Renal Artery Stenosis
Renal artery stenosis is a relatively unpleasant condition causing many complications by affecting the blood flow into the kidney and by disrupting the proper maintenance of blood pressure by the kidney tissue.
Each of the two kidneys is supplied by one renal artery that branches from the abdominal aorta. There are two possible mechanisms of renal artery stenosis. The most common cause is atherosclerosis, which usually affects the renal artery in its branching from the aorta. Typical patient is older obese man with high cholesterol and high blood pressure. Less common cause is so-called fibromuscular dysplasia, which affects the peripheral part of the artery (i.e. closer to the kidney) and this condition is typical for young women.
The stenosis may occur in one or both renal arteries. In unilateral affection, the blood flow through the affected kidney is decreased and the kidney tissue mistakenly believes that the blood pressure in the body is low and that this is the cause of low blood delivery. Kidney tissue is important for maintenance of blood pressure and in this case, it begins to produce hormones to increase blood pressure. High blood pressure slightly increases the blood flow through the narrowed renal artery, but damages the other previously healthy kidney. In addition, the high blood pressure causes many symptoms (fatigue, dizziness and headache), accelerates the process of atherosclerosis and does no well respond to antihypertensive therapy*. Over time, the condition may progress into chronic renal failure.
The scheme shows typical locations of renal artery stenosis. The atherosclerosis narrows the renal artery in place where it leaves the aorta, while fibromuscular dysplasia causes narrowing of its distal part.
The suspicion may grow in a patient with hypertension resistant to therapy and simultaneously present impaired kidney function. If we administer ACE-Inhibitors to such patient, we can await further decrease of kidney functions. When really cautiously listening with a stethoscope, it is theoretically possible to hear a murmur above the narrowed artery, which is caused by quick blood flow through the narrowed space. The stenosis can be in some patients examinable by abdominal ultrasound with Doppler, but this is not totally reliable examination. The best, but invasive procedure is the angiography of the aorta and kidney arteries, which shows the stenosis and helps us to evaluate its location and severity.
The situation can be treated by antihypertensives and hypolipidemics (usually statins), but for solving the stenosis, a more invasive procedure is needed. The best solution is therapeutic angiography, where the doctor can dilate the stenosis by a balloon (angioplasty) and support the artery with a tube-shaped stent to prevent its restenosis. When the narrowing is supposedly caused by fibromuscular dysplasia, the angioplasty is clearly the method of first choice.