Renal artery stenosis is a narrowing of the diameter of one or both renal arteries or their branches, accompanied by a decrease in renal perfusion. It is manifested by the development of renovascular arterial hypertension (up to 200/140-170 mmHg) and ischemic nephropathy. Diagnosis is based on laboratory tests, ultrasound of renal vessels, excretory urography, renal angiography, scintigraphy. Medical therapy, angioplasty and stenting of the renal arteries, bypass surgery, endarterectomy are used in the treatment.
Meaning
Renal artery stenosis is one of the most significant problems in modern urology. Pathology develops due to congenital and acquired changes in arterial vessels, leading to a decrease in renal blood flow and the development of nephrogenic hypertension. Unlike parenchymal hypertension caused by primary kidney diseases (glomerulonephritis, pyelonephritis, nephrolithiasis, hydronephrosis, polycystic fibrosis, tumors, cyst, tuberculosis of the kidney, etc.), secondary symptomatic vasorenal hypertension is formed with renal artery stenosis, which is not associated with damage to the renal parenchyma.
Hypertension caused by occlusive and stenosing lesions of the renal arteries is registered in 10-15% of patients with essential hypertension and in 30% with nephrogenic hypertension. The disease can be accompanied by life-threatening complications: cardiovascular insufficiency, stroke, myocardial infarction, chronic renal failure.
Causes
The most common causes of renal artery stenosis are atherosclerosis (65-70%) and fibromuscular dysplasia (25-30%). Atherosclerotic stenosis occurs in men over 50 years of age 2 times more often than in women. At the same time, atheromatous plaques can be localized in the proximal segments of the renal arteries near the aorta (in 74%), the middle segments of the renal arteries (in 16%), in the bifurcation zone of the arteries (in 5%) or in the distal branches of the renal arteries (in 5% of cases). Atherosclerotic lesion of the renal arteries especially often develops against the background of diabetes mellitus, preceding arterial hypertension, coronary artery disease.
Pathology caused by congenital segmental fibromuscular dysplasia (fibrous or muscular thickening of the membranes of the arteries) is 5 times more often registered in women older than 30-40 years. In most cases, the stenosing lesion is localized in the middle segment of the renal artery. In accordance with the features of morphological and arteriographic characteristics, intimate, medial and perimedial fibromuscular dysplasia are distinguished. Renal artery stenosis in fibromuscular hyperplasia often has a bilateral localization.
In about 5% of cases, the disease is caused by other causes, including arterial aneurysms, arteriovenous shunts, vasculitis, Takayasu disease, thrombosis or embolism of the renal artery, compression of the kidney vessels from the outside by a foreign body or tumor, nephroptosis, aortic coarctation, etc. Narrowing of the renal vessels activates the complex mechanism of the renin-angiotensin-aldosterone system, which is accompanied by stable renal hypertension.
Renal artery stenosis symptoms
Renal artery stenosis is characterized by two typical syndromes: arterial hypertension and ischemic nephropathy. The sharp development of persistent hypertension at the age of less than 50 years, as a rule, makes one think of fibromuscular dysplasia, in patients older than 50 years – of atherosclerotic stenosis. Arterial hypertension in this pathology is resistant to hypotensive therapy and is characterized by high diastolic blood pressure, reaching 140-170 mm Hg. Hypertensive crises in vasorenal hypertension are rare.
The development of arterial hypertension is often accompanied by cerebral symptoms – headache, hot flashes, heaviness in the head, pain in the eyeballs, tinnitus, flashing “flies” in front of the eyes, memory impairment, sleep disorder, irritability. Overload of the left parts of the heart contributes to the occurrence of heart failure, which is manifested by palpitations, pain in the heart, a feeling of tightness behind the sternum, shortness of breath. With severe stenosis, recurrent pulmonary edema may develop.
