Figure 1
CT angiogram right renal artery
Clinical History
A 58 year old Caucasian male presents with refractory hypertension and borderline renal function.
Imaging Findings
As the patient was moderately overweight and had a distant smoking history it was felt that his refractory hypertension may be due to atherosclerotic disease of the renal arteries. A CT angiogram was performed.
The CTA shows the classic “beaded,” or “string of pearls,” appearance of fibromuscular dysplasia in the peripheral renal arteries with relative sparing of the proximal 3 cm bilaterally.
The patient was then booked for an angioplasty of the renal arteries. His initial blood pressure was 144/94 mmHg. Accessing the peripheral renal arteries was very difficult due to the extensive beaded webbed and aneurismal configuration of the arteries themselves. Ultimately, angioplasty was performed using serial balloon dilatation, peripheral to central, to 7 mm.
The patient was discharged four hours later, at which time his blood pressure was 138/90 mmHg. Three days later, he reported a systolic blood pressure of 100 mmHg and was sent back to the referring physician in regards to cessation of his anti hypertensive medications.
The CTA shows the classic “beaded,” or “string of pearls,” appearance of fibromuscular dysplasia in the peripheral renal arteries with relative sparing of the proximal 3 cm bilaterally.
The patient was then booked for an angioplasty of the renal arteries. His initial blood pressure was 144/94 mmHg. Accessing the peripheral renal arteries was very difficult due to the extensive beaded webbed and aneurismal configuration of the arteries themselves. Ultimately, angioplasty was performed using serial balloon dilatation, peripheral to central, to 7 mm.
The patient was discharged four hours later, at which time his blood pressure was 138/90 mmHg. Three days later, he reported a systolic blood pressure of 100 mmHg and was sent back to the referring physician in regards to cessation of his anti hypertensive medications.
Discussion
Fibromuscular dysplasia is an idiopathic disease, most typically affecting the arterial wall musculature of medium-sized vessels. The renal arteries are most commonly affected, followed by the carotid arteries.
There are a variety of subtypes of FMD including:
Intimal fibroplasia – This subtype constitutes less than 10% of recognised FMD cases and can present with ring-like vascular stenosis or a long segment smooth stenosis.
Medial fibroplasia – There are three subtypes of medial fibroplasia – medial dysplasia, perimedial fibroplasia and medial hyperplasia. Medial dysplasia accounts for the majority of recognised FMD cases. The alternating regions of medial collagenised thickening and thinning give the classic “string of pearls” appearance to the involved vessels. Perimedial fibroplasia accounts for 10% of renal FMD and has a similar, if somewhat less pronounced appearance. Medial hyperplasia appears as smooth narrowing of the blood vessel and is exceptionally rare.
Adventitial fibroplasia – This is an extremely rare subtype of FMD in which the vascular adventitium is abnormally collagenised. It can be associated with an appearance similar to retroperitoneal fibrosis due to collagen deposition in surrounding tissues.
Though angiography is the gold standard for diagnosis of FMD, given recent advances in CT imaging, the CT angiogram is sometimes sufficient for diagnosis. The alternating areas of stenosis and aneurysmal dilatation are felt to be beyond the resolution of MR angiography excepting for extreme cases.
The preferred treatment for symptomatic renal FMD is balloon angioplasty. This is felt to be successful based on the theory that cracking the fibrotic web like stenoses in an involved renal artery will allow increased renal perfusion and an associated down-regulation of the renin-angiotensin pathway. There is often a measureable decrease in the patient’s blood pressure within hours of finishing the procedure.
Unlike atherosclerotic renal artery stenosis, there is no proven benefit to using a stent in FMD affected renal arteries.
There are a variety of subtypes of FMD including:
Intimal fibroplasia – This subtype constitutes less than 10% of recognised FMD cases and can present with ring-like vascular stenosis or a long segment smooth stenosis.
