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Renovascular hypertension
Last reviewed: 23.11.2021
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Causes of the renovascular hypertension
The main causes of renovascular hypertension, leading to a narrowing of the lumen of the renal arteries, are arteriosclerosis of the main arteries of the kidneys and fibromuscular (fibromyscular) dysplasia. Among the rare causes of reninovascular arterial hypertension are thrombosis of the renal arteries or their branches (complication of diagnostic and therapeutic vascular interventions, abdominal trauma, atrial fibrillation), nonspecific aortic arteritis (Takayasu's disease), nodular polyangiitis, abdominal aortic aneurysm, tumor, parapelvic cyst of the kidney , tuberculosis of the kidneys, anomalies in their structure and location, leading to an inflection or compression of their main arteries.
Stenosis of the renal artery of an atherosclerotic genesis is most often met, approximately in 2/3 of all cases. The disease, as a rule, develops in elderly and senile people (although it may occur in younger people), more often in men. Risk factors - hyperlipidemia, diabetes, smoking, the presence of widespread atherosclerosis (especially the branches of the abdominal aorta - femoral, mesenteric arteries). However, atherosclerotic changes in the renal arteries may not correspond to the severity of atherosclerosis of other vessels, as well as the degree of increase in serum lipids. Usually, atherosclerotic plaques are localized in the mouth or in the proximal third of the renal arteries, more often the left ones, in about 1/2 to 1/3 of the cases, the lesion is bilateral. Progression of atherosclerosis with the formation of bilateral hemodynamically significant stenosis, the development of cholesterol embolism lead to impaired renal function and their damage within the framework of ischemic kidney disease (details of atherosclerotic lesions of the renal arteries and kidneys, the principles of diagnosis and treatment are described in the article "Ischemic kidney disease").
Fibromuscular dysplasia of the renal arteries is the cause of reninvascular arterial hypertension in about 1/3 of patients. It is a noninflammatory lesion of the vascular wall characterized by the transformation of the smooth muscle cells of the medial into fibroblasts with the simultaneous accumulation of bundles of elastic fibers at the border with the adventitia, leading to the formation of stenoses alternating with the areas of aneurysmal expansions, resulting in the artery becoming rosary. Fibromuscular dysplasia of the renal arteries is observed predominantly in females. Stenosis of the renal artery, due to fibromuscular dysplasia, is the cause of severe arterial hypertension in young or children.
Recent angioprophy studies of kidney donors and healthy individuals using UZDG have shown that the incidence of such stenosis in the general population is significantly higher than previously thought - about 7%, but in most cases there are no clinical manifestations and complications. Fibromuscular dysplasia of the renal arteries can be combined with the defeat of other arteries of the elastic type (carotid, cerebral). Studies of direct relatives of persons suffering from fibromuscular dysplasia of the renal arteries show the presence of a family predisposition to this disease. Among the possible hereditary factors, the role of the mutation of the a1-antitrypsin gene, accompanied by a deficit in its products, is discussed. Changes occur in the middle or, more often, the distal part of the renal artery; segmental arteries may be involved. Pathology develops more often on the right, in a quarter of cases the process is bilateral.
The main link in the pathogenesis of reninvascular hypertension is the activation of the renin-angiotensin-aldosterone system in response to reduced blood supply to the kidney on the affected side. For the first time Goldblatt in 1934 proved this mechanism under experimental conditions, and then he was repeatedly confirmed by clinical studies. As a result of stenosis of the renal artery, the pressure in her distal to the narrowing site decreases, the kidney perfusion worsens, which stimulates renal renin secretion and the formation of angiotensin II, which leads to an increase in systemic blood pressure. Deceleration of renin secretion in response to an increase in systemic arterial pressure (feedback mechanism) does not occur due to narrowing of the renal artery, which leads to a persistent increase in renin level in the ischemic kidney and the preservation of high blood pressure values.
In unilateral stenosis, in response to an increase in systemic arterial pressure, the uncontrolled contralateral kidney intensively removes sodium. At the same time in the contralateral kidney, the mechanisms of self-regulation of renal blood flow are disrupted, aimed at preventing its damage in systemic arterial hypertension. At this stage, drugs that block the renin-angiotensin system cause a marked decrease in blood pressure.
