What Is Renovascular Hypertension?

Renovascular hypertension accounts for 1% to 5% of people with hypertension. Mainly due to the reduction of renal blood flow caused by renal artery stenosis, the renin-angiotensin system can be activated, leading to increased blood pressure and cardiac insufficiency; progressive stenosis of the lumen may cause renal ischemia and cause progressive renal parenchymal damage And changes in kidney structure and function, such as decreased kidney function, leading to renal failure. The asymptomatic population has an incidence of 7%. The prevalence of angiography for other atherosclerosis patients is between 28% (in patients with coronary angiography) and 50% (in patients with peripheral angiography). The most common cause of patient death is a cardiac event. The survival rate of patients also decreased significantly with the progress of atherosclerosis. According to data, for patients with diagnostic arterial catheters who found renal artery stenosis 50%, the 4-year follow-up survival rate was 65% compared with other patients. 86% (P & lt; 0.001).

Basic Information

English name

renal hypertension

Visiting department

Internal medicine

Common causes

Atherosclerosis, fibromuscular dysplasia, Takayasu arteritis, etc.

Common symptoms

Hypertension, renal failure, angina pectoris, recurrent pulmonary edema, proteinuria, etc.

Causes of Renovascular Hypertension

There are three common causes of renal artery stenosis: Atherosclerosis accounts for about 90%. With the improvement of living standards and the popularity of imaging examinations, this proportion is still increasing. It is common in elderly men. The lesions are mostly located at the beginning of the renal artery. Atherosclerotic plaques of different sizes and lengths are formed in the intima of the artery. Fibromuscular dysplasia, in addition to damaging the renal arteries, iliac arteries, mesenteric arteries, and head and arm arteries also occur. They are common in young people, and more women than men. Arterial damage mainly occurs at the middle and distal 1/3 ends, often extending to the branches, and the blood vessels show multiple and bead-like changes. Takayasu arteritis, the disease mainly invades the aorta and its large branches, causing narrowing or occlusion of blood vessels, and rare expansion. Mostly young women, nearly 90% of cases are under 30 years old. Takayasu arteritis invades the renal arteries, accounting for more than 60%. 87% of the lesions invade the renal arteries and the proximal end. Most of the renal arteries are concentric and narrow.

Renovascular hypertension pathophysiology

In RAS, the ipsilateral kidney activates the renin-angiotensin-aldosterone system due to ischemia and causes renal vascular hypertension. The pathophysiology of different types of renal vascular hypertension is also different. In unilateral RAS, the ipsilateral kidney releases renin and causes sodium and sodium retention, while the contralateral kidney develops pressure diuretic sodium excretion, which eventually leads to a negative sodium balance that further increases renin release. In the isolated kidney and bilateral RAS, because there is no effect on the contralateral kidney, the loss of sodium is prevented, and the increase in extracellular fluid volume inhibits the activity of renin. Therefore, hypertension is mainly due to excess fluid. In addition, angiotensin (Ang ) triggers the contraction of the arterioles to partially maintain renal blood flow and filtration rate. Therefore, for patients with decompensated chronic heart failure with bilateral RAS, isolated RAS or sodium failure, Application of angiotensin-converting enzyme inhibitors (ACEI) or Ang receptor blockers (ARB) can cause acute renal failure. The mechanism is that they reduce the hydrostatic pressure of the glomeruli and the filtration rate of the glomeruli. However, the formation of disease is a long process. The study of animal models cannot fully reflect the true pathological process. Even in animal experiments, it has been found that when the stenosis persists, the increase in renin release is transient, so the renal artery There must be other mechanisms involved in the process of stenosis leading to hypertension, which needs further research to be clear.

Clinical manifestations of renal vascular hypertension

Renal artery stenosis is occult and progressive in the early stages of onset. It has only hemodynamic changes and no clinical symptoms for a long time. However, as the stenosis progresses, hypertension, renal failure, angina pectoris, and recurrent attacks may occur. Pulmonary edema, proteinuria, etc. Focusing on clinical clues is key to early detection.

