Incidental renal artery stenosis among a prospective cohort of hypertensive patients undergoing coronary angiography

OBJECTIVE: To determine the feasibility, safety, and clinical yield of angiographic screening among hypertensive patients undergoing coronary angiography. PATIENTS AND METHODS: This study was a prospective cohort analysis of hypertensive patients who underwent cardiac catheterization at a tertiary care referral center from July 1998 to March 1999. Abdominal aortography was performed to screen for renal artery stenosis, the percentage of which was measured. RESULTS: The mean +/- SD age of the 297 study patients was 64.9+/-10.2 years; 58.6% were male, and 98.0% were white. Mean +/- SD systolic/diastolic blood pressure was 142.8+/-22.5/79.6+/-11.4 mm Hg. Aortography required a mean incremental dose of 62+/-9 mL of nonionic contrast agent. No complications were attributable to aortography. Of 680 renal arteries, 611 (90%) were visualized adequately. Also, 53% of patients had normal renal arteries, 28% had stenoses less than 50%, and 19.2% had stenoses of 50% or more. Renal artery stenosis was bilateral in 3.7% of patients and high grade (>70% stenosis) in 7%. Patients with renal artery stenosis were more likely to have had a previous coronary intervention. In multivariate analysis, systolic blood pressure (odds ratio [OR], 1.2; 95% confidence interval [CI], 1.03-138; P=.02), history of stroke or transient ischemic attack (OR, 2.7; 95% CI, 1.27-5.78; P=.01), and cancer (OR, 2.0; 95% CI, 1.02-3.82; P=.04) independently correlated with renal artery stenosis of 50% or more. CONCLUSION: The prevalence of incidental renal artery stenosis among hypertensive patients undergoing coronary catheterization is significant. Therefore, screening abdominal aortography should be considered in these patients to better define their risk of cardiovascular complications.     

Hemodynamic analysis of renal artery stenosis using computational fluid dynamics technology based on unenhanced steady-state free precession magnetic resonance angiography: preliminary results

This study aims to evaluate the feasibility of computational fluid dynamics (CFD) technology in analysis of renal artery stenosis (RAS) based on unenhanced MR angiography (MRA). Thirty hypertensive patients with unilateral RAS, and 10 normal volunteers, underwent unenhanced MRA on a 1.5 T MR scanner. 12 of 30 patients also underwent ultrasound (US) to detect peak systolic velocity. The patient-specific CFD based on MRA was carried out thereafter. Stenosis grades and hemodynamic variables at the stenosis of main renal artery, including pressure difference (PD), velocity and mass flow rate (MFR), were analysed. And the hemodynamic indices of stenoses were compared with the parameters of normal renal arteries and available US velocity profile. High intraclass correlation coefficient (value 0.995) and no significant difference (p > 0.05) was shown between maximum velocity of CFD and peak systolic velocity of US in 12 patients. For normal renal arteries, the average PD, velocity and MFR were all in the reported normal physiological range. However, for stenotic arteries, the translesional PD and velocity of main renal arteries increased with the severity of stenotic degrees, while the MFR decreased. 50 % diameter stenosis was the threshold at which all three hemodynamic parameters experienced significant changes (p < 0.01). This preliminary study shows that unenhanced-MRA-based CFD can be utilized to noninvasively analyse hemodynamic parameters of RAS. The acquired variables may provide meaningful information regarding stratification of the stenosis and further therapeutic treatment.     