In the late phase of renovascular hypertension, when the expressed sclerosis of the contralateral kidney develops as a result of its hypertonic damage and it can no longer excrete excess sodium and water, the mechanism of the development of arterial hypertension becomes no longer renin-dependent but sodium-volatile. The effect of blockade of the renin-angiotensin system will be negligible. With time, the ischemic kidney is sclerosed, its function irreversibly decreases. The contralateral kidney is also gradually sclerosed and decreases in size due to hypertonic damage, which is accompanied by the development of chronic renal failure. However, the speed of her profession is much less with one-sided than with bilateral stenosis.
Symptoms of the renovascular hypertension
In fibromuscular dysplasia, the increase in blood pressure is detected at young or in childhood. Atherosclerotic stenosis of the renal arteries is characterized by de novo development or a sharp aggravation of previous arterial hypertension in elderly or senile age. Renovascular arterial hypertension, as a rule, has a severe, malignant course with severe left ventricular hypertrophy and retinopathy, it is often refractory to multicomponent antihypertensive therapy. In elderly patients with bilateral stenosis of the renal arteries, the symptoms of renovascular arterial hypertension are recurrent episodes of pulmonary edema due to cardiac decompensation on the background of severe volume-dependent hypertension.
Changes from the kidneys are more often detected in atherosclerotic lesions. Attention is drawn to the early and progressive decrease in the filtration function, with deviations in the urinalysis expressed minimally: moderate or trace proteinuria is observed; as a rule, there are no changes in sediment (with the exception of cases of cholesterol embolism and thrombosis of renal vessels). A sharp increase in azotemia in response to the appointment of ACE inhibitors or angiotensin receptor blockers makes it possible to suspect with atherosclerotic stenosis of the renal arteries.
With fibromuscular dysplasia, a decrease in renal function is absent or develops in the late stages of the disease. The presence of a urinary syndrome is not typical; may be noted microalbuminuria or minimal proteinuria.
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Diagnostics of the renovascular hypertension
Based on the history (age of the disease, indication of the presence of cardiovascular diseases and complications), examination and physical examination, as well as routine nephrological clinical and laboratory examination, it is possible to suspect the renovascular nature of arterial hypertension.
On examination and physical examination, priority is given to the symptoms of cardiovascular diseases. Atherosclerotic stenosis of the renal arteries is often combined with signs of impaired permeability of the vessels of the lower extremities (syndrome of intermittent claudication, asymmetry of the pulse, etc.). Diagnostically valuable, albeit not very sensitive symptom of reninvascular hypertension is hearing the noise over the abdominal aorta and in the projection of the renal arteries (noted in half of the patients).
To clarify and verify the diagnosis of renovascular hypertension, special methods of investigation are needed.
Laboratory Diagnostics of Renovascular Hypertension
A urine sample shows moderate or minimal proteinuria, although it is absent in the early stages of the disease. The most sensitive marker of kidney damage is microalbuminuria.
An increase in the level of blood creatinine and a decrease in the glomerular filtration rate in the Reberg sample are characteristic of bilateral atherosclerotic stenosis of the renal arteries. With fibromuscular dysplasia of the renal arteries, renal dysfunction is rare and corresponds to the late stage of the disease.
To clarify the risk factors for atherosclerotic stenosis of the renal artery, the lipid profile and blood glucose level are examined.
For patients with renovascular hypertension, an increase in plasma renin activity and the development of secondary hyperaldosteronism are characteristic. Often observed hypokalemia. However, with bilateral atherosclerotic stenosis of renal arteries with impaired renal function, these changes may be absent. To increase the sensitivity and specificity of this laboratory test, a captopril test is used. It is carried out against the background of the usual sodium intake; for a few days they cancel diuretics and ACE inhibitors. The sample is held in the patient's sitting position, after a 30-minute period of adaptation, blood is taken twice: before ingesting 50 mg of captopril and 1 hour after it. The sample is considered positive if plasma renin activity after taking captopril is above 12 ng / ml / h or its absolute increase is not less than 10 ng / ml / h.
