**3. Hypertension**

Historically, hypertension was believed to be a rare disease in children, mostly due to secondary causes, however, in the past two decades, its prevalence increased significantly, mostly due to obesity, and was estimated from 4.3% among children aged 6 years to 3.3% among those aged 19 years and peaked at 7.9% among those aged 14 years [14].

In children, physiologically, blood pressure increases with age and body size, making it impossible to define a single blood pressure level to establish hypertension, as in adults. Therefore, the definition is based on the normal distribution of blood pressure in healthy children. Hypertension is defined as systolic or diastolic blood pressure above 95th percentile for sex, age and height measured on at least three separate occasions. High-normal blood pressure is defined as above 90th, but less than 95th percentile. For boys and girls, aged 16 or above, the definition is as in adults. In addition, reference values for sex, age and height of ambulatory blood pressure measurement have been obtained from different European populations and provide useful information for diagnosis and management of hypertension. The blood pressure cuff must be appropriate to the size of the child [15, 16].

Secondary hypertension is more frequent in the pediatric population, however, the prevalence varies between studies and has yet to be confirmed. The causes of secondary hypertension are numerous and should be sought for systematically depending on history, examination and clinical results. In brief, they are presented in **Table 1** [16]. Some syndromes, such as Williams's, Turner's and Leigh's, have also been associated with hypertension [16].

After a thorough diagnostic work-up, secondary causes need to be treated appropriately. If none can be established, the diagnosis of essential hypertension is confirmed. Usually, essential hypertension is present among older children with a strong family history of hypertension [16].

First-line treatment, especially in obese, is lifestyle intervention with salt restriction and weight loss. Pharmacological treatment is indicated in hypertensive children unresponsive to lifestyle modifications, as well as in children with symptomatic hypertension, secondary hypertension, target organ damage, diabetes mellitus or chronic kidney disease [17, 18]. Antihypertensive treatment is started with the lowest dose of a single drug and titrated if needed until maximum recommended dose is reached. If blood pressure is still elevated, the second drug can be added and up-titrated. The choice of particular antihypertensive drug is partly dependent on underlying etiology, partly on other relevant factors, such as end organ damage, concurrent disorders, side effects and clinician's preference [17, 18].


#### **Table 1.**

*Causes of secondary hypertension in children.*
