Major advancements in vascular imaging techniques have facilitated the diagnosis of renovascular disease, and modern medical therapies as well as surgical and percutaneous interventional techniques offer the clinician a wide array of therapeutic tools in the management of renovascular disease. Despite these developments however, the indications for medical therapy versus surgical or percutaneous revascularization are controversial, and the clinician's ability to predict the effect of revascularization on clinical outcomes remains limited.
Vascular lesions affecting the renal artery can be caused by atherosclerosis, fibromuscular dysplasia (FMD), aneurysms, congenital or traumatic arteriovenous fistula (AVF), extrinsic compression, trauma, and embolization. The overwhelming majority of arterial artery lesions, however, are secondary to either atherosclerosis or FMD, which will be discussed below. A separate section will be dedicated to renal artery aneurysms, arteriovenous malformations (AVMs), and spontaneous renal artery dissections.
PREVALENCE AND NATURAL HISTORY
Often clinically silent and discovered incidentally, FMD accounts for less than 10% of cases of renal artery stenosis (RAS), and although it can affect the intima, in the majority of cases it involves the media, resulting in the typical "string of beads" appearance (Figure 32-1).1 The cause remains largely unknown; however it may have a genetic component and it is more frequent in hypertensive patients and smokers.2 FMD usually affects women between 15 and 50 years of age, but it can be also observed in males and older patients as well.1 It occurs most frequently in the renal artery, but can also involve the carotid and vertebral arteries, sometimes in association with intracranial aneurysms, as well as other visceral vessels.1,3,4
Fibromuscular dysplasia with "string of beads" appearance involving the mid and distal portions of the renal artery. Differently from atherosclerotic renovascular disease, FMD typically spares the ostium of the renal artery.
Reprinted with permission from Slovut DP, Olin JW. Fibromuscular dysplasia. N Engl J Med. 2004;350(18):1862–1871.
In a series of angiogram of potential renal donors, incidental renal FMD was found in 3.8% patients, 75% of whom were females; in another study of patients with resistant hypertension screened with angiography, 16% had FMD.5,6 Because it is a disease of young patients with few cardiovascular risk factors, FMD is easily distinguishable from atherosclerotic RAS. FMD, unlike atherosclerotic RAS, tends to affect the mid and distal portion of the renal artery, and not the ostium. Its appearance can sometimes resemble vasculitis, but FMD is not an inflammatory process and it lacks the systemic manifestations and abnormal markers typical of vasculitis.
The severity of stenosis can be difficult to accurately measure with both noninvasive testing as well as with catheter-based angiography, but progression of disease has been documented in up to 37% of patients....