The most accurate method is to determine the renin activity of blood plasma obtained by catheterization of the renal vein and compare it with the activity of renin in the systemic bloodstream (in the blood obtained from the inferior vena cava to the site of the admission of the renal veins). However, due to the risk of complications associated with the invasive nature of the study, it is considered justified only in the most severe and complex cases when discussing surgical treatment.
The main role in the diagnosis of renascular arterial hypertension is played not by laboratory, but by radiation diagnosis of renousvascular arterial hypertension.
Ultrasound examination (US) allows to reveal asymmetry of kidney size, signs of cicatricial changes in patients with atherosclerosis, calcification and atherosclerotic deformation of the vascular wall. However, the diagnostic value of conventional ultrasound is small.
As the main screening methods, ultrasonic dopylearography (UZDG) of the renal arteries and dynamic renoscintigraphy are used.
UZDG is a non-invasive, safe study that can be performed even with severe kidney failure. In the regime of energy dopplerography, the method, like angiography, allows visualization of the arterial tree of the kidney - from the renal artery to the arc level, and at high resolution of the apparatus - to the interlobular arteries, to reveal additional renal vessels, visually assess the intensity of renal blood flow, to detect signs of local ischemia in patients with volumetric kidney formations and destructive lesions. To quantify the linear velocity of blood flow in different phases of the cardiac cycle, spectral dopplerography is used.
Highly sensitive and specific symptom of renal artery stenosis> 60% - local sharp increase in blood flow velocity mainly in systole. In this case, the amplitude of the spectrogram waves increases, they become pointed. Systolic linear velocity of blood flow at the site of stenosis reaches a level> 180 cm / s or 2.5 standard deviations more than normal; The renal-aortic index (the ratio of systolic linear velocity of blood flow in the renal artery and aorta) increases> 3.5. When these symptoms are combined, the sensitivity of the method exceeds 95%, the specificity is 90%. At the same time, hyperdiagnosis is possible, since high blood flow is observed not only in atherosclerotic stenosis, but also in certain abnormalities of the structure of the renal vessels, in particular the loose type of the renal artery structure, the presence of additional arteries of thin diameter originating from the aorta, .
More distal to the place of stenosis is the reverse picture: the intrarenal blood flow is sharply impoverished, only segmental, sometimes interlobar arteries are visualized, the blood flow velocity in them is slowed, the systolic-diastolic ratio is decreased, and the acceleration time is increased. On spectrograms, the waves look flat and flattened, which is described as a phenomenon of pulsus parvus et tardus. However, these changes are much less specific than the increase in systolic blood flow velocity at the site of stenosis, and can be noted in edema of the renal parenchyma in patients with acute cold syndrome, hypertensive nephroangiosclerosis, thrombotic microangiopathy, renal failure of any etiology and other conditions.
To increase the sensitivity and specificity of the method, a pharmacological test is used with 25-50 mg of captopril, which allows one to detect the appearance or aggravation of pulsus parvus et tardus one hour after the administration of the drug.
The lack of visualization of renal blood flow in combination with a decrease in the length of the kidney to <9 cm indicates complete occlusion of the renal artery.
Disadvantages of USDG are the high laboriousness and duration of the study, the need for high training and extensive experience of the specialist, the inability to study the renal arteries throughout their entire length, the low information content in obese patients and with significant intestinal disturbances. New modifications of USDG, significantly expanding its capabilities, - the use of intra-arterial sensors and gas contrasting.
Dynamic scintigraphy allows you to visualize and quantify the arrival and accumulation of a radiopharmaceutical (RFP) in the kidney, which reflects the blood flow and activation of the renal renin-angiotensin system. When using RFP, excreted only by filtration (diethylenetriamine pentaacetic acid labeled with technetium-99t- 99m Tc-DTPA), it is possible to separately assess the glomerular filtration rate in each kidney. RFP secreted tubules - labeled with technetium-99m merkaptoatsetiltriglitsin ( "Tc r -MAG 3 ) dimerkaptosuktsinilovaya acid ( 99m Tc-DMSK) - possible to obtain a contrast image showing a distribution of the blood flow in the kidney, and to identify its heterogeneity: local ischemia occlusion segmental arteries, the presence of collateral blood flow, for example, the blood supply of the upper pole of the kidney due to the extra artery.
