renal artery stenosis

Renal artery stenosis: description

Renal artery stenosis is a disease in which a narrowing of the renal artery has formed. The renal arteries branch off from the abdominal aorta (abdominal aorta) at the level of the kidneys. Mostly the stenosis is close to the transition of the abdominal aorta. In general, the risk of renal artery stenosis increases with age – however, depending on the cause of the disease, it can occur at a younger age. The Gefäßgpass can occur on one or both sides. Since the kidneys are significantly involved in the regulation of blood pressure, resulting from the narrowed renal artery in many cases, too high a blood pressure.

The blood pressure regulation by the kidneys takes place via a specialized cell unit (Juxtaglomerularer apparatus), which measures on the one hand the salinity of the blood, on the other hand the blood volume. In renal artery stenosis, the narrowed artery reduces blood flow in the kidneys – they mistakenly register low blood pressure, although it may be normal or even elevated. This activates a cascade of reactions that physicians call the renin-angiotensin-aldosterone system (RAAS).

The specialized kidney cell of Juxtaglomerular apparatus first pour out the protein-splitting enzyme renin. Renin now cleaves angiotensinogen – a protein that is produced in the liver – to angiotensin I. Another enzyme (angiotensin converting enzyme) converts angiotensin I to angiotensin II in the last step. Finally, angiotensin II causes the blood vessels to contract, increasing blood pressure. In addition, angiotensin II stimulates the adrenals to release the hormone aldosterone, which also increases blood pressure.

The activation of this reaction chain by a renal artery stenosis also refer to physicians as gold leaf effect.

Renal artery stenosis: symptoms

The symptoms of renal artery stenosis are in many cases nonspecific, because of the constricted blood vessel sufferers feel nothing. Although hypertension is a typical consequence of vascular change, it often causes little discomfort. The following symptoms may indicate high blood pressure:

• dizziness
• Headache (especially in the morning)
• nervousness
• nausea
• blurred vision

Often, sudden onset of high blood pressure, so-called hypertensive crises, indicates renal artery stenosis. In some cases, as a result of such a blood pressure crisis, water also accumulates in the lungs (pulmonary edema). This reduces the physical capacity and the person suffering from respiratory distress.

Renal artery stenosis: causes and risk factors

Essentially, two types of renal artery stenosis are distinguished:

Arteriosclerotic renal artery sclerosis:

The most common cause of renal artery stenosis (NAST) is arteriosclerosis. Doctors also speak of arteriosclerotic renal artery stenosis, or ANAST for short. It is the cause of vascular change in 75 percent of cases and is more common in men than women. Deposits on the vessel wall (so-called plaques) cause the diameter of the blood vessel to narrow. As vascular deposits tend to increase with age, the risk of renal artery stenosis increases with age.

Fibromuscular renal artery stenosis:

About 25 percent of renal artery stenoses are due to this form. Mostly it affects younger women around the age of 30 years. In about 60 percent of those affected, the arteries of both kidneys are narrowed. The cause of fibromuscular renal artery stenosis is a congenital defect in the structure of the vessel wall.

In addition to these two most common forms, there are also some rare causes of renal artery stenosis. This includes, for example, an aneurysm – a morbid Gefäßaussackung. Also, inflammation of the arteries in specific diseases (e.g., Panarteritis nodosa or Takayasu’s arteritis) may result in narrowing of the renal arteries.

Renal artery stenosis: examinations and diagnosis

In most cases, too high a blood pressure indicates a possible renal artery stenosis. Often the family doctor determines in a routine examination by accident, that the blood pressure is noticeably increased.

The following instructions make the doctor think of a renal artery stenosis:

• High blood pressure in young women around the age of 30
• High blood pressure in men over the age of 50 years
• Hypertensive crises
• Sudden pulmonary edema
• Evidence of kidney weakness

If the doctor suspects a renal artery stenosis, he listens as part of the physical examination of the thorax and abdomen of his patient with the stethoscope. If one or both of the renal arteries are narrowed, a hissing flow noise is often heard near the flanks. Although blood pressure is difficult to restore to normal levels despite antihypertensive medication, there is a suspicion of renal artery stenosis.

If this suspicion hardens, the doctor initiates further examinations. Renal artery stenosis can be detected by the following imaging techniques:

• Duplex sonography: With this ultrasound method, the blood flow within the blood vessel can be made visible in color.
• MRI angiography (MRA): The patient receives a contrast agent during magnetic resonance imaging. This allows the relevant blood vessels represent. In addition, a three-dimensional image can be digitally calculated from the individual slice images of the MRI.
• CT Angiography (CTA): Computed tomography also produces tomographic images of the body which, in contrast to MRI, are not generated by a magnetic field but by X-rays. Similar to MRI angiography, a contrast medium makes the vessels visible, and the doctor also assesses a three-dimensional image here.
• Digital Subtraction Angiography (DSA): This technique allows a very accurate assessment of blood vessels. In the first step, a recording of the respective organ is made without contrast medium, which doctors call “mask”. The patient then receives the contrast agent. Now a series of recordings takes place. These are subtracted from the mask image and hide disturbing picture elements. Doctors will use the DSA only if the other imaging techniques do not provide a clear result and there is still a suspicion of renal artery stenosis.

Renal artery stenosis: treatment

Treatment for renal artery stenosis depends on the extent and associated symptoms. A treatment is indicated under the following conditions:

• The renal artery is at least 70 percent concentrated
• In high blood pressure, which is difficult to influence by drugs
• Sudden pulmonary edema occurs
• If there is kidney failure (renal insufficiency)
• In a fibromuscular renal artery stenosis

The aim of the treatment is to eliminate the bottleneck in the renal artery and thus to ensure normal kidney perfusion. The following methods are suitable for this:

• Percutaneous transluminal angioplasty (PTA): In this method, the doctors insert a narrow, flexible tube (catheter) into the relevant blood vessel. To remove the stenosis, dilate the vessel section with the aid of a small balloon (balloon dilatation) or insert a small metal mesh (stent) tube, which keeps the narrowed artery open.
• Vascular bypass: The surgeons bridge the vascular pit with an artificial or natural vascular prosthesis. Unlike PTA, this procedure requires open-abdominal surgery.

Renal artery stenosis: prevention

Smoking, obesity and diabetes mellitus are considered risk factors for vascular calcification. Although you can not always prevent renal artery stenosis, you can reduce the risk of vascular deposits by:

• do not smoke
• Pay attention to healthy body weight or reduce weight if you are overweight
• Treat and control diabetes if you are diabetic

Renal artery stenosis: disease course and prognosis

Left untreated, renal artery stenosis continues. This can cause numerous complications. In advanced disease can cause kidney weakness. Ultimately, the renal artery can completely occlude and a permanent kidney damage threatens. Also, the high blood pressure that often occurs in this context, can cause other diseases, especially of the heart and circulation.

In fibromuscular renal artery stenosis, blood pressure normalises after treatment in 75 percent of cases. Is an arteriosclerosis the cause of the renal artery stenosis, In some cases hypertension may persist despite therapy. In principle, there is also a certain risk that the blood vessel closes again after the treatment.