Noninvasive imaging for suspected fibromuscular dysplasia

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A 51-year-old woman is evaluated for resistant hypertension. She presented 5 months ago to her primary care physician with a 3-week history of headaches, tinnitus, dizziness, and shortness of breath. BP was 182/94 mm Hg, increased from 124/72 mm Hg 1 year previously. Her 50-year-old brother and 75-year-old father both developed hypertension in their 30s. Medications include amlodipine, carvedilol, indapamide, and hydralazine. On examination, BP in the right arm is 174/88 mm Hg, BP in the left arm is 169/85 mmHg, heart rate is 84/min, and body mass index (BMI) is 34 kg/m². On auscultation, there are left-sided carotid and epigastric bruits. Laboratory data show serum creatinine level of 0.9 mg/dL (reference range, 0.5–1.1), potassium level of 3.6 mEq/L (reference range, 3.5–5.0), and total CO₂ level of 29 mEq/L (reference range, 23–28). Urinalysis is normal. Duplex Doppler ultrasound of the left carotid artery reveals turbulence and increased flow velocity. Which ONE of the following is the best NEXT STEP in evaluating hypertension?

  1. A.Captopril-stimulated renography
  2. B.Plasma aldosterone-to-renin ratio
  3. C.Digital subtraction angiography
  4. D.Renal duplex Doppler ultrasoundCorrect

Explanation

Renal duplex Doppler ultrasound is the next best step in evaluation for this patient with resistant hypertension and abdominal and carotid bruits. The diagnosis of fibromuscular dysplasia (FMD) should be considered for this woman with abrupt onset hypertension in whom there is a consistent family history and abdominal and carotid bruits. Decreased kidney function after starting an ACEI or ARB may be an additional clue to the diagnosis. Patients with suspected FMD should initially undergo noninvasive studies to define anatomy, confirm the diagnosis, and help plan percutaneous intervention. The choice of initial diagnostic study is institution-dependent. Renal duplex Doppler ultrasound, for example, requires technical proficiency, with reported sensitivity and specificity of 60%–90%. Duplex ultrasonography can be used to determine the velocity of the flow in the renal arteries and document kidney size or asymmetry. CT angiography (CTA) has sufficient resolution to identify most FMD lesions in main renal arteries but has decreased sensitivity for branch arteries. Magnetic resonance angiography (MRA) may be less accurate for FMD compared with CTA. For atherosclerotic renal artery stenosis, CTA and MRA are 90% sensitive and specific. FMD registry data show that FMD is diagnosed much later than previously believed, at an average age of 51.9 years. Female predominance (91%) is well known, but the frequency of a strong family history (79%) was not previously appreciated. Patients with renal artery involvement often (68%) have carotid or vertebral involvement as well. The most common presenting symptoms are headache (52%), pulsatile tinnitus (27.5%), and dizziness (26%). Chest pain or shortness of breath was observed in 16% of patients. Several of these symptoms can also be seen with pheochromocytoma, but the suggestion of vascular disease elsewhere should prompt evaluation for FMD. Digital subtraction angiography is the gold standard for the diagnosis of FMD but is reserved for planning catheter-based interventions or for diagnosis when noninvasive studies are inconclusive. This patient has a high pretest probability of FMD, and measures to establish this diagnosis should be pursued before evaluating for other causes of resistant hypertension. If the initial investigation fails to demonstrate evidence of renovascular hypertension, further evaluation for primary aldosteronism by measuring the plasma aldosterone-to-renin ratio would be indicated. Captopril-stimulated renography is not recommended to diagnose FMD because of poor interobserver agreement, variable sensitivity and specificity, and difficulty in interpreting results when there is asymmetric kidney blood flow or function or bilateral disease.

Why each option

A.
Captopril renography has poor interobserver agreement and unreliable accuracy, particularly in bilateral or asymmetric disease, and is no longer recommended.
B.
Primary aldosteronism screening is appropriate in resistant hypertension, but carotid and epigastric bruits make FMD the priority to evaluate first.
C.
Digital subtraction angiography is the gold standard for FMD but is reserved for planning intervention or when noninvasive imaging is inconclusive.
D.
Correct. Abrupt hypertension with carotid and epigastric bruits and family history suggests FMD; noninvasive renal duplex ultrasound defines the renal arteries first.

Reference: Gornik HL, Vasc Med 2019 (First International Consensus on fibromuscular dysplasia); Olin JW, Circulation 2012 (US Registry for Fibromuscular Dysplasia)

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