Diabetic Nephropathy

What Is Diabetic Nephropathy?

Diabetic nephropathy is damage to the kidneys in diabetes caused by elevated blood glucose. It is one of the most common complications of diabetes and occurs in type 1 and type 2 diabetes. 20 to 40 percent of patients with diabetes develop kidney disease in the course of the disease. However, in addition to diabetic nephropathy, there may be other causes of kidney damage in diabetes, such as high blood pressure or kidney inflammation.

Causes: How Does Diabetic Nephropathy Develop?

In diabetic nephropathy, years of elevated blood glucose levels damage the renal corpuscles, which are responsible for the kidney's filtering function.

The renal corpuscles consist of the glomerulus - which are small blood vessel clusters - and a capsule surrounding them. The renal corpuscles filter substances from the blood, which are then excreted in the urine. These are, for example, urea and salts.

The so-called basement membrane of the glomeruli forms a barrier for larger substances such as proteins and blood cells that should not enter the urine. These substances usually cannot pass through the basement membrane and remain in the blood. In diabetes, elevated blood glucose levels over the years damage the walls of the small blood vessels of the renal corpuscles. They become more porous and permeable. Larger substances such as proteins can now pass through the damaged vessels into the urine. Deposits form on the damaged vessel walls and thicken the basement membrane of the glomeruli and the walls of the small arteries (arteriosclerosis) of the kidney. Initially, the function of the kidney is not affected. However, as the disease progresses, the kidney tissue increasingly changes.

In advanced kidney disease, hardening and scarring of the renal corpuscles and thickening of the connective tissue (glomerulosclerosis) may occur. As a result, the renal corpuscles gradually lose their filtering function. As a result, substances that would otherwise be filtered into the urine can no longer be excreted.

Symptoms: How Is Nephropathy Noticed?

In the beginning, patients do not notice the kidney damage. Only after several years with advanced damage to the kidneys do symptoms appear.

Symptoms of kidney disease include itching, fatigue, reduced ability to concentrate, muscle cramps, water retention in the legs and feet, loss of appetite, nausea, and vomiting.

In addition, people with diabetic nephropathy are more likely to develop anemia. This can occur even with mildly impaired kidney function. Erythropoietin is produced in the kidney. This is a hormone that promotes blood formation. In the case of kidney damage, the formation of this hormone is often also disturbed. This results in fewer red blood cells being formed.

High blood pressure also often occurs together with diabetes and kidney disease.

Diagnosis: How Can Diabetic Nephropathy Be Detected?

An early sign of diabetic nephropathy is an elevated protein level in the urine, which can be detected even before patients experience symptoms. For this reason, the protein content in the urine of people with diabetes is also examined during check-ups. For this purpose, the doctor determines the albumins in the urine. Albumins are proteins that are usually only excreted in very small quantities in the urine. Therefore, an increased level of albumins is a sign of incipient kidney disease.

If the albumin content is elevated, the doctor determines the glomerular filtration rate in the urine. This value allows the doctor to assess how well the kidney is functioning.

Sometimes the doctor also performs other tests, mainly to exclude other diseases. These can be laboratory tests or an ultrasound examination of the kidney, for example.

Stages: How Does Diabetic Nephropathy Proceed?

The course of kidney disease can be divided into different stages. There may be several years between each stage.

Stage 1 - kidney damage with normal kidney function: Initial changes in the kidneys and increased protein content in the urine become apparent, but the function is not yet impaired. A distinction is made between stage 1 a with an albumin content of 20-220mg/L urine and stage 1 b with an albumin content of more than 200 mg/L.

Stage 2 - mild renal insufficiency: The function of the kidney is slightly impaired.

Stage 3 - moderate renal insufficiency: The function of the kidney is moderately impaired.

Stage 4 - severe renal failure: The function of the kidney is severely impaired.

Stage 5 - terminal renal failure: In this stage, permanent loss of kidney function is reached. The kidneys fail.

Therapy: What Helps Patients with Diabetic Nephropathy?

High blood sugar levels and also high blood pressure are decisive factors in the development and progression of kidney disease in patients with diabetes. However, good blood glucose and blood pressure control can still halt or even partially reverse the disease in its early stages.

The long-term blood glucose value Hb1Ac should be below 53 mmol/mol. However, hypoglycemia occurs more frequently in people with diabetes and nephropathy. In this case, the HbA1c target value should be adjusted.

In the case of hypertension, ACE inhibitors are suitable for lowering blood pressure. In addition, these inhibit the progression of kidney disease better than other antihypertensive drugs.

For the treatment of diabetic kidney disease, a protein-reduced diet (0.8mg/kg protein per day) is also recommended to relieve the kidneys. In addition, smoking should be avoided. Finally, if patients have a high LDL cholesterol level, this should be lowered to below 100 mg/dl. Statins, a drug that works particularly well in the early stages of kidney disease, are usually used for this purpose.

If patients develop anemia, the physician may inject erythropoietin to stimulate blood formation.

A unique feature of kidney disease is that the effect of medications can change, as many drugs are excreted through the kidneys. Therefore, diabetes drug treatment may need to be adjusted.

There are diabetes medications that are particularly suitable in nephropathy because they have a protective effect on the kidneys. These include SGLT2 inhibitors and GLP-1 receptor agonists.

What Is the Prognosis or Diabetic Nephropathy?

Timely treatment can delay the disease. However, if the disease is already advanced, it cannot be reversed. In the final stage, the kidneys lose their function. Patients then require dialysis or a kidney transplant.

Can Diabetic Nephropathy Be Prevented?

There are some risk factors for diabetic nephropathy that can be influenced. These include high blood sugar levels, high blood pressure, the amount of albumin in the urine, smoking, elevated blood lipids, and obesity.

With a healthy diet, plenty of exercise, no smoking, and reasonable blood sugar control, there is much you can do yourself to minimize risk factors and prevent nephropathy.

Sources:

• Hien, Böhm, Claudi-Böhm, Krämer, Kohlhas. Diabetes- Handbuch, 7. Auflage, 2013
• Helmholtz Zentrum München, Deutsches Zentrum für Diabetesforschung, Deutsches Diabetes-Zentrum. Diabinfo – Das Diabetesinformationsportal. www.diabinfo.de. Aufgerufen am 05.05.2021
• Nationale Versorgungsleitlinie Nierenerkrankungen bei Diabetes im Erwachsenenalter. Langfassung. 1. Auflage. Version 6. 2015