Case presentation

An 81-year-old retired pediatric nurse with longstanding hypertension was referred for further evaluation of uncontrolled hypertension and dyspnea. She was diagnosed with hypertension at least 40 years earlier and is currently on adequate doses of amlodipine, olmesartan, and furosemide with blood pressures remaining in the 140 to 170 mmHg systolic and 85 to 95 mmHg diastolic range. Her only symptom is exertional dyspnea; there is no chest pain, orthopnea, or paroxysmal nocturnal dyspnea. Additional medical history includes prior stroke with no residua 12 years ago, diabetes mellitus, chronic obstructive pulmonary disease, dyslipidemia, and hypothyroidism. Her baseline renal function was normal with a creatinine of 0.9 mg/dL. Her primary care physician ordered an MRI of the renal arteries; this suggested right renal artery stenosis. Because of her exertional dyspnea and atherosclerotic risk factors, she was referred for coronary and renal angiography.

Cardiac catheterization

A diagnostic cardiac catheterization was performed first and revealed mild coronary atherosclerosis with no significant obstruction and preserved left ventricular function. Selective right renal angiography demonstrated the characteristic findings of fibromuscular dysplasia with a “beaded” appearance of the renal artery and the presence of linear “webs” (Figure 50-1 and Video 50-1). This abnormality was also present to a lesser degree in the left renal artery (Figure 50-2 and Video 50-2). After administering 70 U/kg of unfractionated heparin, balloon dilatation was performed at these sites using a 5.5 mm diameter by 20 mm long balloon, which improved the angiographic appearance (Figures 50-3, 50-4 and Videos 50-3, 50-4).

FIGURE 50-1 This is a selective right renal arteriogram demonstrating the classic “string of beads” appearance to the renal artery.

FIGURE 50-2 There are also more subtle findings consistent with fibromuscular dysplasia present in the left renal artery.

FIGURE 50-3 This is the result after balloon angioplasty of the right renal artery.

FIGURE 50-4 This is the result after balloon angioplasty of the left renal artery.

Postprocedural course

She was observed overnight with no complications. Follow-ups 1 month and 1 year later confirmed excellent control of her blood pressure on olmesartan and furosemide alone.

Discussion

Renal artery stenosis is most commonly caused by atherosclerosis, typically affecting the ostium and proximal segment of the renal artery. In roughly 10% of cases, fibromuscular dysplasia is the cause.¹ This condition is more common in young females (less than 50 years old) and involves the distal portion of the renal artery or its branches. Although usually attributed to young women, it has also been recognized as a cause of secondary hypertension in elderly individuals, as shown in this case.²

The diagnosis of fibromuscular dysplasia is made based on the classic angiographic appearance, often referred to as a “string of beads” (Figure 50-5). This finding is due to luminal occupation with webs and ridges of dysplastic media. It is sometimes difficult to decide if these webs and ridges obstruct the lumen to a significant degree. When the angiogram is ambiguous, additional information regarding the hemodynamic significance of an abnormal segment can be determined by measurement of a pressure gradient.³

FIGURE 50-5 This angiogram was obtained in a different patient and is an impressive demonstration of the classic angiographic appearance of this condition.

In general, fibromuscular dysplasia is treated with balloon angioplasty alone. Disruption of the abnormal webs and ridges with a balloon alone is often adequate and stenting is reserved for treatment of flow-limiting dissections caused by the balloon. The clinical response to balloon angioplasty is excellent, with more than 90% cured or improved after the procedure and restenosis occurring in about 20%.⁴