Chapter 38: Renal Artery Stenosis

GENERAL CONSIDERATION AND HISTORY

History

Renal artery stenosis (RAS) is a relatively common problem that manifests in several ways, including renovascular hypertension, ischemic nephropathy and as an incidental finding during abdominal imaging for other disorders (Figure 38-1). Renovascular hypertension due to RAS, a narrowing of one or both renal arteries, is a leading cause of secondary hypertension in adults. While less than 1% of adults with mild hypertension are affected, these numbers climb dramatically in those with severe hypertension, with up to 40% of individuals affected.¹ The prevalence is increased in people with atherosclerosis, including those with coronary artery disease (CAD) and peripheral arterial disease (PAD).

Causes

The overwhelming majority of RAS cases are attributable to atherosclerotic disease (90%), followed by fibromuscular dysplasia (FMD; 8%–10%). Less frequent causes include congenital stenosis, Takayasu’s arteritis, Kawasaki disease, neurofibromatosis and inherited disorders including William’s Syndrome make up the remaining small percentage of cases (1%–2%).

Atherosclerotic RAS (ARAS)

Atherosclerotic RAS (ARAS) is generally a condition of the elderly, with an average age of approximately 70 years at the time of diagnosis. It most commonly affects the ostium, or aortic orifice, and proximal one-third (approximately 1–2 cm) of the renal artery. For many of these patients, the stenosis can be attributed to aortic plaque protruding into the orifice of the renal artery. As with other diseases of the abdominal aorta, the prevalence of RAS increases with traditional cardiovascular risk factors such as pre-existing hypertension, CAD, PAD, hyperlipidemia, diabetes mellitus (DM), hypercholesterolemia, tobacco use, and advanced age. Interestingly, ARAS appears to affect women and men equally, which is in clear distinction from some other atherosclerotic conditions such as CAD which tends to affect men more frequently and at a younger age. Smoking appears to have a marked effect on ARAS, occurring nearly a decade earlier than in non-smokers and resulting in a higher rate of adverse events.²

In the era before effective treatment of atherosclerosis, ARAS was considered a progressive disease, with 31% progression at 3 years and 51% progression at 5 years in a study of 295 kidneys followed by serial duplex ultrasonography.³ Despite the lack of effective treatment at the time of that study, of those arteries with ≥60% stenosis, less than 15% progressed to complete occlusion at 5 years. In a more contemporary study, a elderly hypertensives demonstrated a significant change of renovascular disease (RVD) in only 14.0% of kidneys on follow-up of 8 years (annualized rate, 1.3% per year), progression to significant RVD was observed in only 4% (annualized rate, 0.5% per year), and no prevalent RVD progressed to occlusion.⁴

Many ...