Mesenteric and renal arterial duplex ultrasound: A review.

Duplex ultrasound examinations of the mesenteric and renal circulations are commonly used to detect disease as well as to follow up patients after open surgery or endovascular intervention. The aims of this review were to present essential elements of these duplex ultrasound examinations as well as conduct a literature review of diagnostic criteria. Documentation of appropriate images and data will aid in an accurate interpretation. Spectral Doppler waveforms from various segments of these arterial systems can contribute both direct and indirect evidence of the presence of disease. Various studies have validated the duplex ultrasound diagnostic criteria which more recently have expanded to include specific criteria for stented vessels. This review presents a summary of the fundamental exam components and diagnostic criteria utilized for mesenteric and renal duplex ultrasound.

Noninvasive studies for the peripheral artery disease patient.

Numerous noninvasive diagnostic tests can be performed to detect peripheral arterial disease (PAD), and these can be separated into direct and indirect examinations. The test chosen is determined on the basis of both the presenting symptoms of the patient and the needs of the health care provider. A simple pressure measurement is often used to screen an asymptomatic patient for PAD, and a more specific and detailed test, such as ultrasound, is required to determine disease within a stent or bypass. Indirect testing types include the measurement of systolic pressures within a limb or digit and acquisition of waveforms. The combination of quantitative data from pressures and qualitative data from waveforms is used to provide an accurate assessment of global perfusion in a limb. Direct noninvasive testing is performed with duplex ultrasound techniques. With ultrasound, specific anatomic features can be visualized directly. Spectral waveforms obtained with duplex ultrasound can be characterized and velocities can be measured. Criteria exist to categorize disease on the basis of velocities and velocity ratios and by using this objective hemodynamic data, progression of disease may be followed. The focus of this review was to describe the various types of direct and indirect arterial noninvasive testing for detection and management of PAD. The advantages and disadvantages of each will be explained, as well as common applications for these tests. Direct, indirect, or a combination of direct and indirect testing may be required to accurately determine the presence, level, and severity of PAD.

Optimization of duplex velocity criteria for diagnosis of internal carotid artery (ICA) stenosis: A report of the Intersocietal Accreditation Commission (IAC) Vascular Testing Division Carotid Diagnostic Criteria Committee.

Diagnostic criteria to classify severity of internal carotid artery (ICA) stenosis vary across vascular laboratories. Consensus-based criteria, proposed by the Society of Radiologists in Ultrasound in 2003 (SRUCC), have been broadly implemented but have not been adequately validated. We conducted a multicentered, retrospective correlative imaging study of duplex ultrasound versus catheter angiography for evaluation of severity of ICA stenosis. Velocity data were abstracted from bilateral duplex studies performed between 1/1/2009 and 12/31/2015 and studies were interpreted using SRUCC. Percentage ICA stenosis was determined using North American Symptomatic Carotid Endarterectomy Trial (NASCET) methodology. Receiver operating characteristic analysis evaluated the performance of SRUCC parameters compared with angiography. Of 448 ICA sides (from 224 patients), 299 ICA sides (from 167 patients) were included. Agreement between duplex ultrasound and angiography was moderate (κ = 0.42), with overestimation of degree of stenosis for both moderate (50-69%) and severe (⩾ 70%) ICA lesions. The primary SRUCC parameter for ⩾ 50% ICA stenosis of peak-systolic velocity (PSV) of ⩾ 125 cm/sec did not meet prespecified thresholds for adequate sensitivity, specificity, and accuracy (sensitivity 97.8%, specificity 64.2%, accuracy 74.5%). Test performance was improved by raising the PSV threshold to ⩾ 180 cm/sec (sensitivity 93.3%, specificity 81.6%, accuracy 85.2%) or by adding the additional parameter of ICA/common carotid artery (CCA) PSV ratio ⩾ 2.0 (sensitivity 94.3%, specificity 84.3%, accuracy 87.4%). For ⩾ 70% ICA stenosis, analysis was limited by a low number of cases with angiographically severe disease. Interpretation of carotid duplex examinations using SRUCC resulted in significant overestimation of severity of ICA stenosis when compared with angiography; raising the PSV threshold for ⩾ 50% ICA stenosis to ⩾ 180 cm/sec as a single parameter or requiring the ICA/CCA PSV ratio ⩾ 2.0 in addition to PSV of ⩾ 125 cm/sec for laboratories using the SRUCC is recommended to improve the accuracy of carotid duplex examinations.

