Ultrasound diagnostics of renal artery stenosis

Abstract

Background and purposeAs a non-invasive, side effect-free and cost-effective method, ultrasonography represents the method of choice for the diagnosis of renal artery stenosis. Four different criteria in total, including two direct criteria in peak systolic velocity (PSV) and renal aortic ratio (RAR) and two indirect criteria in resistance index (RI) and acceleration time (AT) for the measurement of relevant renal artery stenosis are described, each demonstrating highly variable accuracy in studies. Furthermore, there is controversy over the degree beyond which stenosis becomes therapeutically relevant and which ultrasound PSV is diagnostically relevant in terms of stenosis grading.Material and methodsThis article gives a critical review based on a selective literature search on measurement methodology and the validity of ultrasound in renal artery stenosis. A critical evaluation of methods and a presentation of measurement principles to establish the most precise measurement method possible compared with the gold standard angiography, as well as an evaluation of the importance of computed tomography angiography (CTA) and magnetic resonance angiography (MRA).Results and conclusionsThe PSV provides high sensitivity and specificity as a direct measurement method in stenosis detection and grading. Most studies found sensitivities and specificities of 85–90 % for > 50 % stenosis at a PSV > 180–200 cm/s in ROC curve analysis. Other methods, such as the ratio of the PSV in the aorta to the PSV in the renal artery (RAR) or indirect criteria, such as side to side differences in RI (dRI) or AT can be additionally used to improve accuracy. Contrast-enhanced ultrasound improves accuracy by means of echo contrast enhancement. Although in the past only high-grade stenosis was considered relevant for treatment, a drop in pressure of > 20 mmHg in > 50 % stenosis (PSV 180 cm/s) is classified as relevant for increased renin secretion. Stenosis in fibromuscular dysplasia can be reliably graded according to the continuity equation. Although the available studies on the grading of in-stent restenosis are the subject of controversy, there is a tendency to assume higher cut-off values for PSV and RAR. Whilst MRA and CTA demonstrate an accuracy of > 90 %, this is at the cost of possible side effects for patients, particularly in the case of pre-existing renal parenchymal damage.Additional online materialThis article includes two additional video sequences on visualizing renal artery stenosis. This supplemental material can be found under: dx.doi.org/10.1007/s00772-015-0060-3

The Value of Contrast-Enhanced Ultrasound versus Doppler Ultrasound in Grading Renal Artery Stenosis

“…A previous study also used CEUS for the diagnosis of renal artery stenosis and showed good results. They found that the sensitivity, specificity, and accuracy of CEUS were similar to selective angiography [ 23 ]. Our study investigated the diagnostic value of CEUS in renal artery stenosis using DSA as the gold standard which is superior to selective angiography that was used in the previous study.…”

“…Therefore, the clinical application of CTA and MRA is limited in some particular cases. Although DUS has been widely used as an initial imaging modality for the diagnosis of renal artery stenosis [ 21 , 22 ], factors such as depth, obesity, complex anatomy, bowl gas, and operator dependent may limit the use of the Doppler ultrasound [ 23 ]. More recently, the use of CEUS in the detection of renal artery stenosis has raised the attention of many researchers [ 24 , 25 ].…”

Clinical value of combining transvaginal contrast-enhanced ultrasonography with serum human epididymisprotein-4 and the resistance index for early-stage epithelial ovarian cancer

“…When U, HE4, and RI were combined for detection, the sensitivity was 91%, and when the U, PI, ER and HE4 were combined, the RI joint detection sensitivity was 92.7%. 24 The combination improves the detection accuracy and decreases the false positivity rate. 25 Our retrospective study is the first to increase the sensitivity of the early detection and differential diagnosis of EOC with TVCEUS combined with HE4 and RI.…”

Ratio of diastolic to systolic blood pressure represents renal resistive index

“…Renal color Doppler ultrasonography is a useful noninvasive physiological examination for the assessment and follow-up of patients with chronic kidney diseases (CKD) [ 1 – 4 ]. In addition to kidney size, routine ultrasonic indices—end-diastolic velocity (EDV), peak systolic velocity (PSV), and resistive index (RI)—are usually measured in multiple regions from the central to peripheral kidney [ 3 , 5 ]. Because renal color Doppler ultrasonography was introduced only in the past few decades, its clinical usefulness and guidelines for interpretation are still being determined.…”