The kidneys play a key role in keeping a person's blood pressure in a healthy range, and blood pressure, in turn, can affect the health of the kidneys. High blood pressure, also called hypertension, can damage the kidneys and lead to chronic kidney disease (CKD).
Blood pressure measures the force of blood against the walls of the blood vessels. Extra fluid in the body increases the amount of fluid in blood vessels and makes blood pressure higher. Narrow, stiff, or clogged blood vessels also raise blood pressure.
Hypertension can result from too much fluid in normal blood vessels or from normal fluid in narrow, stiff, or clogged blood vessels.
People with high blood pressure should see their doctor regularly.
High blood pressure makes the heart work harder and, over time, can damage blood vessels throughout the body. If the blood vessels in the kidneys are damaged, they mfay stop removing wastes and extra fluid from the body. The extra fluid in the blood vessels may then raise blood pressure even more. It's a dangerous cycle.
High blood pressure is one of the leading causes of kidney failure, also called end-stage renal disease (ESRD).
People with kidney failure must either receive a kidney transplant or have regular blood-cleansing treatments called dialysis. Every year, high blood pressure causes more than 25,000 new cases of kidney failure in the United States-United States Renal Data System. USRDS 2007 Annual Data Report.Bethesda, MD: National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Department of Health and Human Services; 2007.
Most people with high blood pressure have no symptoms. The only way to know whether a person's blood pressure is high is to have a health professional measure it with a blood pressure cuff. The result is expressed as two numbers. The top number, called the systolic pressure, represents the pressure when the heart is beating. The bottom number, called the diastolic pressure, shows the pressure when the heart is resting between beats. A person's blood pressure is considered normal if it stays at or below 120/80, which is commonly stated as "120 over 80." People with a systolic blood pressure of 120 to 139 or a diastolic blood pressure of 80 to 89 are considered prehypertensive and should adopt lifestyle changes to lower their blood pressure and prevent heart and blood vessel diseases. A person whose systolic blood pressure is consistently 140 or higher or whose diastolic pressure is 90 or higher is considered to have high blood pressure and should talk with a doctor about the best ways to lower it.
Early kidney disease is a silent problem, like high blood pressure, and does not have any symptoms. People may have CKD but not know it because they do not feel sick. A person's glomerular filtration rate (GFR) is a measure of how well the kidneys are filtering wastes from the blood. GFR is estimated from a routine measurement of creatinine in the blood. The result is called the estimated GFR (eGFR).
Creatinine is a waste product formed by the normal breakdown of muscle cells. Healthy kidneys take creatinine out of the blood and put it into the urine to leave the body. When the kidneys are not working well, creatinine builds up in the blood.
An eGFR with a value below 60 milliliters per minute (mL/min) suggests some kidney damage has occurred. The score means that a person's kidneys are not working at full strength.
Another sign of CKD is proteinuria or protein in the urine. Healthy kidneys take wastes out of the blood but leave protein. Impaired kidneys may fail to separate a blood protein called albumin from the wastes. At first, only small amounts of albumin may leak into the urine, a condition known as microalbuminuria, a sign of failing kidney function. As kidney function worsens, the amount of albumin and other proteins in the urine increases, and the condition is called proteinuria. CKD is present when more than 30 milligrams of albumin per gram of creatinine is excreted in urine, with or without decreased eGFR.
How can kidney damage from high blood pressure be prevented?
The National Heart, Lung, and Blood Institute (NHLBI), one of the National Institutes of Health (NIH), recommends that people with CKD use whatever therapy is necessary, including lifestyle changes and medicines, to keep their blood pressure below 130/80.
The NHLBI recommends five lifestyle changes that help control blood pressure. People with prehypertension or high blood pressure should
maintain their weight at a level close to normal.
eat fresh fruits and vegetables, grains, and low-fat dairy foods.
limit their daily salt, or sodium, intake to 2,000 milligrams. They should limit frozen foods and trips to fast food restaurants. They should read nutrition labels on packaged foods to learn how much sodium is in one serving. Keeping a sodium diary can help monitor sodium intake.
Get plenty of exercises at least 30 minutes of moderate activity, such as walking, cycling, or swimming, most days of the week.
avoid consuming too much alcohol. Men should have no more than two drinks-two 12-ounce servings of beer or two 5-ounce servings of wine or two 1.5-ounce servings of hard liquor a day. Women should have no more than a single serving a day because differences in the way foods are broken down in the body make women more sensitive to the effects of alcohol.
Many people need medicine to control high blood pressure. Several effective blood pressure medicines are available. The most common types of blood pressure medicines doctors prescribe are diuretics, angiotensin-converting enzyme (ACE) inhibitors, angiotensin receptor blockers (ARBs), beta blockers, and calcium channel blockers. Two of these medicines, the ACE inhibitors, and ARBs have an added protective effect on the kidneys. Studies have shown that ACE inhibitors and ARBs reduce proteinuria and slow the progression of kidney damage. Diuretics, also known as "water pills," help a person urinate and get rid of excess fluid in the body. A combination of two or more blood pressure medicines may be needed to keep blood pressure below 130/80.
Everyone has some risk of developing kidney failure from high blood pressure. African Americans, however, are more likely than Caucasians to have high blood pressure and its related kidney problems—even when their blood pressure is only mildly elevated. In fact, African Americans are six times more likely than Caucasians to develop hypertension-related kidney failure.2
People with diabetes also have a greater risk of developing kidney failure. Early management of high blood pressure is especially important for African Americans with diabetes.