ABC | Volume 112, Nº6, June 2019

Statement Vascular Ultrasound Statement from the Department of Cardiovascular Imaging of the Brazilian Society of Cardiology – 2019 Arq Bras Cardiol. 2019; 112(6):809-849 of choice to investigate RAS due to its advantages, such as being non-invasive, low-cost, having no risk of radiation, and, mainly, the lack of contraindications related to the use of nephrotoxic contrast. Ultrasound evaluation of renal arteries has high specificity in competent laboratories, demonstrating that, when the vessels are correctly assessed, its results rarely differ from those obtained by arteriography. 45,48-50 Table 14 shows the main indications to investigate RAS, according to the principal American guidelines. 51,52 The principal objectives of the study of renal arteries are: • Identify the main renal arteries and, if possible, the accessory ones. • Locate and grade stenotic lesions resulting from atherosclerotic disease or not. • Monitor the progression of RAS. • Follow-up after renal artery revascularization. 3.4.2. Examination Protocol (Table 10) • Patient’s position: Supine, using transverse and longitudinal ultrasound planes to analyze the abdominal aorta and origin of renal arteries. • Lateral, using the coronal plane to assess all middle and distal segments of renal arteries. Use this plane to measure the longitudinal diameter of the kidney and analyze the intrarenal flow in segmental or interlobular arteries. 2 • B-scan: used to identify atheroma plaques in the renal artery and evaluate the echogenicity and size of the kidney. • Color flow imaging and/or power Doppler: evaluate artery patency. Power Doppler indicates possible stenosis sites through flow turbulence or reduction in the vessel lumen. • Spectral analysis: Essential to measure systolic and diastolic velocities (PSV and EDV). Use the transverse or coronal plane, keeping the cursor directed at the flow jet, with an insonation angle < 60° in the renal artery and 0° in intraparenchymatous arteries. 53 Table 14 – Clinical indications to investigate renal artery stenosis ● Onset of hypertension in patients aged ≤ 30 years ● Onset of severe hypertension in patients aged ≥ 55 years ● Patients with accelerated hypertension (sudden or persistent worsening of previously controlled hypertension) ● Patients with resistant hypertension (treatment failure with full doses of three antihypertensive drug classes, including diuretics) ● Patients with malignant hypertension (with target-organ damage: acute renal failure, acute congestive heart failure, new visual or neurological disorder, and/or advanced retinopathy) ● Patients with worsening of renal function after administration of angiotensin-converting enzyme inhibitor or angiotensin-receptor blocker ● Patients with unexplained renal atrophy or discrepancy > 1.5 cm from kidney sizes ● Patients with sudden and unexplained pulmonary edema (flash pulmonary edema) ● Patients with renal failure or unexplained congestive heart failure ● Patients with refractory angina ● Patients with multiple vessel coronary artery disease ● Patients with abdominal aortic aneurysm • Measure PSV and EDV at the origin of the renal artery or in any segment with suspicion of stenosis. • Use the longitudinal plane of the aorta, near the origin of the SMA, to measure its PSV and calculate the renal aortic ratio (RAR). 3.4.3. Diagnostic Criteria for Renal Artery Stenosis Diagnostic criteria for RAS are classified as direct and indirect. The first consists of evaluating the renal artery from its origin in the aorta and, if possible, in all its extension. The second analyzes the hemodynamic repercussion of the proximal lesion of the renal artery on intraparenchymatous arteries. The direct criterion comprises renal artery PSV and EDV and aortic PSV to calculate RAR (renal artery PSV/aortic PSV). The low-resistance waveform is considered normal for the renal artery. PSV is the most accurate parameter to grade RAS, with values that range between 180 and 250 m/s from study to study. EDV and RAR are used to aid the RAS evaluation. According to several studies, RAR ranges from 3.2 to 3.7 to estimate hemodynamically significant stenosis. Situations such as aortic coarctation, severe left ventricular dysfunction, aortic dissection or aneurysm, and systolic aortic velocities > 100 cm/s or < 40 cm/s can change the velocities in renal arteries and their relationships. 2 Indirect criteria, represented by the measurement of the kidney size and analysis of intraparenchymatous artery flow, should be combined with direct criteria to optimize the results. A difference of 1.5 cm in kidney size can result from hemodynamically significant stenosis or even renal artery occlusion. Regarding the analysis of intraparenchymatous artery flow, initially, there is a reduction in the first systolic peak (FSP), prolonged acceleration time (AT) with decreased acceleration rate (AR), and flattening of the systolic wave until the parvus/tardus pattern is found. AT > 70 ms is associated with 60% RAS, while the parvus/tardus flow is present in more severe stenosis (80%). 2 827