A 14-year-old girl presents to your office for a routine physical examination. She has history of chronic headaches and complains about abdominal pain after eating. Her vital signs reveal a blood pressure of 163/100 mm Hg. Repeat manual blood pressure is 152/98 mm Hg. You obtain laboratory studies, which reveal a normal serum creatinine, mild hypokalemia, and elevated plasma renin activity and aldosterone level. Her renal ultrasound with Doppler is suspicious for right renal artery stenosis. You start hypertension management with a calcium-channel blocker and refer her to a pediatric nephrologist, who obtains a computed tomography angiography (Figure 71-1) that reveals severe narrowing of right renal artery. Her blood pressure remains sub-optimally controlled with calcium-channel blockers. An angiotensin II receptor blocker is added to her hypertension management.

Renovascular hypertension is hypertension that results from lesions that impair blood flow to one or both kidneys. It is an important cause of reversible hypertension in children.

Renal artery stenosis; renovascular disease.

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  Renovascular hypertension accounts for about 5 to 10 percent of hypertension in children.^1,2

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  Renovascular hypertension is caused by the interplay of renin-mediated mechanisms, sodium-related volume expansion, and increased sympathetic nervous system activity.

  
  
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  Specific causes of renovascular hypertension include:

  
  
  
  
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    Fibromuscular dysplasia.

    
    
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    Vasculitis (e.g., Takayasu’s disease, Polyarteritis nodosa, or Kawasaki disease).

    
    
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    Syndromes (e.g., Neurofibromatosis type 1, Tuberous sclerosis, Williams syndrome, or Marfan syndrome).

    
    
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    Umbilical artery catheterization.

    
    
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    Mid-aortic syndrome.

    
    
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    Renal artery hypoplasia.

    
    
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    Extrinsic compression (e.g., Neuroblastoma, Wilms tumor).

Clinical Features

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  The clinical presentation of renovascular hypertension can be very variable.

  
  
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  Children can be asymptomatic and incidentally found to have severe hypertension or they can present with symptoms secondary to end-organ damage from severe hypertension.

  
  
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  An abdominal or flank bruit, signaling turbulent blood flow, may be heard on physical exam.

Laboratory Testing

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  Increased plasma renin activity (PRA)—PRA may be elevated in children with renovascular hypertension.

  
  
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  Hyperaldosteronism—Aldosterone may be elevated due to activation of rennin-angiotensin-aldosterone system.

  
  
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  Hypokalemia—May be seen due to effect of aldosterone.

  
  
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  Metabolic alkalosis—May be seen due to effect of aldosterone.

Imaging

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  Doppler Ultrasonography—Renal arteries and its branches can be viewed by color and pulsed-wave Doppler. Ultrasonography allows for measurement of peak systolic velocities in the intrarenal branches, although this study may not be sensitive enough to detect distal sites of stenosis.³

  
  
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  Computed Tomography Angiography (CTA)—It provides three-dimensional images. It has better spatial resolution compared to magnetic resonance angiography (MRA). This study can be conducted quickly and without general anesthesia though there is exposure to ionizing radiation (Figures 71-1 and 71-2).⁴

  
  
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  Magnetic Resonance Angiography (MRA)—There is no exposure to ionizing radiation though gadolinium-based contrast is used that can lead to nephrogenic systemic fibrosis in children with glomerular filtration rates (GFR) of less than 30 mL/min/1.73 m². MRA also requires sedation or general anesthesia (Figure 71-3).

  
  
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  Digital Subtraction Angiography (DSA)—It is considered the “gold standard” for diagnosing renovascular abnormalities. DSA can provide excellent images of the branches of renal arteries as well as show the “string of beads” sign of fibromuscular dysplasia. Presence of unilateral stenosis can be confirmed by sampling blood for renin from both renal veins. Another advantage of DSA is the endovascular treatment that can be performed by the interventional radiologist at the time of DSA. DSA requires higher radiation dose than CTA, general anesthesia, and a pediatric vascular surgical backup.