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.     

Natural history of atherosclerotic renal artery stenosis: A prospective study with duplex ultrasonography

Purpose: Although the prevalence of renal artery stenosis in patients with peripheral arterial disease is in the range of 30% to 40%, the role of renal revascularization in patients without severe hypertension or kidney failure is controversial. Duplex scanning is a noninvasive technique that is ideally suited for screening and follow-up of renal artery disease. The purpose of this study was to document the natural history of renal artery stenosis in patients who were not candidates for immediate renal revascularization.Methods: Eighty-four patients with at least one abnormal renal artery detected by duplex scanning were recruited from patients being screened for renal artery stenosis. Of the 168 renal artery/kidney sides, 29 were excluded (15 prior interventions, 6 nondiagnostic duplex scans, 8 presumed nonatherosclerotic lesions), leaving 80 patients with 139 sides for the follow-up protocol. Renal arteries were classified as normal, less than 60% stenosis, 60% or greater stenosis, or occluded by use of previously validated criteria.Results: The study group included 36 men and 44 women with a mean age of 66 years who were monitored for a mean interval of 12.7 months. The initial status of the 139 renal arteries was normal in 36, less than 60% stenosis in 35, 60% or greater stenosis in 63, and occluded in 5. Although none of the initially normal renal arteries showed disease progression, the cumulative incidence of progression from less than 60% to 60% or greater renal artery stenosis was 23% ± 9% at 1 year and 42% ± 14% at 2 years. All four renal arteries that progressed to occlusion had 60% or greater stenoses at the initial visit, and for those sides with a 60% or greater stenosis, the cumulative incidence of progression to occlusion was 5% ± 3% at 1 year and 11% ± 6% at 2 years. The mean decrease in kidney length associated with progression of renal artery stenosis to occlusion was 1.8 cm.Conclusions: Progression of renal artery stenosis, as defined in this study, occurs at a rate of approximately 20% per year. Progression to occlusion is associated with a marked decrease in kidney length. Whether this natural history can be improved by earlier intervention for renal artery stenosis remains to be determined. (J VASC SURG 1994;19:250-8.)     

Critical review of non- or minimally invasive methods (duplex ultrasonography, MR- and CT-angiography) for evaluating stenosis of the proximal internal carotid artery.

OBJECTIVE: to assess the performance of non- or minimally invasive methods (duplex ultrasonography, MR- and CT-angiography) in measuring stenosis of the proximal internal carotid prior to endarterectomy without preoperative intra-arterial digital subtraction angiography (DSA). METHODS: systematic review of the literature (five databases, 1990 to February 2001). The value of each imaging technique was studied through its reproducibility and its sensitivity/specificity compared to DSA. RESULTS: sensitivity exceeded 80% and specificity 90% in over two-thirds of the methodologically sound studies, regardless of technique, although direct comparisons between results had to be avoided since the findings originated from different populations. The main drawback of duplex ultrasonography is its levels of reproducibility. In contrast, only a few studies have addressed the reproducibility of MR- and CT-angiography. When the results of duplex and MR-angiography agree, the combination use of these two techniques provides a better diagnosis than either technique taken alone. CONCLUSIONS: all three techniques appear suitable for measuring stenosis of the proximal internal carotid when compared to DSA.     

Renal blood flow measurement with contrast-enhanced harmonic ultrasonography: evaluation of dopamine-induced changes in renal cortical perfusion in humans

BACKGROUND: An accessible non-invasive method for evaluating renal regional blood flow in real time is highly desirable in the clinical setting. Recent progress in ultrasonography with microbubble contrast has allowed quantification of regional blood flow in animal models. AIMS: Goal ofthis study was to establish a convenient contrast--enhanced harmonic ultrasonography (CEHU) method for evaluating renal cortical blood flow in humans. METHODS: We carried out intermittent second harmonic imaging in 9 healthy volunteers. Pulse interval was progressively decreased from 4 s - 0.2 s during continuous venous infusion of the microbubble contrast agent. RESULTS: Pulse interval versus CEHU-derived acoustic intensity plots provided microbubble velocity (MV) and fractional vascular volume (FVV) during renal cortical perfusion in humans. Low-dose dopamine infusion (2 microg/min/kg) resulted in a significant increase in MV which correlated well with the increase in total renal blood flow (RBF) determined by a conventional study of p-aminohippurate clearance (C(PAH)) (r = 0.956, p < 0.0001). Although FVV was not significantly increased, alterations in CEHU-derived renal cortical blood flow calculated by the products of MV and FVV were also correlated with alterations in total RBF (r = 0.969, p < 0.0001). Thus, low-dose dopamine infusion increases renal cortical blood flow observed in CEHU, mainly by increasing MV. CONCLUSIONS: The present study shows that renal cortical blood flow in humans can be measured non-invasively by CEHU and that CEHU can be used for quantitatively evaluating changes induced by a therapeutic agent such as dopamine in flow velocity and in FVV.     

