The answer to the Image Quiz, May, 2012 is fibromuscular disease (FMD).
The Question
What does this renal angiogram show?
Explanation
FMD is an angiopathy that affects
medium-sized arteries predominantly in young women of childbearing age. FMD
most commonly affects the renal arteries and can cause refractory renovascular
hypertension. Of patients with identified FMD, renal involvement occurs in
60-75%, cerebrovascular involvement occurs in 25-30%, visceral involvement
occurs in 9%, and arteries of the limbs are affected in about 5%.
FMD was first observed in 1938 by Leadbetter and Burkland in
a 5-year-old boy, and described as a disease of the renal arteries.
Fibromuscular dysplasia can be divided into several types
according to arterial anatomy and spread of the disease. Fibromuscular
dysplasia can originate from all layers of the artery (i.e. intima, media or
adventitia).
The most common type of fibromuscular dysplasia is medial
fibroplasia.
The imaging appearance of fibromuscular dysplasia depends on
the type of pathologic lesion present. It can be a classic “string of beads” if
medial fibroplasia is the type or a local stenosis or band in other types.
The diagnosis of fibromuscular dysplasia is done with
imaging studies of blood vessels:
- Duplex ultrasound – duplex ultrasound that demonstrates elevated flow velocities (i.e. renal artery stenosis) in the mid – distal portions of the artery suggests FMD. Sometimes a ‘string of beads’ can be seen.
- CT angiography (CTA) is increasingly being used to scan for renal artery stenosis. Not well validated, although better imaging techniques and reconstruction programs offer very good views of the renal arteries:
- Magnetic resonance angiography (MRA) – MRA lacks the needed resolution for detection of small details, even with use of gadolinium.
- Angiography – Angiography is the “gold standard” for detection of fibromuscular dysplasia. Classical "string of beads" appearance (see above). Angiography can detect lesions as small as 200-300 micrometers. Angiography has the advantage of assessing lesions with IVUS and pressure measurements.
