Kidney disease: What people with diabetes need to know

When I see a patient with diabetes, we talk about the possible complications of the disease, including heart problems, eye disease, and foot problems. Kidney disease is also on this list-diabetes accounts for 44% of new cases of kidney failure. Here's what a Special Health Report from Harvard Medical School has to say about the link between diabetes and kidney failure.

In type 1 diabetes, the kidneys can suffer damage as early as within five years of diagnosis, although it usually takes more than 20 years before kidney failure occurs. Kidney disease is more common in type 1 than in type 2 diabetes. But high blood pressure (also known as hypertension), which is a problem for many with type 2 diabetes, can increase your chances of developing this condition and accelerates its progression.

What goes wrong?

The kidneys filter toxins and wastes from the bloodstream, flushing them out of the body through urine, while retaining important proteins and other useful substances. This filtering work is done by a delicate network of capillaries called glomeruli. But after prolonged exposure to high blood sugar, capillary membranes thicken, and the glomeruli are damaged and distorted.

One of the first signs of kidney disease is an elevation in the level of the protein albumin in the urine. Most healthy people excrete less than 30 mg of albumin, the most abundant protein in blood, in the course of a day. In the initial stage of diabetic kidney disease, called microalbuminuria, more albumin (30-300 mg) appears in the urine each day because of leakage through the damaged glomeruli.

Most people with microalbuminuria go on to develop full-blown kidney disease. The next phase, known as clinical albuminuria (in which up to several grams - the equivalent of thousands of milligrams - of albumin are excreted each day), may not occur for another 10 to 15 years. Over the next 5 to 10 years after the development of clinical albuminuria, more than 90% of those affected will undergo a steady loss of the filtering capacity of their kidneys.

Because healthy kidneys have built-in overcapacity, significant health problems develop only when more than 75% of kidney function has been lost. The inability to eliminate excess water and salt produces or worsens hypertension. Your body starts to retain fluid, causing weight gain and the swelling of your hands and feet. Without an effective filtering system, toxins accumulate, causing symptoms such as nausea, fatigue, vomiting, loss of appetite, weakness, and itching. At this point, kidney function has dropped below 10% to 15%, and the disease has progressed to kidney failure, which threatens survival and requires extreme measures, such as dialysis or transplantation.

Treating and preventing kidney disease

Strict blood sugar control is imperative. Long-term follow-up of the Diabetes Control and Complications Trial found keeping blood sugar close to normal decreases the risk of developing microalbuminuria and clinical albuminuria by 59% and 84% respectively.

Blood pressure must also be carefully controlled. Blood pressure goals are more stringent for everyone with diabetes. Worsening kidney function is associated with high blood pressure, and vice versa. Keeping blood pressure tightly controlled can reduce the rate of progression of kidney damage in people with type 1 and type 2 diabetes. Losing weight and reducing your salt intake can help. If medications are needed, most doctors prescribe ACE inhibitors or angiotensin receptor blockers to control high blood pressure in people with diabetes. These drugs retard the progression of kidney disease and may be used even when blood pressure is normal. Two or more types of blood pressure medications are often required to keep blood pressure within acceptable ranges.

Many doctors recommend low-protein diets for patients whose kidneys are deteriorating. These measures can slow the advancement of kidney disease and the eventual need for dialysis or kidney transplant, but they don't stop the process entirely. Most patients with clinical albuminuria inevitably progress to end-stage renal failure. Although this condition used to be fatal, now there are two treatment options: dialysis (a way to filter out wastes and toxins in the blood) and kidney transplantation.

Do you or someone you know have diabetes-related kidney problems? What have you been doing to treat them?

Julie K. Silver, M.D., is an assistant professor in the Department of Physical Medicine and Rehabilitation at Harvard Medical School. She is also the Chief Editor of Books for Harvard Health Publications.

Diabetes
Nearly 21 million Americans suffer from diabetes, and as anyone who has been affected by the disorder knows, it is about much more than a statistic: it means a new way of life. Diabetes: A plan for living is a special report from Harvard Medical School that will help you learn how to better understand and manage your diabetes, including type 1 and type 2, as well as other variations of the disease. This report will show you that it's not just possible to live with diabetes; it's possible to live well.





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