May be caused by a diverse array of clinical conditions, each with different pathophysiology, treatment approach and prognosis
The two most common forms of RAS are fibromuscular dysplasia (FMD) and atherosclerotic renal vascular disease (ARVD). Traditionally it has been common practice to broadly classify renovascular syndromes into 2 broad categories: renovascular hypertension and ischaemic nephropathy. However, such terminology may be misleading as it automatically implies a causal relationship between RAS and either hypertension or renal dysfunction. A causal relationship would imply that revascularisation of RAS would have a favourable effect on blood pressure and renal function. To date however, clinical data have failed to consistently demonstrate such a benefit (reviewed(49) (50)).
FMD is an uncommon disease with an unknown aetiology. It typically occurs in young women (<30 years of age) and may affect the renal, carotid and femoral arteries. FMD should be considered in young patients with severe hypertension in the absence of obesity, oral contraceptive use or known structural renal parenchymal disease. Unilateral or bilateral FMD may cause hypertension of renovascular origin but is rarely associated with renal failure (51). ARVD is a common clinical syndrome, affecting 7% of patients aged more than 65 years and 60% of patients with hypertension, coronary or peripheral artery disease and impaired renal function (52). ARVD rarely causes renovascular hypertension but is commonly associated with impaired renal function (53).
There are currently no established guidelines for routine screening for RAS. In some cases, the diagnosis is made as an incidental finding following angiographic assessment of lower extremity arterial disease; in other cases a high index of clinical suspicion is required and this should not be part of the routine evaluation of angina, congestive heart failure, coronary artery disease or peripheral arterial disease. Furthermore, ad hoc ‘drive by’ renal angiography during unrelated angiographic procedures is not recommended (49).
Balloon angioplasty is the intervention of choice in patients with FMD with stenting used for ‘”bail out “ indications. Procedural success is close to 100% with restenosis occurring in less than 10% within 10 years (54;55), although better outcomes are seen in short discrete lesions in major renal arteries and worse in diffuse disease in small segmental vessels. Renal arteriography is not reliable for assessment of FMD stenosis and therefore it is recommended that functional assessment with pressure wire and/or intravascular ultrasound occurs (79). Non-obstructive FMD should be managed conservatively. Stenting is recommended in patients with ARVD in order to reduce elastic recoil, minimise dissection and maximally enlarge the vessel lumen. Procedural success rates of 95 to 100% are reported in the literature with residual stenosis of less than 10%, restenosis rates of 10 to 15% within 1 year and major complications inferior to 2% (56).