The characteristic signs of stenosis of the renal artery are a sharp decrease in the intake of RFP in the kidney and a slowdown in its accumulation. The renogram (a curve depicting changes in radiological activity in the projection of the kidney) changes its form: it becomes more flattened, while the vascular and secretory segments become more flat; As a result, the time of maximum activity (T max ) increases significantly.
When using RFP, excreted only by glomerular filtration ( 99m Tc-DTPA), the slowing down of the early accumulation phase (from 2 to 4 min) is of diagnostic importance. With moderate impairment of kidney function (creatinine level in the blood of 1.8-3.0 mg / dl), 99m Tc-DTPA need great care; it is preferable to use RFP, secreted by tubules ( 99m Tc-MAG 3 ). Diagnostic value has a slowing down of the secretory phase, which reflects an increased reabsorption of sodium and water due to a decrease in the hydrostatic pressure in the interstitium under the influence of angiotensin II, causing stenosis of the outgoing arterioles. To increase the sensitivity and specificity of the method, a pharmacological test with captopril is used: 1 hour after the first test, 25-50 mg of captopril is prescribed, 30 minutes later, RFP is reintroduced and scintigraphy is repeated.
In the absence of stenosis, changes in the renograms after captopril administration are not noted. With stenosis of the renal artery, a sharp drop in the glomerular filtration rate and an increase in the duration of fast and slow accumulation phases of RFP in the kidney are observed. It is important to emphasize that a positive test with captopril is not a direct indication of the presence of stenosis, but reflects the activation of the renal renin-angiotensin system. It can be positive in the absence of significant stenosis in patients with hypovolemia, with regular intake of diuretics (the latter should be excluded at least 2 days before the test), with a sharp drop in blood pressure in response to the administration of captopril. With a significant chronic renal failure (creatinine level in the blood from 2.5 to 3.0 mg / dl), the use of captopril is not advisable. Severe chronic renal failure (a creatinine level in the blood of more than 3 mg / dl), at which RFP excretion is rapidly slowed, is a contraindication for radioisotope study.
To verify the diagnosis of stenosis of the renal artery, precise definition of its localization, degree and resolution of the question of the advisability of surgical treatment, determine its tactics, use X-ray methods and magnetic resonance imaging in the angiography (MRI angiography) mode. Given their complexity, high cost and the risk of complications, some authors consider it justified to use these methods only in those patients who have no contraindications to surgical treatment.
The "gold standard" for the diagnosis of stenosis of the renal artery remains angiography with intra-arterial contrast - standard or digital subtraction, which eliminates interference and high contrast images. This method allows to visualize the arterial tree of the kidney with the greatest resolution, to reveal collateral blood flow, to study the structural features of the stenosed section of the artery, and to measure the blood pressure gradient before and after stenosis, that is, it allows to assess the degree of stenosis not only anatomically but also functionally. A significant disadvantage of angiography is the risk of complications associated with catheterization of the abdominal aorta and renal artery, including perforation of the vessel, destruction of unstable atherosclerotic plaques and cholesterol embolism of distal vessels of the kidneys. Intravenous digital subtraction angiography of the kidneys, unlike the intraarterial, is the most safe from the point of view of invasiveness, but requires the introduction of high doses of contrast and is characterized by a much lower resolution.
Spiral computed tomography (CT) of renal vessels with intravenous or intra-arterial contrast injection makes it possible to obtain a three-dimensional image of the renal arterial system with a good resolution. Multispiral tomographs allow not only to study the structure of the arterial tree and the anatomical features of the site of stenosis, but also to evaluate the nature and intensity of the blood flow. It requires a large dose of radiocontrast, which limits the use of the method in severe chronic renal failure. To reduce the risk of acute renal failure, carbon dioxide can be used as a contrast. Compared with conventional angiography, CT angiography often gives false positive results.
Magnetic resonance imaging (MRI) can be used in patients with severe renal dysfunction, since the gadolinium contrast used in this method of study is the least toxic. MRI has a lower resolving power than radiopaque spiral computed tomography and, like it, gives more false positive results compared to conventional angiography. With the help of modern magnetic resonance tomographs with a movable table, a one-stage complex examination of all the main vessels of the body is possible to determine the prevalence of the lesion.
