What are the common causes of Hypertension (HTN) in children under 5 years of age?

Causes of Hypertension in Children Below 5 Years of Age

In children under 5 years, secondary hypertension from renal parenchymal disease is the predominant cause, accounting for 34-79% of cases, and any child in this age group with confirmed hypertension requires thorough evaluation for an underlying structural or pathologic etiology. 1, 2

Age-Specific Etiology Pattern

Secondary causes dominate in young children. Children younger than 6 years have significantly more secondary causes of hypertension compared to older children and adolescents, where 85-95% eventually have primary hypertension. 1

Most Common Causes in Children <5 Years

Renal Parenchymal Disease (Most Common)

• Congenital anomalies of the kidney and urinary tract (CAKUT) are the leading structural causes in this age group 3
• Polycystic kidney disease should be considered, especially with positive family history 3
• Obstructive uropathy from posterior urethral valves or other anatomic obstruction 3
• History of urinary tract infections or recurrent pyelonephritis causing renal scarring 4
• Glomerulonephritis or other inflammatory renal conditions 5, 6

Renovascular Disease (Second Most Common)

• Renal artery stenosis from fibromuscular dysplasia or developmental abnormalities 1, 7
• Accounts for approximately 12-13% of secondary hypertension cases in young children 2
• Suspect when there is discrepant kidney sizes on ultrasound (>1.5 cm difference) 3, 7
• May present with severe or stage 2 hypertension with significant diastolic elevation 3

Coarctation of the Aorta

• Critical cardiovascular cause that must not be missed in young children 1, 2
• Presents with differential blood pressure between upper and lower extremities 3
• Physical exam reveals delayed or absent femoral pulses and radio-femoral pulse delay 3
• More common in children and adolescents than in adults 7

Endocrine Causes (Less Common but Important)

• Primary hyperaldosteronism can occur even in young children, though more typical in adults 2
• Pheochromocytoma should be considered with paroxysmal symptoms 2
• Cushing syndrome with characteristic physical features 2
• Hyperthyroidism affecting blood pressure regulation 7

Clinical Approach to Diagnosis

History Red Flags

• Perinatal complications including prematurity, umbilical artery catheterization, or neonatal intensive care 3
• Family history of polycystic kidney disease or hereditary renal disorders 4, 3
• Recurrent urinary tract infections or known urologic abnormalities 4, 3
• Medication exposure that could elevate blood pressure 3

Physical Examination Priorities

• Cardiovascular assessment for heart murmurs, femoral pulse quality, and upper/lower extremity blood pressure differential to detect coarctation 3
• Abdominal examination for palpable masses (Wilms tumor, neuroblastoma, polycystic kidneys) and renal bruits 3
• Fundoscopic examination for retinal changes, hemorrhages, or papilledema indicating severe hypertension 3

Essential Laboratory Workup

• Serum creatinine with estimated GFR to assess kidney function 3
• Serum electrolytes (hypokalemia suggests aldosteronism or renovascular disease) 3
• Urinalysis to screen for blood, protein, and signs of kidney disease 3
• Urinary albumin-to-creatinine ratio for early kidney damage detection 3
• Complete blood count for anemia or hematologic abnormalities 3

Mandatory Imaging

• Renal ultrasound with Doppler is first-line imaging to assess for structural abnormalities, kidney size discrepancy, hydronephrosis, cystic disease, and renovascular flow patterns 3
• Echocardiography to evaluate for coarctation of the aorta and assess left ventricular mass for target organ damage 3

Critical Clinical Pitfalls

Do not assume primary hypertension in children under 5 years. Unlike older children and adolescents where obesity-related primary hypertension predominates, young children with hypertension almost always have an identifiable secondary cause that requires specific treatment. 1

Severe or stage 2 hypertension in this age group warrants immediate specialist referral within 1 week or initiation of treatment while completing the diagnostic workup. 3

Proper blood pressure measurement technique is essential to avoid false-positive diagnoses—use appropriate cuff size (bladder covering 80-100% of arm circumference), obtain multiple readings, and discard the first oscillometric reading. 1, 3

Secondary hypertension is unlikely to be the only clinical manifestation—look for associated symptoms or signs of the underlying disorder, as management targets both the underlying condition and blood pressure control. 1