Imaging Modalities for Renal Artery Stenosis in Suspected Renovascular Hypertension: Prospective Intraindividual Comparison of Color Doppler US,CT Angiography,GD-Enhanced MR Angiography,and Digital Substraction Angiography

The aim of the study was to evaluate the diagnostic accuracy of Color Doppler US, CT Angiography (CTA), and GD-enhanced MR Angiography (MRA) compared with digital subtraction angiography (DSA) for the detection of renal artery stenosis in patients with clinically suspected renovascular hypertension. Fifty-eight patients with suspected renovascular hypertension were enrolled in the study. All patients underwent Color Doppler US, CTA and GD-enhanced MRA. DSA was the gold standard method for the number of renal arteries, existence and degree of stenosis, or evidence of fibromuscular dysplasia. DSA depicted 132 renal arteries, 16 stenoses, and 4 arteries with fibromuscular dysplasia. Color Doppler US failed to detect 1 main and 14 polar arteries. CTA depicted all main renal arteries and 7/16 polar arteries, but failed to detect stenosis in two accessory vessels. Likewise, MRA did not detect stenotic accessory renal arteries, depicted 9/16 polar renal arteries, but missed two main renal arteries. All methods depicted the four main renal arteries with fibromuscular dysplasia. The overall sensitivity, specificity, and positive and negative predictive accuracy were 75%, 89.6%, 60% and 94.6%, respectively, for color Doppler US; 94%, 93%, 71%, and 99%, respectively, for CTA; and 90%, 94.1%, 75%, and 98%, respectively, for GD-enhanced MRA. CTA and GD-enhanced MRA have comparable and satisfactory results with respect to the negative predictive accuracy of the suspected renal artery stenosis. The concept of an imaging algorithm including US as screening test when appropriate and CTA or MRA as the second step-procedure is suggested. Therefore, DSA may be reserved for cases with major discrepancies or therapeutic interventions.     

Magnetic resonance angiography of the kidney

Magnetic resonance angiography (MRA) of the kidneys has become a clinical standard for detecting renal artery stenosis. This test is performed by injecting a bolus of a gadolinium chelate and scanning with a three-dimensional volumetric data collection sensitized to the T1 shortening effects of gadolinium. In addition to displaying the renal arterial anatomy, atherosclerosis within the aorta and iliac arteries is commonly depicted. MRA is a time efficient and safe test when compared with conventional arteriography. Gadolinium-enhanced MRA has proven to have a high sensitivity for detecting stenoses in main and accessory renal arteries. Although false-negative studies are rare, overestimation of the degree of renal stenosis is problematic and may lead to false-positive diagnosis. To some extent this tendency to overestimate stenoses can be compensated for by performing phase contrast MRA, a type of MRA based on accumulated phase differences. As with conventional angiography, MRA is still only an anatomic test which provides little information about the functional significance of a stenosis. It is highly accurate in determining the number of renal arteries, the size of the kidneys, and the presence of any anatomic variants. Ultimately, MRA, needs to be combined with a functional test similar in concept to captopril renography. This test, termed MR renography together with MRA may replace the current multimodalitiy approach to the work-up of renovascular hypertension.     

Preoperative evaluation of living renal donors with gadolinium-enhanced magnetic resonance angiography

BACKGROUND: Preoperative evaluation of living renal donors includes an intra-arterial digital subtraction angiography (DSA). Inasmuch as this technique is invasive, uses radiation and an iodine-containing contrast medium, an alternative technique would be preferable. The purpose of this study was to determine the accuracy of gadolinium-enhanced magnetic resonance (MR) angiography in the visualization of renovascular anatomy for the preoperative evaluation of renal donors. METHODS: Twenty-four consecutive potential renal donors underwent gadolinium-enhanced MR angiography before the standard of reference, intra-arterial DSA. Both modalities were evaluated in a blinded manner. The results were correlated with the surgical findings. RESULTS: Three MR angiograms were technically unacceptable because of inadequate breath-hold. The remaining 21 donors had 47 renal arteries, including 5 accessory renal arteries, which were all visualized by MR angiography. MR angiography failed to visualize one case of subtle fibromuscular dysplasia in the distal part of a renal artery. In one donor, a small accessory renal artery, which had not been visualized on DSA, was encountered during nephrectomy. CONCLUSION: Gadolinium-enhanced MR angiography is an accurate minimally invasive method for the detection of accessory renal arteries in the preoperative evaluation of potential renal donors. The accuracy for excluding stenosis in general is high; however, the depiction of stenosis that are located far distally, or in the branch vessels, is less accurate. Advantages of gadolinium-enhanced MR angiography over the currently used method, intra-arterial DSA, are the minimal invasive nature, lower costs, and superiority in detecting venous anomalies, renal cysts, and tumors.     