Evaluation of severe transplant renal artery stenosis with Doppler sonography

PURPOSE: To evaluate and determine Doppler criteria for predicting a severe transplant renal artery stenosis (80%-99% diameter reduction) and to compare the Doppler findings in patients with end-to-end and end-to-side anastomosis. METHODS: We performed Doppler sonography on 16 consecutive patients with transplant renal artery stenosis (TRAS) confirmed by digital subtraction arteriography (DSA). Fourteen patients had end-to-end anastomosis, and 2 had end-to-side anastomosis. Eleven patients were re-evaluated with color Doppler sonography within 4 days after intervention. Seven Doppler parameters, including the peak systolic velocity (PSV) in the renal, iliac and interlobar artery, Pre-PSV ratio (the ratio of the PSV in the renal artery to that in the iliac artery), Post-PSV ratio (the ratio of the PSV in the renal artery to that in the interlobar arteries, acceleration time and resistance index, were measured. In the patients with severe TRAS the measurements of these parameters were compared before and after successful intervention. RESULTS: In the 16 patients with a single transplanted kidney, arteriography demonstrated 14 main renal arteries with severe stenosis, and 3 renal arteries with moderate stenosis. When using the cutoff values of Post-PSV ratio >13, renal artery PSV >4 m/sec, acceleration time >0.06 second, and resistance index <0.5 for the detection of all 14 severe stenoses, the sensitivities were 100%, 71%, 93%, and 50%, respectively. For assessing all 14 severe stenoses and 12 severe stenoses of end-to-end anastomosis, the cutoff value of Pre-PSV ratio >5 had sensitivities of 86% and 100%, respectively. Pre-PSV ratios in severe stenoses of end-to-end anastomosis (range, 5.1-11.5) were significantly greater than those recorded in severe stenoses of end-to-side anastomosis (range, 2.8-3.1). Statistically significant differences before and after successful intervention were found for all 7 Doppler parameters in the 7 patients with severe stenosis. CONCLUSIONS: An 80%-99% diameter reduction of the renal artery can be diagnosed based on a Post-PSV ratio >13 for patients with either end-to-end or end-to-side anastomosis. A Pre-PSV ratio >5 for patients with end-to-end anastomosis and acceleration time >0.06 second are helpful in the diagnosis of severe TRAS.     

Peripheral arterial Doppler ultrasonography: diagnostic criteria.

Fifty-one patients (86 legs) were studied from the aorta to the popliteal artery with both duplex ultrasonography and arteriography with the intention of establishing diagnostic ultrasonographic criteria for degrees of stenosis greater than 50% and determining the effect of multi-segment disease on the accuracy of these criteria. Receiver operator characteristic curves were used to determine diagnostic criteria for greater than 50%, greater than 70%, greater than 90% diameter stenoses or occlusions. A stenosis of greater than 70% was diagnosed either if the peak systolic velocity was more than 160 cm/sec (sensitivity 77%, specificity 90%) of if there was an increase in peak systolic velocity of 100% with respect to the arterial segment above the stenosis (sensitivity 80%, specificity 93%). Sequential stenoses were detected with lesser sensitivities. Ratio criteria were more accurate than peak systolic velocity for all degrees of stenosis. For detection of occlusion, duplex ultrasonography was 92% sensitive and 99% specific.     

Frequency,clinical significance and impact on therapy of duplex sonographic vascular findings in renal allograft dysfunction

Objective: The aim of this study was to establish the frequency of vascular findings by color-coded duplex sonography in renal allografts with dysfunction. Furthermore, we estimated the clinical significance of these findings and their impact on therapy. Methods: A total of 184 duplex scans were performed in 119 patients (68 male, 51 female) with insufficient or declining diuresis and/or rising creatinine. Color-coded duplex sonography was used to examine the entire length of the iliac vessels as well as the central and peripheral renal arteries and veins. Results: A total of 45 abnormal vascular findings were identified in 37 patients (31%, including 21 transplant artery stenoses (7 > 50%), 5 iliac stenoses, 11 AV fistulas and 8 venous stenoses. Of all vascular findings, 4 were determined to be responsible for functional deterioration, including 2 high grade kinking stenoses of the transplant artery in the early post-operative period, 1 transplant artery stenosis in the middle segment and 1 high-grade iliac artery stenosis. The other abnormal vascular findings did not appear to cause renal dysfunction. Biopsy results did not explain the functional deterioration in 1.6% of patients without vascular findings but in 13% of patients with vascular findings. Conclusions: Abnormal duplex sonographic vascular findings occur frequently in renal allografts but only a few of them are responsible for deterioration of graft function. Histologic findings insufficient to explain renal dysfunction possibly indicate a potential vascular cause. Due to its non-invasiveness, color-coded duplex sonography is a useful diagnostic tool but all findings need to be interpreted strictly in a clinical context.     

