What Is Renal Artery Stenosis?

Renal artery stenosis is a renal vascular disease caused by a variety of etiologies. The clinical manifestations are renal vascular hypertension and ischemic renal disease. As long as the renal artery stenosis or obstruction is removed in time, and the diseased blood vessels are reopened, hypertension can be cured and renal function can be reversed.

Basic Information

English name

stenosis of renal artery

Visiting department

Vascular surgery

Common causes

Atherosclerosis and fibromuscular hypoplasia

Common symptoms

Renal hypertension, nocturia, urine specific gravity and decreased osmotic pressure, etc.

Causes of renal artery stenosis

Renal arterial stenosis is often caused by atherosclerosis and fibromuscular dysplasia. In Asia, this disease can also be caused by arteritis. Atherosclerosis is the most common cause, accounting for about 80% of patients with renal artery stenosis, and is mainly found in the elderly, while the latter two causes are mainly found in young people, mostly women.

Renal artery stenosis often causes renal vascular hypertension, which is caused by renal ischemia stimulating renin secretion, activation of the renin-angiotensin-aldosterone system (RAAS) in the body, peripheral blood vessel contraction, and water and sodium retention. Renal artery stenosis caused by atherosclerosis and takayasu arteritis can also cause ischemic kidney disease. Ischemia on the affected side leads to glomerulosclerosis, tubular atrophy, and renal interstitial fibrosis.

Clinical manifestations of renal artery stenosis

Renal hypertension

The clinical manifestations are similar to those of essential hypertension, but the history has the following characteristics: more than 35 years of age and 55 years of age, and more common in young people; short history, rapid development of the condition; long-term original Hypertension, which suddenly worsens; Abdominal or lumbar pain or a sharp rise in blood pressure after injury (indicating renal artery embolism or renal artery dissection aneurysm); Most have no family history of hypertension; General antihypertensive drugs are not satisfactory.

2. Ischemic kidney disease

May or may not be associated with renal vascular hypertension. Renal lesions are mainly manifested by slow and progressive decline of renal function. Because renal tubules are sensitive to ischemia, their hypofunction is often preceded (disturbed renal tubules with concentrated dysfunction such as nocturia, urine specific gravity and decreased osmotic pressure), Then glomerular function is impaired (the patient's glomerular filtration rate decreases, and serum creatinine increases). Urine changes are usually slight (mild proteinuria, often <1g / d, small amounts of red blood cells and casts. In the later stage, the kidneys shrink and the sizes of the two kidneys are often asymmetrical (reflecting the degree of renal artery disease on both sides).

In addition, vascular murmurs (high-profile, rough systolic, or biphasic murmurs) may be heard in the abdomen or waist of some patients with renal artery stenosis.

Renal artery stenosis

Screening check

If the screening test is positive or negative but clinically highly suspect, percutaneous renal angiography can be performed. Renal arteriography is the most valuable for the diagnosis of renal artery stenosis. It is a "golden indicator" for the diagnosis of renal vascular disease. It can reflect the location, extent, degree, lesion nature, distal branch and collateral circulation of renal artery stenosis, and can be observed. Changes in kidney morphology and function and judgment of vasodilation or surgical indications.

The incidence of this disease is relatively low, so clinical screening for renal stenosis in all patients with hypertension is generally not recommended. However, no single non-invasive test is sensitive enough to rule out all renal artery stenosis. Therefore, it is often the case that doctors encounter patients with hypertension who have difficulty in determining whether they are renal vascular hypertension.

2. Laboratory inspection

Some patients may have abnormal laboratory tests such as hyperlipidemia and hyperglycemia.

3. Doppler ultrasound technology

The combination of abdominal B ultrasound examination of renal arteries and Doppler measurement of renal blood flow is currently the most commonly used screening method for the diagnosis of renal arterial stenosis. Statistics show that the positive and negative predictive values of this technique in the diagnosis of renal artery stenosis are above 90%. Of course, the operator's experience is very important for accurate diagnosis. During the examination, the development of the renal artery is often affected by gastrointestinal gas, obesity, recent surgery and other nearby renal blood vessels. Sometimes abdominal B ultrasound can also be used as a screening test to understand whether the kidneys have atrophy or morphological changes.

4. Magnetic resonance imaging (MRI) and CT scans

In recent years, magnetic resonance imaging and tomography have also been used to diagnose renal artery stenosis. The specificity of MRI diagnosis can reach 92% to 97%, and recent reports show that CT scan is the most sensitive imaging examination for the diagnosis of renal artery stenosis, with sensitivity and specificity of 98% and 94%, respectively.

5. Radionuclide renal blood flow examination

It is used to detect the renal sub-renal function, assess the damage of renal function, provide a basis for the treatment of renal artery stenosis, and is an important indicator for postoperative follow-up.

6. Captopril-renin challenge test

Under normal circumstances, after taking the conversion enzyme inhibitor captopril, the body's hyperrenin response can be enhanced by inhibiting the negative feedback effect of angiotensin II. This response is particularly prominent in patients with renal arterial stenosis. Plasma renin increased significantly more than essential hypertension after 1 hour of oral captopril. The sensitivity and specificity of the test can reach 93% to 100% and 80% to 95%, respectively.

7. Captopril-Radionuclide

Renal artery stenosis stimulates the activity of the renin-angiotensin system, and through the angiotensin contraction effect on the arterioles, it helps to maintain the glomerular pressure and glomerular filtration rate. Invertase inhibitors (such as captopril) inhibit the production of angiotensin II, which can reduce the glomerular pressure and glomerular filtration rate. Before and after taking captopril, using radionuclide technology can more ideally detect ischemia of unilateral kidneys, and its sensitivity and specificity can reach more than 90%.

Renal artery stenosis treatment

For renal vascular hypertension and ischemic kidney disease caused by renal artery stenosis, the following three treatments currently exist:

Angioplasty

Percutaneous transluminal renal angioplasty (PTRA, balloon dilatation of renal arteries) is often performed. This treatment is particularly suitable for patients with fibromuscular hypoplasia. Because atherosclerosis and Takayasu arteritis patients are prone to restenosis after dilatation and treatment failure, these patients should be placed with vascular stents after dilatation.

2. Surgery

Including endarterectomy, bypass bypass and autologous kidney transplantation, the diseased kidney can regain blood supply.

3. Medical drug treatment

Medication does not prevent the progress of renal artery stenosis, but it can help control hypertension and improve symptoms. For those with unilateral renal artery stenosis with high renin, ACEI or ARB is often preferred, but it must be started in small amounts and gradually increased to prevent blood pressure from falling too quickly or too low. Those with bilateral renal artery stenosis should not take these drugs. In order to effectively control blood pressure, a variety of antihypertensive drugs are often required for compatibility. There are many modern powerful antihypertensive drugs, and drug treatment often can effectively control renal vascular hypertension, and the long-term survival rate of patients is not different from PTRA, so many scholars believe that renal vascular hypertension should be the first choice medical treatement. As for renal artery stenosis that has caused ischemic kidney disease, in order to prevent the progress of stenosis and renal impairment, timely PTRA and placement of vascular stents are still preferred. If PTRA is contraindicated or PTRA and stent placement fail, surgical treatment may be considered.