Incidence of donor renal fibromuscular dysplasia: does it justify routine angiography?

BACKGROUND: The use of digital subtraction angiography (DSA) versus helical CT angiography (CTA) or MR angiography (MRA) for live renal donor evaluation is still controversial. Although CTA and MRA can detect some proximal moderate to severe arterial changes caused by fibromuscular dysplasia (FMD), mild and distal moderate FMD are not detected well without angiography. METHODS: This is a retrospective chart review of all potential, normotensive live renal donors at our center from July 1995 to June 2001. One hundred fifty-nine patients completed the donor evaluation process and underwent DSA. RESULTS: Seven cases of FMD, an incidence of 4.4%, were discovered. These patients were eliminated from donation. The distribution of renal vessels for our 159 patients was single arteries bilaterally, 64.8%; single left with multiple right, 16.4%; double left with single right, 9.4%; and multiple bilateral arteries, 9.4%. Three of the seven FMD patients had bilateral disease. Two of the seven (28.6%) FMD patients have subsequently required antihypertensive medications, with one requiring angioplasty of a progressive FMD stenotic lesion. CONCLUSIONS: We are concerned that CTA or MRA may overlook mild cases of DSA-detectable FMD. All seven FMD patients had single left renal arteries and would have undergone left donor nephrectomy. This would have resulted in their remaining right native kidneys having mild to moderate FMD in six of seven patients and in four donor kidneys having mild to moderate FMD. The need for antihypertensive medications in two of these seven potential donors within 4 years of their evaluation supports previous literature reports.     

Evaluating patients with renal failure for renal artery stenosis with gadolinium-enhanced magnetic resonance angiography

The incidence and prevalence of end-stage renal disease (ESRD) continues to increase, especially in the elderly population. The role of renovascular disease in contributing to ESRD is still not well defined. The objective of this study was to determine the utility of gadolinium (Gd)-enhanced magnetic resonance angiography (MRA) in evaluating elderly patients with renal insufficiency for renal artery stenosis (RAS). A 7-month prospective study conducted in a tertiary referral center evaluated 40 consecutive patients with progressive renal insufficiency (18 men and 22 women; mean age, 70 +/- 5.6 [standard deviation] years) and high clinical suspicion for renovascular disease with Gd-enhanced MRA. Digital subtraction angiography (DSA) was obtained in only those patients with significant RAS detected by MRA. Twelve patients had significant RAS. Six of these patients had percutaneous transluminal renal angioplasty (PTRA), five patients had renal artery bypass surgery, and one patient had a stent placed after PTRA. Seventy-eight renal arteries were satisfactorily evaluated by MRA. Twenty-two renal arteries were evaluated by both MRA and DSA. Of the 12 significant stenoses detected by the MRA, 11 were confirmed by DSA and 1 was confirmed at the time of surgical revascularization. It is concluded that Gd-enhanced MRA is a useful test for the evaluation of RAS in patients with compromised renal function.     

Digital subtraction angiography for noninvasive imaging of the renal artery

Digital subtraction angiography (DSA) is a relatively new radiologic technique for noninvasive imaging of arterial anatomy. DSA has been shown to be effective in defining the renal arteries in patients with known or suspected renovascular disease. DSA is an excellent means of screening for renovascular disease and of following patients with serial studies after surgical revascularization or percutaneous dilatation of renal arterial stenosis. It is excellent for monitoring patients with known renovascular disease.     