The diagnosis of renal artery stenosis by the data from ultrasonic study methods

The purpose of the present investigation was to elaborate diagnostic criteria for stenosing of renal arteries according to ultrasonic dopplerography. The investigation included 35 patients suffering from vasorenal hypertension with stenoses of the renal arteries documented by angiography and 63 patients with stage II essential hypertension, who made up the control group. Ultrasonic scanning of the kidneys and dopplerography of the renal arteries were performed with the use of the Acuson-128 ultrasonic system fitted out with a sector transducer operating at a frequency of 3.5 MHz. The authors have devised a method of an ultrasonic study of the renal arteries by means of the posterolateral access. Established criteria for diagnosing stenosis of the renal artery. Among these are a decline of the pulsation index, the resistive index, and the systolic-diastolic velocity ratio as compared to the contralateral artery and nonstenosed renal arteries in the control group patients.     

Cerebrovascular assessment using a Doppler carotid scanner and real-time frequency analysis

The results of two methods for noninvasively diagnosing carotid disease are described. In the first study, a color-coded continuous-wave Doppler scanner was used. As evaluated by arteriography in 56 sides, the sensitivity and specificity of the Doppler scanner for diagnosing carotid lesions with greater than 50% stenosis was 71% and 82%, respectively. We found that many of our initial problems could be overcome by the concomitant use of a real-time frequency analyzer. Specifically, when the Doppler waveforms were displayed, we found that: 1) signals that had been attenuated by calcification or plaques, or had reduced velocity as a result of a proximal stenosis, could still be detected; 2) when the velocity of flow was increased to compensate for a contralateral carotid stenosis, the waveforms could still be of diagnostic value; 3) distinguishing between the internal and external carotid arteries was easier than relying on the audio signal alone; 4) when the scan showed internal carotid occlusion, morphological evaluation of the external and common carotid waveforms was helpful in verifying the scan result; and 5) artifactual noise on the Doppler waveform could be recognized. In the second study, frequency analysis recordings were evaluated semiquantitatively by measuring peak frequency and the fractional width of the Doppler frequency spectrum at peak systole Our preliminary results show that this approach is of diagnostic value in that it has the potential to detect minor stenoses.     

Doppler velocimetry of maternal renal circulation in pregnancy-induced hypertension.

PURPOSE: The purpose of this study was to evaluate whether the Doppler waveforms of the maternal main renal, segmental, and interlobar arteries are altered in women with pregnancy-induced hypertension (PIH) compared with healthy pregnant women. METHODS: Flow waveforms of the maternal main renal, segmental, and interlobar arteries were obtained from 42 healthy pregnant women between 24 and 41 weeks of gestation and 21 women with PIH between 28 and 40 weeks of gestation using pulsed Doppler sonography. We used spectral analysis to measure the peak systolic and end-diastolic velocities and the acceleration time. The presence or absence of the normal early systolic compliance peak-reflective-wave complex (ESP) was assessed in only the main renal artery. RESULTS: The acceleration times of the segmental and interlobar arteries were significantly prolonged in the PIH group compared with those in the healthy pregnant women. Of the 21 women with PIH, 3 showed loss of the ESP in the renal artery, but these changes were not significant. CONCLUSIONS: Decreased systolic acceleration and the absence of ESP, the hemodynamic indicators for significant proximal stenosis, suggest that severe stenosis or continuous vasospasm in the proximal arteries, such as the main renal or segmental artery, may be implicated in the pathogenesis of PIH.     

