Diabetic Nephropathy: Diagnosis

Diabetic Nephropathy: Diagnosis

Diabetic nephropathy is the leading cause of kidney disease in patients starting renal replacement therapy and affects ∼40% of type 1 and type 2 diabetic patients. It increases the risk of death, mainly from cardiovascular causes, and is defined by increased urinary albumin excretion (UAE) in the absence of other renal diseases. Diabetic nephropathy is categorized into stages: microalbuminuria (UAE >20 μg/min and ≤199 μg/min) and macroalbuminuria (UAE ≥200 μg/min). Hyperglycemia, increased blood pressure levels, and genetic predisposition are the main risk factors for the development of diabetic nephropathy. Elevated serum lipids, smoking habits, and the amount and origin of dietary protein also seem to play a role as risk factors. Screening for microalbuminuria should be performed yearly, starting 5 years after diagnosis in type 1 diabetes or earlier in the presence of puberty or poor metabolic control. In patients with type 2 diabetes, screening should be performed at diagnosis and yearly thereafter. Patients with micro- and macroalbuminuria should undergo an evaluation regarding the presence of comorbid associations, especially retinopathy and macrovascular disease. Achieving the best metabolic control (A1c <7%), treating hypertension (<130/80 mmHg or <125/75 mmHg if proteinuria >1.0 g/24 h and increased serum creatinine), using drugs with blockade effect on the renin-angiotensin-aldosterone system, and treating dyslipidemia (LDL cholesterol <100 mg/dl) are effective strategies for preventing the development of microalbuminuria, in delaying the progression to more advanced stages of nephropathy and in reducing cardiovascular mortality in patients with type 1 and type 2 diabetes.
Diabetic nephropathy is the leading cause of chronic kidney disease in patients starting renal replacement therapy (1) and is associated with increased cardiovascular mortality (2). Diabetic nephropathy has been classically defined by the presence of proteinuria >0.5 g/24 h. This stage has been referred to as overt nephropathy, clinical nephropathy, proteinuria, or macroalbuminuria. In the early 1980s, seminal studies from Europe revealed that small amounts of albumin in the urine, not usually detected by conventional methods, were predictive of the later development of proteinuria in type 1 (3–5) and type 2 (6) diabetic patients. This stage of renal involvement was termed microalbuminuria or incipient nephropathy.

The cumulative incidence of microalbuminuria in patients with type 1 diabetes was 12.6% over 7.3 years according to the European Diabetes (EURODIAB) Prospective Complications Study Group (7) and ∼33% in an 18-year follow-up study in Denmark (8). In patients with type 2 diabetes, the incidence of microalbuminuria was 2.0% per year and the prevalence 10 years after diagnosis 25% in the U.K. Prospective Diabetes Study (UKPDS) (9). Proteinuria occurs in 15–40% of patients with type 1 diabetes, with a peak incidence around 15–20 years of diabetes (8,10,11). In patients with type 2 diabetes, the prevalence is highly variable, ranging from 5 to 20% (2,9).

People with diabetes have a lot to juggle when it comes to their healthcare. Having diabetes puts you at risk of other health problems, including heart attacks, strokes, vision loss, nerve damage, and kidney disease. While all of that may sound overwhelming, there is some good news; many of the steps you need to take to prevent one of those complications may actually help to prevent them all.

The kidneys play an important role in the body: they filter the blood, removing waste products and excess salt and water. If the kidneys become diseased, they falter in their task, leaving the blood polluted.

Finding out that you have early diabetic nephropathy can alert you that your kidneys are in danger. It is important to take steps to protect your kidneys before the problem advances. Information about advanced kidney disease is also available (see "Patient information: Chronic kidney disease (Beyond the Basics)").

In some cases, diabetic nephropathy can eventually cause the kidneys to stop working altogether. If that happens to you, you will need to have a kidney transplant or dialysis, a procedure that filters the blood artificially several times a week. (See "Patient information: Dialysis or kidney transplantation — which is right for me? (Beyond the Basics)".)

DIABETIC NEPHROPATHY SYMPTOMS

Diabetic nephropathy usually causes no symptoms, and people who have the condition often produce normal amounts of urine. To detect diabetic nephropathy, healthcare providers rely on tests that measure protein levels in the urine and blood tests to evaluate the level of kidney function.

When the kidneys are working normally, they prevent protein from leaking into the urine, so finding protein in the urine is a sign that the kidneys are in trouble. Often people who have diabetic nephropathy also have high blood pressure.

DIABETIC NEPHROPATHY RISK FACTORS

There are several factors that can increase your risk of developing diabetic nephropathy. These include:

●Having chronically elevated blood sugar levels
●Being overweight or obese
●Smoking
●Having a diabetes-related vision problem (diabetic retinopathy) or nerve damage (diabetic neuropathy) (see "Patient information: Diabetic neuropathy (Beyond the Basics)")
Having a family history of kidney disease or belonging to certain ethnic groups (eg, African American, Mexican, Pima Indian) can also increase your risk of diabetic nephropathy.

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