Evaluation of the vascular anatomy in potential living kidney donors with gadolinium‐enhanced magnetic resonance angiography: comparison with digital subtraction angiography and intraoperative findings

Asgari MA, Dadkhah F, Ghadian AR, Razzaghi MR, Noorbala MH, Amini E. Evaluation of the vascular anatomy in potential living kidney donors with gadolinium‐enhanced magnetic resonance angiography: comparison with digital subtraction angiography and intraoperative findings.
Clin Transplant 2011: 25: 481–485. © 2010 John Wiley & Sons A/S. Abstract: Background: X‐ray contrast arteriography has traditionally been used for pre‐operative evaluation in living kidney donors. However, magnetic resonance angiography (MRA) offers a non‐invasive alternative, which has been considered to be less accurate. This study was performed to determine whether MRA in the pre‐operative investigation of living kidney donors provides sufficient information. Methods: From December 2005 to December 2007, 173 potential live donors were evaluated in this study. Donors performed digital subtraction angiography (DSA) and those with one or more accessory arteries at least on one side recruited for further evaluation with three‐dimensional gadolinium‐enhanced MRA. Results: A total of 30 donors constituted the study population. When compared with DSA as the reference method, MRA detected 20 of 36 renal accessory arteries which indicates a sensitivity of 55.6%. The difference between MRA and DSA in identifying accessory renal arteries was significant (p‐value <0.001). Considering intraoperative findings as the standard of reference, MRA depicted correctly four of six (66.7%) accessory arteries on the transplanted kidneys. Conclusions: MRA has the advantage of avoiding exposure to ionizing radiation and is non‐invasive. These are important considerations in pre‐operative evaluation of a generally healthy donor population. However, MRA provides suboptimal accuracy in detecting small accessory arteries.     

Feasibility of multi-slice computed tomography in the diagnosis of arteriogenic erectile dysfunction

OBJECTIVE: To compare computed tomography (CT) angiography (CTA) obtained by multi-slice CT (a new minimally invasive method) with the current standard of arterial imaging, digital subtraction angiography (DSA), in diagnosing arteriogenic erectile dysfunction (ED). PATIENTS AND METHODS: Twenty-one patients with suspected arteriogenic ED underwent DSA and CTA after providing informed consent. Prostaglandin E1 was injected into the penile cavernosal body and then non-ionic contrast medium was rapidly infused into the antecubital vein. The DSA and CTA images were diagnosed as showing a normal or abnormal status by three reviewers independently. CTA was undertaken on an outpatient basis but DSA required hospitalization. RESULTS: In the 42 internal pudendal arteries, DSA showed 28 normal and 14 impaired arteries; CTA showed 21 normal arteries and 21 occlusions. The CTA image correlated closely with the diagnosis of stenosis or occlusion in internal pudendal arteries, with a sensitivity of 93%, a specificity of 71% and an accuracy of 79%. In the cavernosal arteries, DSA depicted 14 normal and 28 impaired arteries; CTA showed seven normal arteries and 35 occlusions. The CTA image agreed closely with the diagnosis of stenosis or occlusion in cavernosal arteries, with a sensitivity of 96%, a specificity of 43% and an accuracy of 79%. Of the 42 inferior epigastric arteries, DSA could not depict 11 arteries but CTA showed all 42 inferior epigastric arteries. CONCLUSIONS: CTA images correlated with DSA images; at present DSA is better than CTA in visualizing stenosis in fine arteries. However, CTA is less invasive and relatively inexpensive, and in future will probably provide even greater improvements in graphic quality. CTA would be an adequate replacement for DSA in evaluating internal pudendal arterial stenosis.     

Can magnetic resonance angiogram be a reliable alternative for donor evaluation for laparoscopic nephrectomy?

BACKGROUND: While hand-assisted laparoscopic donor nephrectomy (HLDN) is less invasive, which can encourage kidney donation, it requires more exact information about the renal vascular anatomy because of its limited visual field during nephrectomy. MRA is also an attractive choice because of its minimal invasiveness; further, it is an outpatient-based procedure, it uses non-nephrotoxic contrast material and it has no radiation. The aim of our study was to evaluate the effectiveness of gadolinium enhanced three-dimensional MRA (GdE-3D MRA) in a group of potential live donors who were candidates for HLDN. METHODS: From September 2002 to December 2004, 40 potential live renal donors were evaluated prospectively with GdE-3D MRA, and this imaging modality was performed before the gold standard, the intra-arterial digital subtraction angiogram (IA-DSA), was carried out. All the images were reviewed in a blinded manner by the attending vascular radiologist. The MRA findings were compared with the DSA findings and the surgical findings as the reference methods. We evaluated the accuracy of MRA for imaging the renal architectures, and especially for imaging the renal accessory arteries and the early branching arteries that are important determinants for selection of the donor kidney. RESULTS: Both the MRA and DSA images showed consistent findings with the surgical findings in 92.5% of the 40 donors. There were no discrepant cases in depicting the main renal artery. MRA showed 100% specificity for imaging both the renal accessory arteries and the early branching arteries, when compared with the surgical findings. The kappa values for the MRA and DSA for the accessory arteries were all 0.66 compared with the intraoperative findings. MRA also depicted one huge renal cyst in one donor and many small renal cysts in the other donors that could not be imaged by DSA. There were no adverse events during the MRA procedure. None of the findings missed by MRA resulted in deleterious consequences at laparoscopic nephrectomy for the donor and graft. CONCLUSIONS: Our limited experience with GdE-3D MRA for imaging the renal structures in kidney donor evaluation for HLDN has been quite satisfactory.     

