Hypertension during childhood is not rare, with an estimated prevalence ranging from 1% to 5.8%. Children with hypertension may develop early abnormalities in target organs systems, even in the absence of signs and symptoms. Furthermore, childhood hypertension is a strong risk factor for adult hypertension. An aggressive surveillance system to detect hypertension in children can lead to prompt diagnosis and management, prevention of target organ damage, and a reduced risk of adult hypertension. Recent guidelines suggest that all children older than 3 years should have their BP checked. Younger children should have their BP checked if risk factors for hypertension are present (Table 138.1).

Hypertension in the pediatric population is defined as an average systolic blood pressure (SBP) or diastolic blood pressure (DBP) ≥95% for age, gender, and height, measured on at least three separate occasions. Appropriate technique in BP measurement is required to diagnose hypertension accurately. Auscultation using mercury sphygmomanometry is the gold standard, but many oscillometric devices have been validated for use in children. Regardless of the device employed, the correct cuff size is essential for the accurate measurement of BP. The width of the cuff bladder should be approximately 40% of the arm circumference measured at the midpoint of the upper arm. The length of the cuff bladder should be 80% to 100% of the arm circumference.

Hypertension in children can be classified as primary or secondary. Primary hypertension, also called essential hypertension, does not have an identifiable cause, but rather results from a combination of genetic and environmental factors. It occurs more commonly in adolescents than younger children, and it is associated with overweight, obesity, and other cardiovascular risk factors. Individuals with primary hypertension are often asymptomatic and without evidence of target organ damage at presentation.

Secondary hypertension is more common in younger children and results from an underlying disease process. At presentation, these children are
more likely to have dramatic elevations of BP, symptoms of hypertension, and evidence of target organ damage. The most common cause of secondary hypertension is renal disease. Renal parenchymal disease is more common than renovascular disease. Other causes of secondary hypertension include cardiac diseases such as coarctation of the aorta, medications, and poorly controlled pain. Primary endocrine disorders are rare and include hyperthyroidism, Cushing disease, and endocrine tumors such as pheochromocytoma and neuroblastoma. Table 138.2 provides the common causes of hypertension by age group.