As additional instrumental methods, the examination of the patient should include echocardiogrophy, examination of the vessels of the fundus to assess the degree of damage to target organs; it can be supplemented by USDG or angiography of other vascular pools (lower limb arteries, neck, etc.).
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Differential diagnosis
Renovascular arterial hypertension is differentiated from other types of secondary renal arterial hypertension (in the framework of parenchymal diseases of the kidneys, chronic renal failure) and essential hypertension. Differential diagnosis of fibromuscular dysplasia and atherosclerotic stenosis of the renal arteries, as a rule, is not difficult. However, it is necessary to take into account that it is possible to develop a secondary early atherosclerotic stenosis against the background of previous latent fibromuscular dysplasia. Diagnostics and differential diagnostics of rare causes of renovascular hypertension (vasculitis, destructive kidney lesions, volumetric formations that cause renal vessels compression) is also based, first of all, on the data of radiation research methods.
In patients with newly diagnosed, presumably renal arterial hypertension, it is also necessary to exclude the antiphospholipid syndrome (AFS), which can cause an increase in blood pressure due to ischemic kidney damage at the level of the microcirculatory bed, and lead to the development of stenosis or thrombosis of the renal artery. In favor of antiphospholipid syndrome, there is evidence in the history of recurrent arterial or venous thrombosis, habitual miscarriage, detection of elevated antibody titers to cardiolipin and lupus anticoagulant.
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Treatment of the renovascular hypertension
The treatment of renal arterial hypertension is aimed at normalizing blood pressure, reducing the risk of cardiovascular complications and preventing renal failure. With atherosclerotic stenosis of the renal arteries leading to the development of ischemic kidney disease (see the appropriate chapter), the task of nephroprotection comes first.
Conservative treatment of renovascular hypertension
In the case of renovascular, as well as with essential hypertension, a diet that provides a restriction of consumption of table salt to a level <3 g / day, as well as correction of lipid, purine and carbohydrate metabolism disorders, smoking control and other non-pharmacological treatment of renal arterial hypertension , reducing the risk of cardiovascular disease.
Among antihypertensive drugs in the treatment of patients with renal arterial hypertension, ACE inhibitors and angiotensin receptor blockers acting on the main link of its pathogenesis occupy a special place. In fibromuscular dysplasia, especially in the early stages of arterial hypertension, they have a distinct therapeutic effect in more than 80% of cases. In the later stages, their effectiveness is lower. With moderate unilateral atherosclerotic stenosis of the renal artery, their use is also justified in connection with anti-atherogenic and cardioprotective properties.
At the same time, with hemodynamically significant bilateral stenosis of the renal arteries, drugs blocking the renin-angiotensin system can cause a sharp destabilization of renal hemodynamics (weakening and slowing of blood flow, a drop in pressure in the glomerular capillaries) with the development of acute renal failure and therefore absolutely contraindicated. Particular caution is required in patients with atherosclerotic stenosis, which is characterized by a rapid increase in the degree of constriction and further adherence to the stenosis of the artery of the contralateral kidney.
An obligatory condition for the safety of therapy with ACE inhibitors and angiotensin receptor blockers is the control of the level of creatinine and potassium of blood before and during treatment (at least once every 6-12 months, during the selection of therapy - at least 1 time per month).
The slow calcium channel blockers dihydropyridine line also have a pronounced antihypertensive effect, do not aggravate metabolic disturbances and can inhibit the formation and growth of plaques. They have no limitations in the treatment of patients with renovascular hypertension and can be used as first-line drugs.
In most cases, monotherapy is ineffective and additional prescription of antihypertensive drugs of other classes is required: beta-adrenoblockers, diuretics, alpha-adrenoblockers, imidazoline receptor agonists. In severe renovascular hypertension, 4-5 preparations of different classes at maximum or sub-maximal therapeutic doses may be required.
Atherosclerotic stenosis of the renal arteries, the appointment of antihyperlipidemic drugs - statins in the form of monotherapy or in combination with ezetimibe (see "Ischemic kidney disease") is indicated.