Changes in Internal Carotid Artery Doppler Velocity Measurements With Different Angles of Insonation: A Pilot Study.

OBJECTIVES: Doppler velocity measurements are fundamental diagnostic criteria for vascular ultrasound examinations. Insonation angles are kept to 60° or less to minimize error. The purpose of this study was to assess variance of Doppler-detected peak systolic velocity (PSV) measurements in the internal carotid arteries at different angles (45°, 50°, 55°, and 60°) with different beam steering. METHODS: The PSV was recorded from the right and left internal carotid arteries in 22 asymptomatic volunteers with straight vessels (total of 44 vessels). A standardized approach was used for recording velocities with the Doppler cursor center steered and steered 15° from right to left. An analysis of variance was performed. RESULTS: The PSV varied significantly with the 4 different angles of insonation (P < .01). The maximum variation between 45° and 60° angles within a single vessel was 29 cm/s. The average variation over the 4 angles was 14 ± 6 cm/s. Relative to the calculated mean velocity for all patients, the standard deviation for the PSV at 60° was nearly twice that recorded at 50° (7.9 versus 3.9). The best correlation of the calculated mean velocity for all patients existed between the angles of 45° and 50° [r(36) = 0.92; P < .001 for center-steered data; and r(40) = 0.96; P < .001 for right-steered data]. CONCLUSIONS: These results indicate a statistically significant difference in the PSV measurements taken at varying Doppler angles. The greatest mean, variance, and lowest correlations all result when using 60°. The findings support the need for consistent ultrasound techniques and suggest that further study is warranted regarding the optimal Doppler angle for velocity measurements.

Hemodynamic changes associated with bypass stenosis regression.

OBJECTIVE: Ultrasound scanning is used to detect velocity increases indicative of a bypass stenosis. Subsequent examinations have shown regression of some stenotic lesions. This study examined hemodynamic changes that coincided with stenosis regression. METHODS: Duplex ultrasound scans were used to record the peak systolic velocity (PSV) and volume flow from proximal and distal segments of infrainguinal bypasses. Valve remnants or other image defects were also noted. The PSV ratio (Vr) was calculated as the PSV at a stenosis divided by the PSV proximal to the lesion. A stenosis was defined as Vr >/=2.0. RESULTS: An initial ultrasound scan performed 31 +/- 6 days after surgery revealed a stenosis in 68 of 565 bypasses. In six bypasses, the increased PSV (272 +/- 61 cm/s) and Vr (3.4 +/- 1.3) were sustained during the follow-up period of 8 +/- 3 months. In 27 bypasses with a PSV of 335 +/- 63 cm/s and a Vr of 4.0 +/- 1.6, the stenosis was repaired. In 35 bypasses with a PSV of 261 +/- 82 cm/s and Vr of 3.2 +/- 1.2, stenosis regression occurred with no increases in PSV observed on later scans. In this group, proximal bypass flow decreased during the follow-up interval from 247 +/- 130 mL/min to 151 +/- 135 mL/min and distal flow from 180 +/- 102 mL/min to 103 +/- 54 mL/min ( P < .05, paired t test). Ultrasound image abnormalities were noted in 4 bypasses (67%) with persistent stenoses, 14 with repaired stenoses (52%), and 10 with resolved stenoses (29%). CONCLUSION: These data indicate early postoperative hyperemia is present in bypasses, demonstrating focal velocity increases. Such velocity increases may be the result of the bypass conduit acting as a flow-limiting lesion until the hyperemia subsides. As the blood flow decreases so does the PSV, giving the appearance of stenosis regression.