Prospective study comparing three-dimensional computed tomography and magnetic resonance imaging for evaluating the renal vascular anatomy in potential living renal donors

OBJECTIVE: To prospectively compare the accuracy of multislice spiral computed tomographic angiography (CTA) and magnetic resonance angiography (MRA) in evaluating the renal vascular anatomy in potential living renal donors. SUBJECTS AND METHODS: Thirty-one donors underwent multislice spiral CTA and gadolinium-enhanced MRA. In addition to axial images, multiplanar reconstruction and maximum intensity projections were used to display the renal vascular anatomy. Twenty-four donors had a left laparoscopic donor nephrectomy (LDN), whereas seven had right open donor nephrectomy (ODN); LDN was only considered if the renal vascular anatomy was favourable on the left. CTA and MRA images were analysed by two radiologists independently. The radiological and surgical findings were correlated after the surgery. RESULTS: CTA showed 33 arteries and 32 veins (100% sensitivity) whereas MRA showed 32 arteries and 31 veins (97% sensitivity). CTA detected all five accessory renal arteries whereas MRA only detected one. CTA also identified all three accessory renal veins whereas MRA identified two. CTA had a sensitivity of 97% and 47% for left lumbar and left gonadal veins, whereas MRA had a sensitivity of 74% and 46%, respectively. CONCLUSION: Multislice spiral CTA with three-dimensional reconstruction was more accurate than MRA for both renal arterial and venous anatomy.     

Magnetic resonance angiography for preoperative evaluation of potential kidney donors

BACKGROUND: Careful evaluation of the renovascular anatomy for living kidney donors is essential to optimize donor and recipient outcomes. Arteriography has been the standard for delineating the renovascular anatomy. However, this procedure is invasive. Magnetic resonance angiography (MRA) is an attractive, noninvasive alternative. The aim of this study was to evaluate the accuracy of MRA in potential living kidney donors. METHODS: A retrospective comparison of the preoperative MRA results with the intraoperative anatomy was performed in 189 living kidney donors. RESULTS: MRA interpretations correctly identified the vascular anatomy of the donor kidneys in 173 donors (91.5%). In the remaining 16 patients (8.5%), the MRA interpretation was inaccurate. In 10 patients, the MRA reported fewer arteries than the number encountered during the donor operation, whereas in six patients MRA reported more arteries than what found during operation. In seven patients, MRA supplied additional important anatomical information, including kidney size disparity, the presence of nephrolithiasis, the presence of a renal cyst, and renal artery stenosis. All kidneys were successfully transplanted. The misinterpretation of the MRA did not adversely affect the recipient outcome. CONCLUSION: The noninvasive MRA evaluation of donor renovascular anatomy is an acceptable substitute for traditional angiography.     

Assessment of the arteries in living kidney donors: correlation of magnetic resonance angiography with intraoperative findings

Comprehensive imaging evaluation of kidney donor anatomy is crucial for selecting candidates for living kidney transplantation and for determining the surgical technique to procure the renal graft. In 76 living renal donors we compared the results of preoperative magnetic resonance angiography (MRA) with the intraoperative findings of arterial anatomy. Donors were evaluated for the number of main renal arteries and the presence of any polar arteries. A total of 80 main renal arteries and five polar arteries were observed at MRA. At surgery, 90 main renal arteries and eight polar arteries were identified. MRA demonstrated a sensitivity, specificity, and overall accuracy of 18%, 98%, and 87%, respectively, for main arteries and 25%, 96%, and 88% for polar arteries. Eleven (14.5%) kidneys displayed more than one main artery and MRA only detected two cases. Eight kidneys had polar arteries and MRA only detected two cases. MRA is a reliable method for presurgical evaluation of renal arteries in potential donors, providing valuable information required by the surgeon. But, as the technique misses small-diameter vessels, it cannot be recommended as the sole diagnostic tool in unclear cases.     