正常成人上肢动脉彩色多普勒超声测量

目的　应用彩色多普勒超声检查和测量正常上肢动脉 ,以得出上肢动脉的超声正常值。方法　15 3名健康志愿者 3 0 6条上肢动脉 ,每条上肢分 7个节段。测量解剖学和血流动力学参数。结果　获得上肢动脉各节段各参数超声正常值 ,发现上肢动脉从近心至远心段 ,内径减少 ,管壁变薄 ,收缩期峰值流速、收缩期加速度、搏动指数值下降 (P <0 .0 5 ) ;上肢动脉各节段均可表现多种流速曲线形态 ,近心段以双向三峰所占比例大(67%锁骨下动脉段双向三峰 ) ,腋动脉以远段反向峰渐不明显 (4 5 .2 %肱动脉段单向双峰 )。结论　彩色多普勒超声能成功用于检查上肢动脉 ,发现变异和病变。     

Duplex criteria for determination of 50% or greater carotid stenosis.

Recently the North American Symptomatic Carotid Endarterectomy Trial investigators reported a benefit of carotid endarterectomy compared with medical therapy for symptomatic patients with 50% or greater carotid stenosis. This has necessitated the development of screening parameters for diagnosis of 50% or greater carotid stenosis on the basis of the reference standards used in the study by the North American Symptomatic Carotid Endarterectomy Trial. The duplex scans and arteriograms of 110 patients (210 carotid arteries) were reviewed by blinded readers. Duplex measurements of peak systolic velocity and end diastolic velocity were recorded, and the ratio of these velocities in the internal and common carotid arteries was calculated. The criteria determined for detection of 50% or greater stenosis were as follows: peak systolic velocity of the internal carotid artery greater than 170 cm/s (sensitivity, 92%; specificity, 90%; positive predictive value, 92%; negative predictive value, 90%; and accuracy, 91 %); end diastolic velocity of the internal carotid artery greater than 60 cm/s (sensitivity, 92%; specificity, 86%; positive predictive value, 95%; negative predictive value, 79%; and accuracy, 91 %); ratio of peak systolic velocity of the internal carotid artery to peak systolic velocity of the common carotid artery greater than 2 (sensitivity, 93%; specificity, 75%; positive predictive value, 83%; negative predictive value, 89%; and accuracy, 85%); and ratio of end diastolic velocity of the internal carotid artery to end diastolic velocity of the common carotid artery greater than 2.4 (sensitivity, 96%; specificity, 79%; positive predictive value, 88%; negative predictive value, 92%; and accuracy, 89%). It is concluded that 50% or greater carotid artery stenosis can be reliably determined by duplex criteria. The use of receiver operating characteristic curves allows the individualization of duplex criteria to the clinical situation.     

Transesophageal examination of the left coronary artery with a 7.5 MHz annular array two-dimensional color flow Doppler transducer

To determine the value of a recently developed 7.5 MHz annular array two-dimensional and color flow Doppler transducer for examination of the proximal parts of the left coronary artery, 25 patients were studied immediately after coronary artery bypass surgery, and the findings were compared with preoperative coronary angiograms. With two-dimensional imaging, the left main coronary artery was visualized in 22 patients (88%), left anterior descending in 13 patients (52%), and circumflex in 22 patients (88%). Stenoses were correctly identified in four of four left main coronary arteries, in five of seven left anterior descending arteries, and in none of four left circumflex arteries. Adding color flow to two-dimensional imaging in 20 patients, we found a disturbed flow signal, as a sign of stenosis, in five of five left anterior descending artery and two of four left circumflex artery stenoses. We concluded that these initial findings with this new 7.5 MHz annular array two-dimensional and color flow Doppler transducer, are promising in imaging and detection of stenoses in the proximal parts of the left coronary artery.     

