Diagnosing Hypertension in Children

Specialists at Hassenfeld Children's Hospital of New York at NYU Langone are experienced in diagnosing children with hypertension, or chronic high blood pressure.

Blood pressure is the force of blood as it moves through the arteries. Blood pressure readings include two measurements. Systolic pressure, the top number in a blood pressure value, gauges pressure in the arteries when the heart contracts. Diastolic pressure, the bottom number, measures pressure in the arteries between heartbeats.

What’s considered a normal blood pressure changes as a child grows. Children under age 5 typically have a systolic pressure of 110 and a diastolic pressure of 70, or 110/70 or less. During adolescence, blood pressure can increase to around 120/80. Blood pressure varies throughout the day. It also depends on your child’s position—whether he or she is sitting or standing—and levels of physical activity and emotional stress.

A child has prehypertension when a blood pressure reading is above the 90th percentile compared with other children of the same age, sex, and height. That means that 90 percent of comparable children have a lower blood pressure. Children with a blood pressure reading equal to or above the 95th percentile have hypertension.

Causes and Risk Factors

In young children, hypertension often results from an underlying medical condition. This kind of hypertension, known as secondary hypertension, can be caused by an imbalance of hormones that help to regulate blood pressure.

For instance, children with excess levels of aldosterone, a hormone made in the adrenal glands, often retain water and salt while eliminating too much potassium, which can lead to hypertension.

Cushing’s disease, which causes overproduction of another adrenal hormone, cortisol, may raise a child’s blood pressure. Hypertension can also occur in children with Graves’ disease, in which an increase in thyroid hormone levels raises heart rate.  

Chronic kidney disease, which causes progressive kidney damage, is another important cause of hypertension. Chronic kidney disease can occur in children who are born with a congenital kidney problem, or in those with conditions that affect filtering structures in the kidneys, such as glomerulonephritis and renal tubular disorders. It can also develop in children with other disorders that cause kidney damage, such as lupus. Over time, chronic kidney disease leads to a buildup of excess fluid and sodium and an increase in the production of renin, a hormone that helps regulate blood pressure.

Babies born with a congenital heart defect that causes a narrowing or blockage in the aorta, the large artery that delivers oxygen-rich blood from the heart to the body, are at risk for hypertension later on. If left untreated, the heart may have to work harder to pump blood, which can cause enlargement of the heart, or heart failure.

A narrowing of one or both renal arteries, the vessels that supply the kidneys with blood, can also cause hypertension. It can be treated with a procedure to widen the narrowed blood vessel.

Essential, or primary, hypertension occurs for unknown reasons and is more common in adolescents than young children. Risk is increased in children who are obese or have a family history of hypertension. Conditions that often accompany obesity, such as obstructive sleep apnea, which disrupts breathing during sleep, and type 2 diabetes, which can damage blood vessels, also increase the risk of hypertension in children.

As with adults, children who have hypertension often have no symptoms. Children with extremely high blood pressure may show symptoms such as headaches, vision loss, double vision, chest pain, or difficulty breathing. Severe hypertension can cause kidney damage, but this is less common in children than in adults. Those who have an underlying or associated kidney or heart condition may also have blood in the urine or swollen legs.

Our doctors may recommend measuring your child’s blood pressure during well visits, particularly if your child has risk factors for hypertension. If your child has hypertension, our doctors use additional tests to monitor the condition during treatment and to identify underlying conditions.

Physical Exam

During a physical exam, the doctor looks at your child’s medical and family history to identify risk factors for hypertension. The doctor asks you if your child is taking any medications, such as corticosteroids or over-the-counter decongestants, or eating and drinking foods and beverages that contain caffeine, all of which can increase blood pressure.

In addition, the doctor calculates a ratio of your child’s height to weight, called body mass index, to determine if weight is contributing to hypertension.

Blood Pressure Measurement

A blood pressure cuff, also called a sphygmomanometer, is the device used to measure blood pressure. The cuff is wrapped around your child’s upper arm and is inflated to temporarily stop blood flow in a large artery. The device measures blood pressure as air is gradually released from the cuff, which allows blood to flow through the artery again.

A nurse or other healthcare professional places a stethoscope over the artery as air is released from the cuff, while watching a gauge that measures pressure in millimeters of mercury, or mmHg. The first pulse heard as blood flows through the vessel is the systolic pressure. Diastolic pressure is measured when the pulse is no longer heard.

Blood pressure readings that are higher than the 95th percentile for children of the same age, sex, and height during several different appointments confirm a diagnosis of hypertension.

Ambulatory Blood Pressure Monitor

If your child’s blood pressure is higher than normal during more than one checkup, the doctor may recommend using an ambulatory blood pressure monitor. This small, portable device allows you to monitor your child’s blood pressure at home. The monitor is attached to an inflatable cuff, worn on the arm, wrist, or finger. It records a child’s blood pressure every 20 to 60 minutes for a 24-hour period.

Ambulatory blood pressure monitors are sometimes used to measure blood pressure in children who become anxious during visits to the doctor, which can temporarily increase blood pressure. They can also be used to provide information on changes in a child’s blood pressure at various times of day or to monitor blood pressure in children at risk for kidney damage.

Urinalysis

A urinalysis test can help to identify kidney conditions that can increase blood pressure and monitor the kidneys in children with severe hypertension.

Doctors ask your child to provide a urine sample to look for the presence of substances such as protein, which may indicate that the kidneys are working poorly. The urine sample may also be tested for levels of electrolytes such as potassium, which helps to lower blood pressure.

Blood Tests

The doctor may suggest blood tests to look for signs of conditions that can cause hypertension, such as type 2 diabetes and Graves’ disease, an autoimmune condition that increases the production of thyroid hormones. These tests measure substances such as blood urea nitrogen (BUN), creatinine, blood sugar, cholesterol, calcium, and thyroid stimulating hormone.

Blood tests may also be used to look for antibodies that are produced by autoimmune diseases such as lupus, which can cause kidney damage that leads to hypertension.

Kidney Ultrasound

A doctor may want to take a picture of a child’s kidneys to see if they are enlarged or have any blockages or other structural problems that may lead to hypertension. In a kidney ultrasound, a doctor or technician places a probe called a transducer on your child’s abdomen. The transducer emits high-frequency sound waves that bounce off the kidneys, forming a picture.

Echocardiogram

An echocardiogram is an imaging test that may be used to look for signs of congenital heart conditions such as coarctation of the arteries, which means a portion of the main artery in the heart has narrowed. It can also show if the wall of the heart is thickened, which can occur if the heart works harder than usual to pump blood.

In this test, the doctor or technician places a wand called a transducer on your child’s chest. The transducer emits high-frequency sound waves that bounce off of organs in the chest and produce a precise image of the heart, valves, and blood vessels.

Additional imaging tests may be needed to obtain more detailed information if initial diagnostic tests suggest that your child has an underlying kidney or heart condition. Our kidney experts may refer you to other specialists at Hassenfeld Children's Hospital for further evaluation and treatment of these conditions.

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