Kidney function and blood pressure

Blood pressure and kidney function are interlinked, so high blood pressure (hypertension) can cause kidney damage, while kidney damage or disease can bring about high blood pressure. Early treatment of hypertension may prevent kidney damage from occurring, while correcting a kidney problem (where possible) may correct hypertension in some cases.

Does blood pressure always stay the same?

No, your blood pressure does not stay the same. For this reason a series of blood pressure readings will need to be taken in order to assess your blood pressure accurately.

Your blood pressure will change in order to meet the demands of your body. It is usually at its highest when you exercise, and lowest when you sleep. It can also rise due to anxiety, excitement, activity or nervousness. Find out how blood pressure is measured.

What's so bad about high blood pressure?

If blood pressure is left uncontrolled and remains high, it can damage the vessels that supply oxygenated blood to your internal organs. The very small vessels are often the first to be affected. This can go on to cause kidney disease, heart attack, stroke and loss of vision if left untreated.

How will I know that my blood pressure is high?

Although some people with high blood pressure experience symptoms like headaches, dizziness or nosebleeds, high blood pressure does not usually give warning signs. Often high blood pressure is detected accidentally. The only way to know if your blood pressure is high is to have it checked regularly. You may have high blood pressure and feel perfectly well.

How is high blood pressure related to kidney disease?

High blood pressure is closely related to kidney disease in a couple of different ways.

High blood pressure can cause kidney damage and kidney damage can cause high blood pressure. It is often a bit like the "chicken and egg syndrome". It can sometimes be difficult to tell which came first.

Renin release from kidneys

The kidneys produce a hormone called renin; this helps to control blood pressure in the body. If the kidneys aren't functioning properly, renin release can be increased, raising the blood pressure.

Uncontrolled high blood pressure

If high blood pressure is left unchecked, it can cause blood vessels in the kidneys to become thickened and narrowed, possibly leading to reduced blood supply and reduced kidney function. Severe uncontrolled blood pressure may cause severe or total kidney failure.

High blood pressure can develop as a result of almost all kidney diseases. It can also be caused by renal artery stenosis - narrowing of the main artery to one or both kidneys. In addition, salt and fluid retention in a person with kidney failure can cause high blood pressure.

These effects can be prevented if the blood pressure is brought under control with treatment. Correcting a kidney problem may also eliminate high blood pressure in some cases.

Related topics

Also see: Kidney health

Original material provided by the New Zealand Kidney Foundation. Edited by everybody, August 2005. Reviewed February 2011.