Mesenteric duplex scanning

Duplex scanning of mesenteric arteries was developed in the late 1980s. It's primary clinical application is to identify high-grade stenoses in the superior mesenteric artery (SMA) and celiac artery that may be associated with the clinical condition of chronic mesenteric ischemia. A peak systolic velocity of >275 cm/s in the SMA identifies a >70% SMA stenosis with a sensitivity of 92%, a positive predictive value of 80% and a negative predictive value of 99%. A negative mesenteric duplex study therefore virtually excludes the presence of clinically important mesenteric artery stenosis. A positive study requires confirmation with an additional imaging study prior to mesenteric artery reconstruction. Other applications of mesenteric duplex scanning include identification of reversible compression of the celiac artery, follow-up of mesenteric bypass grafts and physiological studies of the intestinal circulation.     

直接超声参数在肾动脉狭窄诊断中的应用研究

目的 探讨内径狭窄≥50%肾动脉狭窄（RAS）的直接超声参数特点及其诊断价值.方法 经彩色多普勒血流成像（CDFI）检查后并接受肾动脉造影的89例患者共177条肾动脉构成研究组,测量了肾动脉峰值流速（RPSV）、肾动脉与腹主动脉峰值流速比值（RAR）、肾动脉与肾动脉峰值流速比值（RRR）、肾动脉与段动脉峰值流速比值（RSR）和肾动脉与叶间动脉峰值流速比值（RIR）.肾动脉造影显示肾动脉内径狭窄≥50%者确定为RAS.使用ROC曲线分析确定最佳诊断指标.计算这些流速指标不同阈值的敏感性、特异性、阳性预测值、阴性预测值和准确率.结果 在肾动脉造影显示的177条肾动脉中,80条狭窄程度为50%～99%,7条闭塞.在狭窄程度50%～99%的80条肾动脉中,动脉粥样硬化性RAS 46条,大动脉炎RAS 20条,纤维肌性发育不良性RAS 12条,其他病因2条.肾动脉CDFI检查成功率为98.9%（175/177）.RPSV、RAR、RRR、RSR、RIR最佳阈值分别为170 cm/s、2.3、2.0、3.8、5.5.RPSV、RSR和RIR均获得较好的诊断效果（准确率均大于87%）,RAR和RRR的诊断敏感性较差（分别为79%和80%）.结论 对于狭窄≥50%的RAS,RPSV、RIR和RSR均是较好的诊断指标,RAR和RRR的诊断敏感性较差.影响肾动脉和腹主动脉PSV的因素都可导致RAR的诊断准确性下降,而PSV后比参数受腹主动脉PSV的影响较小,且各种原因所致肾动脉主干、肾内动脉PSV等成比例改变对PSV后比参数的影响也较小,其能明显弥补RAR的一些不足.     

Diagnostic imaging evaluation of renovascular hypertension

Over 50 million people in the United States are hypertensive. Renovascular disease accounts for 3–5% of these hypertensive patients. Because renovascular hypertension is potentially curable, much effort has been devoted to detecting and treating renal artery stenosis. Conventional angiography has been traditionally used to diagnose renal artery stenosis. However, because of its invasiveness and cost, conventional angiography cannot be utilized as a screening test in all patients who may have renal artery stenosis. Several noninvasive studies have been advocated for screening in hypertensive patients who may have renovascular disease. However, the accuracy of these noninvasive studies is widely variable, and appropriate use of these noninvasive studies needs to be better defined. Appropriate use of diagnostic imaging examinations for hypertensive patients depends on the index of suspicion for renovascular disease and on the patient's renal function. If certain clinical findings suggest the possibility of renovascular disease, then conventional angiography/intraarterial digital subtraction angiography should be performed. Captopril renography or duplex Doppler sonography could also be utilized if angiography is not desired or is contraindicated because of impaired renal function or a contrast allergy. Magnetic resonance angiography appears to be most helpful in a small, select group of patients who are likely to have proximal renal artery stenosis.     

