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Difficulty: MediumDiagnostic Workup and Test Sequencing

A 6868-year-old man returns to the outpatient clinic for evaluation of persistently elevated blood pressure. He has a history of severe coronary artery disease, for which he underwent coronary artery bypass grafting five years ago, and sick sinus syndrome requiring placement of a dual-chamber permanent pacemaker. His current medications include aspirin, atorvastatin, metoprolol, amlodipine, and lisinopril. The lisinopril was added to his regimen three weeks ago due to uncontrolled hypertension. Today, his blood pressure is 176/98176/98 mm Hg, and his heart rate is 7272/min. Physical examination reveals a soft, high-pitched systolic bruit auscultated just to the right of the umbilicus. Laboratory studies obtained this morning show a serum creatinine level of 2.62.6 mg/dL, an increase from a baseline of 1.41.4 mg/dL recorded one month ago. The estimated glomerular filtration rate (eGFR) is 2424 mL/min/1.731.73 m 2^2. Urinalysis shows no red blood cells or casts. Which of the following is the most appropriate next step in this patient's diagnostic workup?

  1. Duplex ultrasonography of the renal arteriesAnswer
  2. B
    Computed tomography angiography of the abdomen and pelvis
  3. C
    Invasive catheter renal angiography
  4. D
    Magnetic resonance angiography of the renal arteries
  5. E
    Plasma aldosterone-to-renin ratio

Answer

The most appropriate next step is duplex ultrasonography of the renal arteries, as it safely evaluates for renal artery stenosis without utilizing nephrotoxic contrast media.
The correct answer is duplex ultrasonography of the renal arteries. This patient's presentation—resistant hypertension, an abdominal bruit, and an acute, significant increase in serum creatinine following the initiation of an ACE inhibitor—is highly suspicious for atherosclerotic renal artery stenosis (RAS). The initial diagnostic workup for suspected RAS requires noninvasive imaging. Because this patient has stage 4 chronic kidney disease (eGFR <30< 30 mL/min/1.731.73 m 2^2), duplex ultrasonography is the preferred modality. It does not require contrast administration, thereby providing necessary anatomic and hemodynamic information without risking contrast-induced acute kidney injury or nephrogenic systemic fibrosis.

Step-by-Step Solution

1
Analyze the clinical presentation to identify the suspected underlying condition.
The patient has resistant hypertension, a new abdominal bruit, and an acute >30%>30\% increase in serum creatinine following the initiation of an ACE inhibitor (lisinopril). This triad is highly suggestive of bilateral atherosclerotic renal artery stenosis (RAS).
Recognizing the classic clinical syndrome of renovascular hypertension guides the selection of the correct diagnostic pathway.
2
Evaluate the patient's comorbidities and baseline parameters to determine the safest imaging modality.
The patient has an eGFR of 2424 mL/min/1.731.73 m 2^2 (Stage 4 CKD) and an implanted permanent pacemaker.
Diagnostic test sequencing must prioritize patient safety; severe renal impairment and implanted devices dictate which advanced imaging studies are contraindicated.
3
Select the optimal initial diagnostic test based on the identified constraints.
Duplex ultrasonography of the renal arteries is chosen because it is noninvasive, does not require nephrotoxic contrast (unlike CTA), and does not utilize magnetic fields or gadolinium (unlike MRA).
Guidelines recommend duplex ultrasound as the initial screening test of choice for suspected renovascular hypertension in patients with significant renal dysfunction.

Key Concept

In patients with suspected renovascular hypertension and severe chronic kidney disease (eGFR <30< 30 mL/min/1.731.73 m 2^2), duplex ultrasonography of the renal arteries is the most appropriate initial diagnostic test because it avoids the risks of contrast-induced nephropathy and nephrogenic systemic fibrosis.
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Diagnostic Workup and Test Sequencing

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