How Does Diabetes Affect the Kidneys?

Diabetic nephropathy is a serious complication of diabetes in which the kidneys are damaged by elevated blood sugar levels.

Inside kidneys, millions of tiny blood vessels called glomeruli filter out waste products from protein-rich blood. Each glomerulus opens out to a small fluid-collecting tube called a tubule. Each glomerulus-and-tubule unit is called a nephron. Each kidney is composed of about 1 million nephrons. In healthy nephrons, the glomerular membrane allows waste products and extra water to pass into the tubule while keeping blood cells and protein in the bloodstream. Most proteins are too large to pass through the glomeruli. Also, the glomeruli and the proteins repel each other as they are both negatively charged, thus preventing the protein molecules from entering the urine.

People with diabetes have either little insulin or their bodies have become resistant to insulin. Insulin makes it possible for the glucose from the blood to enter the cells and be used for the metabolic activities. The diabetics have high levels of blood glucose or sugar circulating in the body. When excess glucose circulates in the blood, it binds to proteins in the serum and plasma, causing what is called glycosylation. This makes the proteins stick to the vessel walls, causing inflammation. Prolonged excess blood glucose can damage the cell walls in the blood vessels of eyes, nerves and kidneys. Inside the kidneys, the tiny nephrons become damaged and the kidneys can no longer filter toxins out of the blood effectively. Elevated glucose levels increase the speed of blood flow into the kidney, which puts a strain on the filtering glomeruli and raises the blood pressure.

Because of damaged nephrons, albumin, an essential protein, and even red blood cells, leak into the urine. This condition, that is, the appearance of small but abnormal amounts of albumin in the urine is called Microalbuminuria. Albumin and immunoglobulin help coagulation (clotting), balance bodily fluids, and fight infection. They help to retain salt and water inside the blood vessels, so that fluid does not leak out into the tissues.  When albumin leaks into the urine, the blood loses its capacity to absorb extra fluid from the body. Fluid can accumulate outside the circulatory system, causing edema in the face, hands, feet, or ankles. Eventually, some nephrons collapse and the extra load strains those that remain. Under this increased load, the kidney may fail. A person may then have to go on dialysis or receive a kidney transplant.

As kidney disease progresses, physical changes in the kidneys often lead to increased blood pressure. Once the kidneys begin to fail, one may notice swelling (edema), usually in the hands, feet, face, and abdomen. The extra fluid also causes the blood pressure to rise. Other symptoms may include nausea, fatigue, confusion, joint pain, reduced urination, blood in the urine, seizures, headaches, itching, pain in the kidney area, and a yellowish-brown appearance of the skin.

Urine and blood tests help to diagnose diabetic nephropathy. As said earlier, small levels of albumin are an early sign of kidney disease. High albumin levels also increase your risk of heart disease and stroke. Presence of high levels of protein in the urine, a condition called proteinuria and presence of creatinine and urea also indicate kidney dysfunction.

Progress from one stage to the next can take many years. Kidney disease doesn’t manifest obvious symptoms until the disease has progressed far. So it is important that people with diabetes test their urine and blood for possible kidney dysfunction. Uncontrolled sugar and hypertension can progress rapidly towards stage five diabetic nephropathy (ESRD or End Stage Renal Disease).

Not smoking and doing regular exercises help you on your way to recovery.