Nephropathy: Diabetic Kidney Disease

Nephropathy is a microvascular complication of diabetes that affects the renal system (kidneys). Diabetic nephropathy is the leading cause of kidney failure around the world. Approximately 25% of diabetics will suffer from nephropathy at some point over the course of their lifetime. Globally and in the United States incidence of diabetic nephropathy has been on a steady rise along with exploding diabetes rates.

In healthy individuals, the kidneys work to filter toxins, wastes and excess water out of the blood. The resulting fluid then is expelled from the body as urine.

The kidneys have several other functions as well. They are important in regulating the production of certain hormones, such as the parathyroid hormone, which itself regulates calcium and phosphorus levels in the blood and is important in maintaining bone health. The kidneys also help to control blood pressure, aid in the production of red blood cells, and maintain the balance of salts, or electrolytes, such as sodium, within the blood.

Also referred to as diabetic kidney disease, diabetic nephropathy happens when small blood vessels in the kidneys become damaged due to frequent hyperglycemia, or high glucose concentrations in the blood. This can occur in both type 1 and type 2 diabetics.

Nephropathy is diagnosed clinically by abnormally high levels of “proteinuria,” or protein in the urine (greater than 500mg). It may also be diagnosed as reduced glomerular filtration rate (GFR), or some combination of the two. Previously it was believed that elevated proteinuria and its steady rising levels over time (called progressive albuminuria) must proceed GFR, which is the rate of filtered liquid through the kidney, but recent research has been showing that GFR can occur independently or in conjunction with proteinuria.

A common pre-nephropathy phase that is characterized by elevated proteinuria (30-299mg) is called “microalbuminuria,” which if untreated often progresses to diabetic nephropathy. Diagnosis of nephropathy is typically done through a 24 hour urine test, a “spot-urine measurement of microalbumin,” or tests showing reduced GFR, which translates to decreased kidney function.

Damage to the kidneys is irreversible, and the complications of chronic kidney disease can be mild to very severe. One common complication of diabetic nephropathy is swelling, commonly in the arms and legs, a result of fluid retention since the kidneys are not properly filtering excess water and wastes in the blood. Anemia, or low levels of red blood cells, is another common complication of advanced stages of kidney disease (there are five clinical stages, the last being referred to as “end-stage” renal disease). Hypertension, weak bones, fatigue, decreased libido and erectile dysfunction, inability to concentrate, nausea, vomiting and diarrhea, and pulmonary edema (buildup of fluid within the lungs) are further examples of complications of advanced diabetic nephropathy.

For those in end-stage, or stage 5, kidney disease, there comes a point in which kidney function is so low that dialysis or a kidney transplant is necessary to stay alive. This final point in the typically years-long process of kidney deterioration is commonly identified clinically by GFR levels less than 15 and total kidney function less than 10 percent.

Controlling blood glucose levels through diligent self-management, especially with healthful eating and physical activity, or through medications and insulin when necessary, is the most effective way for diabetics to limit the risk of developing nephropathy. Being overweight, smoking, and eating foods high in sodium (such as processed meats) are also known to increase risk of developing kidney disease and suffering from severe complications once diagnosed. Preventing or reducing hypertension, which is both a risk factor for diabetes and a frequent complication for diabetics, has also been shown to be important in preventing nephropathy.

Resources and Further Reading

For some more clinical information about different microvascular and macrovascular diabetic complications:
http://clinical.diabetesjournals.org/content/26/2/77

An in-depth look at diabetic nephropathy:
http://care.diabetesjournals.org/content/28/1/164?ijkey=3f4c5390616ba8744366159a0728da91323969e8&keytype2=tf_ipsecsha

A look at steps to prevent diabetic nephropathy and its progression:
https://www.niddk.nih.gov/health-information/diabetes/overview/preventing-problems/diabetic-kidney-disease

A study about kidney disease incidence in the United States:
https://jamanetwork.com/journals/jama/fullarticle/2542635

Some basic information about the kidneys and the renal system:
www.niddk.nih.gov/health-information/kidney-disease/kidneys-how-they-work

To learn more about dialysis:
https://www.kidney.org/atoz/content/dialysisinfo

Information about stage-5, or end-stage, kidney disease:
http://www.nationalkidneycenter.org/chronic-kidney-disease/stages/stage-5/

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