Renal Artery Stenosis

The blood flow into the kidney is carried from the aorta to the renal artery. As atherosclerotic plaque builds up in the aorta it will extend into the renal artery and slowly decrease the diameter of the artery at its origin. As this process progresses, affected patients will suffer from very difficult to manage hypertension. As a cause of “secondary hypertension” renal artery stenosis is near the top of the list in patients with a history of confirmed vascular disease.

Renal artery atherosclerosis is very common in patients with coronary artery disease. In fact 20 percent of patients with a history of multivessel coronary disease will have an asymptomatic renal artery narrowing. In young women with uncontrolled and aggressive hypertension, fibromuscular dysplasia (FMD) is a common cause of renal artery narrowing. In FMD, muscular bands form in the arteries of the kidney, causing severe blood pressure elevation, and can also be present in the leg and carotid arteries causing leg pain and possibly even stroke.

The kidney is a regulator of volume status and as the renal artery narrows the kidney sees less and less blood flow. This results in an increase in hormonal secretion in an attempt to raise the blood pressure and flow to the kidney. The result for the patient can be an admission to the hospital with the "cardiorenal syndrome." In the cardiorenal syndrome, patients have severely elevated blood pressure, heart failure, mild to moderate kidney failure and often a mild heart attack. The most common patient with renal artery stenosis has a history of severe hypertension on more than three full dose medications for blood pressure and mild renal dysfunction. A clue to the presence of renal artery stenosis in both kidneys is a dramatic worsening of renal function after starting an angiotensin converting enzyme (ACE) inhibitor. Screening for renal artery stenosis includes ultrasound examination, magnetic resonance imaging (MRI), CT angiography or conventional contrast angiography.

The management of renal artery stenosis is controversial. Many physicians advocate medical therapy only. There is little role for surgical revascularization, as a bypass of the renal artery is a very high risk procedure. In FMD, balloon angioplasty alone is highly effective at improving blood pressure control. The accepted clinical indications for renal angioplasty and stent placement in atherosclerotic renal artery stenosis include recurrent heart failure due to severe hypertension (known as flash pulmonary edema) and severe worsening of blood pressure control in a previously well-controlled patient. A fair amount of debate exists about weather to intervene on a patient with renal artery stenosis and severe renal dysfunction. In many cases, renal function may actually worsen after treatment with a stent due to embolization of debris into the smaller arterial branches. Patients with renal artery stenosis have peripheral arterial disease (PAD). This disorder caries with it a high risk of future cardiovascular events, stroke and even death. All patients with PAD are presumed to have coronary artery disease and standard treatment includes aggressive blood pressure control, anti-platelet treatment with aspirin or Plavix, lipid lowering treatment with a statin and smoking cessation.