[36], [37], [38], [39], [40], [41], [42], [43]
Surgical treatment of renovascular hypertension
Surgical treatment of renal vascular hypertension is indicated with insufficient effectiveness of conservative methods. Arguments in favor of surgical methods of treatment are a high risk of side effects, adverse drug interactions and large material costs associated with multicomponent antihypertensive therapy. The technical success of surgical intervention (restoring the patency of the vessel or the formation of adequate collateral blood flow) does not always mean the achievement of positive clinical results.
The main methods of surgical treatment of renal artery stenosis are percutaneous balloon angioplasty and open surgery.
Percutaneous balloon angioplasty is the "stretching" of the stenotic portion of the vessel with a catheter equipped with a special can. For access use large peripheral arteries, usually femoral. Undoubted advantage of this method in comparison with open surgery is a smaller amount of intervention and no need for anesthesia. At the same time, one can not ignore the possibility of developing dangerous complications (vessel rupture, massive bleeding, destruction of unstable plaque with the development of cholesterol embolism of distally located vessels), although their risk, according to large angiosurgical centers, is small.
Localization of stenosis in the area of the mouth of the renal artery and complete occlusion of its lumen are contraindications for percutaneous angioplasty. The main problem with this method is a high risk of restenosis (30-40% during the first year after the intervention), especially in patients with atherosclerosis. The introduction of stenting allowed to reduce the risk of restenosis more than twice, practically reaching the parameters characteristic for open surgery.
Open angioplasty - the removal of atherosclerotic plaque along with the affected area of the intima of the artery or the entire stenotic section of the artery, followed by its reconstruction using the patient's own vessels (large veins, etc.) or prostheses from biocompatible materials. Less commonly, shunting is used. The advantage of open surgery is the possibility of the most complete reconstruction of the vessel, the elimination of blood flow turbulence, the removal of atheromatous masses and the affected intima that support inflammation and promote the development of restenosis. The open operation allows for complex treatment with prosthetics of several large branches of the abdominal aorta (celiac trunk, mesenteric, iliac arteries) with prevalent atherosclerosis. At the same time, the lack of open surgery is a high risk of cardiovascular complications in elderly patients associated with anesthesia, blood loss, hypovolemia and other factors.
Surgical treatment of renovascular hypertension depends on the nature of stenosis, its features and the general condition of the patient.
In young patients with fibromuscular dysplasia of the renal arteries, angioplasty can radically affect the cause of arterial hypertension and achieve complete normalization of blood pressure and abolition of antihypertensive drugs as unnecessary. Complete or partial (decrease in blood pressure and volume of the necessary antihypertensive therapy) the effect is noted in 80-95% of patients. The method of choice is percutaneous balloon angioplasty with stenting. The effect of treatment is usually persistent.
In elderly patients with atherosclerotic stenosis of the renal artery, the effectiveness of surgical treatment for arterial hypertension is much lower - 10-15%, and the risk of complications is higher than in young patients with fibromuscular dysplasia. The least favorable results are noted in patients with long-term arterial hypertension, diabetes mellitus, widespread atherosclerosis, including cerebral vessels.
With the development of ischemic kidney disease, surgical treatment is performed primarily not for the purpose of correcting arterial hypertension, for the preservation of kidney function. Stabilizing or improving function is possible to achieve in more than 3 / 4 patients. However, with small kidney size, prolonged, persistent decrease in filtration function, prolonged history of arterial hypertension, surgical treatment is ineffective and does not prevent the progression of chronic renal failure. High indices of resistance according to the USDG of the vessels of the contralateral kidney are an unfavorable prognostic sign both in terms of pressure decrease in response to surgical treatment and in terms of kidney function.
In most cases, percutaneous balloon angioplasty with stenting is recommended as a method of choice for atherosclerotic stenosis; with stenosis in the mouth area, complete occlusion or ineffectiveness of previous percutaneous intervention - open angioplasty.
Nephrectomy is currently extremely rare in the treatment of severe, resistant renal arterial hypertension-in the event that the kidney function is completely impaired, according to a radioisotope study, the renin activity of blood plasma obtained by catheterization of its vein is significantly higher than in the systemic blood flow.
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Forecast
The prognosis in patients with renovascular hypertension is unfavorable in its natural course due to a very high risk of cardiovascular complications. Modern medical therapy and surgical treatment of renovascular hypertension can radically affect the course of the disease, but success depends on the early diagnosis and timeliness of medical interventions.
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