Overestimation of carotid artery stenosis with magnetic resonance angiography compared with digital subtraction angiography

BACKGROUND AND PURPOSE: Three-dimensional time-of-flight (3D TOF) magnetic resonance angiography (MRA) is generally considered to overestimate the degree of stenosis in the internal carotid artery (ICA) in comparison with the reference standard intraarterial digital subtraction angiography (DSA). We evaluated whether the degree of stenosis was more accurately assessed with 3D TOF MRA if corresponding projections on MRA and DSA were compared instead of comparison of maximal stenosis at MRA with maximal stenosis at DSA. METHODS: From February 1997 to December 1999, we included 186 symptomatic and 17 asymptomatic consecutive patients suspected of having carotid artery stenosis on the basis of clinical presentation and screening with duplex ultrasound scan examination. All patients subsequently underwent DSA and MRA imaging. From each ICA, 12 maximum intensity projections with 3D TOF MRA and two or three projections with DSA were obtained. First, we compared the maximal stenosis at MRA with the maximal stenosis at DSA. Subsequently, we used the stenosis at MRA measured on the projection corresponding with the DSA projection that showed the maximal stenosis. For both strategies, the mean differences in stenosis and sensitivity and specificity for assessment of severe stenosis (70% to 99%) were calculated and compared. RESULTS: The MRA and DSA images of 354 ICAs could be compared. The sensitivity and specificity of MRA with the projection that showed the maximal stenosis were 92.6% (95% CI, 85.3% to 97.0%) and 82.7% (95% CI, 78.1% to 87.3%), respectively. The sensitivity and specificity with the MRA projection, corresponding with the DSA projection showing the maximal stenosis, were 88.3% (95% CI, 81.8% to 94.8%) and 89.6% (95% CI, 85.9% to 93.3%), respectively. The mean difference between maximal stenosis at MRA and DSA was 7.5% (95% CI, 5.2% to 9.9%). The mean difference between stenosis at MRA and DSA in corresponding projections was 0.4% (95% CI, -2.0% to 2.7%). CONCLUSION: If corresponding MRA and intraarterial DSA projections are compared, 3D TOF MRA does not overestimate carotid stenosis.     

Detection of significant renal artery stenosis with color Doppler sonography: combining extrarenal and intrarenal approaches to minimize technical failure

BACKGROUND: Renal artery disease can cause both hypertension and renal failure, and color Doppler sonography (CDS) may be a good screening method to detect it. Presently reported techniques of Doppler sonography have either a high rate of technical failure (4-42%), or low sensitivity and specificity, or detect only stenoses greater than 70%, or exclude patients with renal failure from analysis. In previous studies Doppler detection of renal artery stenosis (RAS) was based either on increased intrastenotic velocity or on the detection of post-stenotic Doppler phenomena. In the present prospective study these two approaches were combined to detect RAS (> or = 50% diameter reduction) in 226 consecutive patients (144 with normal and 82 with impaired renal function). METHODS: Stenosis of 50% or more was diagnosed if the maximal systolic velocity in the main renal artery was more than 180 cm/sec and velocity in the distal renal artery less than one quarter of the maximum velocity. When these velocities could not be determined a diagnosis of RAS was made when the acceleration time in intrarenal segmental arteries exceeded 70 msec. All patients subsequently underwent arteriography as the gold standard for the detection of RAS. RESULTS: With this combined approach, the technical failure rate of CDS was 0% in both patients with normal and those with impaired renal function. The mean time required for the Doppler investigation was 17 minutes. The sensitivity and specificity for detection of a significant stenosis in a given vessel (including accessory arteries), as compared to angiography, were 96.7% and 98.0%. CONCLUSION: Color Doppler sonography, evaluating both main renal and intrarenal arteries is an ideal screening method for detection of RAS of 50% or more because it allows accurate and rapid detection of stenosis in all patients, irrespective of renal function.     

Is duplex scanning the best screening test for renal artery stenosis?

