Your kidneys are two of the hardest-working organs in your body, filtering approximately 50 gallons of fluid from the blood that passes through them daily. After the million or so nephrons in each kidney balance electrolytes and filter toxins, 49.5 gallons of fluid are returned to the bloodstream cleansed and chemically and hormonally balanced. The remaining half-gallon leaves the body as urine.

Blood vessel damage, hypertension, and insufficiently controlled blood glucose can take a serious toll on renal (or kidney) function, damaging this amazing filtration capacity of the kidneys. As a result, diabetes has become the number-one cause of end-stage renal disease (ESRD, or chronic kidney failure), accounting for 38 percent of all U.S. cases.

Both type 1 and type 2 patients are at risk for developing kidney problems, and the risk of developing ESRD increases with the length of time since diabetes diagnosis, probably due to the prevalence of high blood pressure and long-term uncontrolled blood glucose in diabetes and the added stress it places on the kidneys.

In fact, uncontrolled hypertension is the second, most common cause of kidney failure in America, accounting for about 25 percent of the ESRD patient population according to the National Kidney Foundation.

Many people with diabetic kidney disease don't experience any symptoms until the disease has advanced significantly. Signs and symptoms of severe kidney disease include the following:

• Protein (albumin) in the urine

• High blood pressure

• Frequent urination, especially at night

• Leg cramps

• Flank pain

• Puffiness and swelling around the eyes, hands, and feet (edema)

• Excessive itching (pruritis)

• Nausea and vomiting

• Weakness

If your doctor suspects renal impairment, she will run several diagnostic tests to assess your kidney function, including a urine test for microalbumin, or trace amounts of protein in the urine. Microalbuminuria is one of the hallmarks of early kidney disease, and at one time was thought to be the beginning of the end of kidney function for people with diabetes.

However, a Joslin Diabetes Center study published in the New England Journal of Medicine in June 2003 found that 58 percent of type 1 study subjects who developed microalbuminuria were actually able to reverse the condition within six years with good control of blood glucose, blood pressure, and cholesterol levels.

Importance of Good Control

Several large-scale diabetes studies have demonstrated that tight blood glucose control can significantly reduce the risk of nephropathy. In fact, the DCCT found that people with type 1 diabetes who maintained an average A1C of 7.2 percent cut their risk of developing nephropathy and other complications up to 75 percent. And the United Kingdom Prospective Diabetes Study (UKPDS) found that people with type 2 diabetes achieved a 35 percent reduction in risk for nephropathy for each percentage point they lowered their A1C levels.

If you develop kidney disease, you may have to watch your protein intake; a registered dietitian can help you to develop a meal plan that is low in dietary protein and compatible with blood sugar control goals. However, studies are still inconclusive on the benefits of low-protein diets in lowering the risk of developing kidney disease, and the ADA currently recommends that most adults who have diabetes without known kidney damage include approximately 15 to 20 percent of total calories from protein in their diets.

Because diabetic kidney disease often goes hand-in-hand with hypertension, you may be prescribed ACE inhibitors or other medication to control your blood pressure and cut the workload of your kidneys, as well.