From the Guidelines
Fibromuscular dysplasia (FMD) and renal artery stenosis (RAS) have distinct presentations, with FMD typically affecting young to middle-aged women and presenting with a characteristic "string of beads" appearance on angiography, whereas atherosclerotic RAS affects older individuals with cardiovascular risk factors and involves the proximal renal artery with a focal, concentric narrowing on imaging. The difference in presentation between FMD and RAS is crucial for diagnosis and treatment. FMD, as noted in the 2006 guidelines 1, characteristically involves the middle and distal two thirds of the main renal artery and may involve renal artery branches, presenting with resistant hypertension, renal insufficiency, or flank pain. In contrast, atherosclerotic RAS, as discussed in the 2018 scientific statement 1, typically affects older individuals with cardiovascular risk factors and involves the proximal renal artery, often with evidence of systemic atherosclerosis.
Key differences in presentation include:
- Age and gender: FMD typically affects young to middle-aged women, whereas atherosclerotic RAS affects older individuals with cardiovascular risk factors.
- Location of stenosis: FMD characteristically involves the middle and distal two thirds of the main renal artery, whereas atherosclerotic RAS involves the proximal renal artery.
- Imaging appearance: FMD presents with a characteristic "string of beads" appearance on angiography, representing alternating areas of stenosis and dilation, whereas atherosclerotic RAS presents with a focal, concentric narrowing on imaging.
- Associated symptoms: FMD can affect multiple vascular beds, including carotid and vertebral arteries, potentially causing headaches, pulsatile tinnitus, or stroke symptoms, whereas atherosclerotic RAS is often associated with evidence of systemic atherosclerosis, including coronary artery disease or peripheral arterial disease.
The management of FMD and RAS differs, with FMD more likely to respond to angioplasty without stenting, whereas atherosclerotic RAS often requires stenting. As noted in the 2018 scientific statement 1, the management of renal artery stenosis can be challenging, particularly when bilateral lesions are present, and diagnosis depends on clinical suspicion and consideration for arterial imaging. The most reliable predictor for effective BP reduction after revascularization remains a short duration of pressure elevation.
From the Research
Presentation of Fibromuscular Dysplasia and Renal Artery Stenosis
The presentation of fibromuscular dysplasia (FMD) and renal artery stenosis (RAS) can be differentiated based on several factors, including:
- Age of onset: FMD tends to occur in younger individuals, often presenting with secondary hypertension 2, 3, 4
- Angiographic findings: FMD is characterized by a "string of beads" or "beaded" appearance on angiography, whereas RAS may present with a more focal stenosis 2, 3, 5
- Location of stenosis: FMD can affect the main renal arteries, as well as branch arteries, and may present with tubular stenosis and distal tapering 3, 4
- Clinical presentation: FMD may present with asymptomatic hypertension, whereas RAS may present with more severe symptoms, such as abdominal pain and sustained hypertension 4, 6
Diagnostic Imaging
Diagnostic imaging plays a crucial role in differentiating between FMD and RAS, with:
- Contrast-enhanced MR angiography being a sensitive and specific tool for diagnosing FMD 5
- Computed tomography angiography (CTA) and digital subtraction angiography (DSA) being useful for detecting intrarenal infarctions and arterial variants of FMD 3
- Duplex ultrasound and renography being useful for raising suspicion of RAS and evaluating renal function 4, 6
Treatment and Outcomes
Treatment and outcomes for FMD and RAS can vary, with:
- Percutaneous transluminal renal angioplasty (PTRA) being an effective treatment for FMD-related RAS, with improved blood pressure control and renal function 2, 4, 6
- Antihypertensive medication being used to manage hypertension in patients with FMD and RAS 3, 6
- Strict follow-up being required for patients with FMD and RAS to monitor for restenosis and recurrent hypertension 6