Diabetic kidney disease takes many years to develop. In some people, the filtering function of the kidneys is higher than normal in the first few years of their diabetes. Over several years, people who are developing kidney disease will have small amounts of the protein albumin leaking into their urine. This first stage of CKD is called microalbuminuria. The kidney’s filtration function usually remains normal during this period.
As the disease progresses, more albumin leaks into the urine. This stage may be called macroalbuminuria or proteinuria. As the amount of albumin in the urine increases, the kidneys’ filtering function usually begins to drop. The body retains various wastes as filtration falls. As kidney damage develops, blood pressure often rises as well.
Overall, kidney damage rarely occurs in the first 10 years of diabetes, and usually 15 to 25 years will pass before kidney failure occurs. For people who live with diabetes for more than 25 years without any signs of kidney failure, the risk of ever developing it decreases.
People with diabetes should be screened regularly for kidney disease. The two key markers for kidney disease are eGFR and urine albumin.
eGFR stands for estimated glomerular filtration rate. Each kidney contains about 1 million tiny filters made up of blood vessels. These filters are called glomeruli. Kidney function can be checked by estimating how much blood the glomeruli filter in a minute. The calculation of eGFR is based on the amount of creatinine, a waste product, found in a blood sample. As the level of creatinine goes up, the eGFR goes down.
Kidney disease is present when eGFR is less than 60 milliliters per minute.
Urine albumin is measured by comparing the amount of albumin to the amount of creatinine in a single urine sample. When the kidneys are healthy, the urine will contain large amounts of creatinine but almost no albumin. Even a small increase in the ratio of albumin to creatinine is a sign of kidney damage.
Kidney disease is present when urine contains more than 30 milligrams of albumin per gram of creatinine, with or without decreased eGFR.
High blood pressure, or hypertension, is a major risk factor in the development of kidney problems in people with diabetes. Both a family history of hypertension and the presence of hypertension appear to increase chances of developing kidney disease. Hypertension also accelerates the progression of kidney disease when it already exists.
Blood pressure is recorded using two numbers. The first number is called the systolic pressure, and it represents the pressure in the arteries as the heart beats. The second number is called the diastolic pressure, and it represents the pressure between heartbeats. In the past, hypertension was defined as blood pressure higher than 140/90. Recent recommendation suggests that people with diabetes keep their blood pressure below 130/80.
Hypertension can be seen not only as a cause of kidney disease but also as a result of damage created by the disease. As kidney disease progresses, physical changes in the kidneys lead to increased blood pressure. Therefore, a dangerous spiral, involving rising blood pressure and factors that raise blood pressure, occurs. Early detection and treatment of even mild hypertension are essential for people with diabetes.
Scientists have made great progress in developing methods that slow the onset and progression of kidney disease in people with diabetes. Drugs used to lower blood pressure can slow the progression of kidney disease significantly. Two types of drugs, angiotensin-converting enzyme (ACE) inhibitors and angiotensin receptor blockers (ARBs), have proven effective in slowing the progression of kidney disease. Many people require two or more drugs to control their blood pressure. In addition to an ACE inhibitor or an ARB, a diuretic can also be useful. Beta blockers, calcium channel blockers, and other blood pressure drugs may also be needed.
Examples of ACE inhibitors are enalapril, lisinopril and ramipril, which doctors commonly prescribe for treating kidney disease of diabetes. The benefits of these drugs extend beyond its ability to lower blood pressure: it may directly protect the kidneys’ glomeruli. ACE inhibitors have lowered proteinuria and slowed deterioration even in people with diabetes who did not have high blood pressure. Examples of ARBs are losartan, telmisartan or olmesartan, which have also been shown to protect kidney function and lower the risk of cardiovascular events.
Any medicine that helps patients achieve a blood pressure target of 130/80 or lower provides benefits. Patients with even mild hypertension or persistent microalbuminuria should consult a health care provider about the use of antihypertensive medicines.
In people with diabetes, excessive consumption of protein may be harmful. Experts recommend that people with kidney disease of diabetes consume the recommended dietary allowance for protein but avoid high-protein diets. For people with greatly reduced kidney function, a diet containing reduced amounts of protein may help delay the onset of kidney failure. Anyone following a reduced-protein diet should work with a dietitian to ensure adequate nutrition.
Antihypertensive drugs and low-protein diets can slow CKD. A third treatment, known as intensive management of blood glucose or glycemic control, has shown great promise for people with diabetes, especially for those in the early stages of CKD.
The human body normally converts food to glucose, the simple sugar that is the main source of energy for the body’s cells. To enter cells, glucose needs the help of insulin, a hormone produced by the pancreas. When a person does not make enough insulin, or the body does not respond to the insulin that is present, the body cannot process glucose, and it builds up in the bloodstream. High levels of glucose in the blood lead to a diagnosis of diabetes. Intensive management of blood glucose is a treatment regimen that aims to keep blood glucose levels close to normal. The regimen includes testing blood glucose frequently, administering insulin throughout the day based on food intake and physical activity, following a diet and activity plan, and consulting a health care team regularly. Some people use an insulin pump to supply insulin throughout the day.
Several studies have pointed to the beneficial effects of intensive management of blood glucose. Also, studies conducted over the past decades have clearly established that any program resulting in sustained lowering of blood glucose levels will be beneficial to patients in the early stages of CKD.
When people with diabetes experience kidney failure, they must undergo either dialysis or a kidney transplant. Currently, the survival of kidneys transplanted into people with diabetes is about the same as the survival of transplants in people without diabetes. Dialysis for people with diabetes also works well in the short run. Even so, people with diabetes who receive transplants or dialysis experience higher morbidity and mortality because of coexisting complications of diabetes-such as damage to the heart, eyes, and nerves.