供肾动脉带主动脉袖口预防移植肾动脉狭窄

目的:探讨供肾动脉带主动脉袖口预防移植肾动脉狭窄的效果。方法:对955例(1030例次)行肾移植患者的肾移植供肾动脉,全部采用主动脉袖口与受者髂内动脉吻合。应用彩色多普勒血流B超及移植肾动脉血管造影排除移植肾动脉狭窄。结果:955例(1030例次)肾移植无一例出现移植肾动脉狭窄。结论:供肾动脉带腹主动脉袖口可以防止移植后肾动脉狭窄发生。     

Nitric oxide dependence of renal blood flow in patients with renal artery stenosis

In ischemia, nitric oxide (NO) production is increased, possibly to preserve flow. The role of NO was investigated in hypertensive patients with or without renal artery stenosis (RAS). Fifty-five hypertensive patients scheduled to undergo diagnostic renal angiography underwent mean renal blood flow (MRBF) measurements before and after an intrarenal injection of the NO synthase blocker N(g)-monomethyl-L-arginine (L-NMMA) at 0.03 microg/kg, before angiography. A dose-response study indicated that this dose of L-NMMA significantly blocked NO synthesis. MRBF was measured at baseline and 1, 5, 10, and 20 min after L-NMMA treatment. On the basis of the angiographic results, patients were divided into three diagnostic categories, i.e., essential hypertension (n = 26), unilateral RAS (n = 16), or bilateral RAS (n = 8). In essential hypertension, MRBF was decreased by 18 +/- 4% at 20 min. In unilateral RAS, L-NMMA did not affect MRBF in the stenotic kidney but reduced MRBF in the nonstenotic kidney by 40 +/- 9% at 20 min. In bilateral RAS, L-NMMA reduced flow by 32 +/- 14% at 20 min. In the nonstenotic kidney in unilateral RAS, a positive correlation was observed between the effect of NO blockade on MRBF and arterial renin levels (P = 0.009). In the stenotic kidney, in contrast, this correlation was inverse (P = 0.007). In conclusion, MRBF depends on NO in hypertensive patients, except in the stenotic kidney in unilateral RAS. In the nonstenotic kidney in unilateral RAS, NO bioavailability is increased. It is suggested that a compensatory mechanism, regulated by NO and possibly angiotensin II, may preserve renal function.     

肾动脉狭窄合并高血压及肾功能不全患者行血运重建的中期疗效评价

目的评价经皮肾动脉血运重建术(percutaneous transluminal renal artery revascularization,PTRAR)治疗对肾动脉狭窄合并高血压及肾功能不全患者的临床疗效。方法对2011年1月至2015年6月因肾动脉狭窄合并高血压在华中科技大学同济医学院附属同济医院心内科行肾动脉血运重建术的62例患者进行回顾性研究,并对其中18例肾功能不全的患者进行随访观察。结果62例患者共76条肾动脉严重狭窄或闭塞,均成功开通,14条肾动脉仅行球囊扩张,62条肾动脉行支架置入。住院期间未出现任何手术相关并发症;术后24 h血压也有明显的下降[收缩压:(150.8±16.4)mmHg比(132.0±12.8)mmHg;舒张压:(88.6±12.7)mmHg比(80.1±11.1)mmHg,P均0.05]。术后24 h肾功能不全的18例患者平均血压降至(135.7±16.0)/(83.8±11.4)mmHg。针对18例肾功能不全的患者,术后平均随访26个月,结果发现,与术前相比血压明显下降[收缩压:(138.4±11.8)mmHg比(148.7±9.1)mmHg;舒张压:(88.1±10.7)mmHg比(93.5±9.5)mm·Hg,P均0.05]。所有62例患者术后服药种数明显减少。18例肾功能不全者中6例(33.3%)治愈,7例(38.9%)改善,5例(27.8%)无变化;术后血清肌酐水平的监测发现9例患者的肾功能好转,6例患者的肾功能未受明显影响,3例患者的肾功能恶化。结论肾动脉血运重建术对肾动脉狭窄合并高血压患者的血压带来明显的获益,但对肾功能的改善效果有待进一步研究。     

A comparison of duplex Doppler ultrasonography and intrarenal manometry in the diagnosis of acute renal transplant rejection

Renal transplant rejection is frequently difficult to differentiate from other causes of renal dysfunction. This study examined the use of duplex Doppler ultrasound and intrarenal manometry in a consecutive series of 73 patients who underwent renal transplantation. Altogether 327 duplex scans were analyzed and, for each, a resistive index (RI) was calculated. A raised RI predicted rejection in patients with grafts that functioned immediately, but not in those that had delayed function. A rise in intrarenal pressure ( greater than or equal to 40 mmHg) indicated the presence of rejection in both groups. However, neither test had a sensitivity of more than 71% and this was not improved by combining the results of the two tests for each patient. Although both tests have a place in transplantation, renal biopsies may still be required to confirm rejection.