·         Demographics

o       Incidence

§         0.6% via angiography

§         1.1% via autopsy

o       Female to male ratio 3:1

o       Presenting age 25-50

·         Pathology

o       Developmental lesion of unknown etiology which can affect multiple vessels.

o       Consists of areas of heaped-up intima, adventia, and media alternating with areas of medial destruction resulting in small focal aneurysms.

o       3 histologic types

§         Intimal fibroplasia

§         Medial fibroplasia, and

§         Subadventitial (perimedial) fibroplasia of the arterial wall 

§         3 subtypes not always apparent on imaging.  Classic “string of beads” appearance on angiography for medial fibroplasias

o       Some authors describe 5 total subtypes.  Medial fibroplasias divided into medial fibroplasia with aneurysm and medial fibromuscular dysplasia.  Perimedial fibroplasias subdivided into subadventitial and adventitial fibroplasias

o       Medial fibroplasias most common

·         Symptoms

o       Renovascular hypertension (if bilateral renal arteries involved).

o       Transient ischemic attack

o       Intracranial aneurysm/thromboembolic stroke

o       Often asymptomatic

·         Location

o       Renal arteries 85%

§         Only 40% have bilateral renal artery involvement

o       Most often middle and distal 1/3 of renal arteries involved

o       Less commonly affected: Internal carotid (often bilateral), vertebral, mesenteric, celiac, hepatic, iliac arteries

o       If fibromuscular dysplasia (FMD) is found at any location, one must evaluate carotid arteries for lesions

·         Diagnosis

o       Angiography considered gold standard.  CTA and MRA becoming more sensitive.

o       FMD is characterized by

§         Narrowing of the affected vessel with a “string of beads” or nodular appearance, due to focal annular repetitive intimal and medial proliferative changes

 

 CT of the abdomen with IV contrast demonstrates nodularity (string-of-beads sign) of the
right renal artery (arrows) characteristic of fibromuscular dysplasia (hyperplasia)

Click here for the same photo without arrows

 

 

·         Differential

o       Really a classic appearance

o       Only entity on differential is atherosclerosis

·         Treatment

o       If symptomatic (intractable hypertension), improvement to renal blood flow can be me made via surgery or angioplasty

o       Angioplasty is less invasive and cure rate is approximately 50% and improvement in 30% of patients 

o       Angioplasty suitable for noncalcified short segments

o       Surgery reported to have lower re-stenosis rate and greater improvement in GFR