1. High blood pressure found before the age of 30 or after the age of 55, especially in patients without a family history;

2. Abdominal and waist audible murmurs can be heard;

3. Sudden deterioration of refractory hypertension, malignant hypertension or previously stable hypertension;

4. Recurrent hypertension;

5. Unexplained renal failure, while urine routine is normal, especially in the elderly;

6. Concomitant peripheral vascular disease, especially in heavy smoking;

7. Deterioration of renal function during hypertension treatment, especially when using ACEI or ARB;

8.3 to 4 grade hypertensive retinopathy;

9. Renal atrophy on one side or the difference in the length and diameter of bilateral kidneys by 1.5-2.0 cm;

10. Recurrent chronic heart failure or transient pulmonary edema, especially in patients with hypertension but normal left ventricular ejection fraction. Previous studies have shown that about 16% of patients with coronary heart disease are associated with RAS, and the incidence of RAS is higher in older age, long-term smoking, abnormal serum creatinine, multivessel disease, refractory hypertension, and diabetes.

Renal vascular hypertension

There are many ways to detect renal artery stenosis, but the detection method must consider its sensitivity, specificity, and predictive value. At present, the methods that are fully affirmed are:

Color Doppler ultrasound

Color Doppler ultrasound, as a simple and inexpensive screening method for renal artery stenosis, is one of the most widely used non-invasive examination methods. Color Doppler ultrasound may have a specificity of 9% and a sensitivity of 95%, but the accuracy of this technique depends heavily on the patient's patience and experience. It is difficult to check patients with obesity and excessive abdominal gas. It is recommended for re-examination of renal artery stent, and care should be taken as a means of screening and confirming renal artery stenosis outside of centers with extensive examination experience.

2. Magnetic Resonance Angiography

Magnetic resonance imaging (MRA) using three-dimensional contrast imaging can better display the anatomical structure of renal arteries, with a sensitivity of 80% to 100% and a specificity of 9% to 99%. Phase contrast (PC) and Time of Leap (TOF). Magnetic resonance angiography has a better diagnosis of proximal renal artery damage, and it is often easy to miss diagnosis of distal or accessory renal artery. Magnetic resonance angiography can be used without or with a small amount of special contrast agents, and the kidney damage can be used for the diagnosis of patients with renal insufficiency.

3. Spiral Computed Tomography

Spiral computed tomography (CTA) is a reliable means of examination, showing good results on the renal arteries and accessory renal arteries. Its sensitivity and specificity are 88% to 96% and 96% to 100%, respectively. The localization and quantification of abdominal aorta and renal arterial calcification exceed any one of the examination methods (including renal arteriography). Disadvantages: The contrast dose required for CTA is large, 130-150ml, and the injection time is required to be 20-30s during scanning. Moreover, patients with renal artery stenosis often have the potential for renal failure, leading to the risk of contrast nephropathy. The nephrotoxicity of the intravenous contrast agent is significantly less than that of the arterial route. Combined with hydration to reduce the risk, it can be widely used.

4. Renal artery angiography

Currently considered the gold standard for diagnosis of RAS. Indications for angiography: Clinically, there are renal vascular hypertension, ischemic nephropathy, and unstable angina pectoris. One of the three is present plus any of the following conditions:

(1) Non-invasive examination showed that one renal artery stenosis was> 50%, or there was obvious hemodynamic change.

(2) High blood pressure is found before the age of 30 or after the age of 50.

(3) Renal shrinkage and impaired renal function, especially in patients using ACEI preparations.

The test is invasive, expensive, and has limited clinical application. In recent years, in order to avoid the possible renal toxicity caused by contrast agents, the use of CO ₂ as a contrast agent in the diagnosis of renal artery stenosis and balloon dilation in patients with renal insufficiency (including transplanted kidneys) is considered feasible and effective.