Visceral duplex scanning: evaluation before and after artery intervention for chronic mesenteric ischemia

Color duplex ultrasound testing has evolved to be a clinically useful modality to diagnose chronic mesenteric ischemia caused by visceral artery origin atherosclerosis. Testing requires expertise in ultrasound imaging, visceral artery hemodynamics, and duplex scan interpretation. Patient can be accurately screened for severe stenosis or occlusion involving celiac, superior mesenteric, or inferior mesenteric arteries. Duplex testing can also evaluate functional patency following visceral bypass grafting procedures or endovascular stent-angioplasty. The focus of duplex surveillance after visceral artery intervention is to identify severe repair site stenosis, which can develop with symptoms of gut ischemia. Visceral duplex testing of a bypass graft or stent-angioplasty site that shows peak systolic velocities >300 cm/s with end-diastolic velocities >50 to 70 cm/s, or a decreased graft velocity peak systolic velocity <40 cm/s should be considered for interrogation using angiography to confirm or exclude severe (>70%) stenosis. Duplex testing after surgical or endovascular visceral interventions is a screening study, which compliments clinical follow-up by aiding the vascular surgeon in timely identification of visceral repairs that have developed a progressive, high-grade stenosis.     

Transcranial Doppler evaluation of middle cerebral artery stenosis

Symptomatic stenoses of the middle cerebral artery (MCA) are not uncommon, although Corston observed the occurrence of stroke in 24% of patients with MCA stenoses during a 6-year follow-up study. We tried to use transcranial Doppler (TCD) sonography for the detection and evaluation of MCA stenoses. Intra-arterial angiography demonstrated 16 MCA stenoses of more than 30% diameter reduction in 15 patients (14 atheromatous stenoses, 2 dysplasias). Severe associated lesions were present in 2 cases (more than 75% internal carotid artery stenosis). These 15 patients with MCA stenosis were examined with TCD in a blind study. A Doppler signal from the MCA was obtained through the temporal bone and was recognized on the result of common carotid artery compression test. We ascertained MCA stenosis when TCD demonstrated 1) segmental flow acceleration with peak systolic frequency of more than 3 KHz with or without high energy low frequency direct or reverse components; or 2) segmental increase in systolic peak frequency of more than 20%. Using these criteria, we confirmed through TCD the presence of MCA stenosis in nine out of 12 cases with diameter reduction of at least 50%, and one among four cases with less than 50% diameter reduction. Although our results are consistent with Aaslid and von Reutern's figures, methodological problems and diagnostic criteria have to be improved. Nevertheless, TCD seems to be a useful tool for the detection of stenosis with at least 50% diameter reduction, where it proved to offer a 75% sensitivity. Further studies are necessary to improve sensitivity and specificity.     

Redefined duplex ultrasonographic criteria for diagnosis of carotid artery stenosis

OBJECTIVE: To evaluate duplex ultrasonographic criteria for the determination of 50% or more and 70% or more stenosis of the diameter of the internal carotid artery based on conventional angiography in order to align ultrasonographic diagnostic categories with current clinical management schemes. PATIENTS AND METHODS: Between January 1, 1995, and June 30, 1999, 915 patients underwent both carotid duplex ultrasonography and cerebral angiography within 30 days at Mayo Clinic, Rochester, Minn. Of these patients, 294 were excluded from this study because of occlusion of one or both of the internal carotid arteries or atypical flow characteristics. In the remaining 621 patients (61 % male, 39% female; mean age, 67.7 years [range, 14-88 years]), 1218 vessels were available for correlation. Several Doppler ultrasonographic velocity variables were compared with the angiographic findings by use of receiver operating characteristic curve analysis. The primary end point was verification of optimal ultrasonographic criteria to diagnose 70% or more internal carotid artery stenosis. The secondary end point was establishment of threshold values to detect stenosis of 50% or more. RESULTS: At angiography, 382 patients had internal carotid arteries with 70% or more stenosis. Peak systolic and end diastolic velocities of the internal carotid artery and internal carotid artery:common carotid artery peak systolic velocity ratios were measured. For an internal carotid artery stenosis of 70% or more, a peak systolic velocity of 230 cm/s or more resulted in a sensitivity of 86.4%, a specificity of 90.1%, a positive predictive value of 82.7%, a negative predictive value of 92.3%, and an accuracy of 88.8%. An end diastolic velocity of 70 cm/s or more and an internal carotid artery:common carotid artery ratio of 3.2 or more yielded similar values. For an internal carotid artery stenosis of 50% or more, a peak systolic velocity of 130 cm/s or more resulted in a sensitivity of 92.1 %, a specificity of 89.5%, a positive predictive value of 90.3%, a negative predictive value of 91.3%, and an overall accuracy of 90.8%. An internal carotid artery:common carotid artery ratio of 1.6 or more yielded similar values. CONCLUSION: In our ultrasonography laboratory, a carotid artery stenosis of 70% or more (for which carotid endarterectomy is typically recommended in symptomatic patients) is diagnosed reliably with the following duplex ultrasonographic criteria: a peak systolic velocity of 230 cm/s or more, an end diastolic velocity of 70 cm/s or more, or an internal carotid artery:common carotid artery ratio of 3.2 or more.     

