For an 18-year-old male with resistant hypertension despite taking lisinopril (angiotensin-converting enzyme inhibitor) 10 mg, would it be reasonable to order a renal artery ultrasound?

Renal Artery Ultrasound in an 18-Year-Old with Resistant Hypertension

Yes, ordering a renal artery ultrasound is reasonable and indicated for this 18-year-old male, but only after confirming true resistant hypertension and optimizing his current inadequate medication regimen.

First Priority: Confirm This is Actually Resistant Hypertension

Before ordering any imaging, you must verify this patient truly has resistant hypertension, as approximately 50% of apparent cases are pseudoresistance 1:

• Perform ambulatory or home blood pressure monitoring to exclude white-coat hypertension, which accounts for roughly half of apparent resistant cases 1
• Verify medication adherence through direct questioning, pill counts, or pharmacy records 1
• Ensure proper BP measurement technique using appropriate cuff size and correct arm positioning 1

Second Priority: Optimize the Current Inadequate Regimen

This patient is NOT on an adequate regimen for resistant hypertension. Lisinopril 10 mg monotherapy does not meet the definition of resistant hypertension, which requires failure of three drugs from different classes at maximal doses, including a diuretic 1. Before pursuing imaging:

• Add a long-acting thiazide-like diuretic (chlorthalidone 12.5-25 mg or indapamide 1.5-2.5 mg daily), as these are more effective than hydrochlorothiazide 1, 2
• Add a long-acting calcium channel blocker (amlodipine 5-10 mg daily) 1, 2
• Increase lisinopril to maximal tolerated dose (typically 40 mg daily) 1
• Implement lifestyle modifications: sodium restriction <2400 mg/day, weight loss if overweight, regular exercise, and alcohol moderation 1

When to Order Renal Artery Imaging

After optimizing the three-drug regimen, if BP remains ≥130/80 mmHg, then renal artery imaging is strongly indicated given this patient's young age 1. The American Heart Association specifically recommends imaging for renal artery stenosis in young patients, particularly those whose presentation suggests fibromuscular dysplasia 1.

Key Clinical Features Supporting Imaging in This Case:

• Age <30 years is a major red flag for secondary hypertension, particularly fibromuscular dysplasia 1
• Young males and females are at increased risk for fibromuscular dysplasia, which is highly curable with angioplasty 1
• Early-onset hypertension warrants aggressive screening for secondary causes 1

Choice of Imaging Modality:

The preferred modality varies by institutional expertise 1:

• Duplex ultrasound is widely available, non-invasive, and provides both anatomic and functional assessment, though sensitivity varies by laboratory 1, 3
• CT angiography or MR angiography may be preferred if ultrasound quality is suboptimal at your institution 1
• Avoid diagnostic renal arteriography in the absence of suspicious noninvasive imaging 1

Additional Secondary Cause Screening

While pursuing renal artery evaluation, simultaneously screen for other common secondary causes 1:

• Obtain morning plasma aldosterone and plasma renin activity to screen for primary aldosteronism (aldosterone/renin ratio >20-30 is suggestive) 1
• Screen for obstructive sleep apnea if the patient has snoring, witnessed apnea, or excessive daytime sleepiness 1
• Check basic metabolic panel for potassium, creatinine, and calculate eGFR 1
• Obtain urinalysis to assess for renal parenchymal disease 1
• Check TSH to exclude thyroid dysfunction 2

Critical Pitfalls to Avoid

• Do not order abdominal CT to screen for adrenal adenomas without biochemical confirmation of hormonally active tumors first 1
• Do not proceed with renal arteriography without positive noninvasive imaging 1
• Do not accept monotherapy failure as "resistant hypertension" - this patient needs proper three-drug optimization first 1
• Do not delay imaging indefinitely in a young patient once the three-drug regimen fails, as fibromuscular dysplasia is potentially curable 1

Expected Outcome if Renal Artery Stenosis is Found

If fibromuscular dysplasia is identified, angioplasty is the treatment of choice and is often curative, with success rates exceeding 90%, though restenosis may occur in >20% of patients after 1 year 1. This represents a potentially life-changing intervention for an 18-year-old who would otherwise face decades of medication and cardiovascular risk 1.