What is the significance of elevated serum renin and increased renal arterial resistive index in a hypertensive toddler with normal Computed Tomography Angiography (CTA)?

From the Guidelines

The presence of elevated serum renin and increased renal arterial resistive index in a hypertensive toddler with normal Computed Tomography Angiography (CTA) is highly suggestive of renovascular hypertension, which warrants further evaluation and potential treatment with ACE inhibitors or ARBs to manage the condition and prevent long-term cardiovascular damage. The clinical presentation of high serum renin and elevated renal arterial resistive index in a hypertensive toddler, despite normal CTA findings, points towards a diagnosis of renovascular hypertension, which may be due to intrarenal vascular disease not detectable on conventional angiography 1.

Key Considerations

• The elevated renin level indicates hyperactivation of the renin-angiotensin system, which is a key factor in the development of hypertension in this context.
• The increased renal arterial resistive index suggests increased vascular resistance at the microvascular level, further supporting the diagnosis of renovascular hypertension.
• The absence of visible stenosis on CTA does not rule out the presence of intrarenal vascular disease, as these conditions can be subtle and not detectable by conventional imaging techniques.

Management Approach

• Consider initiating treatment with ACE inhibitors or ARBs to target the renin-angiotensin-aldosterone system, such as enalapril 0.08 mg/kg/day divided twice daily, gradually increasing to 0.5 mg/kg/day if needed, or losartan 0.7 mg/kg/day (for children >6 months) 1.
• Close monitoring of blood pressure, renal function, and electrolytes is essential to adjust the treatment regimen as needed.
• Regular follow-up with renal ultrasound and Doppler studies every 3-6 months can help assess the effectiveness of treatment and detect any potential changes in renal function.
• Periodic monitoring of renin levels can also provide valuable information on the response to treatment and guide adjustments to the therapeutic plan.

Long-term Implications

• The goal of treatment is to achieve blood pressure readings below the 90th percentile for age, height, and gender, which can help prevent long-term cardiovascular damage and reduce the risk of complications associated with hypertension.
• Regular monitoring and follow-up are crucial to ensure that the treatment plan is effective and to make adjustments as needed to achieve optimal blood pressure control.

From the Research

Significance of Elevated Serum Renin and Increased Renal Arterial Resistive Index

• Elevated serum renin and increased renal arterial resistive index in a hypertensive toddler may indicate renovascular hypertension, which is caused by kidney hypoperfusion due to anatomic stenosis of the renal artery 2.
• The activation of the Renin Angiotensin-Aldosterone System (RAAS) plays a crucial role in the development of hypertensive crisis in children, and elevated serum renin levels may be an indicator of RAAS activation 3.
• Increased renal arterial resistive index is significantly associated with pulse pressure and left ventricular mass index in hypertensive children, suggesting that it may be a useful marker for assessing the severity of hypertension and its effects on the cardiovascular system 4.

Diagnostic Considerations

• Computed Tomography Angiography (CTA) may not be sufficient to rule out renal artery stenosis, as it has a lower sensitivity at the 2nd- and 3rd-order branches 5.
• Digital subtraction angiography (DSA) remains the gold standard for diagnosing renal artery stenosis, but CTA can be used as a complementary test to assess the main renal artery level 5.
• A normal CTA result does not exclude the possibility of renal artery stenosis, and further evaluation with DSA or other imaging modalities may be necessary 5.

Clinical Implications

• Hypertensive children with elevated serum renin and increased renal arterial resistive index may require closer monitoring and more aggressive management of their hypertension to prevent end-organ damage 3, 2.
• The therapeutic approach should be individualized, and management options may include non-surgical pharmacological therapy and revascularization with percutaneous transluminal renal angioplasty (PTRA) or surgery 2.
• Further studies are required to define the best approach for managing renovascular hypertension in children and to determine the optimal use of imaging modalities such as CTA and DSA 2, 5.