain blood and urine tests don’t suggest another cause, the diagnosis is usually made without a kidney biopsy.

Screening for Diabetic Nephropathy

Except for Type 1 diabetics who were recently diagnosed (< 5 years), it is a good idea to screen all diabetics for protein in their urine at least once a year. If a large amount of protein (> 300 mg/day) is present (overt proteinuria), it can usually be identified by a simple urine dipstick. With earlier disease (microalbuminuria), it is usually necessary to send some urine to the lab to check for urine albumin.

Treating Diabetic Nephropathy

There is no magic bullet for diabetic nephropathy; once it starts, it tends to progress. Treatment is designed to slow down the progression of the disease as much as possible. Currently available options include: strict glucose control, high blood pressure control, ACE inhibitors, low protein diet, control of lipid disorders, and weight reduction.

Importance of Glucose Control

The benefit of glucose control depends on how early it is started (the earlier the better) and how strict it is. If done early enough, it has been shown to partially reverse and delay the progression of the disease, especially if you have Type 1 diabetes. Even if you receive intense treatment only for a little while, the effect can last for years. If the disease progresses to the point where large amount of protein is being lost, the benefits are less impressive.

Blood Pressure Control Is a Must

Control of high blood pressure is important in most kidney diseases, regardless of the cause, because of its role in causing disease progression. Sick kidneys cannot handle the high pressure and fail faster. People who can get their blood pressures less than 120/80 do better (as long as it doesn’t go too low).

ACE Inhibitors Are Standard of Care

ACE inhibitors are a type of blood pressure medication that have been shown to decrease protein loss and help prevent disease progression. In addition to helping to keep the BP under control, they are thought to affect the very small blood vessels to shunt pressure past the glomeruli thus decreasing the stain on them. A similar category of drugs called ARB’s show similar benefits.

Prognosis for Diabetic Nephropathy

The prognosis depends on how early the disease is caught and how good the treatment compliance is. In general, the earlier and more aggressive the treatment, the slower the progression, and the longer you can avoid dialysis. Once overt proteinuria develops, kidney failure is usually a matter of time.