A 42-year old white woman who has had hypertension for three years is referred to you because her blood pressure has become increasingly difficult to control. Family history is notable for hypertension. Her current medications are hydrochlorothiazide, 12.5 mg daily; atenolol, 100 mg daily; and extended-release diltiazem, 240 mg daily, which recently was added to her regimen. Blood pressure is 160/110 mm Hg supine and 159/102 mm Hg standing. Funduscopic examination reveals sharp disc margins with mild arteriolar narrowing. No carotid bruits are noted. Heart rate and rhythm are normal; no S4 is heard, and the cardiac impulse is not displaced. A soft abdominal bruit is heard over the left periumbilical area. No peripheral edema is present.
BUN: 10 mg/dL
Serum creatinine: 1.2 mg/dL
Sodium 140 mEq/L
Potassium 3.6 mEq/L
Chloride 103 mEq/L
Bicarbonate: 27 mEq/L
Urinalysis: Specific gravity 1.015; pH 6.0; trace protein and blood, no glucose; occasional granular and hyaline casts
Duplex Doppler ultrasound reveals features consistent with renal artery stenosis. Acceleration times are normal, and resistive indices are 0.71 on the right and 0.74 on the left.
Based on the ultrasound findings, which of the following should you do next?
A. Order kidney scintigraphy, with and without captopril
B. Add benazepril, 5 mg daily
C. Add irbesartan, 75 mg daily
D. Schedule renal artery angiography
E. Refer for renal artery bypass surgery
(Source: Dr. Brad Denker, Chief of Nephrology, Harvard Vanguard Medical Associates, Nephrology Staff, Beth Israel Deaconess Medical Center and Associate Professor of Medicine, Harvard Medical School)