Renal artery stenosis is the narrowing of one or both renal arteries that carry blood to the kidneys, which prevents normal amounts of oxygen-rich blood from reaching the kidneys. The kidneys need adequate blood flow to help filter waste products and remove excess fluids. Reduced blood flow may increase blood pressure and injure kidney tissue.
It is most often caused by atherosclerosis or fibro-muscular dysplasia.
In general, renal artery stenosis is asymptomatic and it is not associated with any obvious or specific symptoms. Suspicious signs for renal artery stenosis include:
- high blood pressure that is extremely hard to control and responds poorly to treatment;
- severe high blood pressure that develops prior to age 30 or greater than age 50 that was previously well-controlled;
- an incidental finding of one small kidney compared to a normal sized one on the other side;
- deterioration in kidney function, which may develop if both kidneys do not receive adequate blood flow, or when treatment with an ACE inhibitor is initiated.
Typically, unilateral renal artery stenosis may be related to high blood pressure whereas bilateral renal artery stenosis is more often related to diminished kidney function.
Atherosclerosis is the predominant cause of renal artery stenosis in the majority of patients, usually those with a sudden onset of hypertension at age 50 or older. Atherosclerosis is a process in which plaque made up of fats, cholesterol and other materials builds up on the walls of the blood vessels, including those leading to the kidneys.
More rarely, renal artery stenosis can be caused by a condition called fibromuscular dyplasia, in which the cells in the walls of the arteries undergo abnormal growth. More commonly seen in women and younger people, fibromuscular dyplasia is potentially curable.
Renal artery stenosis is often found by accident in patients who are undergoing tests for another reason. Risk factors include:
- Older age;
- Being female;
- Having hypertension;
- Having other vascular disease;
- Having chronic kidney disease;
- Having high cholesterol level;
- Having diabetes;
- Using tobacco;
- Having an abnormal cholesterol level