Screening for renal artery stenosis is indicated in patients with suspected renovascular hypertension or ischemic nephropathy to identify those who could benefit from renal artery interventions. The critical requirements for a clinically useful screening test include safety, low cost, and a high sensitivity or low false-negative rate. Arteriography remains the "gold standard" for the anatomic diagnosis of renal artery disease, but it is unsuitable for screening because of its high cost and invasive nature. Although renal duplex scanning technically is difficult, experienced laboratories have been able to achieve sensitivities and specificities in the range of 93% to 98% for identification of stenoses in the main renal arteries. Renal duplex scanning also provides a method for assessing the renal parenchyma and predicting the clinical outcome of renal revascularization. The principal limitation of renal duplex scanning is failure to identify accessory renal arteries. The finding of one or more widely patent main renal arteries makes ischemic nephropathy unlikely, because this condition results from "total" renal ischemia. However, renovascular hypertension can be present with normal main renal arteries when there are isolated stenoses involving accessory renal arteries, so further testing may be indicated in selected hypertensive patients with normal main renal arteries by duplex scanning. Currently, duplex scanning in a qualified vascular laboratory arguably is the best screening test for renal artery stenosis. Other methods for assessing the renal arteries, particularly spiral computed tomography and magnetic resonance angiography, are evolving rapidly and also may play a role in screening of selected patients.     

Renal duplex sonography: main renal artery versus hilar analysis

OBJECTIVE: The purpose of this study was to compare the accuracy of main renal artery Doppler scanning interrogation and hilar analysis to diagnose hemodynamically significant renal artery disease. METHODS: From January 1998 to August 1999, 41 patients had renal duplex sonography with both main renal artery interrogation and hilar analysis followed by angiography. They form the basis of this review. The sample consisted of 24 men and 17 women, with a mean age of 68.9 +/- 10.2 years, who provided 80 kidneys for comparative analysis. Significant renal artery disease revealed through angiography was defined as >/= 60% diameter-reducing stenosis or occlusion. Peak systolic velocity (PSV) (in meters per second) and the presence of poststenotic turbulence (PST) were determined from main renal artery interrogation. Acceleration time (AT) (in milliseconds) was measured by means of hilar analysis. Significant renal artery stenosis was defined by a PSV of 2.0 m/s or more and a PST or an AT more than 100 ms. Sensitivity analyses of both PSV and AT were examined, and 95% CIs were computed. Receiver operating characteristic curves were used to estimate optimal values for PSV and AT. RESULTS: Angiography revealed hemodynamically significant fibromuscular dysplasia in 5 kidneys (4 patients), atherosclerotic stenosis >/= 60% in 48 kidneys (30 patients), and renal artery occlusion in 4 kidneys (4 patients). Kidneys with significant renal artery stenosis had a higher PSV (2.54 +/- 0.11 vs 1.28 +/- 0.08, P <.001) and AT (82.43 +/- 7.2 vs 30.0 +/- 2.8, P <.001) compared with those without stenosis. Compared with angiography, a PSV of 2.0 m/s or more and PST demonstrated a sensitivity of 91%, specificity of 96%, and overall accuracy of 92% for detection of significant renal artery stenosis. Two of five studies with false-negative results reflected diseased polar vessels. By contrast, AT of more than 100 ms had a sensitivity of 32%, specificity of 100%, and overall accuracy of 54%. Receiver operating characteristic curve analysis revealed a PSV of more than 1.8 m/s and an AT of 58 ms or greater as optimal values. With an AT of 58 ms or more, the sensitivity was 58%, and specificity was 96%, with an overall accuracy of 70%. There were no apparent associations between PSV or AT and type or location of renal artery lesion, serum creatinine level, or end-diastolic ratio. CONCLUSION: Main renal artery interrogation is an accurate screening test to detect significant stenosis or occlusion of the main renal artery. Hilar analysis alone does not provide sufficient sensitivity to be used as a sole screening study. Neither method detects the presence of renovascular disease associated with polar vessels.     

