CLINICAL PRESENTATIONS: HYPERTENSION
An estimated 2% to 4% of children have clinically significant hypertension. Primary, or essential, hypertension is relatively uncommon in children. Approximately 90% of hypertensive children less than 10 years of age have a secondary form. Eighty percent of secondary hypertension in the pediatric age group is related to renal disease. The most common underlying pathology is a parenchymal disease of the kidneys, such as glomerulonephritis, nephritis, or reflux nephropathy. Only 20% of renal hypertension in children is due to abnormalities of the large renal arteries. There are also various endocrinological conditions that can cause hypertension, including corticosteroid medications, pheochromocytoma, adrenal adenoma, adrenocortical carcinoma, adrenogenital syndrome, and primary aldosteronism (Table 52-1).1
Table 52–1.Causes of Hypertension in Children ||Download (.pdf) Table 52–1. Causes of Hypertension in Children
|Renal parenchymal disease ||Chronic pyelonephritis |
|Cystic disease |
|Reflux nephropathy |
|Renal dysplasia |
|Neoplasm || |
|Trauma ||Focal infarction |
|Page kidney |
|Renal vascular disease || |
|Coarctation of the aorta || |
|Endocrine disorders ||Pheochromocytoma |
|Cushing syndrome |
|Adrenogenital syndrome |
|Toxins || |
|Drugs || |
|Metabolic disorders || |
The frequencies of the different causes of childhood hypertension vary somewhat with age. The most common etiologies of hypertension in neonates are renal artery thrombosis, renal artery stenosis, renal anomalies, coarctation of the aorta, and bronchopulmonary dysplasia. Approximately 70% of infants with hypertension have narrowing or occlusion of a major renal artery. In neonates, the typical mechanism is embolization or extension of thrombus from the abdominal aorta precipitated by umbilical artery catheterization. In young children, the most common causes of hypertension are renal parenchymal disease, renal artery stenosis, and coarctation of the aorta. Renal parenchymal disease and renal artery stenosis are the most common causes of hypertension in older children. Teenagers may develop hypertension due to renal parenchymal diseases or obesity.
Individuals with essential hypertension frequently begin to develop elevation of blood pressure during childhood. Although end-organ complications of essential hypertension are uncommon in children, left ventricular hypertrophy and retinal microangiopathy are potential early findings. Studies utilizing sonography have shown subclinical increased intima–media thickness, decreased elasticity, and increased diameter in the carotid arteries of hypertensive children.2 Early findings of arterial damage also can occur in children with obesity, dyslipidemia, and homocystinemia. Essential hypertension is rare in infants.
The term renovascular hypertension indicates renin-mediated elevation of blood pressure in association with a stenotic lesion in the main renal artery or a branch artery. The renal artery stenosis causes diminished renal perfusion pressure that is detected by the juxtaglomerular apparatus in the afferent arterioles. The juxtaglomerular apparatus releases the proteolytic enzyme renin, which converts angiotensin to angiotensin I. Angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II, which is a potent vasoconstrictor and stimulant for release of aldosterone by the adrenal glands. The released aldosterone promotes retention of sodium and water. Elevation of systemic blood pressure occurs by way of increased vascular tone ...