Why your blood pressure matters to your kidneys | The Austin Diagnostic Clinic
×

Why your blood pressure matters to your kidneys

When blood pressure is too high, your kidneys could also suffer.

blood pressure check

Image source: Thinkstock

When we think of keeping our heart and arteries healthy, it’s important to note that high blood pressure — hypertension — doesn’t just affect the heart and brain. It can affect many of your body’s organs, including your kidneys.

According to the American Heart Association, 76.4 million adults in the US have been diagnosed with high blood pressure. Hypertension can be deadly if not treated — and not just because it could lead to heart attack and stroke.

Renal hypertension is a specific kind of hypertension that affects the blood vessels in the kidneys. Renal hypertension could be caused by kidney disease or from a structural disease in the blood vessels supplying kidneys. In turn, can lead to higher blood pressure and poor circulation to the kidneys. Atherosclerosis of these blood vessels can cause blockage, which is called renal artery stenosis. The arteries supplying the kidneys narrow, restricting blood flow.

The prevalence of renovascular hypertension is probably less than 1 percent in patients with mild hypertension, but it may be as high as 10 to 40 percent in patients with sudden, severe, or refractory hypertension. Atherosclerosis primarily affects patients (particularly men) over the age of 45 years. In contrast to atherosclerosis, fibromuscular dysplasia (FMD) most often affects women under the age of 50 years which has similar manifestation.

How do the kidneys affect blood pressure?

Kidneys affect blood pressure in three main ways. The renal sympathetic nerves (the nerves supplying the kidneys):

  1. Cause vasoconstriction.
    This means that narrowing of the blood vessels raises the pressure inside the vessel, causing a rise in blood pressure.
  2. Increase sodium and water absorption.
    Increased salt intake causes more fluid retention. This makes the heart work harder and eventually makes blood vessels narrow and/or harden. Salt also stimulates the brain, kidneys, and adrenal gland, leading to higher blood pressure.
  3. Stimulates renin secretion.
    Renin is a hormone secreted by kidneys which causes production of another hormone called aldosterone, which causes more salt and fluid retention.

How does high blood pressure affect the kidneys?

kidney diagramThere is a regulatory system in the kidneys to keep blood pressure normal. High blood pressure causes a loss in this system which affects:

  • Blood vessels of the kidney.
    Renal hypertension causes thickening and narrowing of blood vessels.
  • Glomerulosclerosis.
    Hypertention scars of a portion of kidney — the part that has tiny filtering units inside — which has vital role in filtration. The kidneys eventually stop removing the waste products and extra fluids. This extra fluid builds up in the blood vessels and then causes blood pressure to rise even further.

Essentially, high blood pressure can cause kidney disease which eventually leads to higher blood pressure. Kidney disease, caused by conditions other than hypertension, can also can cause high blood pressure.

When should someone go to see a nephrologist?

Usually patient is referred to nephrologist by his or her primary care physician or by another specialist, like an endocrinologist, cardiologist, etc. There are various reasons why patients are referred to a kidney specialist.

You may be referred because of worsening kidney function,  protein spillage or blood leaking in urine (proteinuria / hematuria), uncontrolled hypertension or electrolyte abnormalities, like low blood sodium level, high blood levels of potassium, high level of calcium, repeated urinary tract infections and kidney stones.

Once someone is on dialysis or has history of kidney transplant, they have already established care under a nephrologist.

How do you know if you have kidney disease?

Most patients learn they have kidney disease through their primary care provider or specialist, such as an endocrinologist or cardiologist, especially if they have chronic kidney disease.

Most patients may not have any severe symptoms until their kidney disease is advanced; however, many symptoms can eventually develop. Those symptoms include:

  • Feeling more tired;
  • Less energy;
  • Trouble concentrating;
  • Poor appetite;
  • Difficulty sleeping;
  • Muscle cramping at night;
  • Swollen feet and ankles;
  • Puffiness around the eyes, especially in the morning;
  • Dry, itchy skin;
  • The need to urinate more often at night.

What treatments are available for renal hypertension?

Doctors can treat renal hypertension several ways. One way is by controlling blood pressure. Medications are available, including acetylcholine esterase inhibitors and angiotensine receptor blockers.

Doctors also use imaging of the renal arteries through a computer tomography angiogram (CTA), magnetic resonance angiogram (MRA), or renal angiogram — an IV contrast dye injected in the vessels to directly visualize defects.

Finally, there is surgery through angioplasty, stent placement or a nephrectomy for refractory hypertension that does not respond to therapy plus small scarred kidneys.

How can you prevent renal hypertension?

In order to understand what you can do to prevent renal hypertension, it’s important to understand the risk factors. Risk factors include:

  • Hypertension
  • Coronary heart disease
  • Elderly patients with heart failure

What’s important in preventing renal hypertension? The key to prevention is to identify it early. Early diagnosis can help you and your doctor determine the best plan of action, such as controlling blood pressure, cholesterol medication, diabetes control, and other lifestyle modifications including quitting smoking, a low salt diet, weight control and regular exercise.

Remember, healthy habits aren’t just important for your heart. They’re also important to your kidneys and other organs to help you live a vibrant, healthy life.

Sonali Birewar, MD, ADC Nephrology About the Author

Dr. Sonali Birewar is a nephrologist specializing in the diagnosis and treatment of chronic kidney disease, hypertension and dialysis. She sees patients at ADC's Main Clinic and Cedar Park satellite location. Read more about her in her biography here.

Comments

  1. I’m just inquiring for more help in this matter. My mother have been diagnosed with CKD level III. and she have received a MRI that resulted a 25% function of her kidneys. She is 59 years old and I would like to help her pass this state of anxiety and stress. She constantly throws up now and HBP is a very big concern.

    I try to help in aiding for better diet.

    A concerned SOn,

    Ty.
    Peter

    • Dear Peter,
      I am really happy for your mother to have a son like you who is concerned about her. If she has been diagnosed with CKD stage III/IV, it will be advisable to monitor her closely by a nephrologist. The most important aspect will be to reason out the possible cause of the disease and try to control it. As far as the concerned about her high B, there are different ways to handle it, like lifestyle modifications, different medication with proper scheduling, close monitoring by the patient, etc.
      Hope this helps,
      Dr B.