The limitations of magnetic resonance angiography in the diagnosis of renal artery stenosis: comparative analysis with conventional arteriography

PURPOSE: Gadolinium-enhanced magnetic resonance angiography (MRA) is commonly used as a screening modality for the detection of renal artery stenosis. However, evidence supporting its utility in clinical practice is lacking; few rigorous studies have compared MRA with contrast arteriography (CA). After making anecdotal clinical observations that MRA sometimes overestimated the degree of renal artery stenosis, we decided to determine the interobserver variability, sensitivity, specificity, and diagnostic accuracy of MRA compared with CA. METHODS: From September 1999 to April 2003, we evaluated 68 renal arteries in 34 patients with clinically suspected renal artery stenosis using both MRA and CA. All studies were independently reviewed by four blinded observers. Renal arteries were categorized by MRA as normal, <50%, and >50% stenosis/occlusion. The sensitivity, specificity, and accuracy of MRA detection of renal artery stenosis were compared to CA as the gold standard. Interobserver variability (kappa) was also calculated. RESULTS: MRA demonstrated 87% sensitivity, 69% specificity, 85% accuracy, 95% negative predictive value, and 51% positive predictive value for the diagnosis of renal artery stenosis. Interobserver agreement was moderate for MRA (kappa = 0.53) and good for CA (kappa = 0.76). In 21 arteries (31%), MRA was falsely positive. CONCLUSIONS: In patients with a high clinical suspicion of renal artery stenosis, MRA is 87% sensitive in the detection of >50% stenosis. However, MRA is relatively nonspecific compared with CA and results in significant overestimation of renal artery stenosis in nearly one third of patients. To reduce unnecessary CA, clinicians should consider supplemental studies.     

Renal artery stenosis: evaluation with colour duplex ultrasonography

Background: Detection of renal artery stenoses (RAS) by means of duplex Doppler ultrasound with direct scanning of the main renal arteries is subject to numerous limitations. Using semiquantitative analysis of the Doppler curve, which can be recorded from intrarenal arteries, it is possible to detect RAs unaffected by the problems of direct Doppler scanning of the renal arteries. Method: Both angiography of the renal arteries and colour duplex ultrasonography (US) of the intrarenal vessels (interlobar arteries) were performed in 214 patients (53.2±15.1 years) with severe arterial hypertension. Angiography was used as 'gold standard' in the diagnosis of RAS and the Doppler results were compared with the subsequent findings on angiography. At angiography, the reduction of diameter >70% was assessed as haemodynamically effective RAS. For the duplex Doppler diagnosis of RAS the following parameters were calculated: (a) resistive index (RI) of each kidney, and (b) side-to-side differences of the resistive indices (&Dgr;RI) between the right and left kidney. Results: Angiography demonstrated 59 RAS (>70%) in 53 patients, including six with bilateral RAS. By means of duplex US we found a significant difference of RI between kidneys with RAS (0.48±0.11) and without RAS (0.63±0.08; P<0.001). In addition, a significant difference of the &Dgr;RI was noted in patients with RAS (24.4%±12.5%) and the controls without RAS (3.6%±2.7%). Using a combination of both RI and &Dgr;RI, threshold values of RI=0.45 resp. &Dgr;RI=8% yields a sensitivity of 92.5% and a specificity of 95.7% in the detection of haemodynamically effective RAS. Conclusion: Colour duplex US with calculation of the RI and &Dgr;RI of intrarenal arteries is a valuable non-invasive test assessing the haemodynamic effects of RAS. Low costs and safety support the use of the Doppler technique in screening for renovascular disease.     

彩色多普勒对肾血管病变诊断价值探讨

以双功能和彩色多普勒超声诊断５５例肾血管病变，包括肾动脉狭窄、肾小动脉硬化、肾动脉发育不良、肾动静脉畸形、急性肾静脉血肾静脉曲张。与其中３８例有完整肾血管造影检查资料的结果对照，超声诊断符合率９５％。结果认为综合多普勒定量指标、典型的多普勒频谱形态和征象各的彩色血流图象，能够对多种肾血管病变出准确诊断。     

Cure and improvement of renovascular hypertension after percutaneous transluminal angioplasty of renal artery stenosis

In the present study we report our long-term experience in 82 patients with renovascular hypertension (48 with atherosclerotic stenosis, 34 with fibromuscular dysplasia) who were followed up for a mean observation period of 23.6 months after percutaneous transluminal angioplasty (PTA) of renal artery stenosis. Our results show a highly significant decrease in mean systolic and diastolic blood pressure. Cure rates were slightly higher in patients with fibromuscular dysplasia (41% cured, 47% improved) than in those with atherosclerosis (23% cured, 54% improved). Kidney function significantly improved in patients with cure, remained stable in those with improvement and worsened in cases classified as unimproved. These results document the good long-term effect of PTA on blood pressure and kidney function in patients with renal artery stenosis.