5. Renal dynamic imaging

Tc-DTPA renal dynamic imaging can provide RAS indirect information more safely and sensitively, with a sensitivity of 71% to 92% and a specificity of 72% to 98.2%. The diagnostic sensitivity and specificity for renal artery stenosis exceeding 50% can reach more than 80%. The advantage is that it is non-invasive, can evaluate renal function and divide renal function, and can predict the efficacy of angioplasty and the risk of applying ACEI. The disadvantage is that it can not show the location and degree of stenosis, and it is affected by the level of renal function.

Renal vascular hypertension treatment

Drug treatment

The main purpose is to control hypertension and prevent deterioration of renal function.

(1) Calcium channel blocker (CCB) is a safe and effective drug for the treatment of renal vascular hypertension. Its antihypertensive effect is to dilate blood vessels. It does not cause renal function deterioration in patients with bilateral ARS. Drug of choice for blood pressure.

(2) ACEI and ARB for renin-dependent hypertension caused by unilateral RAS can effectively control hypertension and prevent complications when other drugs are ineffective, but these drugs can reduce renal blood flow in the narrow side, Therefore, renal function should be monitored for changes. For volume-dependent hypertension caused by bilateral renal artery stenosis or isolated renal artery stenosis, ACEI or ARB is absolutely contraindicated.

(3) -blockers Because they are effective in reducing blood pressure in renal vascular hypertension, they are mostly used in combination therapy.

(4) The main cause of hypertension caused by diuretics in unilateral RAS is high renin, not increased volume. At this time, the use of diuretics often reduces plasma volume, increases plasma renin activity, and increases sympathetic nerve activity. Do not lower blood pressure, but increase hypertension, so simple unilateral renal artery stenosis caused by hypertension should not theoretically use diuretics. In bilateral RAS, hypertension is characterized by water and sodium retention and volume expansion, and diuretics can lower blood pressure.

2. Percutaneous transluminal renal artery angioplasty (PTRA) with balloon catheter

In 1978, Grntzig et al. First reported that the use of a balloon catheter for percutaneous nephronoplasty for the treatment of hypertension caused by renal artery stenosis was successful. Since then, interventional therapy has been widely used in the treatment of RAS. This technique is currently the preferred treatment for renal artery stenosis caused by fibromuscular dysplasia.

3. Intravascular Stenting

It can be applied to atherosclerotic open lesions or to the remedy of PTRA failure. The indications for interventional therapy for atherosclerotic renal artery stenosis are controversial. In principle, for severe stenosis with hemodynamic significance, revascularization is the preferred treatment method, and for mild to moderate renal artery stenosis with easy control of blood pressure and stable renal function, drug treatment and close follow-up are preferred. Due to various flaws in the existing randomized controlled large-scale clinical trials, the results cannot be widely accepted, and the effectiveness of the conclusions cannot promote the revision of the guidelines. The method of selecting the indications for intervention is still being researched, and there are different conclusions on the values of the plasma renin-aldosterone ratio, BNP, and intraoperative pressure guidewire detection methods, which cannot be used to guide clinical treatment.

4. Purpose of Surgery

It is to lower blood pressure and improve renal function. Surgery includes endarterectomy, bypass of blood vessels and liver, kidney or spleen, and autograft. Due to the good clinical results of angioplasty and stent surgery, surgical vascular reconstruction is much less than in the past. Surgical vascular reconstruction in patients with atherosclerosis is more effective than PTRA, and the rate of cure or improvement of hypertension is higher. Aortic bypass is the most common method, and liver and kidney and spleen-renal artery bypass surgery are also commonly used, and aortic surgery can be avoided. Current indications suitable for surgical vascular reconstruction include: normal renal parenchymal occlusion of the renal parenchyma, RAS muscle fiber dysplasia with arteritis that cannot be treated by balloon angioplasty, restenosis after stenting, or simultaneous aorta Surgical treatment (abdominal aortic aneurysm repair or abdominal aorta-iliac artery disease).