Understanding the link between hypertension and kidney disease

Maintaining healthy blood pressure is important for heart and cardiovascular health. But high blood pressure – also known as hypertension – can affect kidney function as well.

Kidney disease and hypertension are interlinked, meaning that either one can cause the other.

Because of this connection between blood pressure and kidney function, hypertension can sometimes serve as an early indicator of kidney disease, particularly in young children.

"The kidneys play an important role in controlling blood pressure," says Smitha Vidi, M.D., a pediatric nephrologist at Children's Health℠ and Assistant Professor at UT Southwestern.

How do kidneys regulate blood pressure?

Kidneys filter waste and impurities out of the bloodstream and remove them through the production of urine. But they have another important job as well: maintaining a healthy balance of salt and water in the body.

"If you have too much water or salt in your body, your blood pressure goes up," explains Dr. Vidi.

Healthy kidneys sense any salt and water imbalances in your body and regulate it to keep your blood pressure in a heathy range.

More specifically, the kidneys produce an enzyme called renin, which in turn triggers the production of a series of hormones through the renin-angiotensin-aldosterone system (RAAS). This system, together with a hormone called anti-diuretic hormone (ADH), maintains this healthy salt and water balance.

Can kidney disease cause high blood pressure?

In children with kidney disease, the body loses its ability to properly maintain a healthy salt and water balance.

"If you have kidney disease, you can develop high blood pressure. And if you have high blood pressure that is not well controlled, that can eventually cause kidney disease," says Dr. Vidi.

Given this relationship between hypertension and kidney disease, it is recommended that children more than 3 years of age have regular blood pressure checks during healthy visits with their pediatrician. Children who have persistently elevated blood pressures on three or more occasions will need further screening.

In treating children with high blood pressure, physicians screen for:

• Evidence of obesity, the most common cause of hypertension in kids (especially in those older than age 6)
• Signs of kidney disease, the second leading cause of hypertension in children
• Endocrine diseases related to thyroid and adrenal gland, and congenital heart diseases

Physicians can perform initial screens for kidney problems using simple blood and urine tests. Follow-up screenings may require ultrasounds or other tests to look for kidney abnormalities.

How do I tell if my child has hypertension?

Most of the time, there are no symptoms of hypertension in children. Some children who have high blood pressure may experience frequent headaches or blurry vision. Other symptoms of high blood pressure can include dizziness, chest pain and abdominal pain.

Because children with kidney disease can be at increased risk of developing hypertension, they should monitor their blood pressure frequently using a blood pressure monitor at home, Dr. Vidi says.

Monitoring blood pressure in children

Unlike in adults and teenagers – where normal blood pressure is considered anything at or below 120/80 mm Hg – there is no single number for a healthy blood pressure range for children ages 12 and under.

"In young children, there is no set number for healthy blood pressure, because kids come in different sizes," says Dr. Vidi. "Instead, we use percentile charts based on American Academy of Pediatrics recommendations. Based on these charts, we would say that the child has hypertension if they have blood pressures above a certain percentile for their age, sex and height."

Parents should talk with their child's pediatrician to establish what is a "normal" or healthy blood pressure level for each child – and how best to monitor these numbers at home, if necessary.

How is high blood pressure treated in children?

Kids struggling with hypertension are encouraged to adopt a healthy diet, reduce sodium (salt) intake, increase exercise, incorporate stress-reducing activities – such as yoga or meditation – and make other lifestyle changes to reduce their blood pressure.

"Lifestyle and diet modification are the first-line treatments for high blood pressure," says Dr. Vidi.

If lifestyle and diet modifications are not successful in reducing hypertension after six months, blood pressure medications may be prescribed.

In cases where hypertension is directly linked to inherited kidney disease, medications may be required early to achieve healthy blood pressure.

Learn more

Nationally recognized and the largest pediatric nephrology program in North Texas, the Nephrology Department at Children's Health is dedicated to providing comprehensive and family-focused kidney care that addresses all aspects of your child's well-being. Learn more about our Nephrology programs and services.