Pulsed Doppler velocity patterns produced by arterial anastomoses

Centerstream velocity waveforms produced by end-to-end and end-to-side anastomoses constructed in the dog illeofemoral arterial system were studied with a 20 MHz pulsed Doppler velocimeter combined with spectral analysis. Flow disturbance was identified by changes in spectral width during the systolic phase of the cardiac cycle. Measurement of the maximum frequency and the spectral width at peak systole was used to quantify the magnitude of flow disturbance at varying locations proximal and distal to the anastomoses. Disruption of the normal laminar flow pattern observed in the unoperated dog artery was evident distal to both anastomotic configurations. An increase in spectral width reflecting disturbed flow was maximal during the deceleration phase of systole. Flow disturbance was localized to a zone within one diameter distal to the anastomosis and dissipated rapidly downstream. The velocity spectrum changes observed downstream of an anastomosis resemble the flow disturbances produced by low grade, nonpressure reducing arterial stenoses.This study suggests that spectral analysis of pulsed Doppler waveforms is a potentially useful method of anastomosis assessment both to rule out major flow disruption produced by technical error, and to provide insight into the role of turbulence in the development of anastomotic intimal hyperplasia.     

Doppler blood flow velocity waveforms in the fetal renal arteries: variability at proximal and distal sites in the right and left arteries.

OBJECTIVE: To investigate variability in pulsatility/resistance indices and absolute velocities of blood flow in fetal renal arteries dependent on side and sampling site within each vessel. METHODS: Doppler blood flow measurements of pulsatility index (PI), resistance index (RI) and peak systolic velocity (PSV) and end-diastolic velocity (EDV) were performed in the renal arteries of 27 fetuses between 236 and 247 days of gestation. Velocity waveforms were sampled in both the right and left renal arteries at two different sites: proximally, close to the aorta, and distally, before any major visible bifurcation of the vessels. The intraobserver variation was measured in 15 additional fetuses. RESULTS: Mean values of PI and RI were similar in the right and left renal arteries and at the proximal and distal sampling sites of these arteries. Mean PSV and EDV were higher at the proximal compared to the distal site on both sides. For all parameters the 95% limits of agreement between measurements made in the right and left arteries and at proximal and distal sites were wide but tended to be narrower for the left renal artery and at the distal site. Intraclass correlation coefficients for intraobserver variability were 0.88, 0.89, 0.83 and 0.81 for PI, RI, PSV and EDV, respectively. CONCLUSIONS: It is important to standardize the precise site at which Doppler blood flow velocity waveform measurements are made in the renal arteries of the fetus. On the basis of our observations, we suggest that the left renal artery is the preferred vessel for sampling and that measurements should be made in the renal arterial trunk away from the aorta and before any visible branches.