Vasorenal hypertension develops in stages. At the compensation stage, normotension or a moderate degree of arterial hypertension is observed, corrected by medications; kidney function remains intact. The stage of relative compensation is characterized by stable arterial hypertension; a moderate decrease in kidney function and a slight decrease in their size.
In the decompensation stage, arterial hypertension becomes severe, refractory to hypotensive therapy; kidney function is significantly reduced, kidney size is reduced to 4 sm. Arterial hypertension can be malignant (rapid onset and lightning-fast progression), with significant inhibition of renal functions and a decrease in kidney size by 5 or more sm.
Nephropathy is manifested by symptoms of kidney ischemia – a feeling of heaviness or dull pain in the lower back; with a renal infarction – hematuria. Secondary hyperaldosteronism often develops, characterized by muscle weakness, polyuria, polydipsia, nocturia, paresthesia, tetany attacks.
The combination of renal artery stenosis with damage to other vascular basins (with atherosclerosis, nonspecific aortoarteritis) may be accompanied by symptoms of ischemia of the lower or upper extremities, gastrointestinal organs. The progressive course of the pathology leads to dangerous vascular and renal complications – retinal angiopathy, acute cerebrovascular accident, myocardial infarction, renal failure.
Diagnostics
A typical diagnostic sign of renal artery stenosis is listening to noises in the upper quadrants of the abdomen. With percussion, the expansion of the boundaries of the heart to the left is determined, with auscultation – an increase in the apical heartbeat, the emphasis of the II tone on the aorta. During ophthalmoscopy, signs of hypertensive retinopathy are revealed.
A biochemical blood test is characterized by an increase in the level of urea and creatinine; a general urinalysis is characterized by proteinuria, erythrocyturia. Ultrasound of the kidneys reveals a uniform decrease in the size of an ischemic kidney, typical for renal artery stenosis. In order to assess the degree of stenosis and the rate of renal blood flow, ultrasound and duplex scanning of the renal arteries are used.
Excretory urography data are characterized by a decrease in intensity and a delay in the appearance of a contrast agent in the affected kidney, a decrease in the size of the corresponding organ. Conducting radioisotope renography provides information on the shape, size, position and functional state of the kidneys, as well as on the effectiveness of renal blood flow.
Selective renal arteriography serves as a reference method for the diagnosis of renal artery stenosis. According to the angiograms obtained, the localization and extent of stenosis are revealed, its causes and hemodynamic significance are determined. Differential diagnosis is carried out with primary aldosteronism, pheochromocytoma, Cushing’s syndrome, kidney parenchyma diseases.
Renal artery stenosis treatment
Drug therapy is auxiliary, since it does not eliminate the root causes of arterial hypertension and renal ischemia. Symptomatic antihypertensive drugs and ACE blockers (captopril) are prescribed in old age or systemic arterial damage. Angiographically confirmed stenosis serves as an indication for various types of surgical treatment. The most common type of intervention for fibromuscular dysplasia is endovascular balloon dilation and stenting of the renal arteries.
In atherosclerotic stenosis, bypass surgery (ventricular, mesenteric, aortoprenal) and endarterectomy from the renal artery are the methods of choice. In some cases, resection of the stenosed section of the renal artery with reimplantation into the aorta, end-to-end anastomosis or prosthetics of the renal artery with a vascular autograft or synthetic prosthesis is indicated. Pathology caused by nephroptosis requires nephropexy. If it is impossible to perform reconstructive operations, nephrectomy is resorted to.
Prognosis and prevention
Surgical treatment of renal artery stenosis makes it possible to normalize blood pressure in 70-80% of patients with fibromuscular dysplasia and 50-60% with atherosclerosis. The period of postoperative normalization of blood pressure can take up to 6 months. Antihypertensive drugs are prescribed to eliminate residual arterial hypertension. Patients are recommended to follow-up by a nephrologist and cardiologist. Prevention includes timely diagnosis and treatment of diseases leading to the development of stenosis.