Medial fibroplasia – There are three subtypes of medial fibroplasia – medial dysplasia, perimedial fibroplasia and medial hyperplasia. Medial dysplasia accounts for the majority of recognised FMD cases. The alternating regions of medial collagenised thickening and thinning give the classic “string of pearls” appearance to the involved vessels. Perimedial fibroplasia accounts for 10% of renal FMD and has a similar, if somewhat less pronounced appearance. Medial hyperplasia appears as smooth narrowing of the blood vessel and is exceptionally rare.
Adventitial fibroplasia – This is an extremely rare subtype of FMD in which the vascular adventitium is abnormally collagenised. It can be associated with an appearance similar to retroperitoneal fibrosis due to collagen deposition in surrounding tissues.
Though angiography is the gold standard for diagnosis of FMD, given recent advances in CT imaging, the CT angiogram is sometimes sufficient for diagnosis. The alternating areas of stenosis and aneurysmal dilatation are felt to be beyond the resolution of MR angiography excepting for extreme cases.
The preferred treatment for symptomatic renal FMD is balloon angioplasty. This is felt to be successful based on the theory that cracking the fibrotic web like stenoses in an involved renal artery will allow increased renal perfusion and an associated down-regulation of the renin-angiotensin pathway. There is often a measureable decrease in the patient’s blood pressure within hours of finishing the procedure.
Unlike atherosclerotic renal artery stenosis, there is no proven benefit to using a stent in FMD affected renal arteries.
Differential Diagnosis List
Fibromuscular dysplasia
Final Diagnosis
Fibromuscular dysplasia
References
[1] Davison, Alex M.; Stewart J. Cameron; Jean-Pierre Grϋnfeld; Eberhard Ritz; Christopher Winearls (2005) The Oxford Textbook of Clinical Nephrology Third Edition. 1345-1346
Case information
| URL: | https://www.eurorad.org/case/8810 |
| DOI: | 10.1594/EURORAD/CASE.8810 |
| ISSN: | 1563-4086 |
Figure 2
CTA coronal 1
The coronal CT angiogram demonstrates the classic beaded appearance of FMD.
Figure 3
CTA coronal 2
Figure 4
CTA coronal 3
Note the spared proximal portion of both renal arteries.
Figure 5
MIP image
Figure 6
Angiogram 1
Angiography is considered the gold standard for fibromuscular dysplasia.
Figure 7
Angiogram 2
Figure 8
Angiogram 3
Though the aneurysmal portions of the vessel measured up to 10mm, the goal of angioplasty is to break apart the stenotic webs, thus for safety concerns, only a 7 mm balloon was used.
Figure 9
Angiogram 4
Serial balloon angioplasty was performed.
Figure 10
Angiogram 5
The visual result is not perfect, but keep in mind that the goal is a physiologic response.
Figure 11
Angiogram 6
The contralateral side was just as difficult to negotiate. The severity of the appearance was felt to be related to chronicity of disease.
Figure 12
Angiogram 7
Figure 13
Angiogram 8
Figure 14
Angiogram 9
Figure 15
Angiogram 10
CT angiogram right renal artery
CTA coronal 1
The coronal CT angiogram demonstrates the classic beaded appearance of FMD.
CTA coronal 2
CTA coronal 3
Note the spared proximal portion of both renal arteries.
MIP image
Angiogram 1
Angiography is considered the gold standard for fibromuscular dysplasia.
Angiogram 2
Angiogram 3
Though the aneurysmal portions of the vessel measured up to 10mm, the goal of angioplasty is to break apart the stenotic webs, thus for safety concerns, only a 7 mm balloon was used.
Angiogram 4
Serial balloon angioplasty was performed.
Angiogram 5
The visual result is not perfect, but keep in mind that the goal is a physiologic response.
Angiogram 6
The contralateral side was just as difficult to negotiate. The severity of the appearance was felt to be related to chronicity of disease.
Angiogram 7
Angiogram 8
Angiogram 9
Angiogram 10
