Hypertension, Renal

Key Features

• Primary hypertension is a diagnosis of exclusion

• Causes in the newborn include

  • Congenital anomalies of the kidneys or renal vasculature

  • Obstruction of the urinary tract

  • Thrombosis of renal vasculature or kidneys

  • Volume overload

• Umbilical artery catheterization is an important contributor to hypertension in infants and young children

• Infants and children with hypertension require careful evaluation to exclude a secondary cause of hypertension, including

  • Renal parenchymal or renovascular disease (renal arterial or venous thrombosis, congenital vascular stenosis)

  • Other vascular disease (vasculitis, aortic coarctation)

  • Endocrine disorders (thyroid disease, cortisol excess, pheochromocytoma, congenital adrenal hyperplasia, primary hyperaldosteronism)

  • Monogenic hypertension (glucocorticoid remediable aldosteronism, Liddle syndrome)

• Family history should be reviewed for hypertension (particularly early-onset) and cardiovascular disease

Clinical Findings

• A child is normotensive if the average recorded systolic and diastolic blood pressures are lower than the 90th percentile for age, sex, and height

• The 90th percentile in the newborn period is approximately 85–90/55–65 mm Hg for both sexes

• In the first year of life, the acceptable levels are 90–100/60–67 mm Hg

• Incremental increases with growth occur, gradually approaching young adult ranges of 100–120/65–80 mm Hg in the late teens

• A blood pressure between the 90th–95th percentile or exceeding 120/80 in adolescents is consistent with prehypertension

Diagnosis

• Routine laboratory studies include serum blood urea nitrogen (BUN), creatinine and electrolytes, a complete blood cell count, and urinalysis

  • Abnormal BUN and creatinine support underlying renal disease as the cause

  • Serum electrolytes demonstrating hypokalemic alkalosis suggest excess mineralocorticoid effect

• Serum lipids, glucose, hemoglobin A_1C, and thyroid function tests are indicated depending on age of child

• Screening of plasma/urine catecholamines and metanephrines and/or serum cortisol should be obtained as clinically indicated

• Renal ultrasonography with Doppler flow is helpful in determining the presence of renal scarring, urinary tract obstruction or renovascular flow disturbances

• Renal magnetic resonance angiography or CT angiography is indicated when there is high suspicion for renal artery stenosis

Treatment

• Hypertensive emergency exists when CNS signs of hypertension appear, such as papilledema or encephalopathy

• Retinal hemorrhages or exudates also indicate a need for prompt and effective control

• Primary classes of useful antihypertensive drugs

  • ACE inhibitors and angiotensin receptor blockers (the latter used less frequently in children based on less clinical experience and limitations in accurate dosing for smaller children)

  • Calcium channel blockers

  • α- and β-Adrenergic blockers

  • Diuretics

  • Vasodilators

• Nicardipine is a very effective and generally well-tolerated antihypertensive that is administered via continuous intravenous infusion for control of systemic hypertension

• Sodium nitroprusside is a very effective infusion to gain control of malignant hypertension, but long-term usage is limited by concern for rare thiocyanate toxicity, especially when renal failure is present

• Hydralazine is a vasodilator that can be administered intermittently by the intravenous route

• Any vasodilator can induce reflex tachycardia and sodium retention, so concomitant administration of a β-blocker or diuretic may be indicated

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