Diabetic Nephropathy Overview
Diabetic nephropathy is kidney disease that develops as a result of diabetes mellitus (DM). According to the Centers for Disease Control and Prevention (CDC), diabetes affects approximately 8.3 percent of the U.S. population (as of 2010). This disease damages many organs, including the eyes, nerves, blood vessels, heart, and kidneys. Diabetes is the most common cause of kidney failure in the United States and accounts for over one-third of all patients who are on dialysis.
Diabetes mellitus is a disorder in which the body is unable to metabolize carbohydrates (e.g., food starches, sugars, cellulose) properly. The disease is characterized by excessive amounts of sugar in the blood (hyperglycemia) and urine; inadequate production and/or utilization of insulin; and by thirst, hunger, and loss of weight.
Diabetics who require daily insulin shots to maintain life have insulin-dependent diabetes mellitus, or type 1 diabetes. In this type of diabetes, the pancreas secretes little or no insulin and the blood sugar level remains high, unless treated. Type 1 diabetes usually occurs in children and young adults, but it may occur at any age. In the past, this condition was also called juvenile onset diabetes. Onset of type 1 diabetes is abrupt. The patient becomes very sick and requires immediate insulin therapy. Approximately 3 million people in the United States have type 1 diabetes and each year, about 30, 000 people are diagnosed with the condition.
Non-insulin-dependent diabetes, or type 2 diabetes, differs from type 1 in that the main problem is a peripheral resistance to the action of the insulin. DM 2 usually occurs in adults over the age of 40 who are overweight and have a family history of the disease. Some patients can manage their diabetes with weight loss and changes in their diet. Others require medication, and many with DM 2 eventually require insulin. Onset is gradual, and patients may be sick for quite some time without knowing it. Nearly 95 percent of people with diabetes are diagnosed with type 2 diabetes.
Signs and Symptoms of Diabetic Nephropathy
Approximately 25 to 40 percent of patients with type 1 diabetes ultimately develop diabetic nephropathy (DN), which progresses through about five predictable stages.
- 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 (yearly) 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 kidneys' filtering ability has begun to decline steadily, and blood urea nitrogen (BUN) and creatinine (Cr) has 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.
Progression through these five stages is rather predictable because the onset of type 1 diabetes can be identified, and most patients are free from age-related medical problems at diagnosis.
An estimated 5 to 15 percent of type 2 diabetes cases also progress through the five stages of diabetic nephropathy, but the timeline is not as clear. Some patients advance through the stages very quickly.