Renal artery stenosis - Diagnosis

Diagnosis of renal artery stenosis requires a targeted search for atherosclerotic stenosis and depends on the characteristics of arterial hypertension, chronic renal failure, and signs of widespread atherosclerosis. Physical examination may reveal peripheral edema, manifestations of chronic heart failure (hepatomegaly, bilateral crepitations or moist rales in the basal regions of the lungs), as well as murmurs over the aorta and large vessels, including the renal vessels. The sensitivity and specificity of these symptoms are extremely low.

Changes in urine in atherosclerotic renal artery stenosis are limited to "trace" proteinuria, often transient; hematuria and leukocyturia are not typical (except for embolism of intrarenal arteries and arterioles by cholesterol crystals). In most patients with atherosclerotic renovascular hypertension, microalbuminuria can be detected using appropriate qualitative (test strips) or quantitative (immunonephelometry) methods; however, significant changes in urine, including proteinuria exceeding 1 g/day, do not completely refute the assumption of atherosclerotic renal artery stenosis, since they can reflect the presence of concomitant chronic nephropathy (for example, diabetic or due to chronic glomerulonephritis).

Ultrasound examination of the kidneys often reveals their reduction (asymmetrical or symmetrical), uneven contours and thinning of the cortical layer.

Ischemic kidney disease is confirmed by the results of imaging examination methods. Ultrasound Doppler imaging of the renal arteries is not sensitive and specific enough, but it is noninvasive and does not require the introduction of contrast agents, and therefore is preferable for use at the first stage of diagnostics, as well as during dynamic observation.

Multispiral computed tomography of the renal arteries performed in the angiocontrast mode allows for a reliable assessment of the size of the kidneys and the thickness of their cortex, the degree of stenosis of the renal arteries and the condition of atherosclerotic plaques in them and adjacent parts of the abdominal aorta. In terms of sensitivity and specificity, this method is close to contrast angiography, but is safer in terms of the risk of radiocontrast nephropathy.

Magnetic resonance imaging requires the use of contrast agents containing gadolinium, which are virtually safe in renal failure. The high cost limits the widespread use of this method.

Contrast angiography allows the most reliable detection of atherosclerotic stenosis of the renal arteries. The use of this method is associated with the risk of worsening renal dysfunction associated with the introduction of contrast agents, as well as with the danger of cholesterol embolism, which occurs during the destruction of the fibrous cap of atherosclerotic plaques localized in the abdominal aorta during catheter insertion. At the same time, in specialized centers where a large number of angiographies are performed, the incidence of this complication is extremely low.

The results of radioisotope renal scintigraphy (possibly an acute captopril test) confirm deterioration in the function of one or both kidneys, but only indirectly indicate stenotic lesion of the renal arteries. In addition, even a single dose of a short-acting ACE inhibitor can be dangerous in cases of severe hypercreatininemia, as well as in elderly patients with unstable blood pressure.

All patients with atherosclerotic renovascular hypertension should be specifically examined for cardiovascular risk factors (parameters characterizing lipoprotein and glucose metabolism, homocysteine, waist circumference and body mass index) and markers of high risk of cardiovascular complications (increased serum C-reactive protein levels, hyperfibrinogenemia). Automatic 24-hour blood pressure monitoring allows timely detection of disturbances in its daily rhythm, including prognostically unfavorable ones.

The data obtained by echocardiography more reliably reflect the degree of hypertrophy and impairment of systolic and/or diastolic function of the left ventricle, as well as changes in the heart valves (mitral regurgitation and atherosclerotic aortic stenosis, sometimes combined with insufficiency, are possible). Detection of atherosclerotic lesions of the carotid arteries by ultrasound Doppler imaging of the carotid arteries indirectly proves the atherosclerotic nature of renal artery stenosis.

The assessment of the SCF in dynamics is carried out using generally accepted calculation methods (Cockcroft-Gault formulas, MDRD).

There is no generally accepted diagnostic tactic for cholesterol embolism of the intrarenal arteries and arterioles. Kidney biopsy is usually not performed due to the very high probability of life-threatening complications. Cholesterol emboli can be detected by morphological examination of the affected skin areas.

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Differential diagnosis of atherosclerotic renal artery stenosis

The main task of differential diagnostics of atherosclerotic stenosis of the renal arteries is to separate it as early as possible from chronic nephropathies with similar clinical manifestations, which nevertheless require radically different management tactics.

Symptoms of atherosclerotic renal artery stenosis are often mistakenly assessed as signs of involutional changes in renal tissue, which, however, are not characterized by a decrease in SCF and hypercreatininemia, as well as high and/or uncontrolled arterial hypertension.

Hypertensive nephroangiosclerosis is characterized by microalbuminuria with normal or moderately reduced SCF, hypercreatininemia is absent or moderate. Unlike atherosclerotic renal artery stenosis, in hypertensive kidney disease, their function does not usually deteriorate when RAAS blockers are prescribed.

Diabetic nephropathy is characterized by a sequential change of stages from microalbuminuria to increasing proteinuria: a decrease in SCF is recorded only when protein excretion in urine reaches a nephrotic level (>3 g/day). Hypercreatininemia and especially hyperkalemia, which appear when using ACE inhibitors or angiotensin II receptor blockers, require targeted exclusion of atherosclerotic stenosis of the renal arteries in all patients suffering from type 2 diabetes for a long time.

The differences between atherosclerotic renal artery stenosis and fibromuscular dysplasia of the renal arteries are usually obvious. The latter is more often observed in women under 50 years of age; the main symptom is arterial hypertension, while deterioration of renal function is very rare. A combination of renal vascular lesions with involvement of the cerebral arteries and visceral branches of the aorta is possible. On angiography, the stenotic section of the artery has a characteristic "rosary" appearance.

Renovascular hypertension in Takayasu syndrome is usually combined with general signs of a systemic inflammatory response: fever, arthralgia, weight loss, and increased ESR. Coronary arteries, as well as arteries of the intestine and upper extremities, are often affected simultaneously (asymmetry of the pulse and blood pressure is revealed when measured on both arms). Takayasu syndrome usually debuts at a younger age than atherosclerotic stenosis of the renal arteries.

It is necessary to emphasize once again the possibility of a combination of atherosclerotic stenosis of the renal arteries with almost any chronic nephropathy. The detection of signs of the latter in itself does not completely refute the possibility of the simultaneous presence of atherosclerotic stenosis of the renal arteries in the patient.

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