The kidney and blood pressure link

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Sunday May 18, 2008

The kidney and blood pressure link

In conjunction with World Hypertension Day 2008, the National Kidney Foundation explains the link between high blood pressure and kidney disease.

JAMES, 40, is a laid-back kind of guy. Few things ever bother or stress him out. Imagine his surprise when he was diagnosed with high blood pressure. Further examination revealed that he had had the condition for some time as his kidneys were starting to show signs of damage.

Fatimah was 36 when a urine test revealed that she had kidney disease. Several years later, she developed high blood pressure, which the doctors believed, was the result of her failing kidneys. Fatimah was eventually put on dialysis. She passed away recently after a stroke.

Hypertension (high blood pressure) is a global epidemic, with over 1.5 billion people worldwide having the disease. In 2006, it was estimated to afflict 42.6% of Malaysians above age 30. Among those taking their medications, only 26% had their blood pressure under control.
People with high blood pressure should also have their kidney function evaluated regularly.

While usually associated with stroke and heart attack, hypertension is also closely linked with the kidneys. On the one hand, uncontrolled hypertension can damage the kidneys. On the other hand, kidney disease can also bring on hypertension and make it worse.

The kidney-blood pressure connection

Blood pressure, which refers to the force of blood pushing against artery walls as it courses through the body, is regulated by the kidneys. They remove excess salt and fluids from the blood to lower mounting blood pressure and, conversely, retain salt and water to boost low blood pressure.

In people with essential hypertension (i.e. the cause is not identified), prolonged high blood pressure can damage the blood vessels and filters in the kidneys.

This will, in turn, adversely affect the kidneys’ ability to remove waste from the body.

Signs of hypertension-related kidney disease include decrease in the amount of urine, either difficulty urinating or urinating more frequently (especially at night), and swelling of the legs due to fluid retention (oedema).

Then, there are also people with secondary hypertension, specifically that which results from a problem in the kidneys.

One important cause of this type of hypertension (renal hypertension) is the decrease of blood supply to the kidneys due to atherosclerosis (i.e. clogging of the renal artery by fat and cholesterol-laden plaque forming inside the walls of the blood vessel). Deprived of blood, the kidneys and adrenal glands (that sit on top of the kidneys) respond by producing certain hormones that push up the blood pressure.

Renal hypertension is usually suspected when high blood pressure is found in a young individual or a new onset of high blood pressure is discovered in an older person.

Kidney care advice

According to Dr Goh Bak Leong, consultant nephrologist and member of the National Kidney Foundation (NKF) Board of Managers, hypertension is one of the most common causes of end-stage kidney disease.

More importantly, uncontrolled blood pressure will accelerate progression of kidney failure. “Trouble is, one can have hypertension and/or kidney disease without feeling any symptoms,” he says.

Accordingly, it is important for everyone to know whether he or she has hypertension. He advises: “All adults should have their blood pressure measured regularly. Daytime average blood pressure should be below 135/85 mmHg, beyond which treatment may be required. People with diabetes or kidney disease should be treated for hypertension if their blood pressure exceeds 130/80 mmHg.”

He offers some tips on how people with high blood pressure can improve their treatment outcomes.

“Use a blood pressure monitor at home to check your readings on a daily basis. Eat less salt, sauces and condiments that are high in sodium. Make healthy food choices. Get physically active and lose excess body weight; a mere 5% to 10% reduction can significantly reduce high blood pressure. Avoid or, at least, limit alcohol consumption. Finally, do not smoke and learn to manage stress.”

Dr Goh adds that people with high blood pressure should also have their kidney function evaluated regularly. He explains: “Simple urine tests can be taken to detect the presence of proteinuria (protein in the urine). People with diabetes are advised to take a microalbuminuria urine test to detect the presence of the smaller protein molecules.

“If kidney disease is suspected, certain laboratory tests will be performed to confirm whether the kidneys are working properly. These tests include serum creatinine and blood urea nitrogen (BUN); high levels of either can indicate kidney damage.”

Dr SS Gill, Chairman of NKF Board of Managers, stresses that it is very important not to take hypertension and kidney disease for granted. “After diabetes, hypertension is the second most important cause of end-stage kidney failure.

“People with both hypertension and kidney disease are in a very high risk group. For them, the most important measure is to control blood pressure. Failure could have you spending the rest of your life on dialysis.”

People whose kidneys have failed have to undergo dialysis three times a week to filter waste products out of the blood. Presently costing more than RM3,000 per month in private hospitals, dialysis is very costly life-long treatment.

Recognising the tremendous burden, the National Kidney Foundation (NKF) provides subsidised dialysis treatment to poor patients through its 20 dialysis centres across the nation. NKF also offers medication and social welfare support.

“The rising prevalence of hypertension cases is a grave cause for concern as it is responsible for the growing number of end-stage kidney failure patients we see each year,” Dr Gill remarks.

“We hope that more people will seriously safeguard themselves against hypertension and protect their kidneys. We also hope that caring corporations and individuals will come forward and support our efforts to help the poor and needy people for whom dialysis is now their lifeline.”

Article courtesy of NKF KIDNEY CARE, a community education programme by National Kidney Foundation of Malaysia. NKF provides subsidised dialysis treatments and free medications, laboratory tests, follow-ups and welfare assistance to needy patients. NKF also conducts on-going public education initiatives. NKF welcomes public donations to support its work. For more details, please contact NKF Hotline: 1300-88-3110, Website: www.nkf.org.my.

http://thestar.com.my/health/story.asp?file=/2008/5/18/health/21253796&sec=health